Audio delay in external calls

[gmgarrian]

This is a new install with CUCM 8.5.1.  External calls are experiencing a slight delay in the audio which causes a lot of people speaking on top of each other, specifically in conference calls.

This is not limited to conference calls, and those conf calls hosted externally with a single caller from this environment are having the same issue.

There are no other call audio issues, no static, jitter, fade out, etc.

Also, the system connects to the pstn via a 2951 h323 gw.

[Joseph Martini]

If you have the delay only at the beginning of the call you might want to use fast start so that the media information is sent in the H225 SETUP instead of waiting for the CONNECT to get the port for H245 and going through that negotiation.  If you are seeing a problem after calls are initially setup and people are taking take a packet capture at the source and destination to try and see if there is delay in the packets being sent out or arriving, I know you don't have jitter (variation of packets arriving) but there could be a consistent delay.

[Aaron Harrison]

Hi

It sounds to me like you are saying you have a high delay consistent through the call?

If this is the case, you need to work out where the delay originates from. Do you have high delay between the phone endpoint on your network and the location of the gateway? It seems odd that you would only get delays when dialling an external conference service, and not on normal calls, unless normal calls also have high delay and the additional delay incurred on the conference service is simply bringing it over the threshold so it becomes noticeable.

If the delay is a call setup delay (i.e. a delay in setting up the voice in either direction, so one end or both cannot hear the other for a few seconds at the start of the call) then the solution will be different.

Aaron

[gmgarrian]

Yes, the delay seems to be with external calls.  When it was first reported I was told it was only with conference calls but after some test calls it seems that the delay is on all external calls, it's just more noticable on a con call with multiple people talking at once.

[dkemp · Accepted solution]

Hi,

     I would check if you are using an MTP resource for these calls,  if you have external hardware MTP's are they still registered.  CUCM has default internal internal software MTP's that it will fall back to if externals are not registered, not good to use these as system CPU is directly impacted and I have experienced delays and poor quality on external calls when using them.

Cheers

Dave

[gmgarrian]

The hardware MTP was not registered. I checked and the dspfarm profile was shut down.  I did a no shut and it registered.

I'm waiting to hear back from my client to see if things have improved.

Thanks for the help!