[FFmpeg-devel] [PATCH 0/1] avformat/demux: Fix accurate probing of durations in mpegts/ps

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* [FFmpeg-devel] [PATCH 0/1] avformat/demux: Fix accurate probing of durations in mpegts/ps
@ 2024-03-14 17:57 Nicolas Gaullier
  2024-03-14 17:57 ` [FFmpeg-devel] [PATCH 1/1] " Nicolas Gaullier
  0 siblings, 1 reply; 3+ messages in thread
From: Nicolas Gaullier @ 2024-03-14 17:57 UTC (permalink / raw)
  To: ffmpeg-devel; +Cc: Nicolas Gaullier

ff_read_packet() is more lightweight, but it leads to important issues
when looking for accurate durations.
As a side effect, the code looks also simpler with regular av_read_frame() calls.

1)
Updates in the fate tests do exhibit most of the results.

2)
See also more directly the case of an audio PES containing many frames:

>ffprobe tests/data/lavf/lavf.ts -select_streams a -show_entries stream=duration -of flat
Before patch:
  streams.stream.0.duration="0.757556"
After patch:
  streams.stream.0.duration="1.018778"

3)
Here is an additional (commonplace) sample to demonstrate the benefit for twofields-encoded video:
https://0x0.st/HFbm.ts (say h264-50i_mp2.ts)

>ffprobe h264-50i_mp2.ts -show_entries stream=duration -of flat
Before patch:
  streams.stream.0.duration="2.060000"
  streams.stream.1.duration="1.176000"
After patch:
  streams.stream.0.duration="2.080000"
  streams.stream.1.duration="1.200000"

Nicolas Gaullier (1):
  avformat/demux: Fix accurate probing of durations in mpegts/ps

 libavformat/demux.c                           |  30 +---
 tests/ref/fate/concat-demuxer-simple2-lavf-ts | 170 +++++++++---------
 tests/ref/fate/ts-opus-demux                  |   4 +-
 3 files changed, 93 insertions(+), 111 deletions(-)

-- 
2.30.2

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^ permalink raw reply	[flat|nested] 3+ messages in thread

* [FFmpeg-devel] [PATCH 1/1] avformat/demux: Fix accurate probing of durations in mpegts/ps
  2024-03-14 17:57 [FFmpeg-devel] [PATCH 0/1] avformat/demux: Fix accurate probing of durations in mpegts/ps Nicolas Gaullier
@ 2024-03-14 17:57 ` Nicolas Gaullier
  2024-03-14 22:41   ` Michael Niedermayer
  0 siblings, 1 reply; 3+ messages in thread
From: Nicolas Gaullier @ 2024-03-14 17:57 UTC (permalink / raw)
  To: ffmpeg-devel; +Cc: Nicolas Gaullier

Two issues affect accuracy of duration in estimate_timings_from_pts():
- pkt->duration typically reports the duration of a single audio frame,
whereas a pes often contain several audio frames
- for video, compute_frame_duration() use r_frame_rate which is not
reliable; typically, it is the duration of a single field for an
interlaced video using two field pictures.

Packet splitting/parsing is required to get accurate durations, so this
patch replaces ff_read_packet() calls by av_read_frame() calls.

Note that concatdec makes use of avformat_find_stream_info() to stitch
correctly the files, so it benefits from this patch (typically, overlap
is avoided).
e.g. in fate/concat-demuxer-simple2-lavf-ts: the input audio stream
duration is now longer than that of the video, which results in
concatdec joining on audio after the patch instead of joining on video
before that.

Signed-off-by: Nicolas Gaullier <nicolas.gaullier@cji.paris>
---
 libavformat/demux.c                           |  30 +---
 tests/ref/fate/concat-demuxer-simple2-lavf-ts | 170 +++++++++---------
 tests/ref/fate/ts-opus-demux                  |   4 +-
 3 files changed, 93 insertions(+), 111 deletions(-)

diff --git a/libavformat/demux.c b/libavformat/demux.c
index 4c50eb5568..7e75e7149c 100644
--- a/libavformat/demux.c
+++ b/libavformat/demux.c
@@ -1820,20 +1820,17 @@ static void estimate_timings_from_bit_rate(AVFormatContext *ic)
 #define DURATION_MAX_READ_SIZE 250000LL
 #define DURATION_MAX_RETRY 6
 
