Setting g711, getting g722?

[ritsonr]

Sorry, probably a noob question here...

I'm setting g711 in my region config for calls within the same site but when i initiate a call and check the call stats it always shows g722, can anyone tell me why? If i set it to g729 thats shows up fine in the call stats...

Thanks in advance...

Rich

[Jaime Valencia · Accepted solution]

Because you don't really set the codec, but a maximum BW that can be used.

Since G722 uses the same BW as G711, but it's a wideband codec, if both devices can use it then it's preferred unless you disable G722 from your config in CUCM.

HTH

java

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[ritsonr]

ok, so if one of the devices could only work with g711 it would stick with that...

nice one, thanks java....

Rich

[James Hawkins]

You can disable the G.722 codec on a per phone basis by setting Advertise G.722 Codec to disable.

If you do not want to use G.722 at all in the cluster you can set the Enterprise Parameter for Advertise G.722 Codec to disabled (it is enabled by default).

[srsivara]

http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/rel_notes/8_0_1/delta/cm​a​dmin.html#wp1194654

shows the order of preferred codecs (g722 over g711).

The G722 codec causes issues when the a phone capable of doing g722 gets enabled for call recording. If internal phones negotiate g722 codec, the phone enabled for call recording will advertise the same codec (g722) to the recording server. Most of the recording servers don't support g722 codec, resulting in a transcoder allocation request. If no appropriate transcoder to transcode between g722 and g711 / g729 (recording server), the recording call will fail. For this, the Cisco CallManager service parameter 'G722 Codec Enabled' can be set to 'Enabled for All Devices Except Recording-Enabled Devices' or 'Disabled'

- Sriram

[Lamar Demby]

Has anyone seen an instance in which some phones continue to negotiate g.711 when the advertise g.722 has been disabled on one of the phones being used?  I disabled g.722 on 2 phones that will be used for a call recording solution that doesn't support g.722.  One phone works and the other one doesn't.  I've reset both phones and still getting fast-busy on one of the phones when trying to make a call to another internal cisco phone that has g.722 enabled.  The other phone works great everytime.

The working phone is a 7945.

The non-working phone is a 7975.

Both phones are running SCCP 9-2-1SR2S and are in the same Device Pool, Region, CSS, etc.

[Lamar Demby]

Without making any additional changes, the 7975 that was not working yesterday is now working.  Guess it had to sit overnight??  (scratching my head)

[Lamar Demby]

Found another article on this forum that reference Cisco Bug ID CSCtq97254.

https://supportforums.cisco.com/message/3555851#3555851

After upgrading the phones from firmware version 9.2(1) to 9.2(3), that resolved my issue.

[GABRIEL KNEBL TUMOLO]

Adding information in Jaime`s answer. In the defaults codec preference lists, G722 has priority that G711. If you want to use G711, but can`t disable G722, copy than customize a new codec list in region configuration.

Cisco Unified Communications Manager prefers codecs with better audio quality. For example, despite having a maximum bit rate of 32 kb/s, G.722.1 sounds better than some codecs with higher bit rates, such as G.711, which has a bit rate of 64 kb/s.

When you configure the maximum audio bit rate setting in the Region Configuration window (or use the service parameter in the Service Parameter Configuration window), this setting serves as a filter. When an audio codec is selected for a call, Cisco Unified Communications Manager takes the matching codecs from both sides of a call leg, filters out the codecs that exceed the configured maximum audio bit rate, and then picks the preferred codec among the codecs that are remaining in the list.