[asterisk-users] Playback 5% Too Fast?

[David Brazier]

Hi All

I have a problem with IVR scripts which consist mainly of Playback of
audio files, driven from an AGI application.  There are clicks every few
seconds or more frequently that is audible on the remote end (PSTN), but
not on the Asterisk recording of the call.  If I record the remote end
and compare it to the local recording, it appears to be about 5%-7% too
fast - i.e. if I synchronise the starts, the remote end finishes sooner.
I can find points in the remote recording where parts of the waveform
have been missed out, leading to jumps in the waveform, which correspond
to the audible clicks.  These "jumps" seem like dropped packets, and I'm
deducing that Asterisk is sending data slightly too fast (i.e. more
frequently than 50x160 sample per second) for the remote end, which has
to drop data to keep up.  

This is a VoIP-only set up - no Zap hardware.  Thinking this was a
timing issue, I have installed Zaptel to get ztdummy, which is loaded
OK, but that hasn't made any difference.  I have tried it with different
VoIP providers and observed the same problem.

Behaviour has persisted from 1.2 to 1.4 and now 1.4.1.  CentOS 4.4
(2.6.9 kernel), Dell 1950.

Any ideas how to progress?  Is this a timing issue or am I wide of the
mark?

Thanks for any help

David