-/* only usable for MPEG-PS streams */
+/* only usable for MPEG-PS/TS streams */
 static void estimate_timings_from_pts(AVFormatContext *ic, int64_t old_offset)
 {
     FFFormatContext *const si = ffformatcontext(ic);
     AVPacket *const pkt = si->pkt;
-    int num, den, read_size, ret;
+    int read_size, ret;
     int found_duration = 0;
     int is_end;
     int64_t filesize, offset, duration;
     int retry = 0;
 
-    /* flush packet queue */
-    ff_flush_packet_queue(ic);
-
     for (unsigned i = 0; i < ic->nb_streams; i++) {
         AVStream *const st  = ic->streams[i];
         FFStream *const sti = ffstream(st);
@@ -1843,11 +1840,6 @@ static void estimate_timings_from_pts(AVFormatContext *ic, int64_t old_offset)
             st->codecpar->codec_type != AVMEDIA_TYPE_UNKNOWN)
             av_log(ic, AV_LOG_WARNING,
                    "start time for stream %d is not set in estimate_timings_from_pts\n", i);
-
-        if (sti->parser) {
-            av_parser_close(sti->parser);
-            sti->parser = NULL;
-        }
     }
 
     if (ic->skip_estimate_duration_from_pts) {
@@ -1865,6 +1857,7 @@ static void estimate_timings_from_pts(AVFormatContext *ic, int64_t old_offset)
         if (offset < 0)
             offset = 0;
 
+        ff_read_frame_flush(ic);
         avio_seek(ic->pb, offset, SEEK_SET);
         read_size = 0;
         for (;;) {
@@ -1874,7 +1867,7 @@ static void estimate_timings_from_pts(AVFormatContext *ic, int64_t old_offset)
                 break;
 
             do {
-                ret = ff_read_packet(ic, pkt);
+                ret = av_read_frame(ic, pkt);
             } while (ret == AVERROR(EAGAIN));
             if (ret != 0)
                 break;
@@ -1884,15 +1877,6 @@ static void estimate_timings_from_pts(AVFormatContext *ic, int64_t old_offset)
             if (pkt->pts != AV_NOPTS_VALUE &&
                 (st->start_time != AV_NOPTS_VALUE ||
                  sti->first_dts != AV_NOPTS_VALUE)) {
-                if (pkt->duration == 0) {
-                    compute_frame_duration(ic, &num, &den, st, sti->parser, pkt);
-                    if (den && num) {
-                        pkt->duration = av_rescale_rnd(1,
-                                           num * (int64_t) st->time_base.den,
-                                           den * (int64_t) st->time_base.num,
-                                           AV_ROUND_DOWN);
-                    }
-                }
                 duration = pkt->pts + pkt->duration;
                 found_duration = 1;
                 if (st->start_time != AV_NOPTS_VALUE)
@@ -1948,15 +1932,13 @@ skip_duration_calc:
     fill_all_stream_timings(ic);
 
     avio_seek(ic->pb, old_offset, SEEK_SET);
+
+    ff_read_frame_flush(ic);
     for (unsigned i = 0; i < ic->nb_streams; i++) {
         AVStream *const st  = ic->streams[i];
         FFStream *const sti = ffstream(st);
 
         sti->cur_dts     = sti->first_dts;
-        sti->last_IP_pts = AV_NOPTS_VALUE;
-        sti->last_dts_for_order_check = AV_NOPTS_VALUE;
-        for (int j = 0; j < MAX_REORDER_DELAY + 1; j++)
-            sti->pts_buffer[j] = AV_NOPTS_VALUE;
     }
 }
 
