[FFmpeg-devel] [PATCH v2 0/3] Initial support for fragmented TTML muxing

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* [FFmpeg-devel] [PATCH v2 0/3] Initial support for fragmented TTML muxing
@ 2023-09-15 13:16 Jan Ekström
  2023-09-15 13:16 ` [FFmpeg-devel] [PATCH v2 1/3] tests/fate-run: add support for specifying the final encode muxer in `transcode` Jan Ekström
                   ` (3 more replies)
  0 siblings, 4 replies; 10+ messages in thread
From: Jan Ekström @ 2023-09-15 13:16 UTC (permalink / raw)
  To: ffmpeg-devel

Changes compared to v1:

* General rebase.
* A FATE test was added, together with the extension of the "transcode"
  test function to allow for dumping of packets' contents.
* Simplified mov_write_ttml_document_from_queue's loop by getting
  rid of `stop_at_current_packet`.

This enables pushing TTML together with another track (usually video)
as part of CMAF Ingest, as defined by the DASH-IF Live Media Ingest
Protocol.

Currently does not function well with just the subtitle track unless
the API user explicitly requests fragmentation with a nullptr packet,
as the generic fragmentation decision logic is based on tracks which
do not require squashing.

Currently does support overlapping subtitles, but the implementation
utilizes another packet queue for it, which is probably not optimal.
Recommendations on how to improve things are welcome.

Jan

Jan Ekström (3):
  tests/fate-run: add support for specifying the final encode muxer in
    `transcode`
  avcodec/avpacket: add functionality to prepend to AVPacketLists
  avformat/movenc: add support for fragmented TTML muxing

 libavcodec/avpacket.c                       |   20 +-
 libavcodec/packet_internal.h                |    2 +
 libavformat/movenc.c                        |    9 -
 libavformat/movenc_ttml.c                   |  157 ++-
 tests/fate-run.sh                           |    4 +-
 tests/fate/mov.mak                          |   21 +
 tests/ref/fate/mov-mp4-fragmented-ttml-dfxp | 1197 +++++++++++++++++++
 tests/ref/fate/mov-mp4-fragmented-ttml-stpp | 1197 +++++++++++++++++++
 8 files changed, 2588 insertions(+), 19 deletions(-)
 create mode 100644 tests/ref/fate/mov-mp4-fragmented-ttml-dfxp
 create mode 100644 tests/ref/fate/mov-mp4-fragmented-ttml-stpp

-- 
2.41.0

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^ permalink raw reply	[flat|nested] 10+ messages in thread

* [FFmpeg-devel] [PATCH v2 1/3] tests/fate-run: add support for specifying the final encode muxer in `transcode`
  2023-09-15 13:16 [FFmpeg-devel] [PATCH v2 0/3] Initial support for fragmented TTML muxing Jan Ekström
@ 2023-09-15 13:16 ` Jan Ekström
  2023-09-15 13:16 ` [FFmpeg-devel] [PATCH v2 2/3] avcodec/avpacket: add functionality to prepend to AVPacketLists Jan Ekström
                   ` (2 subsequent siblings)
  3 siblings, 0 replies; 10+ messages in thread
From: Jan Ekström @ 2023-09-15 13:16 UTC (permalink / raw)
  To: ffmpeg-devel

From: Jan Ekström <jan.ekstrom@24i.com>

This allows for direct dumping of the packets' contents (useful for
text based formats), while getting the timestamps/sizes etc from
ffprobe.

If used via TRANSCODE, the actually utilized muxer should be added
within the last argument as an additional dependency, as that is not
done automatically.

Signed-off-by: Jan Ekström <jan.ekstrom@24i.com>
---
 tests/fate-run.sh | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/tests/fate-run.sh b/tests/fate-run.sh
index 743d9b3620..9ef1d9b23a 100755
--- a/tests/fate-run.sh
+++ b/tests/fate-run.sh
@@ -257,7 +257,9 @@ transcode(){
     additional_input=$7
     final_decode=$8
     enc_opt_in=$9
+    final_encode_muxer="${10}"
     test -z "$additional_input" || additional_input="$DEC_OPTS $additional_input"
+    test -z "$final_encode_muxer" && final_encode_muxer="framecrc"
     encfile="${outdir}/${test}.${enc_fmt}"
     test $keep -ge 1 || cleanfiles="$cleanfiles $encfile"
     tsrcfile=$(target_path $srcfile)
@@ -267,7 +269,7 @@ transcode(){
     do_md5sum $encfile
     echo $(wc -c $encfile)
     ffmpeg $DEC_OPTS $final_decode -i $tencfile $ENC_OPTS $FLAGS $final_encode \
-        -f framecrc - || return
+        -f $final_encode_muxer - || return
     test -z $ffprobe_opts || \
         run ffprobe${PROGSUF}${EXECSUF} -bitexact $ffprobe_opts $tencfile || return
 }
-- 
2.41.0

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^ permalink raw reply	[flat|nested] 10+ messages in thread

* [FFmpeg-devel] [PATCH v2 2/3] avcodec/avpacket: add functionality to prepend to AVPacketLists
  2023-09-15 13:16 [FFmpeg-devel] [PATCH v2 0/3] Initial support for fragmented TTML muxing Jan Ekström
  2023-09-15 13:16 ` [FFmpeg-devel] [PATCH v2 1/3] tests/fate-run: add support for specifying the final encode muxer in `transcode` Jan Ekström
@ 2023-09-15 13:16 ` Jan Ekström
  2023-09-15 13:17 ` [FFmpeg-devel] [PATCH v2 3/3] avformat/movenc: add support for fragmented TTML muxing Jan Ekström
  2023-12-08 11:52 ` [FFmpeg-devel] [PATCH v2 0/3] Initial " Jan Ekström
  3 siblings, 0 replies; 10+ messages in thread
From: Jan Ekström @ 2023-09-15 13:16 UTC (permalink / raw)
  To: ffmpeg-devel

From: Jan Ekström <jan.ekstrom@24i.com>

Signed-off-by: Jan Ekström <jan.ekstrom@24i.com>
---
 libavcodec/avpacket.c        | 20 +++++++++++++++-----
 libavcodec/packet_internal.h |  2 ++
 2 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/libavcodec/avpacket.c b/libavcodec/avpacket.c
index 9ec1feb068..21e80416de 100644
--- a/libavcodec/avpacket.c
+++ b/libavcodec/avpacket.c
@@ -540,6 +540,7 @@ int avpriv_packet_list_put(PacketList *packet_buffer,
                            int flags)
 {
     PacketListEntry *pktl = av_malloc(sizeof(*pktl));
+    unsigned int update_end_point = 1;
     int ret;
 
     if (!pktl)
@@ -563,13 +564,22 @@ int avpriv_packet_list_put(PacketList *packet_buffer,
 
     pktl->next = NULL;
 
-    if (packet_buffer->head)
-        packet_buffer->tail->next = pktl;
-    else
+    if (packet_buffer->head) {
+        if (flags & FF_PACKETLIST_FLAG_PREPEND) {
+            pktl->next = packet_buffer->head;
+            packet_buffer->head = pktl;
+            update_end_point = 0;
+        } else {
+            packet_buffer->tail->next = pktl;
+        }
+    } else
         packet_buffer->head = pktl;
 
-    /* Add the packet in the buffered packet list. */
-    packet_buffer->tail = pktl;
+    if (update_end_point) {
+        /* Add the packet in the buffered packet list. */
+        packet_buffer->tail = pktl;
+    }
+
     return 0;
 }
 
diff --git a/libavcodec/packet_internal.h b/libavcodec/packet_internal.h
index 52fa6d9be9..9c0f4fead5 100644
--- a/libavcodec/packet_internal.h
+++ b/libavcodec/packet_internal.h
@@ -34,6 +34,8 @@ typedef struct PacketList {
     PacketListEntry *head, *tail;
 } PacketList;
 
+#define FF_PACKETLIST_FLAG_PREPEND (1 << 0) /**< Prepend created AVPacketList instead of appending */
+
 /**
  * Append an AVPacket to the list.
  *
-- 
2.41.0

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^ permalink raw reply	[flat|nested] 10+ messages in thread

* [FFmpeg-devel] [PATCH v2 3/3] avformat/movenc: add support for fragmented TTML muxing
  2023-09-15 13:16 [FFmpeg-devel] [PATCH v2 0/3] Initial support for fragmented TTML muxing Jan Ekström
  2023-09-15 13:16 ` [FFmpeg-devel] [PATCH v2 1/3] tests/fate-run: add support for specifying the final encode muxer in `transcode` Jan Ekström
  2023-09-15 13:16 ` [FFmpeg-devel] [PATCH v2 2/3] avcodec/avpacket: add functionality to prepend to AVPacketLists Jan Ekström
@ 2023-09-15 13:17 ` Jan Ekström
  2023-12-08 12:15   ` Andreas Rheinhardt
  2023-12-08 11:52 ` [FFmpeg-devel] [PATCH v2 0/3] Initial " Jan Ekström
  3 siblings, 1 reply; 10+ messages in thread
From: Jan Ekström @ 2023-09-15 13:17 UTC (permalink / raw)
  To: ffmpeg-devel

From: Jan Ekström <jan.ekstrom@24i.com>

Attempts to base the fragmentation timing on other streams
as most receivers expect media fragments to be more or less
aligned.

Currently does not support fragmentation on subtitle track
only, as the subtitle packet queue timings would have to be
checked in addition to the current fragmentation timing logic.

Signed-off-by: Jan Ekström <jan.ekstrom@24i.com>
---
 libavformat/movenc.c                        |    9 -
 libavformat/movenc_ttml.c                   |  157 ++-
 tests/fate/mov.mak                          |   21 +
 tests/ref/fate/mov-mp4-fragmented-ttml-dfxp | 1197 +++++++++++++++++++
 tests/ref/fate/mov-mp4-fragmented-ttml-stpp | 1197 +++++++++++++++++++
 5 files changed, 2568 insertions(+), 13 deletions(-)
 create mode 100644 tests/ref/fate/mov-mp4-fragmented-ttml-dfxp
 create mode 100644 tests/ref/fate/mov-mp4-fragmented-ttml-stpp

diff --git a/libavformat/movenc.c b/libavformat/movenc.c
index ab92263cd7..aac9a588dd 100644
--- a/libavformat/movenc.c
+++ b/libavformat/movenc.c
@@ -7312,15 +7312,6 @@ static int mov_init(AVFormatContext *s)
                 track->squash_fragment_samples_to_one =
                     ff_is_ttml_stream_paragraph_based(track->par);
 
-                if (mov->flags & FF_MOV_FLAG_FRAGMENT &&
-                    track->squash_fragment_samples_to_one) {
-                    av_log(s, AV_LOG_ERROR,
-                           "Fragmentation is not currently supported for "
-                           "TTML in MP4/ISMV (track synchronization between "
-                           "subtitles and other media is not yet implemented)!\n");
-                    return AVERROR_PATCHWELCOME;
-                }
-
                 if (track->mode != MODE_ISM &&
                     track->par->codec_tag == MOV_ISMV_TTML_TAG &&
                     s->strict_std_compliance > FF_COMPLIANCE_UNOFFICIAL) {
diff --git a/libavformat/movenc_ttml.c b/libavformat/movenc_ttml.c
index 6deae49657..2aefb0b6c3 100644
--- a/libavformat/movenc_ttml.c
+++ b/libavformat/movenc_ttml.c
@@ -54,6 +54,50 @@ static int mov_init_ttml_writer(MOVTrack *track, AVFormatContext **out_ctx)
     return 0;
 }
 
+static void mov_calculate_start_and_end_of_other_tracks(
+    AVFormatContext *s, MOVTrack *track, int64_t *start_pts, int64_t *end_pts)
+{
+    MOVMuxContext *mov = s->priv_data;
+
+    // Initialize at the end of the previous document/fragment, which is NOPTS
+    // until the first fragment is created.
+    int64_t max_track_end_dts = *start_pts = track->end_pts;
+
+    for (unsigned int i = 0; i < s->nb_streams; i++) {
+        MOVTrack *other_track = &mov->tracks[i];
+
+        // Skip our own track, any other track that needs squashing,
+        // or any track which still has its start_dts at NOPTS or
+        // any track that did not yet get any packets.
+        if (track == other_track ||
+            other_track->squash_fragment_samples_to_one ||
+            other_track->start_dts == AV_NOPTS_VALUE ||
+            !other_track->entry) {
+            continue;
+        }
+
+        {
+            int64_t picked_start = av_rescale_q_rnd(other_track->cluster[0].dts + other_track->cluster[0].cts,
+                                                    other_track->st->time_base,
+                                                    track->st->time_base,
+                                                    AV_ROUND_NEAR_INF | AV_ROUND_PASS_MINMAX);
+            int64_t picked_end   = av_rescale_q_rnd(other_track->end_pts,
+                                                    other_track->st->time_base,
+                                                    track->st->time_base,
+                                                    AV_ROUND_NEAR_INF | AV_ROUND_PASS_MINMAX);
+
+            if (*start_pts == AV_NOPTS_VALUE)
+                *start_pts = picked_start;
+            else if (picked_start >= track->end_pts)
+                *start_pts = FFMIN(*start_pts, picked_start);
+
+            max_track_end_dts = FFMAX(max_track_end_dts, picked_end);
+        }
+    }
+
+    *end_pts = max_track_end_dts;
+}
+
 static int mov_write_ttml_document_from_queue(AVFormatContext *s,
                                               AVFormatContext *ttml_ctx,
                                               MOVTrack *track,
@@ -65,13 +109,85 @@ static int mov_write_ttml_document_from_queue(AVFormatContext *s,
     int64_t start_ts = track->start_dts == AV_NOPTS_VALUE ?
                        0 : (track->start_dts + track->track_duration);
     int64_t end_ts   = start_ts;
+    unsigned int time_limited = 0;
+    PacketList back_to_queue_list = { 0 };
+
+    if (*out_start_ts != AV_NOPTS_VALUE) {
+        // we have non-nopts values here, thus we have been given a time range
+        time_limited = 1;
+        start_ts = *out_start_ts;
+        end_ts   = *out_start_ts + *out_duration;
+    }
 
