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

[Jeremy Nickurak]

Disclaimer: I know virtually nothing about audio compression, but this
has me really interested.

The idea here (as i understand it) is to split the data in an audio file
into different parts (the vorbis-encoded bit and the diff) that compress
well. Given that the data in the diff has an organizational form of some
kind (essentially the inverse of vorbis' encoding artifacts), is there a
less generally tuned algorithm then bz2 that would function better here?
I assume the idea that flac could function well on this form of audio
data? Hand off parts of the file to vorbis and parts to flac?

<p>On Thu, 2003-06-26 at 15:48, Graham Mitchell wrote:
> > The way I see it, the combination of ogg and diff file can never be encoded
> > as easily (or as compact) as the original wave file itself.
> 
> I concur.  I've been playing around all afternoon, and I can't find a method 
> diff'ing a decompressed OGG with the original WAV in such a way that the 1) 
> original WAV is completely recoverable, and 2) the OGG + diff is any smaller 
> than a FLAC-compressed version of the original file.
> 
> Using a byte-for-byte XOR I get okay results, and slightly better results with 
> a byte-for-byte difference, but neither approach even equals FLAC, much less 
> beating it.
> 
> The Ogg + diff approach does beat storing the uncompressed WAV, and is 
> lossless, but only on my machine.  And since oggdec isn't guaranteed to 
> produce identical WAVs on different architectures, I'm guessing it's not even 
> a workable solution in general.
> 
> There is a binary diff utility that proposes to work like the "diff/patch pair 
> does with text files", but I can't get it to finish running, even after 
> letting it churn on smallish files (16MB or so WAVs):
> 	g_pochini at virgilio.it/">http://space.virgilio.it/g_pochini@virgilio.it/</a>
> 
> Maybe if someone can get this to complete, it might provide better 
> compression.

-- 
Jeremy Nickurak -= Email/Jabber: atrus at rifetech.com =-
"Whoever fights monsters should see to it that in the process he 
 does not become a monster.  And when you look into an abyss, the
 abyss also looks into you." -- Friedrich Nietzsche


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