X8intra is there!

Now we have X8intra frames support in ffmpeg! Mike has already expressed his joy in his blog. I think anime fans who tried to play WMV3 in AVI would also be glad.

Why this has not been done earlier? Well, sheer disgust. The person who invented this scheme should be either fired or promoted to M$ CTO. Here is the list of reasons:

  • It is used for some keyframes coding so it cannot be skipped
  • Design is totally unlike anything standard
  • You should perform bitexact decoding. If your DCT produces slightly different results or you forgot about loop filtering then you won’t be able to decode picture properly. Hey, that’s utter crap by _any_ standard
  • It has made it to WMV3 too.

To put it mildly, X8Intra is an illegal offspring of JPEG and some early H.264 draft. It is mainly Huffman-coded 8×8 DCT-transformed blocks with spatial prediction and loop filtering. It does not have macroblocks like decent codecs. Spatial prediction has some directions and relies on previously decoded blocks and bits read depending on that. I have not seen anything with such a bad bitstream-transform dependency (in other codecs you can decode coefficients first and then perform image reconstructions but not here). X8Intra excrementum est(pardon my Latin).

Still I very grateful to the person named “someone” who did this. Otherwise I should clean this cesspool.

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