     if ((ret = avformat_write_header(ttml_ctx, NULL)) < 0) {
         return ret;
     }
 
     while (!avpriv_packet_list_get(&track->squashed_packet_queue, pkt)) {
-        end_ts = FFMAX(end_ts, pkt->pts + pkt->duration);
+        int64_t pts_before      = pkt->pts;
+        int64_t duration_before = pkt->duration;
+
+        if (time_limited) {
+            // special cases first:
+            if (pkt->pts + pkt->duration < start_ts) {
+                // too late for our fragment, unfortunately
+                // unref and proceed to next packet in queue.
+                av_log(s, AV_LOG_WARNING,
+                       "Very late TTML packet in queue, dropping packet with "
+                       "pts: %"PRId64", duration: %"PRId64"\n",
+                       pkt->pts, pkt->duration);
+                av_packet_unref(pkt);
+                continue;
+            } else if (pkt->pts >= end_ts) {
+                // starts after this fragment, put back to original queue
+                ret = avpriv_packet_list_put(&track->squashed_packet_queue,
+                                             pkt, av_packet_ref,
+                                             FF_PACKETLIST_FLAG_PREPEND);
+                if (ret < 0)
+                    goto cleanup;
+
+                break;
+            }
+
+            // limit packet pts to start_ts
+            if (pkt->pts < start_ts) {
+                pkt->duration -= start_ts - pkt->pts;
+                pkt->pts = start_ts;
+            }
+
+            if (pkt->pts + pkt->duration > end_ts) {
+                // goes over our current fragment, create duplicate and
+                // put it back to list after iteration has finished in
+                // order to handle multiple subtitles at the same time.
+                int64_t offset = end_ts - pkt->pts;
+
+                ret = avpriv_packet_list_put(&back_to_queue_list,
+                                             pkt, av_packet_ref,
+                                             FF_PACKETLIST_FLAG_PREPEND);
+                if (ret < 0)
+                    goto cleanup;
+
+                back_to_queue_list.head->pkt.pts =
+                back_to_queue_list.head->pkt.dts =
+                back_to_queue_list.head->pkt.pts + offset;
+                back_to_queue_list.head->pkt.duration -= offset;
+
+                // and for our normal packet we just set duration to offset
+                pkt->duration = offset;
+            }
+        } else {
+            end_ts = FFMAX(end_ts, pkt->pts + pkt->duration);
+        }
+
+        av_log(s, AV_LOG_TRACE,
+               "TTML packet writeout: pts: %"PRId64" (%"PRId64"), "
+               "duration: %"PRId64"\n",
+               pkt->pts, pkt->pts - start_ts, pkt->duration);
+        if (pkt->pts != pts_before || pkt->duration != duration_before) {
+            av_log(s, AV_LOG_TRACE,
+                   "Adjustments: pts: %"PRId64", duration: %"PRId64"\n",
+                   pkt->pts - pts_before, pkt->duration - duration_before);
+        }
 
         // in case of the 'dfxp' muxing mode, each written document is offset
         // to its containing sample's beginning.
@@ -100,15 +216,30 @@ static int mov_write_ttml_document_from_queue(AVFormatContext *s,
     ret = 0;
 
 cleanup:
+    while (!avpriv_packet_list_get(&back_to_queue_list, pkt)) {
+        ret = avpriv_packet_list_put(&track->squashed_packet_queue,
+                                     pkt, av_packet_ref,
+                                     FF_PACKETLIST_FLAG_PREPEND);
+
+        // unrelated to whether we succeed or not, we unref the packet
+        // received from the temporary list.
+        av_packet_unref(pkt);
+
+        if (ret < 0) {
+            avpriv_packet_list_free(&back_to_queue_list);
+            break;
+        }
+    }
     return ret;
 }
 
 int ff_mov_generate_squashed_ttml_packet(AVFormatContext *s,
                                          MOVTrack *track, AVPacket *pkt)
 {
+    MOVMuxContext *mov = s->priv_data;
     AVFormatContext *ttml_ctx = NULL;
     // values for the generated AVPacket
-    int64_t start_ts = 0;
+    int64_t start_ts = AV_NOPTS_VALUE;
     int64_t duration = 0;
 
     int ret = AVERROR_BUG;
@@ -119,12 +250,30 @@ int ff_mov_generate_squashed_ttml_packet(AVFormatContext *s,
         goto cleanup;
     }
 
+    if (mov->flags & FF_MOV_FLAG_FRAGMENT) {
+        int64_t calculated_start = AV_NOPTS_VALUE;
+        int64_t calculated_end = AV_NOPTS_VALUE;
+
+        mov_calculate_start_and_end_of_other_tracks(s, track, &calculated_start, &calculated_end);
+
+        if (calculated_start != AV_NOPTS_VALUE) {
+            start_ts = calculated_start;
+            duration = calculated_end - calculated_start;
+            av_log(s, AV_LOG_VERBOSE,
+                   "Calculated subtitle fragment start: %"PRId64", "
+                   "duration: %"PRId64"\n",
+                   start_ts, duration);
+        }
+    }
+
     if (!track->squashed_packet_queue.head) {
         // empty queue, write minimal empty document with zero duration
         avio_write(ttml_ctx->pb, empty_ttml_document,
                    sizeof(empty_ttml_document) - 1);
-        start_ts = 0;
-        duration = 0;
+        if (start_ts == AV_NOPTS_VALUE) {
+            start_ts = 0;
+            duration = 0;
+        }
         goto generate_packet;
     }
 
diff --git a/tests/fate/mov.mak b/tests/fate/mov.mak
index 6cb493ceab..5c44299196 100644
--- a/tests/fate/mov.mak
+++ b/tests/fate/mov.mak
@@ -143,6 +143,27 @@ FATE_MOV_FFMPEG_FFPROBE-$(call TRANSCODE, TTML SUBRIP, MP4 MOV, SRT_DEMUXER TTML
 fate-mov-mp4-ttml-stpp: CMD = transcode srt $(TARGET_SAMPLES)/sub/SubRip_capability_tester.srt mp4 "-map 0:s -c:s ttml -time_base:s 1:1000" "-map 0 -c copy" "-of json -show_entries packet:stream=index,codec_type,codec_tag_string,codec_tag,codec_name,time_base,start_time,duration_ts,duration,nb_frames,nb_read_packets:stream_tags"
 fate-mov-mp4-ttml-dfxp: CMD = transcode srt $(TARGET_SAMPLES)/sub/SubRip_capability_tester.srt mp4 "-map 0:s -c:s ttml -time_base:s 1:1000 -tag:s dfxp -strict unofficial" "-map 0 -c copy" "-of json -show_entries packet:stream=index,codec_type,codec_tag_string,codec_tag,codec_name,time_base,start_time,duration_ts,duration,nb_frames,nb_read_packets:stream_tags"
 
