[vorbis] bitpeeler

[Segher Boessenkool]

Sebastian Gesemann wrote:
> On Tue, 15 Apr 2003, Segher Boessenkool wrote:
> 
> SG>> I'm not sure if it is possible to reencode a vorbis file to
> SG>> a newer better-peelable vorbis-1 file.
> SB> I _am_ sure it is possible, though :)
> 
> Let me put it in a more accurate form. What I meant to say was:
>   I'm not sure that reencoding a vorbis file to a better peelable
>   file by increasing the amount of quantization stages without
>   introducing new quantizazion errors is possible.

Let me just give a small example of how this can be done.
Where first we had a stage that encodes  0, 1, 2, 3  we change
it to two stages that encode  0+0, 0+1, 2+0, 2+1.  This doesn't
take more space if you make the vectors long enough (in fact, it
almost always takes _less_ space), and it can be better peelable
if you order those new vectors in a smart way.

Doing it exactly like this does not result in much better audio
quality for heftily peeled streams; that's where better tricks
prove useful :)

>>Current streams already are multi-stage.
> 
> Ok...
> The only thing that can be done then is IMHO reordering the
> quantization passes of different residue classifications and
> the corresponding residue_cascade[class] flags.
> 
> Did you mean this by 'losslessly reencoding' ?

With losslessly reencoding, I mean encoding the stream again,
with different books and modes, but representing exactly the
same data.

> If yes: Well, this can be done losslessly - I agree.
> If no:  How do you want to get a better peelable file then ??!

<p>Have fun,

Segher

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