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

[Matt Riddell]

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Tim Panton wrote:
> 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.

Hmmm, sounds the same as what I had, but it was the transcoding that
fixed it.  I actually wrote a patch to send packets through a smoother
which fixed it, and use that on all sites with IAX phones.

- --
Kind Regards,

Matt Riddell
Director
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