Hi list,
Has anyone been able to get more than two G729 calls with transcoding of
decent voice quality on AstLinux 0.4 or greater? I was doing some research
into how many calls our hardware was able to transcode from G729 to A-law,
and it seems the limit is two and is not hardware dependent. Once there are
three calls up, the audio on all three calls breaks up. This testing was
done over a LAN, so it shouldn't be a bandwidth problem. CPU on the
original hardware I tested was around 22%, so CPU is not the limiting
factor, and I even tested on much faster hardware (Pentium-M) and the audio
still broke up after the third call. This testing was performed using the
open-source G729 uClibc binaries for AstLinux 0.4 as it is for research and
I didn't want to buy licences which would be of no use if it didn't work and
of little use after the research is finished.
I also tested the open-source glibc G729 binaries with AsteriskNOW on the
same original hardware and I did not have the same problem, so this points
at uClibc as the culprit.
I talked to the maintainer of these open-source G729 binaries, Arkadi
Shishlov, and he already suspected uClibc, which is why I tested with
AsteriskNOW.
Here is part of what he said:
> It is probably uClibc pthread implementation.
> 6-8 g.729 calls with transcoding in both directions should not be a
problem for this CPU.
FYI, the original hardware is able to transcode 15 calls from GSM to A-law
fine on AstLinux IIRC.
I am interested to learn if anyone has been able to get more than two G729
calls up, with either the open-source binary, or the Digium binary.
Kind regards,
Sebastian
P.S. I wrote this e-mail a few months ago, but was going to do a bit more
testing before sending it, but given this apparent flaw with uClibc, and
various other reasons (including possibly more sensibility to jitter than
other distributions), I had to abandon AstLinux (for now at least) and
didn't even have time for more testing. Nevertheless, I thought it might be
interesting to have this discussion in case anyone has anything to
contribute. It would be useful if anyone was able to confirm these
problems, or claim to not have these problems, so I would encourage
interested parties to do their own tests. I would also be interested, of
course, in results from testing the Digium G729 binaries.
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