+FATE_MOV_FFMPEG_FFPROBE-$(call TRANSCODE, TTML SUBRIP, MP4 MOV, LAVFI_INDEV SMPTEHDBARS_FILTER SRT_DEMUXER MPEG2VIDEO_ENCODER TTML_MUXER RAWVIDEO_MUXER) += fate-mov-mp4-fragmented-ttml-stpp
+fate-mov-mp4-fragmented-ttml-stpp: CMD = transcode srt $(TARGET_SAMPLES)/sub/SubRip_capability_tester.srt mp4 \
+  "-map 1:v -map 0:s \
+   -c:v mpeg2video -b:v 2M -g 48 -sc_threshold 1000000000 \
+   -c:s ttml -time_base:s 1:1000 \
+   -movflags +cmaf" \
+  "-map 0:s -c copy" \
+  "-select_streams s -of csv -show_packets -show_data_hash crc32" \
+  "-f lavfi -i smptehdbars=duration=70:size=320x180:rate=24000/1001,format=yuv420p" \
+  "" "" "rawvideo"
+
+FATE_MOV_FFMPEG_FFPROBE-$(call TRANSCODE, TTML SUBRIP, ISMV MOV, LAVFI_INDEV SMPTEHDBARS_FILTER SRT_DEMUXER MPEG2VIDEO_ENCODER TTML_MUXER RAWVIDEO_MUXER) += fate-mov-mp4-fragmented-ttml-dfxp
+fate-mov-mp4-fragmented-ttml-dfxp: CMD = transcode srt $(TARGET_SAMPLES)/sub/SubRip_capability_tester.srt ismv \
+  "-map 1:v -map 0:s \
+   -c:v mpeg2video -b:v 2M -g 48 -sc_threshold 1000000000 \
+   -c:s ttml -tag:s dfxp -time_base:s 1:1000" \
+  "-map 0:s -c copy" \
+  "-select_streams s -of csv -show_packets -show_data_hash crc32" \
+  "-f lavfi -i smptehdbars=duration=70:size=320x180:rate=24000/1001,format=yuv420p" \
+  "" "" "rawvideo"
+
 # FIXME: Uncomment these two tests once the test files are uploaded to the fate
 # server.
 # avif demuxing - still image with 1 item.
diff --git a/tests/ref/fate/mov-mp4-fragmented-ttml-dfxp b/tests/ref/fate/mov-mp4-fragmented-ttml-dfxp
new file mode 100644
index 0000000000..45da22814a
--- /dev/null
+++ b/tests/ref/fate/mov-mp4-fragmented-ttml-dfxp
@@ -0,0 +1,1197 @@
+14998bfa7c79edf90c4280cd957bf47e *tests/data/fate/mov-mp4-fragmented-ttml-dfxp.ismv
+518859 tests/data/fate/mov-mp4-fragmented-ttml-dfxp.ismv
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:00.000"
+        end="00:00:00.000"><span region="Default">Don't show this text it may be used to insert hidden data</span></p>
+      <p
+        begin="00:00:01.500"
+        end="00:00:02.002"><span region="Default">SubRip subtitles capability tester 1.3o by ale5000<br/>Use VLC 1.1 or higher as reference for most things and MPC Home Cinema for others<br/>This text should be blue<br/>This text should be red<br/>This text should be black<br/>If you see this with the normal font, the player don't (fully) support font face</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:00.000"
+        end="00:00:02.002"><span region="Default">SubRip subtitles capability tester 1.3o by ale5000<br/>Use VLC 1.1 or higher as reference for most things and MPC Home Cinema for others<br/>This text should be blue<br/>This text should be red<br/>This text should be black<br/>If you see this with the normal font, the player don't (fully) support font face</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:00.000"
+        end="00:00:00.496"><span region="Default">SubRip subtitles capability tester 1.3o by ale5000<br/>Use VLC 1.1 or higher as reference for most things and MPC Home Cinema for others<br/>This text should be blue<br/>This text should be red<br/>This text should be black<br/>If you see this with the normal font, the player don't (fully) support font face</span></p>
+      <p
+        begin="00:00:00.496"
+        end="00:00:00.496"><span region="Default">Hidden</span></p>
+      <p
+        begin="00:00:00.497"
+        end="00:00:02.002"><span region="Default">This text should be small<br/>This text should be normal<br/>This text should be big</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:00.000"
+        end="00:00:01.494"><span region="Default">This text should be small<br/>This text should be normal<br/>This text should be big</span></p>
+      <p
+        begin="00:00:01.495"
+        end="00:00:02.002"><span region="Default">This should be an E with an accent: È<br/>日本語<br/>This text should be bold, italics and underline<br/>This text should be small and green<br/>This text should be small and red<br/>This text should be big and brown</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:00.000"
+        end="00:00:02.002"><span region="Default">This should be an E with an accent: È<br/>日本語<br/>This text should be bold, italics and underline<br/>This text should be small and green<br/>This text should be small and red<br/>This text should be big and brown</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:00.000"
+        end="00:00:01.490"><span region="Default">This should be an E with an accent: È<br/>日本語<br/>This text should be bold, italics and underline<br/>This text should be small and green<br/>This text should be small and red<br/>This text should be big and brown</span></p>
+      <p
+        begin="00:00:01.491"
+        end="00:00:02.002"><span region="Default">This line should be bold<br/>This line should be italics<br/>This line should be underline<br/>This line should be strikethrough<br/>Both lines<br/>should be underline</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:00.000"
+        end="00:00:02.002"><span region="Default">This line should be bold<br/>This line should be italics<br/>This line should be underline<br/>This line should be strikethrough<br/>Both lines<br/>should be underline</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:00.000"
+        end="00:00:00.486"><span region="Default">This line should be bold<br/>This line should be italics<br/>This line should be underline<br/>This line should be strikethrough<br/>Both lines<br/>should be underline</span></p>
+      <p
+        begin="00:00:00.487"
+        end="00:00:02.002"><span region="Default">&gt;<br/>It would be a good thing to<br/>hide invalid html tags that are closed and show the text in them<br/>but show un-closed invalid html tags<br/>Show not opened tags<br/>&lt;</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:00.000"
+        end="00:00:01.484"><span region="Default">&gt;<br/>It would be a good thing to<br/>hide invalid html tags that are closed and show the text in them<br/>but show un-closed invalid html tags<br/>Show not opened tags<br/>&lt;</span></p>
+      <p
+        begin="00:00:01.485"
+        end="00:00:02.002"><span region="Default">and also<br/>hide invalid html tags with parameters that are closed and show the text in them<br/>but show un-closed invalid html tags<br/>This text should be showed underlined without problems also: 2&lt;3,5&gt;1,4&lt;6<br/>This shouldn't be underlined</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:00.000"
+        end="00:00:02.002"><span region="Default">and also<br/>hide invalid html tags with parameters that are closed and show the text in them<br/>but show un-closed invalid html tags<br/>This text should be showed underlined without problems also: 2&lt;3,5&gt;1,4&lt;6<br/>This shouldn't be underlined</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:00.000"
+        end="00:00:00.480"><span region="Default">and also<br/>hide invalid html tags with parameters that are closed and show the text in them<br/>but show un-closed invalid html tags<br/>This text should be showed underlined without problems also: 2&lt;3,5&gt;1,4&lt;6<br/>This shouldn't be underlined</span></p>
+      <p
+        begin="00:00:00.481"
+        end="00:00:01.480"><span region="Default">This text should be in the normal position...</span></p>
+      <p
+        begin="00:00:01.481"
+        end="00:00:02.002"><span region="Default">This text should NOT be in the normal position</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:00.000"
+        end="00:00:00.478"><span region="Default">This text should NOT be in the normal position</span></p>
+      <p
+        begin="00:00:00.479"
+        end="00:00:02.002"><span region="Default">Implementation is the same of the ASS tag<br/>This text should be at the<br/>top and horizontally centered</span></p>
+      <p
+        begin="00:00:00.479"
+        end="00:00:02.002"><span region="Default">This text should be at the<br/>middle and horizontally centered</span></p>
+      <p
+        begin="00:00:00.479"
+        end="00:00:02.002"><span region="Default">This text should be at the<br/>bottom and horizontally centered</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:00.000"
+        end="00:00:00.476"><span region="Default">Implementation is the same of the ASS tag<br/>This text should be at the<br/>top and horizontally centered</span></p>
+      <p
+        begin="00:00:00.000"
+        end="00:00:00.476"><span region="Default">This text should be at the<br/>middle and horizontally centered</span></p>
+      <p
+        begin="00:00:00.000"
+        end="00:00:00.476"><span region="Default">This text should be at the<br/>bottom and horizontally centered</span></p>
+      <p
+        begin="00:00:00.477"
+        end="00:00:02.002"><span region="Default">This text should be at the<br/>top and horizontally at the left</span></p>
+      <p
+        begin="00:00:00.477"
+        end="00:00:02.002"><span region="Default">This text should be at the<br/>middle and horizontally at the left<br/>(The second position must be ignored)</span></p>
+      <p
+        begin="00:00:00.477"
+        end="00:00:02.002"><span region="Default">This text should be at the<br/>bottom and horizontally at the left</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:00.000"
+        end="00:00:00.474"><span region="Default">This text should be at the<br/>top and horizontally at the left</span></p>
+      <p
+        begin="00:00:00.000"
+        end="00:00:00.474"><span region="Default">This text should be at the<br/>middle and horizontally at the left<br/>(The second position must be ignored)</span></p>
+      <p
+        begin="00:00:00.000"
+        end="00:00:00.474"><span region="Default">This text should be at the<br/>bottom and horizontally at the left</span></p>
+      <p
+        begin="00:00:00.475"
+        end="00:00:02.002"><span region="Default">This text should be at the<br/>top and horizontally at the right</span></p>
+      <p
+        begin="00:00:00.475"
+        end="00:00:02.002"><span region="Default">This text should be at the<br/>middle and horizontally at the right</span></p>
+      <p
+        begin="00:00:00.475"
+        end="00:00:02.002"><span region="Default">This text should be at the<br/>bottom and horizontally at the right</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:00.000"
+        end="00:00:00.472"><span region="Default">This text should be at the<br/>top and horizontally at the right</span></p>
+      <p
+        begin="00:00:00.000"
+        end="00:00:00.472"><span region="Default">This text should be at the<br/>middle and horizontally at the right</span></p>
+      <p
+        begin="00:00:00.000"
+        end="00:00:00.472"><span region="Default">This text should be at the<br/>bottom and horizontally at the right</span></p>
+      <p
+        begin="00:00:00.473"
+        end="00:00:02.002"><span region="Default">This could be the most difficult thing to implement</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:00.000"
+        end="00:00:01.470"><span region="Default">This could be the most difficult thing to implement</span></p>
+      <p
+        begin="00:00:01.471"
+        end="00:00:02.002"><span region="Default">First text</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:00.000"
+        end="00:00:02.002"><span region="Default">First text</span></p>
+      <p
+        begin="00:00:01.468"
+        end="00:00:02.002"><span region="Default">Second, it shouldn't overlap first</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:00.000"
+        end="00:00:02.002"><span region="Default">First text</span></p>
+      <p
+        begin="00:00:00.000"
+        end="00:00:01.466"><span region="Default">Second, it shouldn't overlap first</span></p>
+      <p
+        begin="00:00:01.467"
+        end="00:00:02.002"><span region="Default">Third, it should replace second</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:00.000"
+        end="00:00:02.002"><span region="Default">First text</span></p>
+      <p
+        begin="00:00:00.000"
+        end="00:00:01.464"><span region="Default">Third, it should replace second</span></p>
+      <p
+        begin="00:00:00.465"
+        end="00:00:02.002"><span region="Default">Fourth, it shouldn't overlap first and third</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:00.000"
+        end="00:00:02.002"><span region="Default">First text</span></p>
+      <p
+        begin="00:00:00.000"
+        end="00:00:02.002"><span region="Default">Fourth, it shouldn't overlap first and third</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:00.000"
+        end="00:00:02.002"><span region="Default">First text</span></p>
+      <p
+        begin="00:00:00.000"
+        end="00:00:02.002"><span region="Default">Fourth, it shouldn't overlap first and third</span></p>
+      <p
+        begin="00:00:00.461"
+        end="00:00:02.002"><span region="Default">Fifth, it should replace third</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:00.000"
+        end="00:00:02.002"><span region="Default">First text</span></p>
+      <p
+        begin="00:00:00.000"
+        end="00:00:02.002"><span region="Default">Fourth, it shouldn't overlap first and third</span></p>
+      <p
+        begin="00:00:00.000"
+        end="00:00:02.002"><span region="Default">Fifth, it should replace third</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:00.000"
+        end="00:00:02.002"><span region="Default">First text</span></p>
+      <p
+        begin="00:00:00.000"
+        end="00:00:02.002"><span region="Default">Fourth, it shouldn't overlap first and third</span></p>
+      <p
+        begin="00:00:00.000"
+        end="00:00:01.456"><span region="Default">Fifth, it should replace third</span></p>
+      <p
+        begin="00:00:01.457"
+        end="00:00:02.002"><span region="Default">Sixth, it shouldn't be<br/>showed overlapped</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:00.000"
+        end="00:00:02.002"><span region="Default">First text</span></p>
+      <p
+        begin="00:00:00.000"
+        end="00:00:02.002"><span region="Default">Fourth, it shouldn't overlap first and third</span></p>
+      <p
+        begin="00:00:00.000"
+        end="00:00:02.002"><span region="Default">Sixth, it shouldn't be<br/>showed overlapped</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:00.000"
+        end="00:00:02.002"><span region="Default">First text</span></p>
+      <p
+        begin="00:00:00.000"
+        end="00:00:02.002"><span region="Default">Fourth, it shouldn't overlap first and third</span></p>
+      <p
+        begin="00:00:00.000"
+        end="00:00:02.002"><span region="Default">Sixth, it shouldn't be<br/>showed overlapped</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:00.000"
+        end="00:00:00.450"><span region="Default">First text</span></p>
+      <p
+        begin="00:00:00.000"
+        end="00:00:00.450"><span region="Default">Fourth, it shouldn't overlap first and third</span></p>
+      <p
+        begin="00:00:00.000"
+        end="00:00:00.450"><span region="Default">Sixth, it shouldn't be<br/>showed overlapped</span></p>
+      <p
+        begin="00:00:00.451"
+        end="00:00:02.002"><span region="Default">TEXT 1 (bottom)</span></p>
+      <p
+        begin="00:00:00.451"
+        end="00:00:02.002"><span region="Default">text 2</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:00.000"
+        end="00:00:00.448"><span region="Default">TEXT 1 (bottom)</span></p>
+      <p
+        begin="00:00:00.000"
+        end="00:00:00.448"><span region="Default">text 2</span></p>
+      <p
+        begin="00:00:00.449"
+        end="00:00:02.002"><span region="Default">Hide these tags:<br/>also hide these tags:<br/>but show this: {normal text}</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:00.000"
+        end="00:00:00.446"><span region="Default">Hide these tags:<br/>also hide these tags:<br/>but show this: {normal text}</span></p>
+      <p
+        begin="00:00:00.447"
+        end="00:00:02.002"><span region="Default"><br/>\ N is a forced line break<br/>\ h is a hard space<br/>Normal spaces at the start and at the end of the line are trimmed while hard spaces are not trimmed.<br/>The\hline\hwill\hnever\hbreak\hautomatically\hright\hbefore\hor\hafter\ha\hhard\hspace.\h:-D</span></p>
+      <p
+        begin="00:00:00.447"
+        end="00:00:02.002"><span region="Default"><br/>\h\h\h\h\hA (05 hard spaces followed by a letter)<br/>A (Normal  spaces followed by a letter)<br/>A (No hard spaces followed by a letter)</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:00.000"
+        end="00:00:02.002"><span region="Default"><br/>\ N is a forced line break<br/>\ h is a hard space<br/>Normal spaces at the start and at the end of the line are trimmed while hard spaces are not trimmed.<br/>The\hline\hwill\hnever\hbreak\hautomatically\hright\hbefore\hor\hafter\ha\hhard\hspace.\h:-D</span></p>
+      <p
+        begin="00:00:00.000"
+        end="00:00:00.444"><span region="Default"><br/>\h\h\h\h\hA (05 hard spaces followed by a letter)<br/>A (Normal  spaces followed by a letter)<br/>A (No hard spaces followed by a letter)</span></p>
+      <p
+        begin="00:00:00.445"
+        end="00:00:02.002"><span region="Default">\h\h\h\h\hA (05 hard spaces followed by a letter)<br/>A (Normal  spaces followed by a letter)<br/>A (No hard spaces followed by a letter)<br/>Show this: \TEST and this: \-)</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:00.000"
+        end="00:00:02.002"><span region="Default"><br/>\ N is a forced line break<br/>\ h is a hard space<br/>Normal spaces at the start and at the end of the line are trimmed while hard spaces are not trimmed.<br/>The\hline\hwill\hnever\hbreak\hautomatically\hright\hbefore\hor\hafter\ha\hhard\hspace.\h:-D</span></p>
+      <p
+        begin="00:00:00.000"
+        end="00:00:00.442"><span region="Default">\h\h\h\h\hA (05 hard spaces followed by a letter)<br/>A (Normal  spaces followed by a letter)<br/>A (No hard spaces followed by a letter)<br/>Show this: \TEST and this: \-)</span></p>
+      <p
+        begin="00:00:00.443"
+        end="00:00:02.002"><span region="Default"><br/>A letter followed by 05 hard spaces: A\h\h\h\h\h<br/>A letter followed by normal  spaces: A<br/>A letter followed by no hard spaces: A<br/>05 hard  spaces between letters: A\h\h\h\h\hA<br/>5 normal spaces between letters: A     A<br/><br/>^--Forced line break</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:00.000"
+        end="00:00:00.440"><span region="Default"><br/>\ N is a forced line break<br/>\ h is a hard space<br/>Normal spaces at the start and at the end of the line are trimmed while hard spaces are not trimmed.<br/>The\hline\hwill\hnever\hbreak\hautomatically\hright\hbefore\hor\hafter\ha\hhard\hspace.\h:-D</span></p>
+      <p
+        begin="00:00:00.000"
+        end="00:00:00.440"><span region="Default"><br/>A letter followed by 05 hard spaces: A\h\h\h\h\h<br/>A letter followed by normal  spaces: A<br/>A letter followed by no hard spaces: A<br/>05 hard  spaces between letters: A\h\h\h\h\hA<br/>5 normal spaces between letters: A     A<br/><br/>^--Forced line break</span></p>
+      <p
+        begin="00:00:00.441"
+        end="00:00:02.002"><span region="Default">Both line should be strikethrough,<br/>yes.<br/>Correctly closed tags<br/>should be hidden.</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:00.000"
+        end="00:00:00.438"><span region="Default">Both line should be strikethrough,<br/>yes.<br/>Correctly closed tags<br/>should be hidden.</span></p>
+      <p
+        begin="00:00:00.439"
+        end="00:00:02.002"><span region="Default">It shouldn't be strikethrough,<br/>not opened tag showed as text.<br/>Not opened tag showed as text.</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:00.000"
+        end="00:00:00.436"><span region="Default">It shouldn't be strikethrough,<br/>not opened tag showed as text.<br/>Not opened tag showed as text.</span></p>
+      <p
+        begin="00:00:00.437"
+        end="00:00:02.002"><span region="Default">Three lines should be strikethrough,<br/>yes.<br/>Not closed tags showed as text</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:00.000"
+        end="00:00:00.434"><span region="Default">Three lines should be strikethrough,<br/>yes.<br/>Not closed tags showed as text</span></p>
+      <p
+        begin="00:00:00.435"
+        end="00:00:02.002"><span region="Default">Both line should be strikethrough but<br/>the wrong closing tag should be showed</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:00.000"
+        end="00:00:00.432"><span region="Default">Both line should be strikethrough but<br/>the wrong closing tag should be showed</span></p>
+    </div>
+  </body>
+</tt>
+packet,subtitle,1,0,0.000000,0,0.000000,N/A,N/A,1172,14746,K__,CRC32:bde7afa1
+packet,subtitle,1,20020000,2.002000,20020000,2.002000,N/A,N/A,1015,29540,K__,CRC32:c1cb78f2
+packet,subtitle,1,40040000,4.004000,40040000,4.004000,N/A,N/A,1305,44177,K__,CRC32:267b17fe
+packet,subtitle,1,60060000,6.006000,60060000,6.006000,N/A,N/A,1111,59104,K__,CRC32:d6aaf284
+packet,subtitle,1,80080000,8.008000,80080000,8.008000,N/A,N/A,927,73837,K__,CRC32:0ee24ad7
+packet,subtitle,1,100100000,10.010000,100100000,10.010000,N/A,N/A,1194,88386,K__,CRC32:a9816515
+packet,subtitle,1,120120000,12.012000,120120000,12.012000,N/A,N/A,874,103202,K__,CRC32:c47ebb4e
+packet,subtitle,1,140140000,14.014000,140140000,14.014000,N/A,N/A,1154,117698,K__,CRC32:09b26179
+packet,subtitle,1,160160000,16.016000,160160000,16.016000,N/A,N/A,1240,132474,K__,CRC32:d7e3067e
+packet,subtitle,1,180180000,18.018000,180180000,18.018000,N/A,N/A,960,147336,K__,CRC32:d2d99797
+packet,subtitle,1,200200000,20.020000,200200000,20.020000,N/A,N/A,1251,161918,K__,CRC32:1857892c
+packet,subtitle,1,220220000,22.022000,220220000,22.022000,N/A,N/A,1285,176791,K__,CRC32:76bd9787
+packet,subtitle,1,240240000,24.024000,240240000,24.024000,N/A,N/A,1676,191698,K__,CRC32:1f7cdb75
+packet,subtitle,1,260260000,26.026000,260260000,26.026000,N/A,N/A,1642,206996,K__,CRC32:8fbd701c
+packet,subtitle,1,280280000,28.028000,280280000,28.028000,N/A,N/A,1256,222260,K__,CRC32:2f4ea18e
+packet,subtitle,1,300300000,30.030000,300300000,30.030000,N/A,N/A,868,237138,K__,CRC32:30e6b1f0
+packet,subtitle,1,320320000,32.032000,320320000,32.032000,N/A,N/A,851,251628,K__,CRC32:b806d7ef
+packet,subtitle,1,340340000,34.034000,340340000,34.034000,N/A,N/A,982,266101,K__,CRC32:7f9ea9df
+packet,subtitle,1,360360000,36.036000,360360000,36.036000,N/A,N/A,992,280705,K__,CRC32:024a8bf4
+packet,subtitle,1,380380000,38.038000,380380000,38.038000,N/A,N/A,861,295319,K__,CRC32:d8e3a883
+packet,subtitle,1,400400000,40.040000,400400000,40.040000,N/A,N/A,991,309802,K__,CRC32:cae99334
+packet,subtitle,1,420420000,42.042000,420420000,42.042000,N/A,N/A,991,324415,K__,CRC32:50c2ead7
+packet,subtitle,1,440440000,44.044000,440440000,44.044000,N/A,N/A,1135,339028,K__,CRC32:cc0850dc
+packet,subtitle,1,460460000,46.046000,460460000,46.046000,N/A,N/A,1005,353785,K__,CRC32:807f794c
+packet,subtitle,1,480480000,48.048000,480480000,48.048000,N/A,N/A,1005,368412,K__,CRC32:807f794c
+packet,subtitle,1,500500000,50.050000,500500000,50.050000,N/A,N/A,1226,383039,K__,CRC32:805264b5
+packet,subtitle,1,520520000,52.052000,520520000,52.052000,N/A,N/A,1003,397887,K__,CRC32:79adb2a6
+packet,subtitle,1,540540000,54.054000,540540000,54.054000,N/A,N/A,1381,412512,K__,CRC32:ac83ebab
+packet,subtitle,1,560560000,56.056000,560560000,56.056000,N/A,N/A,1478,427515,K__,CRC32:23a2eb37
+packet,subtitle,1,580580000,58.058000,580580000,58.058000,N/A,N/A,1600,442615,K__,CRC32:4e8548fa
