[FFmpeg-devel] [PATCH, v2 2/4] avc/avcodec: add AV_CODEC_CAP_VARIABLE_DIMENSIONS flag

[Fu, Linjie]

> -----Original Message-----
> From: ffmpeg-devel [mailto:ffmpeg-devel-bounces at ffmpeg.org] On Behalf
> Of Fu, Linjie
> Sent: Thursday, August 1, 2019 22:51
> To: FFmpeg development discussions and patches <ffmpeg-
> devel at ffmpeg.org>
> Subject: Re: [FFmpeg-devel] [PATCH, v2 2/4] avc/avcodec: add
> AV_CODEC_CAP_VARIABLE_DIMENSIONS flag
> 
> > -----Original Message-----
> > From: ffmpeg-devel [mailto:ffmpeg-devel-bounces at ffmpeg.org] On
> Behalf
> > Of Michael Niedermayer
> > Sent: Wednesday, July 31, 2019 14:04
> > To: FFmpeg development discussions and patches <ffmpeg-
> > devel at ffmpeg.org>
> > Subject: Re: [FFmpeg-devel] [PATCH, v2 2/4] avc/avcodec: add
> > AV_CODEC_CAP_VARIABLE_DIMENSIONS flag
> >
> > On Tue, Jul 30, 2019 at 10:27:10AM -0300, James Almer wrote:
> > > On 7/30/2019 6:33 AM, Carl Eugen Hoyos wrote:
> > > > Am Di., 30. Juli 2019 um 11:25 Uhr schrieb Fu, Linjie
> <linjie.fu at intel.com>:
> > > >>
> > > >>> -----Original Message-----
> > > >>> From: ffmpeg-devel [mailto:ffmpeg-devel-bounces at ffmpeg.org]
> On
> > Behalf
> > > >>> Of Carl Eugen Hoyos
> > > >>> Sent: Tuesday, July 30, 2019 16:06
> > > >>> To: FFmpeg development discussions and patches <ffmpeg-
> > > >>> devel at ffmpeg.org>
> > > >>> Subject: Re: [FFmpeg-devel] [PATCH, v2 2/4] avc/avcodec: add
> > > >>> AV_CODEC_CAP_VARIABLE_DIMENSIONS flag
> > > >>>
> > > >>> Am Di., 30. Juli 2019 um 06:46 Uhr schrieb Linjie Fu
> > <linjie.fu at intel.com>:
> > > >>>>
> > > >>>> Add AV_CODEC_CAP_VARIABLE_DIMENSIONS flag to indicate
> > > >>>> whether encoder supports variable dimension encoding.
> > > >>>
> > > >>> Isn't this about variable (or "changing") "resolutions" instead of
> > dimensions?
> > > >>>
> > > >>
> > > >> Comment is welcome and "variable resolutions" is good.
> > > >
> > > >> But is "dimension" not quite suitable for the meaning of "variable size"?
> > > >
> > > > It took me some time to understand that "dimension" implies
> resolution,
> > > > especially since the FFmpeg documentation mentions resolution iirc.
> > > >
> > > > Carl Eugen
> > >
> > > We have a AV_SIDE_DATA_PARAM_CHANGE_DIMENSIONS flag to signal
> > resolution
> > > changes, so both words seem to be used interchangeably.
> > >
> >
> > > This also makes me think that the existing
> > AV_CODEC_CAP_PARAM_CHANGE
> > > codec cap can be used for this already, without the need for a new one.
> > > It should a matter of using AV_PKT_DATA_PARAM_CHANGE packet side
> > data
> > > afterwards in some form.
> >
> > if AV_PKT_DATA_PARAM_CHANGE is used then other parameters would
> > need to
> > be handled too i think.
> > For example pixel format changes alongside width and height.
> > And it leaves some areas of uncertanity which may require more flags
> > like does a aspect ratio change or a change of one of the colorspace
> > parameters need a encoder "flush/restart". (the flush is done from
> > outside the encoder in the patch so the code would need to know)
> >
> > Also for symmetry, if AV_PKT_DATA_PARAM_CHANGE expects sidedata
> on
> > the input side of the decoder, something should produce matching
> > side data on the encoder side.
> >
> > encoder -> decoder should continue working. So only a demuxer
> > generating the side data could be a problem.
> 
> Sounds like a new flag will be more robust?

Ping for this patch set?
https://patchwork.ffmpeg.org/patch/14122/
https://patchwork.ffmpeg.org/patch/14139/
https://patchwork.ffmpeg.org/patch/14140/