[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 James Almer
> Sent: Tuesday, July 30, 2019 21:27
> To: ffmpeg-devel at ffmpeg.org
> Subject: Re: [FFmpeg-devel] [PATCH, v2 2/4] avc/avcodec: add
> AV_CODEC_CAP_VARIABLE_DIMENSIONS flag
> 
> 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.

Thanks.
Saw the modification in fe75dc8583b65612f3a94144ee090e741dc926d5,
and it seems it was designed for decoder at first, like "rawdec/nellymoserdec/interplayvideo".

"Also define a codec capability for codecs that can handle
 parameters changed externally between decoded packets. "

Since currently no encoder is engaged with this flag, it's good for me to reuse this if there is no
other concern.

- linjie