+packet,subtitle,1,600600000,60.060000,600600000,60.060000,N/A,N/A,1519,457837,K__,CRC32:1ee4bd57
+packet,subtitle,1,620620000,62.062000,620620000,62.062000,N/A,N/A,998,472978,K__,CRC32:5cabdc39
+packet,subtitle,1,640640000,64.064000,640640000,64.064000,N/A,N/A,987,487598,K__,CRC32:498ffc7d
+packet,subtitle,1,660660000,66.066000,660660000,66.066000,N/A,N/A,967,502207,K__,CRC32:3c04c24d
+packet,subtitle,1,680680000,68.068000,680680000,68.068000,N/A,N/A,787,516670,K__,CRC32:0896b651
diff --git a/tests/ref/fate/mov-mp4-fragmented-ttml-stpp b/tests/ref/fate/mov-mp4-fragmented-ttml-stpp
new file mode 100644
index 0000000000..08f82851a9
--- /dev/null
+++ b/tests/ref/fate/mov-mp4-fragmented-ttml-stpp
@@ -0,0 +1,1197 @@
+7fe87826c79323c7c97a14021686bd54 *tests/data/fate/mov-mp4-fragmented-ttml-stpp.mp4
+503191 tests/data/fate/mov-mp4-fragmented-ttml-stpp.mp4
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:00.000"
+        end="00:00:00.000"><span region="Default">Don't show this text it may be used to insert hidden data</span></p>
+      <p
+        begin="00:00:01.500"
+        end="00:00:02.002"><span region="Default">SubRip subtitles capability tester 1.3o by ale5000<br/>Use VLC 1.1 or higher as reference for most things and MPC Home Cinema for others<br/>This text should be blue<br/>This text should be red<br/>This text should be black<br/>If you see this with the normal font, the player don't (fully) support font face</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:02.002"
+        end="00:00:04.004"><span region="Default">SubRip subtitles capability tester 1.3o by ale5000<br/>Use VLC 1.1 or higher as reference for most things and MPC Home Cinema for others<br/>This text should be blue<br/>This text should be red<br/>This text should be black<br/>If you see this with the normal font, the player don't (fully) support font face</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:04.004"
+        end="00:00:04.500"><span region="Default">SubRip subtitles capability tester 1.3o by ale5000<br/>Use VLC 1.1 or higher as reference for most things and MPC Home Cinema for others<br/>This text should be blue<br/>This text should be red<br/>This text should be black<br/>If you see this with the normal font, the player don't (fully) support font face</span></p>
+      <p
+        begin="00:00:04.500"
+        end="00:00:04.500"><span region="Default">Hidden</span></p>
+      <p
+        begin="00:00:04.501"
+        end="00:00:06.006"><span region="Default">This text should be small<br/>This text should be normal<br/>This text should be big</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:06.006"
+        end="00:00:07.500"><span region="Default">This text should be small<br/>This text should be normal<br/>This text should be big</span></p>
+      <p
+        begin="00:00:07.501"
+        end="00:00:08.008"><span region="Default">This should be an E with an accent: È<br/>日本語<br/>This text should be bold, italics and underline<br/>This text should be small and green<br/>This text should be small and red<br/>This text should be big and brown</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:08.008"
+        end="00:00:10.010"><span region="Default">This should be an E with an accent: È<br/>日本語<br/>This text should be bold, italics and underline<br/>This text should be small and green<br/>This text should be small and red<br/>This text should be big and brown</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:10.010"
+        end="00:00:11.500"><span region="Default">This should be an E with an accent: È<br/>日本語<br/>This text should be bold, italics and underline<br/>This text should be small and green<br/>This text should be small and red<br/>This text should be big and brown</span></p>
+      <p
+        begin="00:00:11.501"
+        end="00:00:12.012"><span region="Default">This line should be bold<br/>This line should be italics<br/>This line should be underline<br/>This line should be strikethrough<br/>Both lines<br/>should be underline</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:12.012"
+        end="00:00:14.014"><span region="Default">This line should be bold<br/>This line should be italics<br/>This line should be underline<br/>This line should be strikethrough<br/>Both lines<br/>should be underline</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:14.014"
+        end="00:00:14.500"><span region="Default">This line should be bold<br/>This line should be italics<br/>This line should be underline<br/>This line should be strikethrough<br/>Both lines<br/>should be underline</span></p>
+      <p
+        begin="00:00:14.501"
+        end="00:00:16.016"><span region="Default">&gt;<br/>It would be a good thing to<br/>hide invalid html tags that are closed and show the text in them<br/>but show un-closed invalid html tags<br/>Show not opened tags<br/>&lt;</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:16.016"
+        end="00:00:17.500"><span region="Default">&gt;<br/>It would be a good thing to<br/>hide invalid html tags that are closed and show the text in them<br/>but show un-closed invalid html tags<br/>Show not opened tags<br/>&lt;</span></p>
+      <p
+        begin="00:00:17.501"
+        end="00:00:18.018"><span region="Default">and also<br/>hide invalid html tags with parameters that are closed and show the text in them<br/>but show un-closed invalid html tags<br/>This text should be showed underlined without problems also: 2&lt;3,5&gt;1,4&lt;6<br/>This shouldn't be underlined</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:18.018"
+        end="00:00:20.020"><span region="Default">and also<br/>hide invalid html tags with parameters that are closed and show the text in them<br/>but show un-closed invalid html tags<br/>This text should be showed underlined without problems also: 2&lt;3,5&gt;1,4&lt;6<br/>This shouldn't be underlined</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:20.020"
+        end="00:00:20.500"><span region="Default">and also<br/>hide invalid html tags with parameters that are closed and show the text in them<br/>but show un-closed invalid html tags<br/>This text should be showed underlined without problems also: 2&lt;3,5&gt;1,4&lt;6<br/>This shouldn't be underlined</span></p>
+      <p
+        begin="00:00:20.501"
+        end="00:00:21.500"><span region="Default">This text should be in the normal position...</span></p>
+      <p
+        begin="00:00:21.501"
+        end="00:00:22.022"><span region="Default">This text should NOT be in the normal position</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:22.022"
+        end="00:00:22.500"><span region="Default">This text should NOT be in the normal position</span></p>
+      <p
+        begin="00:00:22.501"
+        end="00:00:24.024"><span region="Default">Implementation is the same of the ASS tag<br/>This text should be at the<br/>top and horizontally centered</span></p>
+      <p
+        begin="00:00:22.502"
+        end="00:00:24.024"><span region="Default">This text should be at the<br/>middle and horizontally centered</span></p>
+      <p
+        begin="00:00:22.503"
+        end="00:00:24.024"><span region="Default">This text should be at the<br/>bottom and horizontally centered</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:24.024"
+        end="00:00:24.500"><span region="Default">Implementation is the same of the ASS tag<br/>This text should be at the<br/>top and horizontally centered</span></p>
+      <p
+        begin="00:00:24.024"
+        end="00:00:24.501"><span region="Default">This text should be at the<br/>middle and horizontally centered</span></p>
+      <p
+        begin="00:00:24.024"
+        end="00:00:24.502"><span region="Default">This text should be at the<br/>bottom and horizontally centered</span></p>
+      <p
+        begin="00:00:24.501"
+        end="00:00:26.026"><span region="Default">This text should be at the<br/>top and horizontally at the left</span></p>
+      <p
+        begin="00:00:24.502"
+        end="00:00:26.026"><span region="Default">This text should be at the<br/>middle and horizontally at the left<br/>(The second position must be ignored)</span></p>
+      <p
+        begin="00:00:24.503"
+        end="00:00:26.026"><span region="Default">This text should be at the<br/>bottom and horizontally at the left</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:26.026"
+        end="00:00:26.500"><span region="Default">This text should be at the<br/>top and horizontally at the left</span></p>
+      <p
+        begin="00:00:26.026"
+        end="00:00:26.501"><span region="Default">This text should be at the<br/>middle and horizontally at the left<br/>(The second position must be ignored)</span></p>
+      <p
+        begin="00:00:26.026"
+        end="00:00:26.502"><span region="Default">This text should be at the<br/>bottom and horizontally at the left</span></p>
+      <p
+        begin="00:00:26.501"
+        end="00:00:28.028"><span region="Default">This text should be at the<br/>top and horizontally at the right</span></p>
+      <p
+        begin="00:00:26.502"
+        end="00:00:28.028"><span region="Default">This text should be at the<br/>middle and horizontally at the right</span></p>
+      <p
+        begin="00:00:26.503"
+        end="00:00:28.028"><span region="Default">This text should be at the<br/>bottom and horizontally at the right</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:28.028"
+        end="00:00:28.500"><span region="Default">This text should be at the<br/>top and horizontally at the right</span></p>
+      <p
+        begin="00:00:28.028"
+        end="00:00:28.501"><span region="Default">This text should be at the<br/>middle and horizontally at the right</span></p>
+      <p
+        begin="00:00:28.028"
+        end="00:00:28.502"><span region="Default">This text should be at the<br/>bottom and horizontally at the right</span></p>
+      <p
+        begin="00:00:28.501"
+        end="00:00:30.030"><span region="Default">This could be the most difficult thing to implement</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:30.030"
+        end="00:00:31.500"><span region="Default">This could be the most difficult thing to implement</span></p>
+      <p
+        begin="00:00:31.501"
+        end="00:00:32.032"><span region="Default">First text</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:32.032"
+        end="00:00:34.034"><span region="Default">First text</span></p>
+      <p
+        begin="00:00:33.500"
+        end="00:00:34.034"><span region="Default">Second, it shouldn't overlap first</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:34.034"
+        end="00:00:36.036"><span region="Default">First text</span></p>
+      <p
+        begin="00:00:34.034"
+        end="00:00:35.500"><span region="Default">Second, it shouldn't overlap first</span></p>
+      <p
+        begin="00:00:35.501"
+        end="00:00:36.036"><span region="Default">Third, it should replace second</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:36.036"
+        end="00:00:38.038"><span region="Default">First text</span></p>
+      <p
+        begin="00:00:36.036"
+        end="00:00:37.500"><span region="Default">Third, it should replace second</span></p>
+      <p
+        begin="00:00:36.501"
+        end="00:00:38.038"><span region="Default">Fourth, it shouldn't overlap first and third</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:38.038"
+        end="00:00:40.040"><span region="Default">First text</span></p>
+      <p
+        begin="00:00:38.038"
+        end="00:00:40.040"><span region="Default">Fourth, it shouldn't overlap first and third</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:40.040"
+        end="00:00:42.042"><span region="Default">First text</span></p>
+      <p
+        begin="00:00:40.040"
+        end="00:00:42.042"><span region="Default">Fourth, it shouldn't overlap first and third</span></p>
+      <p
+        begin="00:00:40.501"
+        end="00:00:42.042"><span region="Default">Fifth, it should replace third</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:42.042"
+        end="00:00:44.044"><span region="Default">First text</span></p>
+      <p
+        begin="00:00:42.042"
+        end="00:00:44.044"><span region="Default">Fourth, it shouldn't overlap first and third</span></p>
+      <p
+        begin="00:00:42.042"
+        end="00:00:44.044"><span region="Default">Fifth, it should replace third</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:44.044"
+        end="00:00:46.046"><span region="Default">First text</span></p>
+      <p
+        begin="00:00:44.044"
+        end="00:00:46.046"><span region="Default">Fourth, it shouldn't overlap first and third</span></p>
+      <p
+        begin="00:00:44.044"
+        end="00:00:45.500"><span region="Default">Fifth, it should replace third</span></p>
+      <p
+        begin="00:00:45.501"
+        end="00:00:46.046"><span region="Default">Sixth, it shouldn't be<br/>showed overlapped</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:46.046"
+        end="00:00:48.048"><span region="Default">First text</span></p>
+      <p
+        begin="00:00:46.046"
+        end="00:00:48.048"><span region="Default">Fourth, it shouldn't overlap first and third</span></p>
+      <p
+        begin="00:00:46.046"
+        end="00:00:48.048"><span region="Default">Sixth, it shouldn't be<br/>showed overlapped</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:48.048"
+        end="00:00:50.050"><span region="Default">First text</span></p>
+      <p
+        begin="00:00:48.048"
+        end="00:00:50.050"><span region="Default">Fourth, it shouldn't overlap first and third</span></p>
+      <p
+        begin="00:00:48.048"
+        end="00:00:50.050"><span region="Default">Sixth, it shouldn't be<br/>showed overlapped</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:50.050"
+        end="00:00:50.500"><span region="Default">First text</span></p>
+      <p
+        begin="00:00:50.050"
+        end="00:00:50.500"><span region="Default">Fourth, it shouldn't overlap first and third</span></p>
+      <p
+        begin="00:00:50.050"
+        end="00:00:50.500"><span region="Default">Sixth, it shouldn't be<br/>showed overlapped</span></p>
+      <p
+        begin="00:00:50.501"
+        end="00:00:52.052"><span region="Default">TEXT 1 (bottom)</span></p>
+      <p
+        begin="00:00:50.502"
+        end="00:00:52.052"><span region="Default">text 2</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:52.052"
+        end="00:00:52.500"><span region="Default">TEXT 1 (bottom)</span></p>
+      <p
+        begin="00:00:52.052"
+        end="00:00:52.501"><span region="Default">text 2</span></p>
+      <p
+        begin="00:00:52.501"
+        end="00:00:54.054"><span region="Default">Hide these tags:<br/>also hide these tags:<br/>but show this: {normal text}</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:54.054"
+        end="00:00:54.500"><span region="Default">Hide these tags:<br/>also hide these tags:<br/>but show this: {normal text}</span></p>
+      <p
+        begin="00:00:54.501"
+        end="00:00:56.056"><span region="Default"><br/>\ N is a forced line break<br/>\ h is a hard space<br/>Normal spaces at the start and at the end of the line are trimmed while hard spaces are not trimmed.<br/>The\hline\hwill\hnever\hbreak\hautomatically\hright\hbefore\hor\hafter\ha\hhard\hspace.\h:-D</span></p>
+      <p
+        begin="00:00:54.502"
+        end="00:00:56.056"><span region="Default"><br/>\h\h\h\h\hA (05 hard spaces followed by a letter)<br/>A (Normal  spaces followed by a letter)<br/>A (No hard spaces followed by a letter)</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:56.056"
+        end="00:00:58.058"><span region="Default"><br/>\ N is a forced line break<br/>\ h is a hard space<br/>Normal spaces at the start and at the end of the line are trimmed while hard spaces are not trimmed.<br/>The\hline\hwill\hnever\hbreak\hautomatically\hright\hbefore\hor\hafter\ha\hhard\hspace.\h:-D</span></p>
+      <p
+        begin="00:00:56.056"
+        end="00:00:56.501"><span region="Default"><br/>\h\h\h\h\hA (05 hard spaces followed by a letter)<br/>A (Normal  spaces followed by a letter)<br/>A (No hard spaces followed by a letter)</span></p>
+      <p
+        begin="00:00:56.501"
+        end="00:00:58.058"><span region="Default">\h\h\h\h\hA (05 hard spaces followed by a letter)<br/>A (Normal  spaces followed by a letter)<br/>A (No hard spaces followed by a letter)<br/>Show this: \TEST and this: \-)</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:00:58.058"
+        end="00:01:00.060"><span region="Default"><br/>\ N is a forced line break<br/>\ h is a hard space<br/>Normal spaces at the start and at the end of the line are trimmed while hard spaces are not trimmed.<br/>The\hline\hwill\hnever\hbreak\hautomatically\hright\hbefore\hor\hafter\ha\hhard\hspace.\h:-D</span></p>
+      <p
+        begin="00:00:58.058"
+        end="00:00:58.500"><span region="Default">\h\h\h\h\hA (05 hard spaces followed by a letter)<br/>A (Normal  spaces followed by a letter)<br/>A (No hard spaces followed by a letter)<br/>Show this: \TEST and this: \-)</span></p>
+      <p
+        begin="00:00:58.501"
+        end="00:01:00.060"><span region="Default"><br/>A letter followed by 05 hard spaces: A\h\h\h\h\h<br/>A letter followed by normal  spaces: A<br/>A letter followed by no hard spaces: A<br/>05 hard  spaces between letters: A\h\h\h\h\hA<br/>5 normal spaces between letters: A     A<br/><br/>^--Forced line break</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:01:00.060"
+        end="00:01:00.500"><span region="Default"><br/>\ N is a forced line break<br/>\ h is a hard space<br/>Normal spaces at the start and at the end of the line are trimmed while hard spaces are not trimmed.<br/>The\hline\hwill\hnever\hbreak\hautomatically\hright\hbefore\hor\hafter\ha\hhard\hspace.\h:-D</span></p>
+      <p
+        begin="00:01:00.060"
+        end="00:01:00.500"><span region="Default"><br/>A letter followed by 05 hard spaces: A\h\h\h\h\h<br/>A letter followed by normal  spaces: A<br/>A letter followed by no hard spaces: A<br/>05 hard  spaces between letters: A\h\h\h\h\hA<br/>5 normal spaces between letters: A     A<br/><br/>^--Forced line break</span></p>
+      <p
+        begin="00:01:00.501"
+        end="00:01:02.062"><span region="Default">Both line should be strikethrough,<br/>yes.<br/>Correctly closed tags<br/>should be hidden.</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:01:02.062"
+        end="00:01:02.500"><span region="Default">Both line should be strikethrough,<br/>yes.<br/>Correctly closed tags<br/>should be hidden.</span></p>
+      <p
+        begin="00:01:02.501"
+        end="00:01:04.064"><span region="Default">It shouldn't be strikethrough,<br/>not opened tag showed as text.<br/>Not opened tag showed as text.</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:01:04.064"
+        end="00:01:04.500"><span region="Default">It shouldn't be strikethrough,<br/>not opened tag showed as text.<br/>Not opened tag showed as text.</span></p>
+      <p
+        begin="00:01:04.501"
+        end="00:01:06.066"><span region="Default">Three lines should be strikethrough,<br/>yes.<br/>Not closed tags showed as text</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:01:06.066"
+        end="00:01:06.500"><span region="Default">Three lines should be strikethrough,<br/>yes.<br/>Not closed tags showed as text</span></p>
+      <p
+        begin="00:01:06.501"
+        end="00:01:08.068"><span region="Default">Both line should be strikethrough but<br/>the wrong closing tag should be showed</span></p>
+    </div>
+  </body>
+</tt>
+<?xml version="1.0" encoding="utf-8"?>
+<tt
+  xmlns="http://www.w3.org/ns/ttml"
+  xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
+  xmlns:tts="http://www.w3.org/ns/ttml#styling"
+  xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+  ttp:cellResolution="384 288"
+  xml:lang="">
+  <head>
+    <layout>
+      <region xml:id="Default"
+        tts:origin="3% 0%"
+        tts:extent="97% 97%"
+        tts:displayAlign="after"
+        tts:textAlign="center"
+        tts:fontSize="16c"
+        tts:fontFamily="Arial"
+        tts:overflow="visible" />
+    </layout>
+  </head>
+  <body>
+    <div>
+      <p
+        begin="00:01:08.068"
+        end="00:01:08.500"><span region="Default">Both line should be strikethrough but<br/>the wrong closing tag should be showed</span></p>
+    </div>
+  </body>
+</tt>
+packet,subtitle,1,0,0.000000,0,0.000000,N/A,N/A,1172,14302,K__,CRC32:bde7afa1
+packet,subtitle,1,2002,2.002000,2002,2.002000,N/A,N/A,1015,28648,K__,CRC32:bd3bd4bc
+packet,subtitle,1,4004,4.004000,4004,4.004000,N/A,N/A,1305,42837,K__,CRC32:c8ff5017
+packet,subtitle,1,6006,6.006000,6006,6.006000,N/A,N/A,1111,57316,K__,CRC32:f0b10da6
+packet,subtitle,1,8008,8.008000,8008,8.008000,N/A,N/A,927,71601,K__,CRC32:55a7bb1b
+packet,subtitle,1,10010,10.010000,10010,10.010000,N/A,N/A,1194,85702,K__,CRC32:03dc4753
+packet,subtitle,1,12012,12.012000,12012,12.012000,N/A,N/A,874,100070,K__,CRC32:c7a092d4
+packet,subtitle,1,14014,14.014000,14014,14.014000,N/A,N/A,1154,114118,K__,CRC32:b476fe9c
+packet,subtitle,1,16016,16.016000,16016,16.016000,N/A,N/A,1240,128446,K__,CRC32:912e694c
+packet,subtitle,1,18018,18.018000,18018,18.018000,N/A,N/A,960,142860,K__,CRC32:bba73912
+packet,subtitle,1,20020,20.020000,20020,20.020000,N/A,N/A,1251,156994,K__,CRC32:4c7b87d8
+packet,subtitle,1,22022,22.022000,22022,22.022000,N/A,N/A,1285,171419,K__,CRC32:c0368927
+packet,subtitle,1,24024,24.024000,24024,24.024000,N/A,N/A,1676,185878,K__,CRC32:9811b98f
+packet,subtitle,1,26026,26.026000,26026,26.026000,N/A,N/A,1642,200728,K__,CRC32:7965715d
+packet,subtitle,1,28028,28.028000,28028,28.028000,N/A,N/A,1256,215544,K__,CRC32:433e322a
+packet,subtitle,1,30030,30.030000,30030,30.030000,N/A,N/A,868,229974,K__,CRC32:20edc13a
+packet,subtitle,1,32032,32.032000,32032,32.032000,N/A,N/A,851,244016,K__,CRC32:a850ce43
+packet,subtitle,1,34034,34.034000,34034,34.034000,N/A,N/A,982,258041,K__,CRC32:ffdc63b7
+packet,subtitle,1,36036,36.036000,36036,36.036000,N/A,N/A,992,272197,K__,CRC32:9189e069
+packet,subtitle,1,38038,38.038000,38038,38.038000,N/A,N/A,861,286363,K__,CRC32:b7df1508
+packet,subtitle,1,40040,40.040000,40040,40.040000,N/A,N/A,991,300398,K__,CRC32:16ace16f
+packet,subtitle,1,42042,42.042000,42042,42.042000,N/A,N/A,991,314563,K__,CRC32:524854ca
+packet,subtitle,1,44044,44.044000,44044,44.044000,N/A,N/A,1135,328728,K__,CRC32:c51f8b6e
+packet,subtitle,1,46046,46.046000,46046,46.046000,N/A,N/A,1005,343037,K__,CRC32:e9b7c12f
+packet,subtitle,1,48048,48.048000,48048,48.048000,N/A,N/A,1005,357216,K__,CRC32:82c319d0
+packet,subtitle,1,50050,50.050000,50050,50.050000,N/A,N/A,1226,371395,K__,CRC32:c73960aa
+packet,subtitle,1,52052,52.052000,52052,52.052000,N/A,N/A,1003,385795,K__,CRC32:e435cc83
+packet,subtitle,1,54054,54.054000,54054,54.054000,N/A,N/A,1381,399972,K__,CRC32:99f63187
+packet,subtitle,1,56056,56.056000,56056,56.056000,N/A,N/A,1478,414527,K__,CRC32:4d110a91
+packet,subtitle,1,58058,58.058000,58058,58.058000,N/A,N/A,1600,429179,K__,CRC32:d3133412
+packet,subtitle,1,60060,60.060000,60060,60.060000,N/A,N/A,1519,443953,K__,CRC32:86713143
+packet,subtitle,1,62062,62.062000,62062,62.062000,N/A,N/A,998,458646,K__,CRC32:0badc63b
+packet,subtitle,1,64064,64.064000,64064,64.064000,N/A,N/A,987,472818,K__,CRC32:1771dfd4
+packet,subtitle,1,66066,66.066000,66066,66.066000,N/A,N/A,967,486979,K__,CRC32:0cb5eddc
+packet,subtitle,1,68068,68.068000,68068,68.068000,N/A,N/A,787,501002,K__,CRC32:2fe77499
-- 
2.41.0