diff --git a/tests/ref/fate/concat-demuxer-simple2-lavf-ts b/tests/ref/fate/concat-demuxer-simple2-lavf-ts
index 548cab01c6..86e5e6670f 100644
--- a/tests/ref/fate/concat-demuxer-simple2-lavf-ts
+++ b/tests/ref/fate/concat-demuxer-simple2-lavf-ts
@@ -62,90 +62,90 @@ audio|0|86988|0.966533|86988|0.966533|2351|0.026122|209|N/A|K__
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+audio|0|126956|1.410622|126956|1.410622|2351|0.026122|209|N/A|K__
+audio|0|129307|1.436744|129307|1.436744|2351|0.026122|209|N/A|K__
+audio|0|131658|1.462867|131658|1.462867|2351|0.026122|209|N/A|K__
+audio|0|134009|1.488989|134009|1.488989|2351|0.026122|209|N/A|K__
+audio|0|136360|1.515111|136360|1.515111|2351|0.026122|209|N/A|K__
+audio|0|138711|1.541233|138711|1.541233|2351|0.026122|209|N/A|K__
+audio|0|141062|1.567356|141062|1.567356|2351|0.026122|209|N/A|K__
+audio|0|143413|1.593478|143413|1.593478|2351|0.026122|209|N/A|K__
+audio|0|145764|1.619600|145764|1.619600|2351|0.026122|209|N/A|K__
+audio|0|148115|1.645722|148115|1.645722|2351|0.026122|209|N/A|K__
+audio|0|150466|1.671844|150466|1.671844|2351|0.026122|209|N/A|K__
+audio|0|152817|1.697967|152817|1.697967|2351|0.026122|209|N/A|K__
+audio|0|155168|1.724089|155168|1.724089|2351|0.026122|209|N/A|K__
+video|1|157472|1.749689|153872|1.709689|3600|0.040000|13836|281624|___|MPEGTS Stream ID|224
+video|1|161072|1.789689|157472|1.749689|3600|0.040000|12163|295912|___|MPEGTS Stream ID|224
+video|1|164672|1.829689|161072|1.789689|3600|0.040000|12692|311516|___|MPEGTS Stream ID|224
+video|1|168272|1.869689|164672|1.829689|3600|0.040000|10824|325052|___|MPEGTS Stream ID|224
+video|1|171872|1.909689|168272|1.869689|3600|0.040000|11286|336144|___|MPEGTS Stream ID|224
+audio|0|157519|1.750211|157519|1.750211|2351|0.026122|209|386716|K__|MPEGTS Stream ID|192
+audio|0|159870|1.776333|159870|1.776333|2351|0.026122|209|N/A|K__
+audio|0|162221|1.802456|162221|1.802456|2351|0.026122|209|N/A|K__
+audio|0|164572|1.828578|164572|1.828578|2351|0.026122|209|N/A|K__
+audio|0|166923|1.854700|166923|1.854700|2351|0.026122|209|N/A|K__
+audio|0|169274|1.880822|169274|1.880822|2351|0.026122|209|N/A|K__
+audio|0|171625|1.906944|171625|1.906944|2351|0.026122|209|N/A|K__
+audio|0|173976|1.933067|173976|1.933067|2351|0.026122|209|N/A|K__
+audio|0|176327|1.959189|176327|1.959189|2351|0.026122|209|N/A|K__
+audio|0|178678|1.985311|178678|1.985311|2351|0.026122|209|N/A|K__
+audio|0|181029|2.011433|181029|2.011433|2351|0.026122|209|N/A|K__
+video|1|175472|1.949689|171872|1.909689|3600|0.040000|12678|347800|___|MPEGTS Stream ID|224
+video|1|179072|1.989689|175472|1.949689|3600|0.040000|24711|361336|K__
+video|1|140290|1.558778|136690|1.518778|3600|0.040000|12692|311516|___|MPEGTS Stream ID|224
+video|1|143890|1.598778|140290|1.558778|3600|0.040000|10824|325052|___|MPEGTS Stream ID|224
+video|1|147490|1.638778|143890|1.598778|3600|0.040000|11286|336144|___|MPEGTS Stream ID|224
+audio|0|133137|1.479300|133137|1.479300|2351|0.026122|209|386716|K__|MPEGTS Stream ID|192
+audio|0|135488|1.505422|135488|1.505422|2351|0.026122|209|N/A|K__
+audio|0|137839|1.531544|137839|1.531544|2351|0.026122|209|N/A|K__
+audio|0|140190|1.557667|140190|1.557667|2351|0.026122|209|N/A|K__
+audio|0|142541|1.583789|142541|1.583789|2351|0.026122|209|N/A|K__
+audio|0|144892|1.609911|144892|1.609911|2351|0.026122|209|N/A|K__
+audio|0|147243|1.636033|147243|1.636033|2351|0.026122|209|N/A|K__
+audio|0|149594|1.662156|149594|1.662156|2351|0.026122|209|N/A|K__
+audio|0|151945|1.688278|151945|1.688278|2351|0.026122|209|N/A|K__
+audio|0|154296|1.714400|154296|1.714400|2351|0.026122|209|N/A|K__
+audio|0|156647|1.740522|156647|1.740522|2351|0.026122|209|N/A|K__
+video|1|151090|1.678778|147490|1.638778|3600|0.040000|12678|347800|___|MPEGTS Stream ID|224
+video|1|154690|1.718778|151090|1.678778|3600|0.040000|24711|361336|K__
+video|1|162598|1.806644|158998|1.766644|3600|0.040000|12135|155852|___|MPEGTS Stream ID|224
+video|1|166198|1.846644|162598|1.806644|3600|0.040000|12282|168448|___|MPEGTS Stream ID|224
+video|1|169798|1.886644|166198|1.846644|3600|0.040000|24786|181420|K__|MPEGTS Stream ID|224
