[FFmpeg-devel] [PATCH] mov.c: allow reading fragment start dts/pts from fragmented mp4
Mika Raento
mikie at iki.fi
Mon Oct 13 07:54:31 CEST 2014
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.
Mika
>
>
> [...]
>
> --
> Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
>
> Dictatorship naturally arises out of democracy, and the most aggravated
> form of tyranny and slavery out of the most extreme liberty. -- Plato
>
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel at ffmpeg.org
> http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>
More information about the ffmpeg-devel
mailing list