[FFmpeg-devel] [PATCH v2 6/6] avcodec/libsvtav1: support constant quality mode

[mypopy at gmail.com]

On Sat, Sep 25, 2021 at 8:36 PM Jan Ekström <jeebjp at gmail.com> wrote:
>
> On Thu, Sep 23, 2021 at 6:08 PM <lance.lmwang at gmail.com> wrote:
> >
> > On Thu, Sep 23, 2021 at 05:11:49PM +0300, Jan Ekström wrote:
> > > On Thu, Sep 23, 2021 at 4:46 PM Christopher Degawa <ccom at randomderp.com> wrote:
> > > >
> > > > On Sun, Sep 19, 2021 at 2:02 PM Christopher Degawa <ccom at randomderp.com>
> > > > wrote:
> > > >
> > > > >
> > > > >
> > > > > On Fri, Sep 17, 2021 at 9:28 PM <lance.lmwang at gmail.com> wrote:
> > > > >
> > > > >> From: Limin Wang <lance.lmwang at gmail.com>
> > > > >>
> > > > >> Signed-off-by: Limin Wang <lance.lmwang at gmail.com>
> > > > >>
> > > > > As a note, I personally favor this patch over mine since I don't think
> > > > > `enable_tpl_la` is worth exposing to the user if its main role is to switch
> > > > > between crf and cqp
> > > > >
> > > >
> > > > Ping on this patch, this has been requested on SVT-AV1's side as well
> > >
> > > I think my further comments on the previous version were mostly to
> > > move off from the rc option for rate control, which has become more
> > > and more seemingly unnecessary (and different from most other encoders
> > > for no obvious reason).
> > >
> > > The only option that with a quick look doesn't match just setting
> > > quantizer|bit rate|CRF is "cvbr", but it doesn't seem to be impossible
> > > to either rework "rc" for it, or to utilize a separate option for it.
> >
> > Do you think it's OK to remove the rc option? to match other encoders,
> > We can choose the rate control by the related parameters like:
> >
> > if (crf >= 0)
> >     choose crf rate control;
> > else if (bitrate > 0)
> >     choose cvbr rate control;
> > else if (cqp >=0 )
> >     choose cqp rate control;
> >
>
> In general that is the idea, yes (except bit rate would mean either
> vbr or cvbr). It would be nice to follow whatever is the default on
> SVT-AV1's side by default, and then if the user specifies a rate
> control mode that is not the default, his selection is honored. Not
> sure what the best way for that is to be honest. Possibly the style of
> setting AVCodecDefault a la libx265?
>
> For the rc option, given how much SVT-AV1 itself is in flux, I would
> be OK with removing the option, or making it an option that decides
> between cvbr and vbr (essentially making it "VBR bit rate control
> mode"). I wish cvbr would instead be something like VBV/HRD elsewhere,
> so we could just utilize maxrate&bufsize for controlling it, instead
> of having it as another discrete rate control mode.
>
> As these things change, I also hope that SVT-AV1 will soon get a
> key=value style of option API, that way the wrapper will not have to
I agree with this part , now FFmpeg SVT-AV1 wrapper needs to update
with the SVT-AV1's structural mapping if want to enable a new feature
> be updated constantly according to the changes in the library :) . As
> I feel SVT-AV1 will be changed quite a bit in the future (due to its
> recent age).
>