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marsbewohner

MoH Soundquality

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Hi,

 

is it possible to measure the quality of the MoH sound? We're experiencing that the MoH sound is accompanied by a very disturbing noise when played by the PBX, if you open the file (default SnomOne moh.wav) with Windows Media Player for example everything is fine.

 

CPU or media load can't be the reason, the CPU is bored at 5%.

 

Could it be some kind of codec issue?

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Is that a file that came with the audio files for the PBX or did you create it on your own? The PBX understands only a narrow subset of the WAV file capabilities, for example it will not take stereo files and the sampling frequency must be 8 kHz.

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Between mars and earth? Usually when the sound does not sound like packet loss, it is a problem with excessive transcoding. Remember from information theory, transcoding can only reduce the audio quality, even when transcoding "to" a great codec. If you do that a couple of times, it really sounds like smoke signs on a mointain. Least common denominator!

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Maybe, if necessary ;) Transcoding might be a reason, but it also sounds like this when having MoH internally. Although I must admit that it's much more worse when you're calling from/to external, no matter if it's landline or mobile. Will do some tests on this...

 

As a question, we're using Asterisk as internal SIP registrar for Sangoma cards which are connected to T1s, the trunk PBX <-> Asterisk should be G711, but in case the outgoing line operates in a lower codec, will the Asterisk handle the transcoding or the SnomOne itself?

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Asterisk can do transcoding as well. It all depends on the setup. But this could be another transcoding step. IMHO the easiest is to keep it to G711 by default, then the transcoding to the PSTN (PRI, ISDN) can be loss less.

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I am having the same issue. I have been able to narrow it down to be that the call has to be with a cell phone. I do not think that packet loss is an issue(MOS on cal is 4.7). We are using g.729 as our default codec and g.711 as the second choice. Can you suggest the .wav format to use to try and correct this.

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G.729A is not good with music. Nothing will change that. My recommendation is to keep the volume as low as possible; everything else will be painful.

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