====== ffmpeg - Conversions - Convert H264 to AV1 - libaom - Constant Quality ======

**libaom-av1** has a constant quality (CQ) mode (like CRF in x264 and x265) which will ensure that every frame gets the number of bits it deserves to achieve a certain (perceptual) quality level, rather than encoding each frame to meet a bit rate target. 

  * This results in better overall quality.
  * If you do not need to achieve a fixed target file size, this should be your method of choice. 

----

<code bash>
time ffmpeg -i a.mp4 -c:v libaom-av1 -crf 30 -f mp4 out.mp4
</code>

returns:

<code bash>
...
real	260m18.018s
user	1514m33.124s
sys	0m43.892s
</code>

<WRAP info>
**NOTE:** 

  * Input test size:  75.5M
  * Output test size:  24.5M

</WRAP>


<WRAP info>
**NOTE:**  

  * **crf**:  This value can be from 0–63.
    * Lower values mean better quality and greater file size.
    * 0 means lossless.
    * A CRF value of 23 yields a quality level corresponding to CRF 19 for x264 (​source), which would be considered visually lossless.

</WRAP>