Re: [FFmpeg-devel] [Internet]Re: [PATCH v2 5/7] avcodec/mediacodecenc: remove the strategy to create DTS

["Zhao Zhili" <quinkblack@foxmail.com>]

> -----Original Message-----
> From: ffmpeg-devel <ffmpeg-devel-bounces@ffmpeg.org> On Behalf Of Anton Khirnov
> Sent: 2023年1月4日 23:16
> To: 'FFmpeg development discussions and patches' <ffmpeg-devel@ffmpeg.org>
> Subject: Re: [FFmpeg-devel] [Internet]Re: [PATCH v2 5/7] avcodec/mediacodecenc: remove the strategy to create DTS
> 
> Quoting Zhao Zhili (2023-01-04 15:46:52)
> >
> > > From: ffmpeg-devel <ffmpeg-devel-bounces@ffmpeg.org> On Behalf Of Tomas Härdin
> > > Sent: 2023年1月4日 22:00
> > > To: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org>
> > > Subject: Re: [FFmpeg-devel] [Internet]Re: [PATCH v2 5/7] avcodec/mediacodecenc: remove the strategy to create DTS
> > >
> > > ons 2023-01-04 klockan 19:31 +0800 skrev zhilizhao(赵志立):
> > > >
> > > > > On Jan 4, 2023, at 18:16, Anton Khirnov <anton@khirnov.net> wrote:
> > > > >
> > > > > Does this mean the encoder will produce packets with
> > > > > dts=AV_NOPTS_VALUE?
> > > >
> > > > MediaCodec should not encode B frames by default, so dts = pts by
> > > > default.
> > > > B frames can be enabled explicitly, in that case dts is
> > > > AV_NOPTS_VALUE.
> > > >
> > > > Android system’s MP4 muxer works very hard to recreate dts to
> > > > workaround
> > > > the limitation of MediaCodec API. It create ‘valid’ but almost
> > > > useless
> > > > files with a lot of jitters.
> > >
> > > Maybe we should disallow B-frames entirely until the MediaCodec API is
> > > fixed so as to not add to this mess?
> >
> > There are some valid usecases. For example, RTP works fine without DTS.
> > With some restriction or precondition, use can create DTS too. So I'd like
> > to keep the feature.
> 
> It is currently an API guarantee that all encoders return valid DTS
> values, so this encoder is behaving in an invalid way.

It's an reasonable requirement, but could you elaborate on where is the doc
explicitly says that?

> 
> If you want to keep B-frame functionality in this half-working state,
> I'd say it should be hidden behind something like -strict experimental.

Will do.

> 
> --
> Anton Khirnov
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