> I have done a quick search and there are some nice lookingdsp-pci cards out there. (Dunno abt prices). It may take some coding to get them working with Asterisk , and one would not require a super-power quad xeon processor if it had a huge dsp card.
Perhaps but the fundamental premise upon which the Asterisk/Digium hardware is predicated is that commodity MIPS (i.e. generic server systems) are much cheaper than speciality DSP MIPS -- which is why the architecture used by Asterisk/Digium is to use board that are trivially simple (i.e. merely interface between the analog/digital trunks and the PCI bus) leaving all the signal processing to the server CPU. DSPs may be more "efficient" in some sense but because of the incredible volume of generic servers being shipped and the competitive pressure on pricing, they turn out to have better price/performance. DSP boards ship in volumes orders of magnitude smaller which makes them much more expensive.
If power/density is an issue and you don't need the PCI slots to interface to digital trunks, take a look at using blade servers.
g.
I make the argument quite often that using generic processors for DSP-like functions is obviously the way of the future for generic tasks. As an example, processing power in MIPs vs. price for Intel or Intel-like processors looks pretty good when viewed from a distance - those curves seem to favor moving pretty much everything but the most exotic DSP work into the central CPU. I firmly believe that telephony is a software problem now, not a hardware problem. "The DSP has died - long live dsp.c!"
However...
For transcoding and echo cancellation, we're not there yet for the high end telephony applications. For Asterisk, this is OK, since most people on this list don't run "high end applications" with their Asterisk servers. They have 1, or 5, or even 100 extensions on a PBX replacement, which works great - I don't consider that "high end", and therefore Asterisk works well for it's primary tasks. But Asterisk aspires to higher goals with certain firms and certain tasks, and the generic processors on which it currently runs just can't hack it yet. Echo cancellation and transcoding still are out of reach for Asterisk when compared with DSP-based platforms, if you're talking about density of channels per RU or per dollar. Yes, I've done the cost comparisons with (as an example) RLX blade servers vs. Cisco AS5800, and the 5800 loses in cost, but not in space (it's smaller) and certainly not in hassle. I can get a Cisco box up in an afternoon (and get physical interfaces as a bonus) but getting a dozen RLX boxes turned up and happy isn't something to be done without significant planning, standardization, administration, MANAGEMENT (see my post of a day or two ago) etc. which adds up. In this industry, time is usually more valuable than long-term capital expense budget (whee! sounds like 1998, doesn't it?)
Maybe in two years (maybe more, maybe less) the processor market will crest that magic cost vs. performance barrier where I'll change my mind, and this can be done on a smaller number of physical systems. After all, the processing load for dealing with human voice remains consistent, and processors are getting faster. But not yet.
Today, for the truly "massive" scale, perhaps blade servers win when you have full time staff to do nothing but care for and feed hundreds upon hundreds of Asterisk servers. Google has proven their point. But there are step functions here to consider, and cost is not the only factor that must be considered - no one solution is right for everything, and claiming that DSPs are dead is a bit premature at the carrier end of the spectrum.
The point of this is: I'd love to see an _inexpensive_ board that does DSP co-processing and echo cancellation, that plays well with Asterisk. Getting better density (and better echo cancellation!) would be a big win, and if it could be less costly than the Digium physical interface boards of the same capacity, then that might be a nice combination. I'd rather pay an additional $1200 for a card I can move around into various other platforms rather than pay an additional $1500 for the upgrade to a dual 3.0ghz system I'd need to handle (maybe) the same number of channels.
(before someone mis-quotes me as saying Asterisk doesn't work for carriers, I'd suggest you read this message over again and contemplate very closely the exact wordings I've used. If English isn't your primary language, please be careful of the landmines I've laid.)
JT
_______________________________________________ Asterisk-Users mailing list [EMAIL PROTECTED] http://lists.digium.com/mailman/listinfo/asterisk-users To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
