LibSVTAV1 as alternative (or even default?) for AVIF encoding

[golemus]

Currently it seems that AVIF pics are encoded with AOM. It is notoriously slow (it is or at least was not multi-threaded).

I converted in ffmpeg avif with default settings and it takes about 8 secs. Then i used svtav1 with preset5 (which appeared to make abt. same filesize) and took 2 secs so 4x faster speed.

Of course I have little experience in encoding still images with svtav1 (but a lot for encoding video). I dunno if the quality is as good as with aom but there is many use cases where encoding speed is high priority.

If it were to be implemented I guess also some testing should be made which are good parameters (e.g. preset value and "quality" aka crf which is 0-63 in ffmpeg, dunno how it is mapped to 0-100 of image editors.



2. a little bit offtopic but avif seems to have progressive encoding nowadays. I am not sure how often this would be needed but FYI anyway.