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^ permalink raw reply	[flat|nested] 10+ messages in thread

* Re: [FFmpeg-devel] [PATCH v2 3/3] avformat/movenc: add support for fragmented TTML muxing
  2023-09-15 13:17 ` [FFmpeg-devel] [PATCH v2 3/3] avformat/movenc: add support for fragmented TTML muxing Jan Ekström
@ 2023-12-08 12:15   ` Andreas Rheinhardt
  2023-12-08 15:36     ` Dennis Mungai
  0 siblings, 1 reply; 10+ messages in thread
From: Andreas Rheinhardt @ 2023-12-08 12:15 UTC (permalink / raw)
  To: ffmpeg-devel

Jan Ekström:
> From: Jan Ekström <jan.ekstrom@24i.com>
> 
> Attempts to base the fragmentation timing on other streams
> as most receivers expect media fragments to be more or less
> aligned.
> 
> Currently does not support fragmentation on subtitle track
> only, as the subtitle packet queue timings would have to be
> checked in addition to the current fragmentation timing logic.
> 
> Signed-off-by: Jan Ekström <jan.ekstrom@24i.com>
> ---
>  libavformat/movenc.c                        |    9 -
>  libavformat/movenc_ttml.c                   |  157 ++-
>  tests/fate/mov.mak                          |   21 +
>  tests/ref/fate/mov-mp4-fragmented-ttml-dfxp | 1197 +++++++++++++++++++
>  tests/ref/fate/mov-mp4-fragmented-ttml-stpp | 1197 +++++++++++++++++++

Am I the only one who thinks that this is a bit excessive?

