
Originally Posted by
thorfdbg
That's not quite correct. There are many modes of JPEG that are not widely supported. Consider the hierarchical mode, consider the lossless mode or the AC-coding mode. The above image is just another example of something that is not widely supported, and should not be done. It uses a 3x3 chroma subsampling, rather pointless.
JPEG would even allow a 7/5th subsampling for component 1 and a 5/13 subsampling for component 2 if asked for. How many codecs support this? None.