VoiIP Codec and config

[zain_gabon]

Hi Support,

i read that for configuring VoIP, you must considere codec points, the code G.711 and G.729A.

I want to know regarding configuring routers or swicthes, how can i chose one or other codec?

How can i decide to use G.711 or another codec?

Regards

[Jaime Valencia · Accepted solution]

The configuration depends on the call control agent you'll be using.

Most usually you choose the codec based on the BW you have or the MOS you need.

HTH

java

If this helps, please rate

www.cisco.com/go/pdihelpdesk

[Payal Bhaduri · Accepted solution]

Each codec provides a certain quality of speech. The quality of transmitted speech is a subjective response of the listener. A common benchmark used to determine the quality of sound produced by specific codecs is the mean opinion score (MOS). With MOS, a wide range of listeners judge the quality of a voice sample (corresponds to a particular codec) on a scale of 1 (bad) to 5 (excellent). The scores are averaged to provide the MOS for that sample. This table shows the relationship between codecs and MOS scores.

Compression Method	Bit Rate (kbps)	MOS Score	Compression Delay (ms)
G.711 PCM	64	4.1	0.75
G.726 ADPCM	32	3.85	1
G.728 LD-CELP	16	3.61	3 to 5
G.729 CS-ACELP	8	3.92	10
G.729 x 2 Encodings	8	3.27	10
G.729 x 3 Encodings	8	2.68	10
G.729a CS-ACELP	8	3.7	10
G.723.1 MP-MLQ	6.3	3.9	30
G.723.1 ACELP	5.3	3.65	30

This document will help you understand about codecs

http://www.cisco.com/en/US/tech/tk1077/technologies_tech_note09186a00800b6710.shtml

[dijohn · Accepted solution]

Depends on the Bandwidth

Inter-site -- G729

Intra-site - G711/G722

There's a slight difference between G711 and G729 audio quality..but a user wouldn't notice this in the course of a conversation.

HTH

PS: Rate useful posts.!

[zain_gabon]

Thanks for your quick response

but can you please provide me with an example

if i have a wan link 512 kb/s, how can i choose code?

do you have router commande to choose codec?

regars

[Jaime Valencia · Accepted solution]

Assuming you're using H323 in the VOIP dial peer config mode just type codec ? and you'll get the list of options.

HTH

java

If this helps, please rate

www.cisco.com/go/pdihelpdesk

[dijohn · Accepted solution]

IP Phone A----- R1 ------ R2 --- IP Phone B

A(1000) calls B(2000)

R1  - Outgoing Dial-peer

dial-peer voice 2000 voip

destination-pattern 2...

session-target ipv4:

codec g729

R2 - incoming Dial-peer

dial-peer voice 9999 voip

incoming-called number 2...

codec g729

now the call hits Phone B as a G729 call :-)

If you are using CUCM use "regions"

[zain_gabon]

Thanks for your quick supports

Regards

[dijohn · Accepted solution]

This post helps you to understand dial-peer matching...

http://www.cisco.com/en/US/tech/tk652/tk90/technologies_tech_note09186a008010fed1.shtml

HTH

PS: Rate useful posts..