>  5 files changed, 2568 insertions(+), 13 deletions(-)
>  create mode 100644 tests/ref/fate/mov-mp4-fragmented-ttml-dfxp
>  create mode 100644 tests/ref/fate/mov-mp4-fragmented-ttml-stpp
> 
> diff --git a/tests/fate/mov.mak b/tests/fate/mov.mak
> index 6cb493ceab..5c44299196 100644
> --- a/tests/fate/mov.mak
> +++ b/tests/fate/mov.mak
> @@ -143,6 +143,27 @@ FATE_MOV_FFMPEG_FFPROBE-$(call TRANSCODE, TTML SUBRIP, MP4 MOV, SRT_DEMUXER TTML
>  fate-mov-mp4-ttml-stpp: CMD = transcode srt $(TARGET_SAMPLES)/sub/SubRip_capability_tester.srt mp4 "-map 0:s -c:s ttml -time_base:s 1:1000" "-map 0 -c copy" "-of json -show_entries packet:stream=index,codec_type,codec_tag_string,codec_tag,codec_name,time_base,start_time,duration_ts,duration,nb_frames,nb_read_packets:stream_tags"
>  fate-mov-mp4-ttml-dfxp: CMD = transcode srt $(TARGET_SAMPLES)/sub/SubRip_capability_tester.srt mp4 "-map 0:s -c:s ttml -time_base:s 1:1000 -tag:s dfxp -strict unofficial" "-map 0 -c copy" "-of json -show_entries packet:stream=index,codec_type,codec_tag_string,codec_tag,codec_name,time_base,start_time,duration_ts,duration,nb_frames,nb_read_packets:stream_tags"
>  
> +FATE_MOV_FFMPEG_FFPROBE-$(call TRANSCODE, TTML SUBRIP, MP4 MOV, LAVFI_INDEV SMPTEHDBARS_FILTER SRT_DEMUXER MPEG2VIDEO_ENCODER TTML_MUXER RAWVIDEO_MUXER) += fate-mov-mp4-fragmented-ttml-stpp
> +fate-mov-mp4-fragmented-ttml-stpp: CMD = transcode srt $(TARGET_SAMPLES)/sub/SubRip_capability_tester.srt mp4 \
> +  "-map 1:v -map 0:s \
> +   -c:v mpeg2video -b:v 2M -g 48 -sc_threshold 1000000000 \
> +   -c:s ttml -time_base:s 1:1000 \
> +   -movflags +cmaf" \
> +  "-map 0:s -c copy" \
> +  "-select_streams s -of csv -show_packets -show_data_hash crc32" \
> +  "-f lavfi -i smptehdbars=duration=70:size=320x180:rate=24000/1001,format=yuv420p" \
> +  "" "" "rawvideo"

Would it speed the test up if you used smaller dimensions or a smaller
bitrate?
Anyway, you probably want the "data" output format instead of rawvideo.

> +
> +FATE_MOV_FFMPEG_FFPROBE-$(call TRANSCODE, TTML SUBRIP, ISMV MOV, LAVFI_INDEV SMPTEHDBARS_FILTER SRT_DEMUXER MPEG2VIDEO_ENCODER TTML_MUXER RAWVIDEO_MUXER) += fate-mov-mp4-fragmented-ttml-dfxp
> +fate-mov-mp4-fragmented-ttml-dfxp: CMD = transcode srt $(TARGET_SAMPLES)/sub/SubRip_capability_tester.srt ismv \
> +  "-map 1:v -map 0:s \
> +   -c:v mpeg2video -b:v 2M -g 48 -sc_threshold 1000000000 \
> +   -c:s ttml -tag:s dfxp -time_base:s 1:1000" \
> +  "-map 0:s -c copy" \
> +  "-select_streams s -of csv -show_packets -show_data_hash crc32" \
> +  "-f lavfi -i smptehdbars=duration=70:size=320x180:rate=24000/1001,format=yuv420p" \
> +  "" "" "rawvideo"
> +
>  # FIXME: Uncomment these two tests once the test files are uploaded to the fate
>  # server.
>  # avif demuxing - still image with 1 item.


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^ permalink raw reply	[flat|nested] 10+ messages in thread

* Re: [FFmpeg-devel] [PATCH v2 3/3] avformat/movenc: add support for fragmented TTML muxing
  2023-12-08 12:15   ` Andreas Rheinhardt
@ 2023-12-08 15:36     ` Dennis Mungai
  2023-12-08 17:05       ` Jan Ekström
  0 siblings, 1 reply; 10+ messages in thread
From: Dennis Mungai @ 2023-12-08 15:36 UTC (permalink / raw)
  To: FFmpeg development discussions and patches

On Fri, 8 Dec 2023 at 15:14, Andreas Rheinhardt <
andreas.rheinhardt@outlook.com> wrote:

> Jan Ekström:
> > From: Jan Ekström <jan.ekstrom@24i.com>
> >
> > Attempts to base the fragmentation timing on other streams
> > as most receivers expect media fragments to be more or less
> > aligned.
> >
> > Currently does not support fragmentation on subtitle track
> > only, as the subtitle packet queue timings would have to be
> > checked in addition to the current fragmentation timing logic.
> >
> > Signed-off-by: Jan Ekström <jan.ekstrom@24i.com>
> > ---
> >  libavformat/movenc.c                        |    9 -
> >  libavformat/movenc_ttml.c                   |  157 ++-
> >  tests/fate/mov.mak                          |   21 +
> >  tests/ref/fate/mov-mp4-fragmented-ttml-dfxp | 1197 +++++++++++++++++++
> >  tests/ref/fate/mov-mp4-fragmented-ttml-stpp | 1197 +++++++++++++++++++
>
> Am I the only one who thinks that this is a bit excessive?
>
> >  5 files changed, 2568 insertions(+), 13 deletions(-)
> >  create mode 100644 tests/ref/fate/mov-mp4-fragmented-ttml-dfxp
> >  create mode 100644 tests/ref/fate/mov-mp4-fragmented-ttml-stpp
> >
> > diff --git a/tests/fate/mov.mak b/tests/fate/mov.mak
> > index 6cb493ceab..5c44299196 100644
> > --- a/tests/fate/mov.mak
> > +++ b/tests/fate/mov.mak
> > @@ -143,6 +143,27 @@ FATE_MOV_FFMPEG_FFPROBE-$(call TRANSCODE, TTML
> SUBRIP, MP4 MOV, SRT_DEMUXER TTML
> >  fate-mov-mp4-ttml-stpp: CMD = transcode srt
> $(TARGET_SAMPLES)/sub/SubRip_capability_tester.srt mp4 "-map 0:s -c:s ttml
> -time_base:s 1:1000" "-map 0 -c copy" "-of json -show_entries
> packet:stream=index,codec_type,codec_tag_string,codec_tag,codec_name,time_base,start_time,duration_ts,duration,nb_frames,nb_read_packets:stream_tags"
> >  fate-mov-mp4-ttml-dfxp: CMD = transcode srt
> $(TARGET_SAMPLES)/sub/SubRip_capability_tester.srt mp4 "-map 0:s -c:s ttml
> -time_base:s 1:1000 -tag:s dfxp -strict unofficial" "-map 0 -c copy" "-of
> json -show_entries
> packet:stream=index,codec_type,codec_tag_string,codec_tag,codec_name,time_base,start_time,duration_ts,duration,nb_frames,nb_read_packets:stream_tags"
> >
> > +FATE_MOV_FFMPEG_FFPROBE-$(call TRANSCODE, TTML SUBRIP, MP4 MOV,
> LAVFI_INDEV SMPTEHDBARS_FILTER SRT_DEMUXER MPEG2VIDEO_ENCODER TTML_MUXER
> RAWVIDEO_MUXER) += fate-mov-mp4-fragmented-ttml-stpp
> > +fate-mov-mp4-fragmented-ttml-stpp: CMD = transcode srt
> $(TARGET_SAMPLES)/sub/SubRip_capability_tester.srt mp4 \
> > +  "-map 1:v -map 0:s \
> > +   -c:v mpeg2video -b:v 2M -g 48 -sc_threshold 1000000000 \
> > +   -c:s ttml -time_base:s 1:1000 \
> > +   -movflags +cmaf" \
> > +  "-map 0:s -c copy" \
> > +  "-select_streams s -of csv -show_packets -show_data_hash crc32" \
> > +  "-f lavfi -i
> smptehdbars=duration=70:size=320x180:rate=24000/1001,format=yuv420p" \
> > +  "" "" "rawvideo"
>
> Would it speed the test up if you used smaller dimensions or a smaller
> bitrate?
> Anyway, you probably want the "data" output format instead of rawvideo.
>
> > +
> > +FATE_MOV_FFMPEG_FFPROBE-$(call TRANSCODE, TTML SUBRIP, ISMV MOV,
> LAVFI_INDEV SMPTEHDBARS_FILTER SRT_DEMUXER MPEG2VIDEO_ENCODER TTML_MUXER
> RAWVIDEO_MUXER) += fate-mov-mp4-fragmented-ttml-dfxp
> > +fate-mov-mp4-fragmented-ttml-dfxp: CMD = transcode srt
> $(TARGET_SAMPLES)/sub/SubRip_capability_tester.srt ismv \
> > +  "-map 1:v -map 0:s \
> > +   -c:v mpeg2video -b:v 2M -g 48 -sc_threshold 1000000000 \
> > +   -c:s ttml -tag:s dfxp -time_base:s 1:1000" \
> > +  "-map 0:s -c copy" \
> > +  "-select_streams s -of csv -show_packets -show_data_hash crc32" \
> > +  "-f lavfi -i
> smptehdbars=duration=70:size=320x180:rate=24000/1001,format=yuv420p" \
> > +  "" "" "rawvideo"
> > +
> >  # FIXME: Uncomment these two tests once the test files are uploaded to
> the fate
> >  # server.
> >  # avif demuxing - still image with 1 item.
>

Hello Jan,

Taking this note into account, and I quote:

 " Currently does not support fragmentation on subtitle track only, as the
subtitle packet queue timings would have to be checked in addition to the
current fragmentation timing logic."

Wouldn't it be ideal to have this merged until after support for
fragmentation in subtitle-only tracks is complete, at the very least? That
way, the fate tests for such a workflow (case in point CMAF) would
therefore be feature complete?
The typical workloads that depend on such functionality, such as ingesting
CMFT require a subtitle-only stream be present in such a representation.

