Why when encoding AVIF images with avifenc on slowest speed file size get bigger?
My source file is lossless PNG, 576x767, file size 1.26 mb.
I experiment with encoding AVIF format and read, that higher encoding speed setting will run faster, but produce worse compression efficiency and quality. If I get it right, the slowest encoding speed should provide the smallest file size at the cost of extra processing time.
In my case, I get the opposite: faster speed gets smaller file size. Here are the encoding settings I played with in a batch file and AVIF file size that I got as a result:
avifenc --min 0 --max 63 --yuv 420 -a end-usage=q -a cq-level=53 -a tune=ssim --jobs 1 --speed 10 image.png image.avif12.9 kb
avifenc --min 0 --max 63 --yuv 420 -a end-usage=q -a cq-level=53 -a tune=ssim --jobs 1 --speed 0 image.png image.avif30.5 kb
avifenc --min 50 --max 63 --yuv 420 -a end-usage=q -a cq-level=53 -a tune=ssim --jobs 1 --speed 10 image.png image.avif12.9 kb
avifenc --min 50 --max 63 --yuv 420 -a end-usage=q -a cq-level=53 -a tune=ssim --jobs 1 --speed 0 image.png image.avif13.1 kb
avifenc --min 20 --max 23 --yuv 420 -a end-usage=q -a cq-level=53 -a tune=ssim --jobs 1 --speed 0 image.png image.avif54 kb
avifenc --min 20 --max 23 --yuv 420 -a end-usage=q -a cq-level=53 -a tune=ssim --jobs 1 --speed 10 image.png image.avif61.5 kb
What am I doing wrong? Why faster speed brings better results?
Also, why lowering min/max values or their spread file size grows dramatically?
