[FFmpeg-devel] [PATCH 1/3] lavc/avcodec: Add caps for the support of variable dimension encoding

[Fu, Linjie]

> From: ffmpeg-devel <ffmpeg-devel-bounces at ffmpeg.org> On Behalf Of
> Linjie Fu
> Sent: Monday, June 8, 2020 23:11
> To: FFmpeg development discussions and patches <ffmpeg-
> devel at ffmpeg.org>
> Subject: Re: [FFmpeg-devel] [PATCH 1/3] lavc/avcodec: Add caps for the
> support of variable dimension encoding
> 
> > From: "Anton Khirnov" <anton at khirnov.net>
> > Sent Time: 2020-06-08 18:50:43 (Monday)
> > To: "FFmpeg development discussions and patches" <ffmpeg-
> devel at ffmpeg.org>
> > Cc:
> > Subject: Re: [FFmpeg-devel] [PATCH 1/3] lavc/avcodec: Add caps for the
> support	of variable dimension encoding
> >
> > Quoting Linjie Fu (2020-06-08 10:58:03)
> > > And declare AV_CODEC_CAP_VARIABLE_DIMENSIONS for rawvideo and
> > > wrapped_avframe.
> > >
> > > Signed-off-by: Linjie Fu <linjie.fu at intel.com>
> > > ---
> > >  doc/APIchanges               | 3 +++
> > >  fftools/cmdutils.c           | 2 ++
> > >  libavcodec/avcodec.h         | 4 +++-
> > >  libavcodec/codec.h           | 5 +++++
> > >  libavcodec/rawenc.c          | 1 +
> > >  libavcodec/version.h         | 2 +-
> > >  libavcodec/wrapped_avframe.c | 1 +
> > >  7 files changed, 16 insertions(+), 2 deletions(-)
> >
> > During the last iteration, I asked how is this preferable to just making
> > a new encoder instance. Don't think I got a sufficient reply.
> 
> Thanks Anton for the remind, indeed making a new encoder instance would
> be
> more general and suitable for all encoders, with resolution changing in key
> frames.
> 
> In this patch set, I prefer to restrict the implementation/support to
> rawvideo and wrapped_avframe encoders, since they don't need to be
> recreated
> when resolution/dimension changes and are required. at this moment.
> 
> Also as we've discussed about whether it's worthwhile:
> 
> >> Do we get sufficient benefits from having parameter change capability
> inside
> >> encoders over just creating a new encoder instance when needed? Do
> people
> >> really need to change resolution mid-GOP?
> 
> This implementation didn't touch the logic of encoders which supports
> variable
> resolution encoding on inter frames(vp9, av1), since such
> enhancement/requirement
> seems to be rare for now.

Sent the encoder instance recreate patch set for review as a follow-up step, please
help to review:
https://patchwork.ffmpeg.org/project/ffmpeg/list/?series=1450

- Linjie