Ross Vandegrift schrieb:>
> Hello everyone,
Hello Ross!
> I'm a student at the Universtiy of Delaware, and will be soon
starting
> some research on the effects of lossy audio compression on speech sounds.
I
> will be preforming test with both mp3 and vorbis.
Sounds interesting. Oh... by the way - isn´t Gian-Carlo Pascutto working
on a speech-optimized tuning of the encoder?
> First of all, if I use the '--ogg' switch to lame, does
lame use GPSYCHO
> to encode the wave, or some other psychoacoustic model (perhaps one
designed for
> the vorbis algorith)? Along these lines, I'm unable to get lame-3.89
and
> libvorbis rc2 to play nicely together. The lame build breaks when
compiling
> ogg support (this is probably a known bug, so I'm not posting relevant
details.
> If I'm wrong about it being know, we'll go from there).
Long, long ago (your grandparents may remember their grandparents
knew about it... ;-) you could compile Vorbis support into
lame. Due to API-changes this isn´t possible anymore - and the
lame guys don´t seem to be interested in updating their
Vorbis-interface.
But this isn´t as bad as it sounds: Lame´s Vorbis-output was
_exactly_ the same as oggenc´s output. Lame simply used the
routines of libvorbis - so does oggenc.
The "--ogg" switch never influenced MP3-Output and it never
will. AFAIK the MP3-psychoacoustic model is somewhat different
from the Vorbis one - you can´t exchange them.
> Second, since audio compression is based on the idea of a plausable
> psychoacoutic model. There seems to be some documentation on GPSYCHO,
which
> lame uses. But the link 'The Vorbis probability model' on xiph.org
is noteably
> not a link. Is there any addition documentation about the psychoacoustic
model
> that vorbis uses?
I´m neither a developer nor involved in documentation. Hmmm... I don´t
know where to find it.
> Finally, does anyone know of similar studies that have already been
> performed, either academic or not?
I never heard of such studies. But I never searched for those studies
:-)
> Thanks,
> Ross Vandegrift
> ross@willow.seitz.com
Hope this was useful,
Maik Merten
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