[vorbis-dev] lossless ogg encoding with good compression rate

[Carsten Haese]

On Wed, 2003-06-25 at 20:40, General purpose mail wrote:
> 
> Follow the description of how I've tested it:
> 1) create a wav file [A.wav]:
> 2) encode it in ogg format (my best result with high 7) [B.ogg]
> 3) decode the ogg into a wav again [C.wav] (the size will be the same as A.wav)
> 4) create a file with the diff of each sample from A.wav with B.wav [D.tmp] also with the  same size at least of the header.
> 5) bzip2 the D.tmp [D.tmp.bz2]
> 6) keep B.ogg and D.tmp.bz2 (the size will be around 17% of the original for each file)
> 
> simply is't it?
> 
> I think it's simple to recreate the a wave from this.

Besides the difficulty in reproducing your astonishing results that
others have mentioned on this thread, there is another problem with your
approach. Different decoders (e.g. on different platforms) are not
guaranteed to produce the same wav from the same Ogg Vorbis file. In
order for your approach to be lossless, you need the exact same Vorbis
decoder on the decode side as the one that was used for calculating the
difference signal on the encode side. Unfortunately, this requirement
places your idea anywhere between impractical and impossible.

Best regards,

Carsten Haese.

<p>--- >8 ----
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