See:
1.
https://www.unified-streaming.com/blog/cmaf-conformance-is-this-really-cmaf
2. https://www.unified-streaming.com/blog/live-media-ingest-cmaf
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^ permalink raw reply	[flat|nested] 10+ messages in thread

* Re: [FFmpeg-devel] [PATCH v2 3/3] avformat/movenc: add support for fragmented TTML muxing
  2023-12-08 15:36     ` Dennis Mungai
@ 2023-12-08 17:05       ` Jan Ekström
  2023-12-08 17:09         ` Jan Ekström
  0 siblings, 1 reply; 10+ messages in thread
From: Jan Ekström @ 2023-12-08 17:05 UTC (permalink / raw)
  To: FFmpeg development discussions and patches

On Fri, Dec 8, 2023 at 5:37 PM Dennis Mungai <dmngaie@gmail.com> wrote:
>
> On Fri, 8 Dec 2023 at 15:14, Andreas Rheinhardt <
> andreas.rheinhardt@outlook.com> wrote:
>
> > Jan Ekström:
> > > From: Jan Ekström <jan.ekstrom@24i.com>
> > >
> > > Attempts to base the fragmentation timing on other streams
> > > as most receivers expect media fragments to be more or less
> > > aligned.
> > >
> > > Currently does not support fragmentation on subtitle track
> > > only, as the subtitle packet queue timings would have to be
> > > checked in addition to the current fragmentation timing logic.
> > >
> > > Signed-off-by: Jan Ekström <jan.ekstrom@24i.com>
> > > ---
> > >  libavformat/movenc.c                        |    9 -
> > >  libavformat/movenc_ttml.c                   |  157 ++-
> > >  tests/fate/mov.mak                          |   21 +
> > >  tests/ref/fate/mov-mp4-fragmented-ttml-dfxp | 1197 +++++++++++++++++++
> > >  tests/ref/fate/mov-mp4-fragmented-ttml-stpp | 1197 +++++++++++++++++++
> >
> > Am I the only one who thinks that this is a bit excessive?
> >
> > >  5 files changed, 2568 insertions(+), 13 deletions(-)
> > >  create mode 100644 tests/ref/fate/mov-mp4-fragmented-ttml-dfxp
> > >  create mode 100644 tests/ref/fate/mov-mp4-fragmented-ttml-stpp
> > >
> > > diff --git a/tests/fate/mov.mak b/tests/fate/mov.mak
> > > index 6cb493ceab..5c44299196 100644
> > > --- a/tests/fate/mov.mak
> > > +++ b/tests/fate/mov.mak
> > > @@ -143,6 +143,27 @@ FATE_MOV_FFMPEG_FFPROBE-$(call TRANSCODE, TTML
> > SUBRIP, MP4 MOV, SRT_DEMUXER TTML
> > >  fate-mov-mp4-ttml-stpp: CMD = transcode srt
> > $(TARGET_SAMPLES)/sub/SubRip_capability_tester.srt mp4 "-map 0:s -c:s ttml
> > -time_base:s 1:1000" "-map 0 -c copy" "-of json -show_entries
> > packet:stream=index,codec_type,codec_tag_string,codec_tag,codec_name,time_base,start_time,duration_ts,duration,nb_frames,nb_read_packets:stream_tags"
> > >  fate-mov-mp4-ttml-dfxp: CMD = transcode srt
> > $(TARGET_SAMPLES)/sub/SubRip_capability_tester.srt mp4 "-map 0:s -c:s ttml
> > -time_base:s 1:1000 -tag:s dfxp -strict unofficial" "-map 0 -c copy" "-of
> > json -show_entries
> > packet:stream=index,codec_type,codec_tag_string,codec_tag,codec_name,time_base,start_time,duration_ts,duration,nb_frames,nb_read_packets:stream_tags"
> > >
> > > +FATE_MOV_FFMPEG_FFPROBE-$(call TRANSCODE, TTML SUBRIP, MP4 MOV,
> > LAVFI_INDEV SMPTEHDBARS_FILTER SRT_DEMUXER MPEG2VIDEO_ENCODER TTML_MUXER
> > RAWVIDEO_MUXER) += fate-mov-mp4-fragmented-ttml-stpp
> > > +fate-mov-mp4-fragmented-ttml-stpp: CMD = transcode srt
> > $(TARGET_SAMPLES)/sub/SubRip_capability_tester.srt mp4 \
> > > +  "-map 1:v -map 0:s \
> > > +   -c:v mpeg2video -b:v 2M -g 48 -sc_threshold 1000000000 \
> > > +   -c:s ttml -time_base:s 1:1000 \
> > > +   -movflags +cmaf" \
> > > +  "-map 0:s -c copy" \
> > > +  "-select_streams s -of csv -show_packets -show_data_hash crc32" \
> > > +  "-f lavfi -i
> > smptehdbars=duration=70:size=320x180:rate=24000/1001,format=yuv420p" \
> > > +  "" "" "rawvideo"
> >
> > Would it speed the test up if you used smaller dimensions or a smaller
> > bitrate?
> > Anyway, you probably want the "data" output format instead of rawvideo.
> >
> > > +
> > > +FATE_MOV_FFMPEG_FFPROBE-$(call TRANSCODE, TTML SUBRIP, ISMV MOV,
> > LAVFI_INDEV SMPTEHDBARS_FILTER SRT_DEMUXER MPEG2VIDEO_ENCODER TTML_MUXER
> > RAWVIDEO_MUXER) += fate-mov-mp4-fragmented-ttml-dfxp
> > > +fate-mov-mp4-fragmented-ttml-dfxp: CMD = transcode srt
> > $(TARGET_SAMPLES)/sub/SubRip_capability_tester.srt ismv \
> > > +  "-map 1:v -map 0:s \
> > > +   -c:v mpeg2video -b:v 2M -g 48 -sc_threshold 1000000000 \
> > > +   -c:s ttml -tag:s dfxp -time_base:s 1:1000" \
> > > +  "-map 0:s -c copy" \
> > > +  "-select_streams s -of csv -show_packets -show_data_hash crc32" \
> > > +  "-f lavfi -i
> > smptehdbars=duration=70:size=320x180:rate=24000/1001,format=yuv420p" \
> > > +  "" "" "rawvideo"
> > > +
> > >  # FIXME: Uncomment these two tests once the test files are uploaded to
> > the fate
> > >  # server.
> > >  # avif demuxing - still image with 1 item.
> >
>
> Hello Jan,
>
> Taking this note into account, and I quote:
>
>  " Currently does not support fragmentation on subtitle track only, as the
> subtitle packet queue timings would have to be checked in addition to the
> current fragmentation timing logic."
>
> Wouldn't it be ideal to have this merged until after support for
> fragmentation in subtitle-only tracks is complete, at the very least? That
> way, the fate tests for such a workflow (case in point CMAF) would
> therefore be feature complete?
> The typical workloads that depend on such functionality, such as ingesting
> CMFT require a subtitle-only stream be present in such a representation.
>
> See:
> 1.
> https://www.unified-streaming.com/blog/cmaf-conformance-is-this-really-cmaf
> 2. https://www.unified-streaming.com/blog/live-media-ingest-cmaf

It would be ideal, but there are a few points to keep in mind:

1. For such streaming, you are generally required to be synchronized
in your fragmentation against other media (either video or audio). If
subtitle only fragmentation is implemented and you have a TTML-only
mux, then you may set something like time-based fragmentation (time of
your expected GOP duration or so), but nothing would make sure you are
fragmenting according to those other tracks.
2. Subtitle-only fragmentation is possible via the API client already
with this implementation, which for a one-mux = one track output is
the only way to make sure you are in sync with those other tracks as
the muxer has no idea of where they are going (as they would be in
other AVFormatContexts).
3. I have tested this code against this vendor, with the subtitles
together in a single mux with a track that is not sparse in order to
keep the fragmentation in sync.

In other words, given how CMAF is defined I would say you are supposed
to be controlling all muxes from a central point as synchronization is
required. That is already possible with these changes. I can
definitely implement time-based fragmentation for TTML only muxes, but
I think there are some reasons to consider that not that high
priority.

Jan
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^ permalink raw reply	[flat|nested] 10+ messages in thread

* Re: [FFmpeg-devel] [PATCH v2 3/3] avformat/movenc: add support for fragmented TTML muxing
  2023-12-08 17:05       ` Jan Ekström
@ 2023-12-08 17:09         ` Jan Ekström
  2023-12-08 17:17           ` Jan Ekström
  0 siblings, 1 reply; 10+ messages in thread
From: Jan Ekström @ 2023-12-08 17:09 UTC (permalink / raw)
  To: FFmpeg development discussions and patches

On Fri, Dec 8, 2023 at 7:05 PM Jan Ekström <jeebjp@gmail.com> wrote:
>
> On Fri, Dec 8, 2023 at 5:37 PM Dennis Mungai <dmngaie@gmail.com> wrote:
> >
> > On Fri, 8 Dec 2023 at 15:14, Andreas Rheinhardt <
> > andreas.rheinhardt@outlook.com> wrote:
> >
> > > Jan Ekström:
> > > > From: Jan Ekström <jan.ekstrom@24i.com>
> > > >
> > > > Attempts to base the fragmentation timing on other streams
> > > > as most receivers expect media fragments to be more or less
> > > > aligned.
> > > >
> > > > Currently does not support fragmentation on subtitle track
> > > > only, as the subtitle packet queue timings would have to be
> > > > checked in addition to the current fragmentation timing logic.
> > > >
> > > > Signed-off-by: Jan Ekström <jan.ekstrom@24i.com>
> > > > ---
> > > >  libavformat/movenc.c                        |    9 -
> > > >  libavformat/movenc_ttml.c                   |  157 ++-
> > > >  tests/fate/mov.mak                          |   21 +
> > > >  tests/ref/fate/mov-mp4-fragmented-ttml-dfxp | 1197 +++++++++++++++++++
> > > >  tests/ref/fate/mov-mp4-fragmented-ttml-stpp | 1197 +++++++++++++++++++
> > >
> > > Am I the only one who thinks that this is a bit excessive?
> > >
> > > >  5 files changed, 2568 insertions(+), 13 deletions(-)
> > > >  create mode 100644 tests/ref/fate/mov-mp4-fragmented-ttml-dfxp
> > > >  create mode 100644 tests/ref/fate/mov-mp4-fragmented-ttml-stpp
> > > >
> > > > diff --git a/tests/fate/mov.mak b/tests/fate/mov.mak
> > > > index 6cb493ceab..5c44299196 100644
> > > > --- a/tests/fate/mov.mak
> > > > +++ b/tests/fate/mov.mak
> > > > @@ -143,6 +143,27 @@ FATE_MOV_FFMPEG_FFPROBE-$(call TRANSCODE, TTML
> > > SUBRIP, MP4 MOV, SRT_DEMUXER TTML
> > > >  fate-mov-mp4-ttml-stpp: CMD = transcode srt
> > > $(TARGET_SAMPLES)/sub/SubRip_capability_tester.srt mp4 "-map 0:s -c:s ttml
> > > -time_base:s 1:1000" "-map 0 -c copy" "-of json -show_entries
> > > packet:stream=index,codec_type,codec_tag_string,codec_tag,codec_name,time_base,start_time,duration_ts,duration,nb_frames,nb_read_packets:stream_tags"
> > > >  fate-mov-mp4-ttml-dfxp: CMD = transcode srt
> > > $(TARGET_SAMPLES)/sub/SubRip_capability_tester.srt mp4 "-map 0:s -c:s ttml
> > > -time_base:s 1:1000 -tag:s dfxp -strict unofficial" "-map 0 -c copy" "-of
> > > json -show_entries
> > > packet:stream=index,codec_type,codec_tag_string,codec_tag,codec_name,time_base,start_time,duration_ts,duration,nb_frames,nb_read_packets:stream_tags"
> > > >
> > > > +FATE_MOV_FFMPEG_FFPROBE-$(call TRANSCODE, TTML SUBRIP, MP4 MOV,
> > > LAVFI_INDEV SMPTEHDBARS_FILTER SRT_DEMUXER MPEG2VIDEO_ENCODER TTML_MUXER
> > > RAWVIDEO_MUXER) += fate-mov-mp4-fragmented-ttml-stpp
> > > > +fate-mov-mp4-fragmented-ttml-stpp: CMD = transcode srt
> > > $(TARGET_SAMPLES)/sub/SubRip_capability_tester.srt mp4 \
> > > > +  "-map 1:v -map 0:s \
> > > > +   -c:v mpeg2video -b:v 2M -g 48 -sc_threshold 1000000000 \
> > > > +   -c:s ttml -time_base:s 1:1000 \
> > > > +   -movflags +cmaf" \
> > > > +  "-map 0:s -c copy" \
> > > > +  "-select_streams s -of csv -show_packets -show_data_hash crc32" \
> > > > +  "-f lavfi -i
> > > smptehdbars=duration=70:size=320x180:rate=24000/1001,format=yuv420p" \
> > > > +  "" "" "rawvideo"
> > >
> > > Would it speed the test up if you used smaller dimensions or a smaller
> > > bitrate?
> > > Anyway, you probably want the "data" output format instead of rawvideo.
> > >
> > > > +
> > > > +FATE_MOV_FFMPEG_FFPROBE-$(call TRANSCODE, TTML SUBRIP, ISMV MOV,
> > > LAVFI_INDEV SMPTEHDBARS_FILTER SRT_DEMUXER MPEG2VIDEO_ENCODER TTML_MUXER
> > > RAWVIDEO_MUXER) += fate-mov-mp4-fragmented-ttml-dfxp
> > > > +fate-mov-mp4-fragmented-ttml-dfxp: CMD = transcode srt
> > > $(TARGET_SAMPLES)/sub/SubRip_capability_tester.srt ismv \
> > > > +  "-map 1:v -map 0:s \
> > > > +   -c:v mpeg2video -b:v 2M -g 48 -sc_threshold 1000000000 \
> > > > +   -c:s ttml -tag:s dfxp -time_base:s 1:1000" \
> > > > +  "-map 0:s -c copy" \
> > > > +  "-select_streams s -of csv -show_packets -show_data_hash crc32" \
> > > > +  "-f lavfi -i
> > > smptehdbars=duration=70:size=320x180:rate=24000/1001,format=yuv420p" \
> > > > +  "" "" "rawvideo"
> > > > +
> > > >  # FIXME: Uncomment these two tests once the test files are uploaded to
> > > the fate
> > > >  # server.
> > > >  # avif demuxing - still image with 1 item.
> > >
> >
> > Hello Jan,
> >
> > Taking this note into account, and I quote:
> >
> >  " Currently does not support fragmentation on subtitle track only, as the
> > subtitle packet queue timings would have to be checked in addition to the
> > current fragmentation timing logic."
> >
> > Wouldn't it be ideal to have this merged until after support for
> > fragmentation in subtitle-only tracks is complete, at the very least? That
> > way, the fate tests for such a workflow (case in point CMAF) would
> > therefore be feature complete?
> > The typical workloads that depend on such functionality, such as ingesting
> > CMFT require a subtitle-only stream be present in such a representation.
> >
> > See:
> > 1.
> > https://www.unified-streaming.com/blog/cmaf-conformance-is-this-really-cmaf
> > 2. https://www.unified-streaming.com/blog/live-media-ingest-cmaf
>
> It would be ideal, but there are a few points to keep in mind:
>
> 1. For such streaming, you are generally required to be synchronized
> in your fragmentation against other media (either video or audio). If
> subtitle only fragmentation is implemented and you have a TTML-only
> mux, then you may set something like time-based fragmentation (time of
> your expected GOP duration or so), but nothing would make sure you are
> fragmenting according to those other tracks.
> 2. Subtitle-only fragmentation is possible via the API client already
> with this implementation, which for a one-mux = one track output is
> the only way to make sure you are in sync with those other tracks as
> the muxer has no idea of where they are going (as they would be in
> other AVFormatContexts).
> 3. I have tested this code against this vendor, with the subtitles
> together in a single mux with a track that is not sparse in order to
> keep the fragmentation in sync.
>
> In other words, given how CMAF is defined I would say you are supposed
> to be controlling all muxes from a central point as synchronization is
> required. That is already possible with these changes. I can
> definitely implement time-based fragmentation for TTML only muxes, but
> I think there are some reasons to consider that not that high
> priority.