+video|1|173398|1.926644|169798|1.886644|3600|0.040000|17440|206988|___|MPEGTS Stream ID|224
+video|1|176998|1.966644|173398|1.926644|3600|0.040000|15019|224848|___|MPEGTS Stream ID|224
 0|mp2|unknown|audio|[3][0][0][0]|0x0003|s16p|44100|1|mono|0|0|N/A|0/0|0/0|1/90000|0|0.000000|N/A|N/A|64000|N/A|N/A|N/A|N/A|89|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|this is stream 0
 1|mpeg2video|4|video|[2][0][0][0]|0x0002|352|288|0|0|0|0|1|1:1|11:9|yuv420p|8|tv|unknown|unknown|unknown|left|progressive|1|N/A|25/1|25/1|1/90000|N/A|N/A|N/A|N/A|N/A|N/A|N/A|N/A|N/A|60|22|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|this is stream 1|CPB properties|0|0|0|49152|-1
diff --git a/tests/ref/fate/ts-opus-demux b/tests/ref/fate/ts-opus-demux
index 961b7f2a92..62d1856ae0 100644
--- a/tests/ref/fate/ts-opus-demux
+++ b/tests/ref/fate/ts-opus-demux
@@ -510,5 +510,5 @@ packet|codec_type=audio|stream_index=0|pts=914400|pts_time=10.160000|dts=914400|
 packet|codec_type=audio|stream_index=0|pts=916200|pts_time=10.180000|dts=916200|dts_time=10.180000|duration=1800|duration_time=0.020000|size=760|pos=508728|flags=K__|data_hash=CRC32:fdf0ce4a|side_datum/mpegts_stream_id:side_data_type=MPEGTS Stream ID|side_datum/mpegts_stream_id:id=189
 packet|codec_type=audio|stream_index=0|pts=918000|pts_time=10.200000|dts=918000|dts_time=10.200000|duration=1800|duration_time=0.020000|size=761|pos=510044|flags=K__|data_hash=CRC32:75113c11|side_datum/mpegts_stream_id:side_data_type=MPEGTS Stream ID|side_datum/mpegts_stream_id:id=189
 packet|codec_type=audio|stream_index=0|pts=919800|pts_time=10.220000|dts=919800|dts_time=10.220000|duration=1800|duration_time=0.020000|size=759|pos=510984|flags=K__|data_hash=CRC32:59fc266f|side_datum/mpegts_stream_id:side_data_type=MPEGTS Stream ID|side_datum/mpegts_stream_id:id=189
-stream|index=0|codec_name=opus|profile=unknown|codec_type=audio|codec_tag_string=Opus|codec_tag=0x7375704f|sample_fmt=fltp|sample_rate=48000|channels=8|channel_layout=7.1|bits_per_sample=0|initial_padding=0|ts_id=51338|ts_packetsize=188|id=0x44|r_frame_rate=0/0|avg_frame_rate=0/0|time_base=1/90000|start_pts=0|start_time=0.000000|duration_ts=919800|duration=10.220000|bit_rate=N/A|max_bit_rate=N/A|bits_per_raw_sample=N/A|nb_frames=N/A|nb_read_frames=N/A|nb_read_packets=512|extradata_size=29|extradata_hash=CRC32:6d6089a7|disposition:default=0|disposition:dub=0|disposition:original=0|disposition:comment=0|disposition:lyrics=0|disposition:karaoke=0|disposition:forced=0|disposition:hearing_impaired=0|disposition:visual_impaired=0|disposition:clean_effects=0|disposition:attached_pic=0|disposition:timed_thumbnails=0|disposition:non_diegetic=0|disposition:captions=0|disposition:descriptions=0|disposition:metadata=0|disposition:dependent=0|disposition:still_image=0
-format|filename=test-8-7.1.opus-small.ts|nb_streams=1|nb_programs=1|nb_stream_groups=0|format_name=mpegts|start_time=0.000000|duration=10.220000|size=512000|bit_rate=400782|probe_score=50
+stream|index=0|codec_name=opus|profile=unknown|codec_type=audio|codec_tag_string=Opus|codec_tag=0x7375704f|sample_fmt=fltp|sample_rate=48000|channels=8|channel_layout=7.1|bits_per_sample=0|initial_padding=0|ts_id=51338|ts_packetsize=188|id=0x44|r_frame_rate=0/0|avg_frame_rate=0/0|time_base=1/90000|start_pts=0|start_time=0.000000|duration_ts=921600|duration=10.240000|bit_rate=N/A|max_bit_rate=N/A|bits_per_raw_sample=N/A|nb_frames=N/A|nb_read_frames=N/A|nb_read_packets=512|extradata_size=29|extradata_hash=CRC32:6d6089a7|disposition:default=0|disposition:dub=0|disposition:original=0|disposition:comment=0|disposition:lyrics=0|disposition:karaoke=0|disposition:forced=0|disposition:hearing_impaired=0|disposition:visual_impaired=0|disposition:clean_effects=0|disposition:attached_pic=0|disposition:timed_thumbnails=0|disposition:non_diegetic=0|disposition:captions=0|disposition:descriptions=0|disposition:metadata=0|disposition:dependent=0|disposition:still_image=0
+format|filename=test-8-7.1.opus-small.ts|nb_streams=1|nb_programs=1|nb_stream_groups=0|format_name=mpegts|start_time=0.000000|duration=10.240000|size=512000|bit_rate=400000|probe_score=50
-- 
2.30.2

