[FFmpeg-devel] [PATCH] mov.c: allow reading fragment start dts/pts from fragmented mp4
Michael Niedermayer
michaelni at gmx.at
Mon Oct 13 12:36:30 CEST 2014
On Mon, Oct 13, 2014 at 08:54:31AM +0300, Mika Raento wrote:
> On 11 October 2014 23:02, Michael Niedermayer <michaelni at gmx.at> wrote:
> > On Sat, Oct 11, 2014 at 08:38:14PM +0300, Mika Raento wrote:
> >> On 11 October 2014 20:20, Michael Niedermayer <michaelni at gmx.at> wrote:
> >> > On Sat, Oct 11, 2014 at 06:43:48PM +0300, Mika Raento wrote:
> >> >> This introduces a new option to the mov demuxer: -use_mfra_for
> >> >> (pts|dts). When it's given and moofs and a MFRA are present, the MFRA's
> >> >> TFRAs are read for fragment start times.
> >> >>
> >> >> Unfortunately some programs that produce fragmented mp4s use the TFRA
> >> >> time field for dts and some for pts. There is no realistic way to detect
> >> >> which is the case, hence the responsibility is punted onto the user.
> >> >> This also means that no behavioural change is enabled by default - you
> >> >> must pass either dts or pts for anything to happen.
> >> >>
> >> >> Without this change, timestamps for some discontinuous fragmented mp4 are
> >> >> wrong, and cause audio/video desync and are not usable for generating
> >> >> HLS.
> >> >> ---
> >> > [...]
> >> >> @@ -3943,6 +4111,15 @@ static const AVOption options[] = {
> >> >> 0, 1, AV_OPT_FLAG_VIDEO_PARAM|AV_OPT_FLAG_DECODING_PARAM},
> >> >> {"ignore_editlist", "", offsetof(MOVContext, ignore_editlist), FF_OPT_TYPE_INT, {.i64 = 0},
> >> >> 0, 1, AV_OPT_FLAG_VIDEO_PARAM|AV_OPT_FLAG_DECODING_PARAM},
> >> >> + {"use_mfra_for",
> >> >> + "use mfra for fragment timestamps",
> >> >> + offsetof(MOVContext, use_mfra_for), FF_OPT_TYPE_INT, {.i64 = 0},
> >> >> + 0, FF_MOV_FLAG_MFRA_PTS, AV_OPT_FLAG_VIDEO_PARAM|AV_OPT_FLAG_DECODING_PARAM,
> >> >> + "use_mfra_for"},
> >> >
> >> > maybe a FF_MOV_FLAG_MFRA_AUTO which is set by default could be used to
> >> > guess based on some encoder/muxer identification what to do.
> >> >
> >> > do the files which need this option have something that idenifies
> >> > them? like in metadata, compatible brands or other?
> >> > and can you share a file/testcase which needs this patch ?
> >>
> >> I can share a file privately (copyrighted). I do not have a reduced
> >> test case. Let me know if you think that's helpful.
> >
> > dunno, might be usefull
> >
> >
> >>
> >> The files come from a commercial packager that is getting
> >> discontinuous input from a commercial transcoder. My understanding is
> >> that, the timestamp issue comes from the packager, rather than the
> >> transcoder. The underlying software in the packager is Code-shop's
> >> Unified Streaming, but it's been fed from proprietary software.
