[Freeswitch-users] Session recording performance

Stanislav Sinyagin ssinyagin at gmail.com
Wed Sep 20 13:45:57 UTC 2017


I'm building an environment for voice quality testing, and found a
strange behavior. Maybe someone has an explanation.

Two identical physical computers (PC Engines APU2), connected back to
back (A and B).

A initiates the test calls to B's SIP address, and then both ends go
through a small dialplan (less than 100 lines of XML, similar to
https://github.com/voxserv/fsqa/blob/master/fsqa.xml
and start recording the session.

The dialplan initiates session recording to a Raw file, and plays back
a 20-second audio sample, and then inserts the filename into a Redis
queue, then hangs up. Then the files get processed by Sevana AQuA
software in lowest CPU priority, and deleted. The files are written
into a tmpfs filesystem.

With 2 calls per second, I get 48 simultaneous calls, and B indicates
frame drops in the audio recordings, while A shows good results. The
CPU average idle time is always above 50% on both computers.

Why is the B side (the one receiving INVITEs) getting more frame drops
than the A (the one originating the calls)?  I flipped the sides, and
then the other machine started to get more drops.

At first I started recording in WAV format, and similar effect started
to appear at a call every 2 seconds, resulting in 12 simultaneous
calls. With raw recording, the performance is much better, but still
it's a mistery why there are dropped frames in the audio.

The CPU is always running at its highest frequency, under
"performance" governor.



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