[FFmpeg-user] VBR encoding for libsvtav1.

[Aditya Dandavate]

On Mon, 27 Nov, 2023, 7:32 am Aditya Dandavate, <adityadandavate04 at gmail.com>
wrote:

> On Mon, 27 Nov, 2023, 4:16 am Ferdi Scholten, <ferdi at sttc-nlp.nl> wrote:
>
>> What is the quality rate control when encoding in VBR mode ?
>> > I get message :
>> >
>> > Svt[warn]: The input q value is ignored in vbr mode 20 when I set the
>> -crf
>> > to 20 when enabling the -svtav1-params rc=1.
>> > When I set -qp 20, the conversion fails.
>> >
>> > Which mode to set quality when encoding in VBR mode ?
>> >
>> vbr encoding does not support quality setting, you get the maximum
>> quality that fits the specified bitrate and it uses lower bitrates if
>> possible if the content does not require high bitrates.
>>
>>
>> If you want CRF with a cap on the bitrate you need to set mbr
>> (MaximumBitRate)
>>
>>      -crf 20 -svtav1-params mbr=5000k
>>
>> You do not need to specify rc=0, because that is default. You also do not
>> specify -b:v 5000k
>>
>>
>> Or if you want VBR
>>
>>      -svtav1-params rc=1 -b:v 5000k
>>
>> No quality settings like crf or qp as they require rc=0 you can however
>> set -qmin (default 1) and -qmax (default 63)
>>
>>
>> OR if you want CQP
>>
>>      -qp 20 -svtparams aq-mode=0 -b:v 5000k
>>
>> qp only works when aq-mode=0 (default aq-mode=2)
>>
>>
>> Hope that helps?
>
>
Also, a quick question about Constrained Quality Mode:

In VP9, we trigger it by combination of '-crf' and 'b:v' and the value of
bitrate is must be non zero to trigger the mode.

How to trigger it in libsvtav1 ?

>