Back in the day when I was involved with video codec fw, I remember we were having trouble with some codec's (VP8?) deblocking pass, We had to implement that in

Back in the day when I was involved with video codec fw, I remember we were having trouble with some codec's (VP8?) deblocking pass, We had to implement that in SW because the particular method that codec used wasn't possible with our HW. A very legitimate question we asked ourselves was whether we could skip it altogether: the pass did smooth out edges between MacroBlocks, but on our test streams you really had to look closely at still frames to see the difference. So I can imagine different codecs implementing different parts of standard, as long as you could produce a valid stream/image that was acceptable to the human eye. (I don't remember what the final decision was for our deblocking. I would guess that certified compliance required it to be implemented)