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^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [FFmpeg-devel] [PATCH 1/1] avformat/demux: Fix accurate probing of durations in mpegts/ps
  2024-03-14 17:57 ` [FFmpeg-devel] [PATCH 1/1] " Nicolas Gaullier
@ 2024-03-14 22:41   ` Michael Niedermayer
  0 siblings, 0 replies; 3+ messages in thread
From: Michael Niedermayer @ 2024-03-14 22:41 UTC (permalink / raw)
  To: FFmpeg development discussions and patches


[-- Attachment #1.1: Type: text/plain, Size: 2269 bytes --]

On Thu, Mar 14, 2024 at 06:57:39PM +0100, Nicolas Gaullier wrote:
> Two issues affect accuracy of duration in estimate_timings_from_pts():
> - pkt->duration typically reports the duration of a single audio frame,
> whereas a pes often contain several audio frames
> - for video, compute_frame_duration() use r_frame_rate which is not
> reliable; typically, it is the duration of a single field for an
> interlaced video using two field pictures.
> 
> Packet splitting/parsing is required to get accurate durations, so this
> patch replaces ff_read_packet() calls by av_read_frame() calls.
> 
> Note that concatdec makes use of avformat_find_stream_info() to stitch
> correctly the files, so it benefits from this patch (typically, overlap
> is avoided).
> e.g. in fate/concat-demuxer-simple2-lavf-ts: the input audio stream
> duration is now longer than that of the video, which results in
> concatdec joining on audio after the patch instead of joining on video
> before that.
> 
> Signed-off-by: Nicolas Gaullier <nicolas.gaullier@cji.paris>
> ---
>  libavformat/demux.c                           |  30 +---
>  tests/ref/fate/concat-demuxer-simple2-lavf-ts | 170 +++++++++---------
>  tests/ref/fate/ts-opus-demux                  |   4 +-
>  3 files changed, 93 insertions(+), 111 deletions(-)

for some reason this seems to loose a resolution of some subtitle stream when probing:

make -j32 && ./ffprobe -v 99 -analyzeduration 2G -probesize 2G -i tickets/2471/part.ts 2>&1 | grep dvb_teletext
  Stream #0:2[0x240](eng), 1020, 1/90000: Subtitle: dvb_teletext (libzvbi_teletextdec) ([6][0][0][0] / 0x0006), 492x250
  Stream #0:4[0x247](eng), 1902, 1/90000: Subtitle: dvb_teletext (libzvbi_teletextdec) ([6][0][0][0] / 0x0006), 492x250
vs.
  Stream #0:2[0x240](eng), 1020, 1/90000: Subtitle: dvb_teletext (libzvbi_teletextdec) ([6][0][0][0] / 0x0006), 492x250
  Stream #0:4[0x247](eng), 1902, 1/90000: Subtitle: dvb_teletext (libzvbi_teletextdec) ([6][0][0][0] / 0x0006)

ive not looked at this so i have no idea this is a bug, just wanted to report it

thx

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I have often repented speaking, but never of holding my tongue.
-- Xenocrates

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^ permalink raw reply	[flat|nested] 3+ messages in thread

end of thread, other threads:[~2024-03-14 22:41 UTC | newest]

Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2024-03-14 17:57 [FFmpeg-devel] [PATCH 0/1] avformat/demux: Fix accurate probing of durations in mpegts/ps Nicolas Gaullier
2024-03-14 17:57 ` [FFmpeg-devel] [PATCH 1/1] " Nicolas Gaullier
2024-03-14 22:41   ` Michael Niedermayer

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