Archive for March, 2015

Some Notes on Lossless Video Codecs

Saturday, March 21st, 2015

While reading a nice PhD thesis from 2014 (in Russian) about new lossless video compression method I laughed hard at lossless video codec descriptions (here’s the link for unbelievers – http://gorkoff.ru/wp-content/uploads/articles/dissertation.pdf, translation below is mine):

To date various lossless videostream compression methods and algorithms have been developed. They are used in the following widespread codecs:

* CorePNG employs deflate algorithm for independent compression of every frame. Theoretically the codec supports delta frames but this option is not used.

* FFV1 employs prediction coding with following entropy coding or prediction error.

* Huffyuv, like FFV1 algorithm, employs predictive coding but prediction error is effectively coded with Huffman algorithm.

* MSU Lossless Video Codec has been developed for many years at Moscow State University labs.

And yet some real world tasks demand more effective compression and thus a challenge of developing new more effective lossless video compression methods still remains actual.

Readers are welcome to find inaccurate, erroneous and outright bullshit statements in this quote themselves. I’d rather talk about lossless video codecs as I know them.
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Posted in Lossless Video Codecs, Screen Codecs, Useless Rants | 3 Comments »

Some notes on VP4

Sunday, March 1st, 2015

Well, this information should’ve been posted by someone else but those people seem to be lazier than me. In return I’m not going to use XViD or FLIC for encoding my content.

So, REing VP4 is rather easy – you just download original VP3.2 decoder source (still available at Xiph SVN servers) and compare it to the structure in vp4vfw.dll. There are differences in structures and a bit in code layout but mostly it’s the same code with new additions.

So, VP4 is based on VP3 (surprise!) and introduces a new bitstream version (which is 3 for some reason). Here’s an incomplete list of differences I’ve spotted:

  • Base frame header has some additional fields (I didn’t care enough to decipher their meaning though);
  • Superblock coding uses a bit different scheme with new universal codes resembling exp-Golomb but with VP4 quirk;
  • Frame data decoding differs for frame types;
  • Motion vector component extraction uses Huffman tables and sign from the previous block.

And yet it uses the same coding principles and even token coding seems to be left untouched. It was suspected for a long time that even-numbered On2 codecs were simply an improvements over previous version while odd-numbered On2 codecs were more innovative but not much was known about VP4 to prove it:

  1. Duck TrueMotion 1 — a new codec;
  2. Duck TrueMotion 2 — mostly like TrueMotion 1 but with Huffman encoding;
  3. Duck/On2 TrueMotion VP3 — DCT + static Huffman coding;
  4. On2 TrueMotion VP4 — VP3 with some bitstream coding changes;
  5. On2 TrueCast VP5 — DCT + arithmetic coder;
  6. On2 VP6 — VP5 with some bitstream changes;
  7. On2 VP7 — H.264 ripoff with their own arithmetic coder;
  8. On2 VP8 — VP7 with some small changes;
  9. Baidu VP9 — H.265 ripoff with their own arithmetic coder;
  10. rumoured Baidu VP10 — since there’s no H.266 in the works for now…

It’s all kinda Intel CPUs but without confusing codenames (and Xiph hasn’t produced too many codecs to confuse whether Daalawell came before Theorabridge or after).

P.S. Many thanks to big G for releasing no information on that codec or any other codecs from On2. Oh, and is VP9 “specification” still under NDA?

P.P.S. I should really work on a game codec named after chemical warfare instead.

Posted in TrueMotion, Useless Rants | 4 Comments »