[FFmpeg-devel] [PATCH v11 0/6] RCWT Closed Captions demuxer (v11)

[FFmpeg-devel] [PATCH v11 0/6] RCWT Closed Captions demuxer (v11)

[Marth64]

Since v9:
* Removes .bin extension association in demuxer and muxer
* Updates examples in documentation

Signed-off-by: Marth64 <marth64@proxyid.net>
-- 
2.34.1

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[FFmpeg-devel] [PATCH v11 1/6] avformat/subtitles: extend ff_subtitles_queue_insert() to support not yet available events

[Marth64]

If ff_subtitles_queue_insert() were given a NULL buffer
with 0 length, it would still attempt to grow the packet
or memcpy depending on if merge option is enabled.

In this commit, allow passing a NULL buffer with 0 length
without attempting to do such operations. This way, if a
subtitle demuxer happens to pass an empty cue or wants to
use av_get_packet() to read bytes, there are no unnecessary
operations on the packet after it is allocated.

Signed-off-by: Marth64 <marth64@proxyid.net>
---
 libavformat/subtitles.c | 23 +++++++++++++++--------
 libavformat/subtitles.h |  2 +-
 2 files changed, 16 insertions(+), 9 deletions(-)

diff --git a/libavformat/subtitles.c b/libavformat/subtitles.c
index d7723c497f..69e4df88a3 100644
--- a/libavformat/subtitles.c
+++ b/libavformat/subtitles.c
@@ -21,6 +21,7 @@
 #include "avformat.h"
 #include "subtitles.h"
 #include "avio_internal.h"
+#include "libavutil/avassert.h"
 #include "libavutil/avstring.h"
 #include "libavutil/mem.h"
 
@@ -112,15 +113,19 @@ AVPacket *ff_subtitles_queue_insert(FFDemuxSubtitlesQueue *q,
 {
     AVPacket **subs, *sub;
 
+    av_assert1(event || len == 0);
+
     if (merge && q->nb_subs > 0) {
         /* merge with previous event */
 
         int old_len;
         sub = q->subs[q->nb_subs - 1];
         old_len = sub->size;
-        if (av_grow_packet(sub, len) < 0)
-            return NULL;
-        memcpy(sub->data + old_len, event, len);
+        if (event) {
+            if (av_grow_packet(sub, len) < 0)
+                return NULL;
+            memcpy(sub->data + old_len, event, len);
+        }
     } else {
         /* new event */
 
@@ -134,14 +139,16 @@ AVPacket *ff_subtitles_queue_insert(FFDemuxSubtitlesQueue *q,
         sub = av_packet_alloc();
         if (!sub)
             return NULL;
-        if (av_new_packet(sub, len) < 0) {
-            av_packet_free(&sub);
-            return NULL;
+        if (event) {
+            if (av_new_packet(sub, len) < 0) {
+                av_packet_free(&sub);
+                return NULL;
+            }
+            memcpy(sub->data, event, len);
         }
-        subs[q->nb_subs++] = sub;
         sub->flags |= AV_PKT_FLAG_KEY;
         sub->pts = sub->dts = 0;
-        memcpy(sub->data, event, len);
+        subs[q->nb_subs++] = sub;
     }
     return sub;
 }
diff --git a/libavformat/subtitles.h b/libavformat/subtitles.h
index 88665663c5..ad6b96ca6a 100644
--- a/libavformat/subtitles.h
+++ b/libavformat/subtitles.h
@@ -112,7 +112,7 @@ typedef struct {
 /**
  * Insert a new subtitle event.
  *
- * @param event the subtitle line, may not be zero terminated
+ * @param event the subtitle line (not zero terminated) or NULL on not yet available event
  * @param len   the length of the event (in strlen() sense, so without '\0')
  * @param merge set to 1 if the current event should be concatenated with the
  *              previous one instead of adding a new entry, 0 otherwise
-- 
2.34.1

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[FFmpeg-devel] [PATCH v11 2/6] avformat/rcwtdec: add RCWT Closed Captions demuxer

[Marth64]

RCWT (Raw Captions With Time) is a format native to ccextractor,
a commonly used OSS tool for processing 608/708 Closed Captions (CC).
RCWT can be used to archive the original extracted CC bitstream.
The muxer was added in January 2024. In this commit, add the demuxer.

One can now demux RCWT files for rendering in ccaption_dec or interop
with ccextractor (which produces RCWT). Using the muxer/demuxer combo,
the CC bits can be kept for processing or rendering with either tool.
This can be an effective way to backup an original CC stream, including
format extensions like EIA-708 and overall original presentation.

