[FFmpeg-devel] [PATCH 2/2] lavc/libaomenc: Support lossless encoding

[Ryo Hirafuji]

> I would prefer this but I am not the maintainer.

Oh, I see.

Hi, Rostislav Pehlivanov, please tell me your idea.
(How can I address him/her in ML...?)

I think it is more useful to execute this line when "-crf 0" is set:

> codecctl_int(avctx, AV1E_SET_LOSSLESS, ctx->lossless);

It could let users force lossless video more easily and robustly, because
libaom prepared such an option.

It is true the following settings will enable lossless encoding, but these
conditions may change with libaom change:

> If these conditions are not met, "-crf 0" will be lossless:
>
> <<FFmpeg options>>
>   "-bit_rate 0" (which means, enccfg.rc_end_usage = AOM_Q)
>   "-aq-mode none"
>   "-enable_restoration 0"
>
> <<the libaom settings which can't be configured from FFmpeg yet>>
>   AV1E_SET_ENABLE_CHROMA_DELTAQ must be 0
>   AV1E_SET_ENABLE_SUPERRES must be 0


2020年4月5日(日) 18:06 Carl Eugen Hoyos <ceffmpeg at gmail.com>:

> Am Sa., 4. Apr. 2020 um 18:46 Uhr schrieb Ryo Hirafuji
> <ryo.hirafuji at link-u.co.jp>:
> >
> > > In an ideal world, crf 0 would force all other settings for a lossless
> > > encoding.
> >
> > I forgot to say that if "-lossless 1" is set, "crf" will also be 0 (in
> > libaom, internally).
> >
> > All those conditions will be forced (ot at least checked by libaom) if we
> > execute this line:
> >
> > > codecctl_int(avctx, AV1E_SET_LOSSLESS, ctx->lossless);
> >
> > So, how about executing this line if the "-crf 0" is set?
>
> I would prefer this but I am not the maintainer.
>
> See also:
>
> https://patchwork.ffmpeg.org/project/ffmpeg/patch/CAB0OVGr6o6yR3bVAgJix7R7mZCRRVruw=jqA7wGJb+hQ2BvZUQ@mail.gmail.com/
>
> Carl Eugen
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