[vorbis] question about codebook

[Segher Boessenkool]

Áô©~ªº ¦Ñ¤H wrote:
> Hi, all
> 
> I am studying the ogg-vorbis algorithm but I have less knowledge about 
> the codebook structure of vorbis. After tracing the release source code, 
> I found it doesn't use huffman tree to decode the huffman code instead 
> of using a special mapping and pre-look.

This is just an optimized decoding algorithm; the Huffman
tree is still there, just in a different data structure.

[Also, there's a shortcut for very short Huffman words].

 > The memory requirement seems similar with huffman tree decoding.

Yes, the memory requirements are the same as with some other
Huffman decoding algo's, but only half that of the "obvious"
algorithm.

 > Could anyone tell me how the vorbis
> huffman decoding works and the difference or advantage. Or where can I 
> get the information. Thanks...

a) This is just how libvorbis works, there's no requirement for
a different Vorbis implementation to do it in the same way.
b) Read the code, again and again and again...
c) If you have more specific questions, ask at vorbis-dev at .
But I don't think anyone there will take you by the hand and give
you a walkthrough, either; you'll just have to read the code
yourself.  Sorry...

<p>Segher

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