Or I guess another way would be to make sure the "fragment on each
packet" option's logic works with a TTML-only mux, and instead of
feeding the packet to the subtitle queue, you just fragment & output
with each fed TTML packet.

Jan
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^ permalink raw reply	[flat|nested] 10+ messages in thread

* Re: [FFmpeg-devel] [PATCH v2 3/3] avformat/movenc: add support for fragmented TTML muxing
  2023-12-08 17:09         ` Jan Ekström
@ 2023-12-08 17:17           ` Jan Ekström
  0 siblings, 0 replies; 10+ messages in thread
From: Jan Ekström @ 2023-12-08 17:17 UTC (permalink / raw)
  To: FFmpeg development discussions and patches

On Fri, Dec 8, 2023 at 7:09 PM Jan Ekström <jeebjp@gmail.com> wrote:
>
> On Fri, Dec 8, 2023 at 7:05 PM Jan Ekström <jeebjp@gmail.com> wrote:
> >
> > On Fri, Dec 8, 2023 at 5:37 PM Dennis Mungai <dmngaie@gmail.com> wrote:
> > >
> > > On Fri, 8 Dec 2023 at 15:14, Andreas Rheinhardt <
> > > andreas.rheinhardt@outlook.com> wrote:
> > >
> > > > Jan Ekström:
> > > > > From: Jan Ekström <jan.ekstrom@24i.com>
> > > > >
> > > > > Attempts to base the fragmentation timing on other streams
> > > > > as most receivers expect media fragments to be more or less
> > > > > aligned.
> > > > >
> > > > > Currently does not support fragmentation on subtitle track
> > > > > only, as the subtitle packet queue timings would have to be
> > > > > checked in addition to the current fragmentation timing logic.
> > > > >
> > > > > Signed-off-by: Jan Ekström <jan.ekstrom@24i.com>
> > > > > ---
> > > > >  libavformat/movenc.c                        |    9 -
> > > > >  libavformat/movenc_ttml.c                   |  157 ++-
> > > > >  tests/fate/mov.mak                          |   21 +
> > > > >  tests/ref/fate/mov-mp4-fragmented-ttml-dfxp | 1197 +++++++++++++++++++
> > > > >  tests/ref/fate/mov-mp4-fragmented-ttml-stpp | 1197 +++++++++++++++++++
> > > >
> > > > Am I the only one who thinks that this is a bit excessive?
> > > >
> > > > >  5 files changed, 2568 insertions(+), 13 deletions(-)
> > > > >  create mode 100644 tests/ref/fate/mov-mp4-fragmented-ttml-dfxp
> > > > >  create mode 100644 tests/ref/fate/mov-mp4-fragmented-ttml-stpp
> > > > >
> > > > > diff --git a/tests/fate/mov.mak b/tests/fate/mov.mak
> > > > > index 6cb493ceab..5c44299196 100644
> > > > > --- a/tests/fate/mov.mak
> > > > > +++ b/tests/fate/mov.mak
> > > > > @@ -143,6 +143,27 @@ FATE_MOV_FFMPEG_FFPROBE-$(call TRANSCODE, TTML
> > > > SUBRIP, MP4 MOV, SRT_DEMUXER TTML
> > > > >  fate-mov-mp4-ttml-stpp: CMD = transcode srt
> > > > $(TARGET_SAMPLES)/sub/SubRip_capability_tester.srt mp4 "-map 0:s -c:s ttml
> > > > -time_base:s 1:1000" "-map 0 -c copy" "-of json -show_entries
> > > > packet:stream=index,codec_type,codec_tag_string,codec_tag,codec_name,time_base,start_time,duration_ts,duration,nb_frames,nb_read_packets:stream_tags"
> > > > >  fate-mov-mp4-ttml-dfxp: CMD = transcode srt
> > > > $(TARGET_SAMPLES)/sub/SubRip_capability_tester.srt mp4 "-map 0:s -c:s ttml
> > > > -time_base:s 1:1000 -tag:s dfxp -strict unofficial" "-map 0 -c copy" "-of
> > > > json -show_entries
> > > > packet:stream=index,codec_type,codec_tag_string,codec_tag,codec_name,time_base,start_time,duration_ts,duration,nb_frames,nb_read_packets:stream_tags"
> > > > >
> > > > > +FATE_MOV_FFMPEG_FFPROBE-$(call TRANSCODE, TTML SUBRIP, MP4 MOV,
> > > > LAVFI_INDEV SMPTEHDBARS_FILTER SRT_DEMUXER MPEG2VIDEO_ENCODER TTML_MUXER
> > > > RAWVIDEO_MUXER) += fate-mov-mp4-fragmented-ttml-stpp
> > > > > +fate-mov-mp4-fragmented-ttml-stpp: CMD = transcode srt
> > > > $(TARGET_SAMPLES)/sub/SubRip_capability_tester.srt mp4 \
> > > > > +  "-map 1:v -map 0:s \
> > > > > +   -c:v mpeg2video -b:v 2M -g 48 -sc_threshold 1000000000 \
> > > > > +   -c:s ttml -time_base:s 1:1000 \
> > > > > +   -movflags +cmaf" \
> > > > > +  "-map 0:s -c copy" \
> > > > > +  "-select_streams s -of csv -show_packets -show_data_hash crc32" \
> > > > > +  "-f lavfi -i
> > > > smptehdbars=duration=70:size=320x180:rate=24000/1001,format=yuv420p" \
> > > > > +  "" "" "rawvideo"
> > > >
> > > > Would it speed the test up if you used smaller dimensions or a smaller
> > > > bitrate?
> > > > Anyway, you probably want the "data" output format instead of rawvideo.
> > > >
> > > > > +
> > > > > +FATE_MOV_FFMPEG_FFPROBE-$(call TRANSCODE, TTML SUBRIP, ISMV MOV,
> > > > LAVFI_INDEV SMPTEHDBARS_FILTER SRT_DEMUXER MPEG2VIDEO_ENCODER TTML_MUXER
> > > > RAWVIDEO_MUXER) += fate-mov-mp4-fragmented-ttml-dfxp
> > > > > +fate-mov-mp4-fragmented-ttml-dfxp: CMD = transcode srt
> > > > $(TARGET_SAMPLES)/sub/SubRip_capability_tester.srt ismv \
> > > > > +  "-map 1:v -map 0:s \
> > > > > +   -c:v mpeg2video -b:v 2M -g 48 -sc_threshold 1000000000 \
> > > > > +   -c:s ttml -tag:s dfxp -time_base:s 1:1000" \
> > > > > +  "-map 0:s -c copy" \
> > > > > +  "-select_streams s -of csv -show_packets -show_data_hash crc32" \
> > > > > +  "-f lavfi -i
> > > > smptehdbars=duration=70:size=320x180:rate=24000/1001,format=yuv420p" \
> > > > > +  "" "" "rawvideo"
> > > > > +
> > > > >  # FIXME: Uncomment these two tests once the test files are uploaded to
> > > > the fate
> > > > >  # server.
> > > > >  # avif demuxing - still image with 1 item.
> > > >
> > >
> > > Hello Jan,
> > >
> > > Taking this note into account, and I quote:
> > >
> > >  " Currently does not support fragmentation on subtitle track only, as the
> > > subtitle packet queue timings would have to be checked in addition to the
> > > current fragmentation timing logic."
> > >
> > > Wouldn't it be ideal to have this merged until after support for
> > > fragmentation in subtitle-only tracks is complete, at the very least? That
> > > way, the fate tests for such a workflow (case in point CMAF) would
> > > therefore be feature complete?
> > > The typical workloads that depend on such functionality, such as ingesting
> > > CMFT require a subtitle-only stream be present in such a representation.
> > >
> > > See:
> > > 1.
> > > https://www.unified-streaming.com/blog/cmaf-conformance-is-this-really-cmaf
> > > 2. https://www.unified-streaming.com/blog/live-media-ingest-cmaf
> >
> > It would be ideal, but there are a few points to keep in mind:
> >
> > 1. For such streaming, you are generally required to be synchronized
> > in your fragmentation against other media (either video or audio). If
> > subtitle only fragmentation is implemented and you have a TTML-only
> > mux, then you may set something like time-based fragmentation (time of
> > your expected GOP duration or so), but nothing would make sure you are
> > fragmenting according to those other tracks.
> > 2. Subtitle-only fragmentation is possible via the API client already
> > with this implementation, which for a one-mux = one track output is
> > the only way to make sure you are in sync with those other tracks as
> > the muxer has no idea of where they are going (as they would be in
> > other AVFormatContexts).
> > 3. I have tested this code against this vendor, with the subtitles
> > together in a single mux with a track that is not sparse in order to
> > keep the fragmentation in sync.
> >
> > In other words, given how CMAF is defined I would say you are supposed
> > to be controlling all muxes from a central point as synchronization is
> > required. That is already possible with these changes. I can
> > definitely implement time-based fragmentation for TTML only muxes, but
> > I think there are some reasons to consider that not that high
> > priority.
>
> Or I guess another way would be to make sure the "fragment on each
> packet" option's logic works with a TTML-only mux, and instead of
> feeding the packet to the subtitle queue, you just fragment & output
> with each fed TTML packet.

Argh, I keep remembering things as I respond. Sorry for this.

All this stuff is specifically for *paragraph* based TTML packets. If
you feed the MP4 writer already full TTML document packets (such as
with codec copy), fragmentation should work like with any other track
even right now.

This is because actual TTML document packets do not utilize the
subtitle queue as they are already complete and timed.

Jan
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^ permalink raw reply	[flat|nested] 10+ messages in thread

* Re: [FFmpeg-devel] [PATCH v2 0/3] Initial support for fragmented TTML muxing
  2023-09-15 13:16 [FFmpeg-devel] [PATCH v2 0/3] Initial support for fragmented TTML muxing Jan Ekström
                   ` (2 preceding siblings ...)
  2023-09-15 13:17 ` [FFmpeg-devel] [PATCH v2 3/3] avformat/movenc: add support for fragmented TTML muxing Jan Ekström
@ 2023-12-08 11:52 ` Jan Ekström
  3 siblings, 0 replies; 10+ messages in thread
From: Jan Ekström @ 2023-12-08 11:52 UTC (permalink / raw)
  To: ffmpeg-devel

On Fri, Sep 15, 2023 at 4:17 PM Jan Ekström <jeebjp@gmail.com> wrote:
>
> Changes compared to v1:
>
> * General rebase.
> * A FATE test was added, together with the extension of the "transcode"
>   test function to allow for dumping of packets' contents.
> * Simplified mov_write_ttml_document_from_queue's loop by getting
>   rid of `stop_at_current_packet`.
>
> This enables pushing TTML together with another track (usually video)
> as part of CMAF Ingest, as defined by the DASH-IF Live Media Ingest
> Protocol.
>
> Currently does not function well with just the subtitle track unless
> the API user explicitly requests fragmentation with a nullptr packet,
> as the generic fragmentation decision logic is based on tracks which
> do not require squashing.
>
> Currently does support overlapping subtitles, but the implementation
> utilizes another packet queue for it, which is probably not optimal.
> Recommendations on how to improve things are welcome.
>
> Jan
>

Ping.

As this is a piece of seemingly working functionality, I'd like to
understand whether people think subtitle-only fragmented MP4 documents
with more than one fragment is something that is required for this to
get merged.

Also I have changed an existing test function, so I'd like a note
whether people think this is an OK change.

Jan
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^ permalink raw reply	[flat|nested] 10+ messages in thread

end of thread, other threads:[~2023-12-08 17:17 UTC | newest]

Thread overview: 10+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2023-09-15 13:16 [FFmpeg-devel] [PATCH v2 0/3] Initial support for fragmented TTML muxing Jan Ekström
2023-09-15 13:16 ` [FFmpeg-devel] [PATCH v2 1/3] tests/fate-run: add support for specifying the final encode muxer in `transcode` Jan Ekström
2023-09-15 13:16 ` [FFmpeg-devel] [PATCH v2 2/3] avcodec/avpacket: add functionality to prepend to AVPacketLists Jan Ekström
2023-09-15 13:17 ` [FFmpeg-devel] [PATCH v2 3/3] avformat/movenc: add support for fragmented TTML muxing Jan Ekström
2023-12-08 12:15   ` Andreas Rheinhardt
2023-12-08 15:36     ` Dennis Mungai
2023-12-08 17:05       ` Jan Ekström
2023-12-08 17:09         ` Jan Ekström
2023-12-08 17:17           ` Jan Ekström
2023-12-08 11:52 ` [FFmpeg-devel] [PATCH v2 0/3] Initial " Jan Ekström

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