[vorbis] Ogg Vorbis files can be compressed ?!?

[Monty]

On Fri, Jan 17, 2003 at 12:22:25PM -0500, Peter Harris wrote:
> Nescafe wrote:
> >Hi there.
> >
> >I have a short .ogg with Vorbis stream @56kbps
> >from a 44.1 16bits stereo sample, which weights
> >exactly 135'781 bytes. Packed to ZIP, it goes
> >down to 109'485 bytes, that's a 80% ratio !
> >Even worse with latest RAR3 archive, with
> >which the file size goes to 104'349 (76%).
> 
> Have you tried rehuff? This is a program that will recompute the huffman 
> codebooks for better packing. Over long files, the default codebooks are 
> usually fairly close to optimal. On short files, rehuff can usually get 
> quite a few percent savings (and sometimes as much as you indicate 
> ZIP/RAR gets).
> 
> Search the archives for the source code, or wait for the final release 
> if you don't have a compiler.

Next thing to ask: what does 'ogginfo' say about the file?  If it's an
old version of Vorbis (or a random buggy third party one), I'd like to
know that before looking more closely.  Beta-release files are
especially prone to being further compressed.  1.0 full release files
should not be.

Lastly, what Peter wrote is true; our encoder's codebook model is a
good compromise for 99% of the general case, but some things like, for
example, perfect digital silence) will end up being repetitive 'this
is silence' markers.  In some of these cases, compressing out that
redundancy renders the file impossible to seek.

Monty
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