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

Ryo Hirafuji ryo.hirafuji at link-u.co.jp
Sun Apr 5 13:57:39 EEST 2020


Lynne, could you tell me your idea?

2020年4月5日(日) 19:39 Ryo Hirafuji <ryo.hirafuji at link-u.co.jp>:

> > 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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>


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