Decoding single tile AVIF with multiple threads causes a performance regression
You need to build avifdec from libavif with dav1d decode support.
Now transcode the attached AVIF file with avifdec. $ time avifdec -j 1 input.avif output.png
As you increase the number of threads with the "-j" parameter the overall time to transcode the image will increase. You may need to run a few times to get an average. -j 16 is slower than -j 8 is slower than -j 4 is slower than -j2 is slower than -j 1.