Signed-off-by: Marth64 <marth64@proxyid.net>
---
 doc/demuxers.texi        |  30 ++++++++++
 libavformat/Makefile     |   1 +
 libavformat/allformats.c |   1 +
 libavformat/rcwtdec.c    | 122 +++++++++++++++++++++++++++++++++++++++
 4 files changed, 154 insertions(+)
 create mode 100644 libavformat/rcwtdec.c

diff --git a/doc/demuxers.texi b/doc/demuxers.texi
index b70f3a38d7..04293c4813 100644
--- a/doc/demuxers.texi
+++ b/doc/demuxers.texi
@@ -1038,6 +1038,36 @@ the command:
 ffplay -f rawvideo -pixel_format rgb24 -video_size 320x240 -framerate 10 input.raw
 @end example
 
+@anchor{rcwtdec}
+@section rcwt
+
+RCWT (Raw Captions With Time) is a format native to ccextractor, a commonly
+used open source tool for processing 608/708 Closed Captions (CC) sources.
+For more information on the format, see @ref{rcwtenc,,,ffmpeg-formats}.
+
+This demuxer implements the specification as of March 2024, which has
+been stable and unchanged since April 2014.
+
+@subsection Examples
+
+@itemize
+@item
+Render CC to ASS using the built-in decoder:
+@example
+ffmpeg -i CC.rcwt.bin CC.ass
+@end example
+Note that if your output appears to be empty, you may have to manually
+set the decoder's @option{data_field} option to pick the desired CC substream.
+
+@item
+Convert an RCWT backup to Scenarist (SCC) format:
+@example
+ffmpeg -i CC.rcwt.bin -c:s copy CC.scc
+@end example
+Note that the SCC format does not support all of the possible CC extensions
+that can be stored in RCWT (such as EIA-708).
+@end itemize
+
 @section sbg
 
 SBaGen script demuxer.
diff --git a/libavformat/Makefile b/libavformat/Makefile
index 44aa485029..5d77cba7f1 100644
--- a/libavformat/Makefile
+++ b/libavformat/Makefile
@@ -493,6 +493,7 @@ OBJS-$(CONFIG_QOA_DEMUXER)               += qoadec.o
 OBJS-$(CONFIG_R3D_DEMUXER)               += r3d.o
 OBJS-$(CONFIG_RAWVIDEO_DEMUXER)          += rawvideodec.o
 OBJS-$(CONFIG_RAWVIDEO_MUXER)            += rawenc.o
+OBJS-$(CONFIG_RCWT_DEMUXER)              += rcwtdec.o subtitles.o
 OBJS-$(CONFIG_RCWT_MUXER)                += rcwtenc.o subtitles.o
 OBJS-$(CONFIG_REALTEXT_DEMUXER)          += realtextdec.o subtitles.o
 OBJS-$(CONFIG_REDSPARK_DEMUXER)          += redspark.o
diff --git a/libavformat/allformats.c b/libavformat/allformats.c
index 9df42bb87a..ae925dcf60 100644
--- a/libavformat/allformats.c
+++ b/libavformat/allformats.c
@@ -391,6 +391,7 @@ extern const FFInputFormat  ff_qoa_demuxer;
 extern const FFInputFormat  ff_r3d_demuxer;
 extern const FFInputFormat  ff_rawvideo_demuxer;
 extern const FFOutputFormat ff_rawvideo_muxer;
+extern const FFInputFormat  ff_rcwt_demuxer;
 extern const FFOutputFormat ff_rcwt_muxer;
 extern const FFInputFormat  ff_realtext_demuxer;
 extern const FFInputFormat  ff_redspark_demuxer;
diff --git a/libavformat/rcwtdec.c b/libavformat/rcwtdec.c
new file mode 100644
index 0000000000..f6a007cbdb
--- /dev/null
+++ b/libavformat/rcwtdec.c
@@ -0,0 +1,122 @@
+/*
+ * RCWT (Raw Captions With Time) demuxer
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/*
+ * RCWT (Raw Captions With Time) is a format native to ccextractor, a commonly
+ * used open source tool for processing 608/708 Closed Captions (CC) sources.
+ *
+ * This demuxer implements the specification as of March 2024, which has
+ * been stable and unchanged since April 2014.
+ *
+ * A free specification of RCWT can be found here:
+ * @url{https://github.com/CCExtractor/ccextractor/blob/master/docs/BINARY_FILE_FORMAT.TXT}
+ */
+
+#include "avformat.h"
+#include "demux.h"
+#include "internal.h"
+#include "subtitles.h"
+#include "libavutil/intreadwrite.h"
+
+#define RCWT_HEADER_SIZE                    11
+
+typedef struct RCWTContext {
+    FFDemuxSubtitlesQueue q;
+} RCWTContext;
+
+static int rcwt_read_header(AVFormatContext *avf)
+{
+    RCWTContext *rcwt = avf->priv_data;
+
+    AVStream      *st;
+    uint8_t       header[RCWT_HEADER_SIZE];
+    int           ret;
+
+    /* read header */
+    ret = ffio_read_size(avf->pb, header, RCWT_HEADER_SIZE);
+    if (ret < 0)
+        return ret;
+
+    if (AV_RB16(header + 6) != 0x0001) {
+        av_log(avf, AV_LOG_ERROR, "RCWT format version is not compatible "
+                                  "(only version 0.001 is known)\n");
+        return AVERROR_INVALIDDATA;
+    }
+
+    av_log(avf, AV_LOG_DEBUG, "RCWT writer application: %02X version: %02x\n",
+                              header[3], header[5]);
+
+    /* setup stream */
+    st = avformat_new_stream(avf, NULL);
+    if (!st)
+        return AVERROR(ENOMEM);
+
+    st->codecpar->codec_type = AVMEDIA_TYPE_SUBTITLE;
+    st->codecpar->codec_id   = AV_CODEC_ID_EIA_608;
+
+    avpriv_set_pts_info(st, 64, 1, 1000);
+
+    /* demux */
+    while (!avio_feof(avf->pb)) {
+        AVPacket      *sub;
+        int64_t       cluster_pos       = avio_tell(avf->pb);
+        int64_t       cluster_pts       = avio_rl64(avf->pb);
+        int           cluster_nb_blocks = avio_rl16(avf->pb);
+
+        if (cluster_nb_blocks == 0)
+            continue;
+
+        sub = ff_subtitles_queue_insert(&rcwt->q, NULL, 0, 0);
+        if (!sub)
+            return AVERROR(ENOMEM);
+
+        ret = av_get_packet(avf->pb, sub, cluster_nb_blocks * 3);
+        if (ret < 0)
+            return ret;
+
+        sub->pos = cluster_pos;
+        sub->pts = cluster_pts;
+    }
+
+    ff_subtitles_queue_finalize(avf, &rcwt->q);
+
+    return 0;
+}
+
+static int rcwt_probe(const AVProbeData *p)
+{
+    return p->buf_size > RCWT_HEADER_SIZE   &&
+           AV_RB16(p->buf) == 0xCCCC        &&
+           AV_RB8(p->buf + 2) == 0xED       &&
+           AV_RB16(p->buf + 6) == 0x0001    ? 50 : 0;
+}
+
+const FFInputFormat ff_rcwt_demuxer = {
+    .p.name         = "rcwt",
+    .p.long_name    = NULL_IF_CONFIG_SMALL("RCWT (Raw Captions With Time)"),
+    .p.flags        = AVFMT_TS_DISCONT,
+    .priv_data_size = sizeof(RCWTContext),
+    .flags_internal = FF_INFMT_FLAG_INIT_CLEANUP,
+    .read_probe     = rcwt_probe,
+    .read_header    = rcwt_read_header,
+    .read_packet    = ff_subtitles_read_packet,
+    .read_seek2     = ff_subtitles_read_seek,
+    .read_close     = ff_subtitles_read_close
+};
-- 
2.34.1

