[Asterisk-Dev] 16 KHz audio ?

[Eric Bart]

> Actually, it 
> doesn't take many extra bits to code the higher frequencies. The bulk of 
> the bits concentrate on the first 4kHz.

Right. And there's not much compressed rate difference from a 16K to a 24K 
bandwidth. So why not choose directly 24 KHz ?!


> The wideband iLBC isn't available for royalty free use, as far as I 
> know. They only allow the narrowband to be used in that way.

I don't know what codec would be usable for gnu. But you should definetely
find one for a "medium" output rate (ie for a lan usage).

If we still want a low output rate codec, maybe we could use a
"free for the public" codec, something like a real audio codec. As long as 
this codec is only used by the phone (iaxcomm), there is no license problem 
for asterisk. Asterisk will just forward frames back and forth between the 
parties. 

I've said that if we don't want Asterisk to downsample, we'll have to tell 
the phone to get back to a 8 KHz sampling. Same thing for the decoding, if 
we don't want to decode the proprietary codec, then will ask the phone to 
get back to a 8 KHz sampling (with a gnu codec), then we'll be able to 
stream prompts and things ...