[VoiceOps] Hardware transcoding solutions?

[Moises Silva]

On Thu, Aug 27, 2015 at 3:45 PM, Simon Perreault <sperreault at jive.com>
wrote:

> Le 2015-08-27 15:38, Brooks Bridges a écrit :
> > Our total requirement is > 5000 channels, however I'm more than
> > willing to deploy multiple devices to reach this number as long as
> > the power and space requirements aren't horribly restrictive.
>
> One can easily transcode 5000 729<->711 channels in software on a
> generic 1U server. Have you even tried?
>

I'm curious. Can you be more precise on what you mean exactly by generic 1U
server? What matters mostly is the processor, not the rack unit, so I'd be
interested in hearing your experience with transcoding 5000 g729 to g711
channels.

Here are some precise numbers that I run on a dual xeon 1U server earlier
this month for a presentation at the FreeSWITCH conference, ClueCon.

The tests were run using 1,000 calls at 50cps (using FreeSWITCH). However,
I did test at lower cps, same max calls and results are quite similar
because the bulk of the load is the transcoding as it can be seen in the
graphs below.

Without transcoding (just PCMU to PCMU bridging with standard 20ms
packetization):

http://moythreads.com/vmstat/xeon-sqlitefullmem-lwarn-sprof-glibc-1000@50cps/report.html

And with G.722 to PCMU transcoding:

http://www.moythreads.com/vmstat/xeon-sqlitefullmem-lwarn-sprof-glibc-transcodingG722-1000@50cps/report.html

At 1,000 calls you already maxed the CPUs with G.722 transcoding, see the
last graph, that's what's more relevant, showing how the idle cpu on the
server went from 80% to 15% idle on average just when adding transcoding.
Granted, there's more powerful boxes out there, but this should give people
a clear idea of the cost of transcoding. The algorithmic complexity of G722
is on par with G.729, in fact, G.729 is a bit more complex. Not to mention
other codecs such as iLBC or AMR.

Overall, I agree software can give very decent results, so it's really a
matter of using what you see fits better your needs.

-
Moy
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