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[FFmpeg-devel] [PATCH v11 3/6] avformat/rcwtenc: don't assume .bin extension

[Marth64]

Signed-off-by: Marth64 <marth64@proxyid.net>
---
 libavformat/rcwtenc.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/libavformat/rcwtenc.c b/libavformat/rcwtenc.c
index f2459ef1d3..ed613d45f5 100644
--- a/libavformat/rcwtenc.c
+++ b/libavformat/rcwtenc.c
@@ -159,7 +159,6 @@ static int rcwt_write_trailer(AVFormatContext *avf)
 const FFOutputFormat ff_rcwt_muxer = {
     .p.name             = "rcwt",
     .p.long_name        = NULL_IF_CONFIG_SMALL("RCWT (Raw Captions With Time)"),
-    .p.extensions       = "bin",
     .p.flags            = AVFMT_GLOBALHEADER | AVFMT_VARIABLE_FPS | AVFMT_TS_NONSTRICT,
     .p.video_codec      = AV_CODEC_ID_NONE,
     .p.audio_codec      = AV_CODEC_ID_NONE,
-- 
2.34.1

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[FFmpeg-devel] [PATCH v11 4/6] avformat/rcwtenc: remove repeated documentation

[Marth64]

The high level summary of RCWT can be delegated doc/muxers, which
makes it easier to maintain and more consistent with the documentation
of the demuxer.

