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
On 13 Mar 2007, at 00:32, David Brazier wrote:> 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 > > DavidIt would be interesting to see an ethereal trace of the packets going to your PRI gateway. Ideally the packet capture would be done by a separate system, so that the clock of your Dell won't also be the 'reference' clock. Do you run NTP on that system. If you do, take a look at the skew over a day or so and see if the Dell is running fast. It might be worth investing in a low end digium card just to generate a clock that is independent of your CPU clock. Tim Panton www.mexuar.net www.westhawk.co.uk/
I've had similar behavior on my own IVR. I moved my sound files to a ram disk and all pops and ticks stopped! David Brazier wrote:> 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 > _______________________________________________ > --Bandwidth and Colocation provided by Easynews.com -- > > asterisk-users mailing list > To UNSUBSCRIBE or update options visit: > http://lists.digium.com/mailman/listinfo/asterisk-users > >