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

[Beni Cherniavsky]

Carsten Haese wrote on 2003-06-26:

> 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.
>
This statement worries me.  The spec specifies the matematically
"right" decoding when you have infinite precision FP, doesn't it?  So
is this just a matter of FP errors in actual implementations?  It's an
acceptable tradeoff to pay with small noise for effecient decoding but
it is still desirable to have the "one true" decoding defined and
possible.  If you decode with libvorbis to 24bit and then round,
wouldn't you get it right?  Perhaps if you replace all floats with
doubles in libvorbis and recompile?


-- 
Beni Cherniavsky <cben at tx.technion.ac.il>

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