[vorbis] Re: [vorbis-dev] rehuff [source attached]

[Segher Boessenkool]

"Christian.Buchner" wrote:
> 
> This thread taken from vorbis-deff
> 

why not leave it on vorbis-dev.  thank you.

> > Yes, it's true.  A new version of rehuff, the tool that losslessly compresses
> > Vorbis files: one that is easy to compile, and that works with
> > newer-than-two-years-ago streams, too!
> 
> Erm. So what exactly does "rehuff" it do?
> 
> Does it re-calculate more optimal codebooks, recompress the
> stream and generate a new and shorter version of the original
> stream?

yes.

> 
> So if rehuff can do that kind of magic, why can't Ogg Vorbis 1.0
> generate a better coded stream?

Because you need to know all data in advance, to calculate optimal
codes.  libvorbis can stream, so that's a no-no.

> Why is there a need for such a tool?
> 

Not much need on normal streams; it only saves a few percent.

But on otherwise recoded streams (peeled streams, stereo-to-mono coded streams,
etc.) it saves a bunch.  Also, you get much smaller headers this way
(which is
very helpful for fast-start network streams).

Cheers,

Segher

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