[cisco-voip] Transcoder garbles audio

[Kevin Thorngren]

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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