[vorbis-dev] Using the vorbis psychoacoustics model

[Monty]

> I need a psychoacoustics model for some experiments and would like to use the
> one included in vorbis. Is there any documentation about how to use it? Looks
> like the relevent code is in psy.c, but I can't go further.

The psychoacoustics in Vorbis are directly taken from two papers by R. Ehmer
published in the Journal of the Acoustical Society of America in 1959.  They
take the raw data for pure tone and noise masking (by band/dB) from those
papers and apply them to the short-time MDCT spectrum of the input signal,
finding a noise and tone masking curve for the input.  Later, I also apply an
ATH cutoff.

As for using that code, it it easily divorced from the rest of Vorbis.  You 
need psy.c/psy.h and the info_psy typedef from codec.h.  Transform functions 
from other modules may also be used; look at the includes at the top of psy.c. 
 It should all work outside of Vorbis without modification.

> Also I would like to know whether I can be of any help in vorbis. I have some
> knowledge in speech coding (I doing my master at the University of Sherbrooke's
> speech coding lab) and I'm fluent in C/C++. I am not that familiar with "general
> audio" coding.

Get a feel for the code and let us know if you see something that needs doing
(at this point, the majority of the work can be split into (a)API improvements
(b) optimization (c) audio quality improvements in the encoder). Since you have
a background in speech coding, I actually have some issues in LSP fitting I'm
trying to solve right now.  You up to answering a few questions on LSP
behavior?

Monty

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