[CELT-dev] 22 kHz version of CELT

Marc Padellini marc.padellini at gmail.com
Thu May 28 07:06:50 PDT 2009

>  Adjusting the code to reduce/merge bands is someplace on my todo list,
> but you can try it easily enough by adjusting bark_freq in
> libcelt/modes.c and change the 12000 to 11024 and you should be able
> to get the full bandpass of your 22050 signal.

Thanks a lot. This worked perfectly.

> Would you really need support for 22050 at 24kbit/sec if CELT could
> produce identical results at 44100 24kbit/sec?  If your interest is
> just in operating at lower bitrates then there is a lot we can achieve
> by running at full rate and low-passing internally.

Yes, I am looking for lower bitrates, optimized for 22 kHz signals. Ideally
I'd like to have good quality for speech at about 40 kbit/sec and get better
quality than Speex. So far, by doing your hack and removing the two highest
bands I get completely transparent quality at 62 kbit/sec.

The results I get with CELT at 42 kbit/sec are also pretty good, but the
highest bands get some noise  in the 8-11 kHz frequency range. I am going to
see what I can do, and try to optimize the band allocation or other parts of
the codec. For comparison, AAC-LC achieves transparent quality for speech at
about 48 kbit/sec.

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