2nd refined attempt to smuggle AVIF images inside an AV1 webm. Not sure what else I can improve, ffmpeg doesn't want to retain CICP values, maybe because it expects true video values? Anyway I fixed that now...
I haven't worked out how to script this yet, these are raw windows CLI commands.
avifenc parameters: --sharpyuv -s 4 -d 10 -y 420 --cicp 1/13/1 -a tune=iq -q 70
(echo file '1.avif' & echo file '2.avif' & echo file '3.avif' & echo file '4.avif' & echo file '5.avif') > filelist.txt
ffmpeg -f concat -safe 0 -i filelist.txt -c copy -color_primaries 1 -color_trc 13 -colorspace 1 out.webm
ffmpeg -skip_frame nokey -i out.webm -c copy -color_primaries 1 -color_trc 13 -colorspace 1 -f image2 %0d.avif
AV1 Webm (~90% smaller than webm related RGB lossless VP9 webm)
https://files.catbox.moe/skt1qb.webm
AVIF images extracted from that AV1 Webm
https://files.catbox.moe/3s9g54.zip