Signed-off-by: Marth64 <marth64@proxyid.net>
---
 libavformat/rcwtenc.c | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/libavformat/rcwtenc.c b/libavformat/rcwtenc.c
index ed613d45f5..270154b701 100644
--- a/libavformat/rcwtenc.c
+++ b/libavformat/rcwtenc.c
@@ -21,11 +21,6 @@
 /*
  * RCWT (Raw Captions With Time) is a format native to ccextractor, a commonly
  * used open source tool for processing 608/708 Closed Captions (CC) sources.
- * It can be used to archive the original, raw CC bitstream and to produce
- * a source file for later CC processing or conversion. As a result,
- * it also allows for interopability with ccextractor for processing CC data
- * extracted via ffmpeg. The format is simple to parse and can be used
- * to retain all lines and variants of CC.
  *
  * This muxer implements the specification as of March 2024, which has
  * been stable and unchanged since April 2014.
-- 
2.34.1

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[FFmpeg-devel] [PATCH v11 5/6] doc/muxers: refresh the RCWT muxer's doc to be consistent with the demuxer

[Marth64]

Signed-off-by: Marth64 <marth64@proxyid.net>
---
 doc/muxers.texi | 29 +++++++++++++++++++----------
 1 file changed, 19 insertions(+), 10 deletions(-)

diff --git a/doc/muxers.texi b/doc/muxers.texi
index a10a8e216f..c960af1bdc 100644
--- a/doc/muxers.texi
+++ b/doc/muxers.texi
@@ -3038,19 +3038,18 @@ ogg files can be safely chained.
 
 @end table
 
-@anchor{rcwt}
+@anchor{rcwtenc}
 @section rcwt
 
-Raw Captions With Time (RCWT) is a format native to ccextractor, a commonly
-used open source tool for processing 608/708 closed caption (CC) sources.
-It can be used to archive the original, raw CC bitstream and to produce
-a source file for later CC processing or conversion. As a result,
-it also allows for interopability with ccextractor for processing CC data
-extracted via ffmpeg. The format is simple to parse and can be used
-to retain all lines and variants of CC.
+RCWT (Raw Captions With Time) is a format native to ccextractor, a commonly
+used open source tool for processing 608/708 Closed Captions (CC) sources.
+It can be used to archive the original extracted CC bitstream and to produce
+a source file for later processing or conversion. The format allows
+for interoperability between ccextractor and FFmpeg, is simple to parse,
+and can be used to create a backup of the CC presentation.
 
-This muxer implements the specification as of 2024-01-05, which has
-been stable and unchanged for 10 years as of this writing.
+This muxer implements the specification as of March 2024, which has
+been stable and unchanged since April 2014.
 
 This muxer will have some nuances from the way that ccextractor muxes RCWT.
 No compatibility issues when processing the output with ccextractor
@@ -3060,6 +3059,16 @@ and outputs will not be a bit-exact match.
 A free specification of RCWT can be found here:
 @url{https://github.com/CCExtractor/ccextractor/blob/master/docs/BINARY_FILE_FORMAT.TXT}
 
+@subsection Examples
+
+@itemize
+@item
+Extract Closed Captions to RCWT using lavfi:
+@example
+ffmpeg -f lavfi -i "movie=INPUT.mkv[out+subcc]" -map 0:s:0 -c:s copy -f rcwt CC.rcwt.bin
+@end example
+@end itemize
+
 @anchor{segment}
 @section segment, stream_segment, ssegment
 
-- 
2.34.1

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[FFmpeg-devel] [PATCH v11 6/6] doc/indevs: update CC extraction example to use RCWT muxer

[Marth64]

Signed-off-by: Marth64 <marth64@proxyid.net>
---
 doc/indevs.texi | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/doc/indevs.texi b/doc/indevs.texi
index d1b2bacf8b..734fc65752 100644
--- a/doc/indevs.texi
+++ b/doc/indevs.texi
@@ -1069,9 +1069,9 @@ ffplay -f lavfi "movie=test.avi[out0];amovie=test.wav[out1]"
 @end example
 
 @item
-Dump decoded frames to images and closed captions to a file (experimental):
+Dump decoded frames to images and Closed Captions to an RCWT backup:
 @example
-ffmpeg -f lavfi -i "movie=test.ts[out0+subcc]" -map v frame%08d.png -map s -c copy -f rawvideo subcc.bin
+ffmpeg -f lavfi -i "movie=test.ts[out0+subcc]" -map v frame%08d.png -map s -c copy -f rcwt subcc.bin
 @end example
 
 @end itemize
-- 
2.34.1

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Re: [FFmpeg-devel] [PATCH v11 0/6] RCWT Closed Captions demuxer (v11)

[Stefano Sabatini]

On date Tuesday 2024-04-02 00:24:52 -0500, Marth64 wrote:
> Since v9:
> * Removes .bin extension association in demuxer and muxer
> * Updates examples in documentation

Patchset applied, thanks.

I also added the missing Changelog next entrypoint and updated the
Changelog with the new entry while at it.
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Re: [FFmpeg-devel] [PATCH v11 0/6] RCWT Closed Captions demuxer (v11)

[Marth64]

Thank you Stefano & all who helped facilitate this through.
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