[Asterisk-Users] Hardware based DSP

[Jim Van Meggelen]

asterisk-users-bounces at lists.digium.com wrote:
> Thank you all for your explanations related to my question.
> 
> I have one follow-up question though.
> 
> When I said that all dsp related stuff has to be handled
> by software within asterisk, I was thinking of
> conferencing at the time.
> 
> I mean in order to be able to conference a sip session with
> a PSTN call, it would have to be handled by software, even
> if both the channels had hardware dsp capabilities. Right ??

Hmmm. Ultimately, yes, I suppose there's always going to be some of
that. Where the DSP work gets really intensive is when what is going
into the DSP is quite different from what's coing out. If a hardware
device existed for Asterisk to transcode all channels into a common
format, so that internally the same codec was being used, then the CPU
would have relatively little DSP work to do when connecting them
together. I don't know if this would be a problem in other areas, so
what I'm saying is more of a brainstorm than anything I think needs to
happen.

> If you are dealing with just a single channel, then the
> driver may handle codec/echo cancelation stuff with hardware help (??)

That sounds pretty much correct. I know there's been some talk about
using the powerful floating-point capabilities of 3d video cards to do
transcoding; other ideas are in the works as well.

> As an aside, what is the best way to go about learnig about
> the aritecture of asterisk, other than "using the source" ??

There simply isn't enough documentation in that regard. At least not
that anyone's found in a single repository . . . other than the wiki, of
course.

> The Wiki pages are great, but I have not (yet) found any info
> about asterisks architecture itself (in depth that is).

Nor has anyone, to my knowledge (other than reading the source).

> Some linked websites / blogs provide good info on some
> topics, but is there a good high level design doc available anywhere ?

The Asterisk Documentation Project has that very thing as one of it's
goals. It's a big job, and there are few of us, so it's not happening as
fast as everyone would like. There is so much to write, and so little
time . . .

> It would stop people like me asking so many basic questions
> in the -dev list.

There's no doubt that more documentation is needed.