[FFmpeg-devel] [REQUEST] avcodec/scpr: revert d70276921348

[Michael Niedermayer]

On Tue, Aug 20, 2019 at 06:13:49PM -0300, James Almer wrote:
> On 8/20/2019 3:32 PM, Michael Niedermayer wrote:
> > On Tue, Aug 20, 2019 at 02:52:49PM -0300, James Almer wrote:
> >> On 8/20/2019 2:46 PM, Michael Niedermayer wrote:
> >>> On Tue, Aug 20, 2019 at 02:49:13PM +0200, Paul B Mahol wrote:
> >>>> Hi,
> >>>>
> >>>> I kindly ask that following commit: d702769213487923c0fb0abe4b61f4d9ebddb88b
> >>>> is reverted as it does contradicts with reference decoder.
> >>>
> >>> Noone is listed in MAINTAINERs for scpr.c
> >>> the main author of scpr.c is you, so  i think you are the closest to a
> >>> maintainer.
> >>>
> >>> So if after everyone who wants to comment has commented you still want this
> >>> reverted. Then ill revert (or you can revert too)
> >>> but personally i think that skiping duplicated frames has many advantages
> >>> and its better to skip them
> >>>
> >>> Thanks
> >>
> >> I suggested on IRC to add an option somewhere (new AVCodecContext field?
> >> ffmpeg cli option? Mapping it to AV_CODEC_FLAG2_FAST?) to tell crf
> >> decoders to instead output vrf in situations like this.
> > 
> > IMHO never output known duplicate frames is best. But if people want to
> > change this. A flag/field is the next best option.
> 
> > AV_CODEC_FLAG2_FAST does not solve this as the flag has a different
> > meaning.
> 
> How so? The doxy says "Allow non spec compliant speedup tricks.".
> Outputting vfr when cfr is the spec compliant behavior sure sounds like
> it's a good fit for this feature.

AV_CODEC_FLAG2_FAST will cause output to differ in pixel values from
a compliant decoder.

while droping duplicated frames can be reversed by duplicating again with
no pixel differences.

So a user application which needs pixel exact values can use the flag to
drop duplicate frames but cannot use AV_CODEC_FLAG2_FAST


> 
> A new flag/field would be needed

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Elect your leaders based on what they did after the last election, not
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