G.711 vs G.729

[lwmoseley]

On my 2901 router, the config on my dial-peer voice for VOIP is set to use voice-class codec 1 which is defined in the router as G.729.  However, within the call manager, the Region Audio Codec is set to G.711.

Which one is it using?  Which takes precedence?  Should the codecs match?  Which codec is better for voice?

Thanks in advance

[Aaron Harrison]

Hi

A regions config of G711 actually means 'use up to 64kbps of bandwidth per call'. That's why it can use G722 or G711 as it sees fit.

In this case, G729 (8K)is less than G711 (64k) and is the only codec your CME is going to claim to support, so it should use that.

You can hit ? twice in quick succesion on the phone to see what codec is in use on the current cal.

Aaron

[lwmoseley]

So it is irrelevant the setting that the router is set to use becuase the CME is going to dictate which codec?  I just did a test call and it was using G.711.  I am questioning this because we are having some call quality/jitter issues and I wonder if I sould set the CME to G729 for all regions so it won't use as much bandwidth.

[Aaron Harrison]

Hi

Did you call CUCM-->CME, or CME-->CUCM?

Can you post up your dial-peer config, called/calling number, and a debug voip dialpeer taken when you make the call?

Aaron

[lwmoseley]

Sorry, I am running CUCM v7.0.

the sending and receiving codec has been confirmed as G.711.  Just tested.  Still curious as to whether or not I should change over to G.729 in order to conserve bandwidth on the regions.  Seems no matter what the router codec preference is set to the CUCM is going to use what is defined to that region.

[Aaron Harrison]

Well- you can guess, or you can troubleshoot.

Aaron

[lwmoseley]

With all due respect, I am not guessing.  I saw the output on my handset.  Here is some of what you requested.  I am spacing on how to view the output of the debug...

voice class codec 1

     codec preference 1 g729r8

     codec preference 2 g711ulaw

     codec preference 3 g723r63

     codec preference 4 g723r53

dial-peer voice 5701 voip

     description Jackson PLAR number

     preference 1

     destination-pattern 5796

     progress_ind setup enable 3

     session target ipv4:172.18.2.10

     voice-class codec 1

     dtmf-relay h245-alphanumberic

     no vad

[Ayodeji Okanlawon]

Hi,

In this scenario...

for inbound calls to CUCM, CCME is going to advertise TCS with G729, G711,G723...

CUCM is going to send back its own TCS with only G711 because the region setting is set to use only G711....Hence G711 will be used.

To see the actual media negotitation,

debug h225 asn1

debug h245 asn1

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[Chris Deren]

Just to add to some great points here from my colleagues, the behavior is different in CUCM 9.X and on vs. previous versions, as Aaron described the region config up until version 9 defines the max codec rate, so if G711 is specified in the region it does not mean G711 will be used but rather that up to G711 can be used. With version 9.X "Audio codec preferecnce" list has been added where you can define a list of preferred codecs similar to codec-class on the router.

HTH,

Chris