This Frequently Asked Questions (FAQ) document clarifies the codec
support for some of the most common IP Telephony Server solutions and provides
a consolidation of codec support information in one location.
Technical Tips Conventions for more information on document
What codecs does the Cisco TAPI service provider (TSP) support?
A. The Cisco WAVE driver included with the Cisco TSP only supports G.711.
What codecs are supported by Cisco CallManager 4.x?
A. Cisco CallManager 4.x supports these codecs:
G.711 a-law and u-law.
G.723 (only supported by the IP phones VIP30 and SP12+).
Automated bandwidth selection.
G.729 Annex A and Annex B.
Global System for Mobile Communications (GSM)-Enhanced Full Rate
(EFR) and Full Rate (FR).
Wideband audio - proprietary 16-bit resolution and 16 kHz sampled
What codecs are supported by Cisco Unified Communications Manager
(CallManager) 5.x and 6.x?
A. Cisco Unified Communications Manager 5.x supports the codecs supported
by CallManager 4.x and these codecs:
Cisco Unified Communications Manager 6.x supports the codecs supported
by CallManager 4.x and these codecs:
What codecs does Cisco Customer Response Applications (CRA) support?
A. These codecs are supported by the associated CRA version:
CRA 2.2.x only supports G.711 u-law.
Customer Response Solution (CRS) releases up to and including 3.0(2)
support G.711 encoding only (a-law and u-law).
CRS release 3.1(x) also supports G.729 Annex A (G.729A) encoding.
Any CRS 3.1(x) system can have either G.711 or G.729 Annex A
(G.729A), but not both.
Any CRS 3.1(x) system installed that wishes to change to the other
encoding must perform a reinstall of the entire system.
Automatic Speech Recognition (ASR)/Text-to-Speech (TTS) does not work
with G.729 Annex A (G.729A) codec. The G.729 Annex A (G.729A) and ASR/TTS are
What codecs does Cisco Unity Support?
A. These audio codecs are supported for use with all versions of Cisco
G.711 u-law and a-law.
G.729 Annex A (G.729A) at 20 ms packetization rate ONLY. Cisco Unity
TAPI Service Provider (TSP) 7.0.3 and later supports g.729a from 10 ms up to 60
ms packetization rate.
Intel Dialogic OKI ADPCM 8 kHz.
Intel Dialogic OKI ADPCM 6 kHz.
In addition, the G.726 codec is supported for use with a Cisco Unity
version 4.0(1) or later system that runs Microsoft Exchange and uses the Voice
Profile for Internet Messaging (VPIM) networking option.
What codecs does the Cisco CallManager Music On Hold (MOH) server
A. These audio codecs are supported by the Cisco CallManager MOH server:
What codecs does the Cisco Conference Connection support?
A. Cisco Conference Connection supports G.711 u-law only. You must use a
transcoder if you use any other codec.
What codecs does the Cisco CallManager Software Conference Bridge
A. Cisco CallManager Software Conference Bridge supports only G.711 a-law
and G.711 u-law.
What codecs does the Personal Assistant support?
A. Only G.711 u-law is currently supported.
Do Cisco 7940 and Cisco 7960 IP Phones support G.729 Annex B when running
A. No, Cisco 7940 and Cisco 7960 IP Phones do not support G.729 Annex B
when running SIP load. If you need to use 7940 or 7960 IP Phones that run SIP
instead of SCCP for some particular reason, you can use a hardware transcoder
to support G.729 Annex B out the H.323 trunk.
How do you play out voice mails over a Personal Digital Assistant
A. In order to allow your voice mails to be played over the PDA, you can
change the record format in unity. You can do this via Tools
Depot > Audio Management Tools > Set
Record format. This will allow you to change it to gsm
6.10. A restart is required to have this take effect.
What codecs are supported by Cisco Unified Mobility
A. Cisco Unified Mobility Advantage supports voice messages stored in the
G.711 and GSM 6.10 audio formats.