3 ms·

In my evaluation AVIF's tools occasionally create artefacts on the image even at relatively high quality (above that of mozjpeg). Most often this is blurring or

In my evaluation AVIF's tools occasionally create artefacts on the image even at relatively high quality (above that of mozjpeg). Most often this is blurring or banding occuring in the image. Look at sky here for an example of the blurring: https://storage.googleapis.com/demos.webmproject.org/webp/cmp/2021_12_15/index.html#white-dune-mui-ne*3:1&AVIF-AOM=b&Original=b&subset1 https://storage.googleapis.com/demos.webmproject.org/webp/cm... This kind of blurring can occasionally happen on the face of a portrait, too. An example of banding here: https://storage.googleapis.com/demos.webmproject.org/webp/cmp/2021_12_15/index.html#moscow-july-2011-4a*3:1&AVIF-AOM=b&Original=b&subset1 https://storage.googleapis.com/demos.webmproject.org/webp/cm... WebP, WebP2, and AVIF show banding in the sky, MOZJPEG to some extend, JXL and HEIF seem to be mostly free of banding.

JyrkiAlakuijala 5y ago
My understanding is that if you want to avoid the occasional oversmoothing artefacts when using AVIF, you need to turn off many of the tools giving compression density. For example main smoothing tools have control fields that govern 64x64 pixels at once -- so you end up having either too little or too much smooting in some areas. In JXL the respective smoothing control field is 8x8, so you have much more opportunity to do the right thing.
ncmncm 5y ago
I don't understand what "blurring" means applied to a sky. That would seem to require some detail to get blurred. Do you mean the skyline? And, I do not see any banding, even at "tiny", in these images.
- JyrkiAlakuijala 5y ago
  Original on left has noise/grain in the sky. In AVIF compression, this grain has been blurred away. JXL and HEIF keep the grain. I can see banding in the AVIF image at all densities, including 'big' at 1.7 bpp. The banding is easier to see when brightness is increased, but is visible to me in normal viewing conditions. Perhaps your monitor is at dark settings or you have a plenty of light in your room. The bands are horizontal stripes in the Moscow image.
  - ncmncm 5y ago
    I see now... I was on mobile. Probably all the images I saw were "original".

JyrkiAlakuijala 5y ago

My understanding is that if you want to avoid the occasional oversmoothing artefacts when using AVIF, you need to turn off many of the tools giving compression density. For example main smoothing tools have control fields that govern 64x64 pixels at once -- so you end up having either too little or too much smooting in some areas. In JXL the respective smoothing control field is 8x8, so you have much more opportunity to do the right thing.

ncmncm 5y ago

I don't understand what "blurring" means applied to a sky. That would seem to require some detail to get blurred. Do you mean the skyline? And, I do not see any banding, even at "tiny", in these images.

JyrkiAlakuijala 5y ago
Original on left has noise/grain in the sky. In AVIF compression, this grain has been blurred away. JXL and HEIF keep the grain. I can see banding in the AVIF image at all densities, including 'big' at 1.7 bpp. The banding is easier to see when brightness is increased, but is visible to me in normal viewing conditions. Perhaps your monitor is at dark settings or you have a plenty of light in your room. The bands are horizontal stripes in the Moscow image.
- ncmncm 5y ago
  I see now... I was on mobile. Probably all the images I saw were "original".