[Ekiga-list] Aliasing in audio codecs

[Stefan Bruens]

Am Montag, 29. Januar 2007 12:55 schrieb Jean-Marc Valin:
> If that's what I think it is, it's not related to Speex, iLBC or any
> other audio codec. It's actually ALSA that finds that your soundcard
> cannot do 8/16 kHz, so it automatically does resampling (usually to 48
> kHz). The only problem is that ALSA uses LINEAR INTERPOLATION RESAMPLING
> which is about the worst you can do. The only solutions are 1) to fix
> ALSA 2) use PulseAudio 3) implement decent resampling code in Ekiga
> (I've got an alpha resampler in Speex svn now).
>
> 	Jean-Marc

Alsa since version 1.0.11 supports libsamplerate for rate conversion. Just 
put 'defaults.pcm.rate_converter "samplerate"' into your .asoundrc 
or /etc/asound.conf

BTW, if you are using dmix, your will always have to resample, as you have a 
fixed rate for mixing the streams.

Hope this helps,

Lurchi

-- 
Stefan Brüns  /  Kastanienweg 6 - Zimmer 1206  /  52074 Aachen
mailto:lurch at gmx.li  http://www.kawo1.rwth-aachen.de/~lurchi/
   phone: +49 241 169-4206     mobile: +49 160 3797725
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