----- Original Message -----
From: "C F" <[EMAIL PROTECTED]>
Sent: Tuesday, January 24, 2006 2:20 AM
> Thanks for the reply. According to those numbers, I would not rely on
> any of these systems to do transcoding, and if such is needed, I would
> rather have a bigger machine do it. This all means that the solid
> state system will just be a good geteway, but nothing more then that,
> of course I'm wrong to say *nothing* since it runs Asterisk, but I
> mean in terms of transcoding, and I'm guessing conferencing as well.
> Correct me if I'm wrong.
Well, you may also build a solid state system with a very powerful CPU:
nothing prevents you from mounting an IDE CF adapter in place of a
conventional hard disk. Of course, if you plan for a lot of transcoding
you need CPU power as well; small embedded systems, especially if based on
CPU's lacking hardware Floating Point Unit, are not going to cut it with
heavy codecs (especially with the floating point implementations of the
latter).
However, GSM is not very demanding, and to a lesser extent also G.726
(which however requires higher bandwidth). The tiny WRT54GS I have at
home, running OpenWRT, has a not-so-macho 200 MHz Broadcomm 4712 CPU
(without FPU, so I didn't bother installing iLBC, LPC10 and Speex codecs)
but still appears to be capable of transcoding up to 13 channels at a time
(1000/(22+54)) between GSM and G.711:
g723 gsm ulaw alaw g726 adpcm slin lpc10 g729 speex ilbc
g723 - - - - - - - - - - -
gsm - - 22 22 71 25 21 - - - -
ulaw - 54 - 1 51 5 1 - - - -
alaw - 54 1 - 51 5 1 - - - -
g726 - 101 49 49 - 52 48 - - - -
adpcm - 56 4 4 53 - 3 - - - -
slin - 53 1 1 50 4 - - - - -
Of course, 13 is an absolute maximum and I wouldn't try to go beyond half
that figure, as the CPU has other things to do.
Also, transcoding may be pushed to the edge, e.g. offloaded to devices
such as the Sipura ATA's (which can handle G.729: two channels at the same
time with the SPA-2100). In that case, Asterisk can act as pass-through,
and let the endpoints do the heavy work.
Enzo
P.S. Kris, have you got any "show translation" output for the Gumstix?
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