[Asterisk-Users] ADPCM - vs - G.726

[Martin Joseph]

On Mar 11, 2006, at 6:25 AM, Whisker, Peter wrote:

> The G.726 codec is the current Asterisk 1.2  version (revision 7221). 
> I am using G.711a (alaw) between a Sipura ATA and Asterisk at each end 
> of the link and am testing alternative codecs on an IAX link (not in 
> trunk mode) between the two Asterisk servers. (Yes, I know that the 
> Sipura can do G.726-32 also).
>
> When I have G.726 switched in as the codec, it seems to add a little 
> gain as well as the clipping clicks. If I use G.711 on the 
> Asterisk-Asterisk link there is no problem. ADPCM seems to behave 
> better than G.726 but is percepibly "fuzzy".
>
> GSM as I expected sounds like an old pre-EFR mobile phone. And the 
> rest are worse or like G.729 or Speex, eat processor power. I have 
> G.723 and G.729 compiled from the Intel distro.
>
Not to belabor to obvious,  but you really want to eliminate any 
translation if possible.  I found in my setup that using uLaw over IAX 
produced loud cracks for me?  I could really trouble shoot this 
further, but using G729 over IAX or using uLaw over SIP did not have 
these issues.

I ended up using the SIP option, although I had really hoped to use 
IAX.  I think this might be an asterisk issue, but have no way to prove 
it,  so I am going to wait a while and if future releases help.

Again,  to to restate the obvious, using G729 only eats CPU if it's 
translating.

Good Luck,
marty