> >>
> >> This is what ffprobe says, it's not very specific:
> >>
> >> (multiprofile-streamers)mikie at universe:~/devel/multiprofile-streamers$
> >> ffprobe -i ../multiprofile-fixer/hls-disco/50603088.ismv
> >> ffprobe version N-66765-g67d95df Copyright (c) 2007-2014 the FFmpeg developers
> >> built on Oct 11 2014 18:42:41 with Apple LLVM version 6.0
> >> (clang-600.0.51) (based on LLVM 3.5svn)
> >> configuration: --prefix=/usr/local/Cellar/ffmpeg/HEAD
> >> --enable-shared --enable-pthreads --enable-gpl --enable-version3
> >> --enable-nonfree --enable-hardcoded-tables --enable-avresample
> >> --enable-vda --cc=clang --host-cflags= --host-ldflags=
> >> --enable-libx264 --enable-libfaac --enable-libmp3lame --enable-libxvid
> >> --enable-debug --disable-stripping --enable-libass
> >> libavutil 54. 10.100 / 54. 10.100
> >> libavcodec 56. 4.101 / 56. 4.101
> >> libavformat 56. 9.100 / 56. 9.100
> >> libavdevice 56. 1.100 / 56. 1.100
> >> libavfilter 5. 1.103 / 5. 1.103
> >> libavresample 2. 1. 0 / 2. 1. 0
> >> libswscale 3. 1.100 / 3. 1.100
> >> libswresample 1. 1.100 / 1. 1.100
> >> libpostproc 53. 1.100 / 53. 1.100
> >> Input #0, mov,mp4,m4a,3gp,3g2,mj2, from
> >> '../multiprofile-fixer/hls-disco/50603088.ismv':
> >> Metadata:
> >> major_brand : isom
> >> minor_version : 1
> >> compatible_brands: isomiso2
> >> Duration: 02:17:00.14, start: 0.000000, bitrate: 4411 kb/s
> >> Stream #0:0(mul): Audio: aac (mp4a / 0x6134706D), 48000 Hz,
> >> stereo, fltp, 124 kb/s (default)
> >> Metadata:
> >> handler_name : Sound Handler
> >> Stream #0:1(mul): Audio: aac (mp4a / 0x6134706D), 48000 Hz,
> >> stereo, fltp, 29 kb/s (default)
> >> Metadata:
> >> handler_name : Sound Handler
> >> Stream #0:2(und): Video: h264 (Main) (avc1 / 0x31637661),
> >> yuv420p(tv, bt470bg), 480x270 [SAR 1:1 DAR 16:9], 597 kb/s, 25 fps, 25
> >> tbr, 10000k tbn, 50 tbc (default)
> >> Metadata:
> >> handler_name : Video Handler
> >> encoder : AVC Coding
> >> Stream #0:3(und): Video: h264 (Main) (avc1 / 0x31637661),
> >> yuv420p(tv, bt470bg), 640x360 [SAR 1:1 DAR 16:9], 1195 kb/s, 25 fps,
> >> 25 tbr, 10000k tbn, 50 tbc (default)
> >> Metadata:
> >> handler_name : Video Handler
> >> encoder : AVC Coding
> >> Stream #0:4(und): Video: h264 (High) (avc1 / 0x31637661),
> >> yuv420p(tv, bt470bg), 768x432 [SAR 1:1 DAR 16:9], 2487 kb/s, 25 fps,
> >> 25 tbr, 10000k tbn, 50 tbc (default)
> >> Metadata:
> >> handler_name : Video Handler
> >> encoder : AVC Coding
> >>
> >>
> >> >
> >> > Also ISO/IEC 14496-12:2008(E) seems to say this:
> >> > This box provides only a hint as to where random access points are; the movie fragments themselves are
> >> > definitive. It is recommended that readers take care in both locating and using this box as modifications to the
> >> > file after it was created may render either the pointers, or the declaration of random access points, incorrect.
> >> >
> >> > so if i understand it correctly, using these boxes requires some care
> >> > like maybe checking for some brand or muxer/encoder which makes further
> >> > gurantees about their validity.
> >>
> >> From the differences between the packagers and the different
> >> interpretations of the spec, I'm not very eager to attempt
> >> autodetection.
> >>
> >> Consider ffmpeg: we'll at some point change the fragmentation code to
> >> use pts. Whether that'll be visible in the file metadata is unclear.
> >
> > LIBAVFORMAT_IDENT will change as the version will change
>
>
> I know we aren't exactly ecstatic about this change, but from my POV I
> don't see a way to make it better: I am not working on a new version,
> and would like to get this committed. Obviously, if committers
> disagree I will try to address any issues they have.
hmm, patch applied
thanks
[...]
--
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
Opposition brings concord. Out of discord comes the fairest harmony.
-- Heraclitus
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