[vorbis] Archival quality for music

[Craig Dickson]

Olaf Marzocchi wrote:

> This mail depends upon the fact that I don't have a couple of good 
> earphones ;-)

Meaning you can't do your own comparisons on reasonable equipment.
All right.

> I read in the site that q=6 is a very high quality, but does it contain 
> perceivable differencies from the original? (for 95% of people, of course).

I don't know about 95% of people, but I suspect q=5 is adequate for the
overwhelming majority of people... for some reasonable value of
"overwhelming majority" that I'm not currently prepared to supply.

> I also found q=6 to produce files slightly bigger (1/10 bigger) than those 
> produced with lame VBR q=2 (about 192 bps on average). I always thought 
> LAME VBR q=2 produced files with very little (if audible) differencies. May 
> OGG obtain better results than mp3 only at low bitrates? (I don't think so, 
> but I don't have enough skills to be sure).
> I also think that ogg q=6 is the minimum quality level to use with ogg 
> because it has a better way to encode stereo than q=5.x.

It does? 5.0 is where Vorbis transitions from lossy stereo to lossless
stereo. I'm not aware of any particular change at 6.0.

> To summarize, I need an advice about the quality level to set in order to 
> achieve comparable or better results than mp3s (LAME) at about 192 kbps or, 
> as preferred alternative, to produce files with very little perceivable 
> differencies form originals.

In my experience, Vorbis, at any given average bit rate, is _always_
better than any MP3 encoder at the same bit rate. (The differences are
more subtle at higher bit rates simply because even MP3 does a fair job
at, say, 256k, so the average listener probably can't detect a
difference at that rate.) So to equal or surpass the quality of a 192k
MP3, go for about 160k average bit rate in Vorbis. q=5 should do nicely.

Craig

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