[FFmpeg-devel] [PATCH] ffmpeg: apply discontinuity adjustment per-stream
Gyan Doshi
ffmpeg at gyani.pro
Tue Jan 10 05:49:11 EET 2023
On 2023-01-07 09:50 am, Gyan Doshi wrote:
>
>
> On 2023-01-03 03:52 pm, Gyan Doshi wrote:
>> At present, the offset for discontinuity adjustment is applied
>> per-file but
>> the check for discontinuity is intra-stream so the same discontinuity
>> when
>> seen in multiple streams with copyts, leads to compounded adjustment
>> of the
>> discontinuity offset. This introduces gaps in streams, leading to
>> loss of sync
>> or even de facto loss of stream.
>>
>> The ts_offset_discont parameter is transferred to InputStream and
>> adjusted
>> based on intra-stream gaps.
>
> Comments?
Plan to push in 48h.
Regards,
Gyan
>
>> ---
>> Here's a simulated example to demonstrate the issue:
>> 1) generate input
>> ffmpeg -f lavfi -i nullsrc=s=32x32:r=1,format=gray -f lavfi -i
>> anullsrc=cl=mono:r=8000 -c:v libx264 -preset superfast -bf 0 -crf 50
>> -c:a aac -b:a 64k -muxpreload 0 -muxdelay 0 -output_ts_offset 95000
>> -t 100000 src-100000s.ts
>>
>> 2) demo
>> ffmpeg -copyts -i "src-100000.ts" -vf "showinfo=checksum=0" -af
>> "ashowinfo" -f null - -report
>>
>> ==Before patch==
>>
>> timestamp discontinuity for stream #0:1 (id=257, type=audio):
>> -95443717689, new offset= 95443717689
>> timestamp discontinuity for stream #0:0 (id=256, type=video):
>> -95443717689, new offset= 190887435378
>>
>> [Parsed_ashowinfo_0 @ 000002700af98800] n:0 pts:759998976
>> pts_time:94999.9
>> [Parsed_ashowinfo_0 @ 000002700af98800] n:1 pts:760000000 pts_time:95000
>> ...
>> [Parsed_ashowinfo_0 @ 000002700af98800] n:745202 pts:1523085824
>> pts_time:190386
>> [Parsed_ashowinfo_0 @ 000002700af98800] n:745203 pts:1523086848
>> pts_time:190386
>> [Parsed_ashowinfo_0 @ 000002700af98800] n:745204 pts:2286637614
>> pts_time:285830
>> [Parsed_ashowinfo_0 @ 000002700af98800] n:745205 pts:2286638638
>> pts_time:285830
>>
>>
>> [Parsed_showinfo_0 @ 000002700ec34700] n: 0 pts:8550000000
>> pts_time:95000
>> [Parsed_showinfo_0 @ 000002700ec34700] n: 1 pts:8550090000
>> pts_time:95001
>> ...
>> [Parsed_showinfo_0 @ 000002700ec34700] n:95380 pts:17134200000
>> pts_time:190380
>> [Parsed_showinfo_0 @ 000002700ec34700] n:95381 pts:17134290000
>> pts_time:190381
>> [Parsed_showinfo_0 @ 000002700ec34700] n:95382 pts:25724314592
>> pts_time:285826
>> [Parsed_showinfo_0 @ 000002700ec34700] n:95383 pts:25724404592
>> pts_time:285827
>>
>> ==After patch==
>>
>> timestamp discontinuity for stream #0:1 (id=257, type=audio):
>> -95443717689, new stream offset= 95443717689
>> timestamp discontinuity for stream #0:0 (id=256, type=video):
>> -95443717689, new stream offset= 95443717689
>>
>> [Parsed_ashowinfo_0 @ 0000023c773c8880] n:0 pts:759998976
>> pts_time:94999.9
>> [Parsed_ashowinfo_0 @ 0000023c773c8880] n:1 pts:760000000 pts_time:95000
>> ...
>> [Parsed_ashowinfo_0 @ 0000023c773c8880] n:745202 pts:1523085824
>> pts_time:190386
>> [Parsed_ashowinfo_0 @ 0000023c773c8880] n:745203 pts:1523086848
>> pts_time:190386
>> [Parsed_ashowinfo_0 @ 0000023c773c8880] n:745204 pts:1523087872
>> pts_time:190386
>> [Parsed_ashowinfo_0 @ 0000023c773c8880] n:745205 pts:1523088896
>> pts_time:190386
>>
>>
>> [Parsed_showinfo_0 @ 0000023c795d07c0] n: 0 pts:8550000000
>> pts_time:95000
>> [Parsed_showinfo_0 @ 0000023c795d07c0] n: 1 pts:8550090000
>> pts_time:95001
>> ...
