[Speex-dev] Need some help about speex settings

Eugene Leviant evgeny.leviant at gmail.com
Tue Aug 25 02:59:30 PDT 2009

Hi, Everyone!

I'm developing VoIP application using Speex, have some questions:

1) When ultra-wideband mode should I use 32000 Hz sampling rate only?
If I use 44100 Hz the voice quality seems to be better comparing to 32 KHz.

2) When I use wideband mode with 16 KHz sampling rate bandwidth usage is
greater comparing to 32 KHz, ultra-wideband. Why? Voice
quality is worse when using 16KHz wideband comparing to ultra-wideband

3) Speex samples testenc_wb and testenc_uwb gets SPEEX_GET_LOOKAHEAD
parameter and skip appropriate number of samples. Should I do the same in
VoIP ? What this value means and how is it used in Speex?

4) If sampling rate is 44100 and I use wideband (not ultra) coding bandwidth
usage is very high (about 9 KB/sec). Is it normal and just happens because
Speex wideband coding targeted for 16 KHz only?

5) Is there any other way to improve voice quality except setting quality
(1-10) Speex parameter? I noticed that quality with Speex is worse comparing
to Skype. I use ultra wideband, 44100, quality=8

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