[cisco-voip] Transcoder garbles audio

[Kevin Thorngren]

Hi Kris,

One thing I forgot to mention.  The best way to capture this would be 
to capture three different locations simultaneously; 1 the Transcoder, 
2 the G.729 phone and 3 the CallManager.  This will allow us to see 
each device independently.

Also, I did notice in the duplicate RTP packets from the CallManager to 
the Transcoder - one of them has a DSCP value of 0 and the other has a 
value of 0x2E.  Maybe there is an issue with the marking of these 
packets and QoS.

Kevin
On Mar 17, 2005, at 9:30 PM, Kevin Thorngren wrote:

> Hi Kris,
>
> I took a quick look at your TAC case.  I briefly looked at the last
> packet capture you provided.  It looks like you have 3 phones using the
> CCM software CFB with one of them being G.729 and the other two G.711.
>
> How did you capture this?
>
> The packets to and from the Transcoder are duplicated in the trace.  I
> have seen this before when trying to use a span port or port monitor.
> We will first need to get a clean capture that does not have duplicated
> packets.  This will allow use to get a better idea of where the problem
> might be.
>
> Have you considered that the problem might not be with the Transcoder
> but that the problem might be with the CCM software CFB?
> You have used two different hardware platforms but in both cases have
> used CCM 4.0(2a).
>
> Do you have the option to use a hardware conference bridge to try
> isolating the problem to either CCM or the Transcoder?
>
> I have not heard of nor did I find (after a quick search) any issues
> pointing toward either a CCM issue or Transcoder issue.
>
> What hardware do you have in the 2801 for Transcoding?
>
> Thanks,
> Kevin
>
> On Mar 17, 2005, at 8:01 PM, Kris Seraphine wrote:
>
>> I have a customer who's been complaining about audio becoming garbled
>> and unintelligible for g729 participants in conference calls.  I
>> finally
>> had some time to replicate the scenario in my lab and I can reproduce
>> it
>> at will but for the life of me I can't figure out a solution.
>>
>> On any call that goes through a transcoder, after approx. 30 minutes,
>> the g729 audio becomes garbled and stays this way for 8 minutes; at
>> which point it clears up.  This is 100 % reproduceable and always
>> happens with the same timing (plus/minus a minute or two).  During the
>> time the g729 end hears the garbled audio, the other participants can
>> hear the g729 user clearly.
>>
>> It happens on conference calls and direct two party calls that go
>> through a transcoder; so the problem has to be either the transcoder 
>> or
>> phone load I'd guess.  The customer is running CCM 4.02a.  I'm using
>> 4.02asr1.  I'm using a 2801 in the lab so my ios options are limited
>> but
>> the customer is using a 1760 and I've tried 12.3(8)T and 12.3(11)T and
>> the problem exists in both.
>>
>> It's hard to beleive this isn't a known issue since its so easily
>> reproducible and seems to exist across platforms and ios releases but 
>> I
>> can't find anything in the bug tool.  The TAC seems to be stumped as
>> well.  I've had a case open for about a month now.
>>
>> Just wondering if anyone has any suggestions or maybe has seen this
>> issue themselves.
>>
>>
>> Kris Seraphine
>>
>>
>>
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