[vorbis-dev] Look what I found under the Xmas tree!

Segher Boessenkool segher at wanadoo.nl
Sat Dec 23 23:23:48 PST 2000

Hello people,

Looks like Santa Claus thinks I've been a good boy this year.

Here's the third in my performance patch series: d.m.l

Apply after applying d.o.n and d.n.m; I don't know how much of
those got applied to the CVS tree.

What's inside:

Request for help! Look in os.h if you're using a compiler or
processor I don't use (I use gcc on K5, K7, G3).

New MDCT! Now we have two; competition is a good thing. Let's
see which one is fastest :-)

Completely overhauled psycha! Well, actually, the only big change
is that it does all of its computations in the dB domain, and does
some things just a little bit different, to improve performance.

Changed the ATH_Bark_dB array. This removes some very annoying
artifacts when encoding low-frequency, tonal sounds.

MDCT_COOR: this should reduce the blocking artifacts the MDCT
creates. This #define is tunable; smaller is less correction.
The algorithm is only exact for sine windows, but is ok for the
Vorbis window as well, as long as the flr[] is reasonably smooth
(in the high freq region). This should help low bitrates.

And, of course, the quantization control magic. Never thought
69kbps would sound that good. Still need some VQ training; I
just can't figure how to use the tools correctly (currently,
huffbuild is segfaulting on me).

Yoho yoho! And off you go!


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