[FFmpeg-user] VBR encoding for libsvtav1.

Ferdi Scholten ferdi at sttc-nlp.nl
Mon Nov 27 00:46:05 EET 2023

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 

     -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?

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