[vorbis-dev] Low bitrate high-band coding...

[Jean-Marc Valin]

OK, I have just finished quantizing my coefficients and the result is better
than I had expected... 345 bps for the whole 11-22 kHz band. The audio files are
still at ftp://freespeech.sourceforge.net/pub/freespeech/

bach10-diffquant.sw  : The high band is quantized with 8 bits/frame, thus 345
bps
bach10-diffquant2.sw : I used shorter frames to get better results, 690 bps

In order to get these bitrates, I used differential vector quantization in the
cepstral domain. There are two things left to try:

1) Use intra-frame LPC interpolation (in the LSF domain)
2) Predict the high-band envelope from the LSP masking curve, and further reduce
the bit-rate

By the way, what I'm proposing here is probably not something that would go in
the 64 kbits/channel modes, but in a very low bitrate modes, when there are
(almost) no bits left for the high band.

        Jean-Marc


-- 
Jean-Marc Valin
Universite de Sherbrooke - Genie Electrique
valj01 at gel.usherb.ca

--- >8 ----
List archives:  http://www.xiph.org/archives/
Ogg project homepage: http://www.xiph.org/ogg/
To unsubscribe from this list, send a message to 'vorbis-dev-request at xiph.org'
containing only the word 'unsubscribe' in the body.  No subject is needed.
Unsubscribe messages sent to the list will be ignored/filtered.