>> [Parsed_showinfo_0 @ 0000023c795d07c0] n:95380 pts:17134200000
>> pts_time:190380
>> [Parsed_showinfo_0 @ 0000023c795d07c0] n:95381 pts:17134290000
>> pts_time:190381
>> [Parsed_showinfo_0 @ 0000023c795d07c0] n:95382 pts:17134380000
>> pts_time:190382
>> [Parsed_showinfo_0 @ 0000023c795d07c0] n:95383 pts:17134470000
>> pts_time:190383
>>
>>
>>
>> fftools/ffmpeg.c | 12 ++++++------
>> fftools/ffmpeg.h | 8 ++++----
>> 2 files changed, 10 insertions(+), 10 deletions(-)
>>
>> diff --git a/fftools/ffmpeg.c b/fftools/ffmpeg.c
>> index 881d6f0af2..b967055059 100644
>> --- a/fftools/ffmpeg.c
>> +++ b/fftools/ffmpeg.c
>> @@ -3418,13 +3418,13 @@ static void ts_discontinuity_detect(InputFile
>> *ifile, InputStream *ist,
>> if (fmt_is_discont) {
>> if (FFABS(delta) > 1LL * dts_delta_threshold *
>> AV_TIME_BASE ||
>> pkt_dts + AV_TIME_BASE/10 < FFMAX(ist->pts,
>> ist->dts)) {
>> - ifile->ts_offset_discont -= delta;
>> + ist->ts_offset_discont -= delta;
>> av_log(NULL, AV_LOG_DEBUG,
>> "timestamp discontinuity for stream #%d:%d "
>> - "(id=%d, type=%s): %"PRId64", new offset=
>> %"PRId64"\n",
>> + "(id=%d, type=%s): %"PRId64", new stream
>> offset= %"PRId64"\n",
>> ist->file_index, ist->st->index, ist->st->id,
>> av_get_media_type_string(ist->par->codec_type),
>> - delta, ifile->ts_offset_discont);
>> + delta, ist->ts_offset_discont);
>> pkt->dts -= av_rescale_q(delta, AV_TIME_BASE_Q,
>> ist->st->time_base);
>> if (pkt->pts != AV_NOPTS_VALUE)
>> pkt->pts -= av_rescale_q(delta, AV_TIME_BASE_Q,
>> ist->st->time_base);
>> @@ -3447,10 +3447,10 @@ static void ts_discontinuity_detect(InputFile
>> *ifile, InputStream *ist,
>> fmt_is_discont && ifile->last_ts != AV_NOPTS_VALUE) {
>> int64_t delta = pkt_dts - ifile->last_ts;
>> if (FFABS(delta) > 1LL * dts_delta_threshold * AV_TIME_BASE) {
>> - ifile->ts_offset_discont -= delta;
>> + ist->ts_offset_discont -= delta;
>> av_log(NULL, AV_LOG_DEBUG,
>> "Inter stream timestamp discontinuity %"PRId64",
>> new offset= %"PRId64"\n",
>> - delta, ifile->ts_offset_discont);
>> + delta, ist->ts_offset_discont);
>> pkt->dts -= av_rescale_q(delta, AV_TIME_BASE_Q,
>> ist->st->time_base);
>> if (pkt->pts != AV_NOPTS_VALUE)
>> pkt->pts -= av_rescale_q(delta, AV_TIME_BASE_Q,
>> ist->st->time_base);
>> @@ -3463,7 +3463,7 @@ static void ts_discontinuity_detect(InputFile
>> *ifile, InputStream *ist,
>> static void ts_discontinuity_process(InputFile *ifile, InputStream
>> *ist,
>> AVPacket *pkt)
>> {
>> - int64_t offset = av_rescale_q(ifile->ts_offset_discont,
>> AV_TIME_BASE_Q,
>> + int64_t offset = av_rescale_q(ist->ts_offset_discont,
>> AV_TIME_BASE_Q,
>> ist->st->time_base);
>> // apply previously-detected timestamp-discontinuity offset
>> diff --git a/fftools/ffmpeg.h b/fftools/ffmpeg.h
>> index 5527dbe49b..d7bba8a190 100644
>> --- a/fftools/ffmpeg.h
>> +++ b/fftools/ffmpeg.h
>> @@ -352,6 +352,10 @@ typedef struct InputStream {
>> int64_t next_pts; ///< synthetic pts for the next decode
>> frame (in AV_TIME_BASE units)
>> int64_t pts; ///< current pts of the decoded frame
>> (in AV_TIME_BASE units)
>> int wrap_correction_done;
>> + /**
>> + * Extra timestamp offset added by discontinuity handling.
>> + */
>> + int64_t ts_offset_discont;
>> // the value of AVCodecParserContext.repeat_pict from the
>> AVStream parser
>> // for the last packet returned from ifile_get_packet()
>> @@ -444,10 +448,6 @@ typedef struct InputFile {
>> */
>> int64_t start_time_effective;
>> int64_t ts_offset;
>> - /**
>> - * Extra timestamp offset added by discontinuity handling.
>> - */
>> - int64_t ts_offset_discont;
>> int64_t last_ts;
>> int64_t start_time; /* user-specified start time in
>> AV_TIME_BASE or AV_NOPTS_VALUE */
>> int64_t recording_time;
>
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