Using asterisk with DSP chips

Home » Asterisk Users » Using asterisk with DSP chips
Asterisk Users 5 Comments


I have to use asterisk with some dedicated DSP chips, which will do the
expensive G729 CODEC computing, so that the server processor has minimum
load. I was informed, I’ve to use GPAK to implement this. So far I’ve
researched, I’ve found that, Asterisk uses Dahdi to *talk* to external

Can you please direct me to references/documentations that clarifies,

1. The over all architecture of asterisk with dedicated DSP chips,
i.e., how does asterisk integrates with dedicated dsp chips?
2. Whether embedded scenario is a must for such development or is it
possible to use asterisk on server and dsp’s through some PCI/Ethernet?
3. What could possibly be the build process in such scenario? Tools
i.e., cross compilers etc?
4. How do asterisk know, that when a call arrives it has to use a
particular DSP chip for Encoding/Decoding?

The GPAK user’s manual states,

The physical layer of communication between the host processor and a G.PAK
> DSP is often dependent upon the hardware design. This interface can be via
> a host port interface (HPI), shared memory, a PCI bus, Ethernet or any
> other fast data pathway.

So far I’ve comprehended from the above quotation, it is possible to use
asterisk on a server and DSPs on some remote location (say, not built into
the same board where asterisk is running) . Am I correct?

Thank you very much for patient reading.

5 thoughts on - Using asterisk with DSP chips

  • Sazzad wrote:

    Is it the wrong place for the question? No. Does anybody that has read
    your message know the answer, probably not.


  • *@David*
    Thanks for your reply. The specification for this job is not clear yet.
    Like whether we’ll be provided with related DAHDI driver or not. If not, I
    have to write one. So I was interested about the ‘know how’. Hence I think
    my precise question will be:

    Is there any open source DAHDI driver for a DSP chip, that Asterisk uses


    Eric, thanks. I think you’ve got the point. Thanks for those links. I
    remember I’ve compiled Asterisk with all those DAHDI drivers.
    Specially, wctc4xxp drivers meant to be used for TC400 series (according to
    documentation). Yes, now I think, we are not provided with Sangoma/Digium
    cards (which they hopefully have drivers prepared), I’ve to seek some
    wisdom at dev-list for other DSP chips.