Oh, and the transcoder was giving discontinuous input because there
was packetloss in the original DVB stream it was getting.
On 11 October 2014 20:38, Mika Raento <mi...@iki.fi> wrote:
> On 11 October 2014 20:20, Michael Niedermayer <michae...@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.
>
> 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@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.
>
> I'm not sure the MFRA is meant to be used to fix up the timestamps, it
> just that for these files it's the only source for them.
>
> I'll ask our vendor for their opinion too, though I'm not too
> optimistic about them saying anything useful.
>
> Mika
>
>>
>> Thanks
>>
>> [...]
>> --
>> Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
>>
>> Rewriting code that is poorly written but fully understood is good.
>> Rewriting code that one doesnt understand is a sign that one is less smart
>> then the original author, trying to rewrite it will not make it better.
>>
>> _______________________________________________
>> ffmpeg-devel mailing list
>> ffmpeg-devel@ffmpeg.org
>> http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>>
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