[vorbis] bitrtate peeling and lossless compression

[Keith Wright]

> From: Larry Fenske <lfenske at yahoo.com>
> 
> --- ndrw mchl grnbrg <amg at bewley.net> wrote:
> > Nathan Johnson <johnsonn at agcs.com> wrote:

> > So, neither Vorbis nor Squish can encode losslessly and
> > peel the bit-rate back to lossy encoding.  Would it be
> > practical to make an encoding scheme that would be
> > capable of this?
> > 

> Well, considering that lossless encoding needs to use
> completely different methods of compression than lossy
> encoding uses, the compressed file would almost *have* to
> be the size of the lossless encoded file + the lossy
> encoded file together, which would probably be as large as
> the original pcm file if not larger.
> 
> I don't know whether lossless and lossy need to use
> completely different methods or not (I haven't looked at
> methods for either),

I have looked, but not fully understood, so we are both
unbiased by knowledge of what speak, but...

> ...but even if they did, the resulting file would usually
> still be smaller.
>
>    <$(cat X.flac x.ogg) is smaller than $(cat X.wav)>
> 
> 1411Kb/s*50% + 350Kb/s is about 3/4 the size of the original.  
> 
> Granted, that's not a great size, but even if it did
> expand the pcm file, if it would play back the original
> bits, and I could peel it (perhaps initially removing the
> lossless part) to lower bitrates, that would satisfy my
> wants.  Of course, the smaller the compressed file, the
> better.

You have just proven that putting a lossless and a lossy
compressed file in one directory suffices to accomplish what
you say you are trying to do.  So Nathan was a bit off on
the details, but was right to be wondering just exactly what
is the point.  Why do you not just encode losslessly to
archive, and re-encode vorbisly to compress?  Is Flac too
slow?  Do you want an all vorbis system for political or
aesthetic reasons?  Would you be happy with a GUI interface
with buttons for both Flac and Vorbis on the same panel?


-- 
     -- Keith Wright  <kwright at free-comp-shop.com>

Programmer in Chief, Free Computer Shop <http://www.free-comp-shop.com>
         ---  Food, Shelter, Source code.  ---

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