CRF with AV1

[gheppell]

Hello.

I am trying to encode avi video to mp4 using the av1 codec and notice that when I use SVT-AV1 there is a CRF option but the encoding mode has only 3 options:  1) constant bitrate, 2) variable, and 3) constant quantizer/rate control.   Similarly, aomenc has no enconding option or otherwise that implies no CRF.  

Further, when I run the encoder, I notice in the Jobs tab, that constant quantizer is being used, even when I have CRF on with SVT-AV1 and, as note, there is no CRF with aomenc.

Am I missing something?  How do I use CRF with either of SVT-AV1 or aomenc.

Thank you.

[Selur]

aomenc supports:

--end-usage=<arg>           Rate control mode
                                             vbr, cbr, cq, q

cq 'constrained quality' is probably the most similar to crf.

svt-av1 supports:

--rc                         Rate control mode, default is 0 [0: CRF or CQP (if `--aq-mode` is 0), 1: VBR, 2: CBR]
  -q, --qp                         Initial QP level value, default is 35 [1-63]
      --crf                        Constant Rate Factor value, setting this value is equal to `--rc 0 --aq-mode 2 --qp x`, default is 35 [1-63]
      --tbr                        Target Bitrate (kbps), only applicable for VBR and CBR encoding, default is 7000 [1-100000]
      --mbr                        Maximum Bitrate (kbps) only applicable for CRF encoding, default is 0 [1-100000]

so using "constant quantizer / rate control" with 'CRF' enabled is what you want, since it sets `--rc 0 --aq-mode 2 --qp x`


Cu Selur

[gheppell]

Hmmm, what about aomenc?  How do I select Rate Control Mode?

copilot is telling me that I don't have a full install.  Might this be correct?

[gheppell]

Hmmm, what about aomenc?  How do I select Rate Control Mode?

copilot is telling me that I don't have a full install.  Might this be correct?

[Selur]

Like I wrote:

cq 'constrained quality' is probably the most similar to crf.

Cu Selur

[gheppell]

Just for my clarity.  This means that at this point, there is no way to set aomenc or svt-av1 directly as crf.  Is that correct?

[Selur]

Yes, there is no single option with parameter where you set crf xy, but both offer something that can be called 'constant rate factor' encoding, but it is not exactly the same as what x264 and x265 crf implementation, since the formats differ quite a bit.
svtav1, even calls it crf in their documentation.
So I would say using the parameter encoders the way I described, you get crf encoding.

Cu Selur