From: "\"zhilizhao(赵志立)\"" <quinkblack@foxmail.com> To: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org> Subject: Re: [FFmpeg-devel] [PATCH v3 1/4] avformat/movenc: fix assert failure in get_cluster_duration() Date: Tue, 29 Mar 2022 12:59:04 +0800 Message-ID: <tencent_1B96359D80BE348D3EE3573D9CEAE12A5A09@qq.com> (raw) In-Reply-To: <tencent_11133EE3574F9D96E1D45AC235C9800E3409@qq.com> > On Mar 1, 2022, at 9:32 PM, zhilizhao(赵志立) <quinkblack@foxmail.com> wrote: > > >> On Feb 27, 2022, at 2:49 PM, Gyan Doshi <ffmpeg@gyani.pro> wrote: >> >> >> >> On 2022-02-27 12:04 pm, "zhilizhao(赵志立)" wrote: >>> Ping. >>> >>>> On Dec 31, 2021, at 7:36 PM, Zhao Zhili <quinkblack@foxmail.com> wrote: >>>> >>>> When editlist is disabled, the workaournd method of shift dts to >>>> zero and increase the first sample duration doesn't work if the >>>> timestamp is larger than mp4 spec restriction (e.g., sample_delta >>>> in stts entry). Further more, it triggers get_cluster_duration() >>>> assert failure. This patch will drop large offsets between >>>> multiple tracks. >>>> --- >>>> libavformat/movenc.c | 13 ++++++++++++- >>>> 1 file changed, 12 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/libavformat/movenc.c b/libavformat/movenc.c >>>> index 0f912dd012..f5bb785b01 100644 >>>> --- a/libavformat/movenc.c >>>> +++ b/libavformat/movenc.c >>>> @@ -5917,7 +5917,18 @@ int ff_mov_write_packet(AVFormatContext *s, AVPacket *pkt) >>>> * to signal the difference in starting time without an edit list. >>>> * Thus move the timestamp for this first sample to 0, increasing >>>> * its duration instead. */ >>>> - trk->cluster[trk->entry].dts = trk->start_dts = 0; >>>> + if (pkt->dts + pkt->duration <= INT32_MAX) { >>>> + trk->cluster[trk->entry].dts = trk->start_dts = 0; >>>> + } else { >>>> + /* Impossible to write a sample duration >= UINT32_MAX. >> >> As per 14496-12 (2005), sample_delta is stored as >> >> unsigned int(32) sample_delta; >> >> The only restriction is that no delta shall be zero except the last sample, which means UINT32_MAX is allowed. >> INT32_MAX had been set as max allowed delta in mov.c since inception. See my recent changes in mov.c correcting that. >> >> Will this patch break remuxing of files with large deltas? >> Let's not clamp if the spec does not call for it. > > Since get_cluster_duration() checks dts against INT_MAX, remove > the clamp at here can still trigger abort() after. > > ``` > av_assert0(next_dts <= INT_MAX); > > ``` > > The prototype of get_cluster_duration() which returns int needs > to be fixed, and a bunch of places. > > And then we can get regression issues: movenc.c output files with > delta larger than INT32_MAX can be dangerous, which is not the > case of mov.c demuxer. > > It’s a clever trick here, by using a large sample duration to > handle start time difference between multiple tracks. Since it’s > not a standard method like editlist, I think we can turn off the > strategy safely (FFmpeg abort before the patch, so it’s already > turned off in a hard way). > > What do you think? Ping. Another idea is return error instead of abort(). > >> >> Regards, >> Gyan >> _______________________________________________ >> ffmpeg-devel mailing list >> ffmpeg-devel@ffmpeg.org >> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel >> >> To unsubscribe, visit link above, or email >> ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe". > _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe".
prev parent reply other threads:[~2022-03-29 4:59 UTC|newest] Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-12-31 11:36 Zhao Zhili 2022-02-27 6:34 ` "zhilizhao(赵志立)" 2022-02-27 6:49 ` Gyan Doshi 2022-02-27 12:42 ` Paul B Mahol 2022-03-01 13:32 ` "zhilizhao(赵志立)" 2022-03-29 4:59 ` "zhilizhao(赵志立)" [this message]
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