[asterisk-users] Distorted audio over Eicon Diva Server BRI

[Tim Panton]

On 8 Jan 2008, at 08:17, Armin Schindler wrote:

> On Tue, 8 Jan 2008, CSB wrote:
>> We are experiencing slightly distorted audio with playing of  
>> recordings on
>> our Asterisk server when the call comes in over our Eicon Diva  
>> Server BRI
>> card. An example is an incoming call to IVR and playing some of the  
>> standard
>> Asterisk voice prompts. Note that there is no audio problem with  
>> internal
>> access to the same recording. Neither is there a problem with calls  
>> not
>> involving the playing of recordings. The problem occurs  
>> consistently and is
>> not related to system load. According to Eicon support:
>>
>> Asterisk is sending it's data packets (160 bytes each, i.e. 20ms)  
>> in too
>> large intervals. This causes the transmitter of the Diva Server  
>> card to
>> underrun and thus to fill with idle samples in regular intervals.  
>> It's
>> almost between any two packets where we have to insert samples.
> ...
>> I wonder if anyone could provide any advice on how to continue
>> troubleshooting this issue?
>
> I never heard of that problem before. Which versions of asterisk and
> chan_capi (I assume you use chan_capi) do you use?
>
> If possible, can you provide a trace with
>   set verbose 9
>   capi debug
> to me directly (not on the list, it is very big).
> Also, a full ditrace would help too.
>
> Armin


I saw something similar with mISDN.
If your recordings aren't an exact multiple of 20ms then
asterisk sends a short frame for the last one.

Here's a quick hack that fixed the problem for me,
record the files in GSM. This forces the length of the recording to be
an exact multiple of 20ms.


Hope that helps.

Tim.