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3-6
Design Guide for Cisco Unity Release 5.x
OL-14619-01
Chapter 3 Network Infrastructure Requirements
Audio Codecs
TTS, TTY, Pocket PCs, and Hand-Held Computers
For Cisco Unity sites using Text to Speech (TTS), any supported codec can be used to record messages.
However, TTS output is currently available only in G.711 and G.729a audio formats.
For Cisco Unity sites using TTY, G.711 is required. The TTY standard does not support other codecs.
GSM 6.10 is supported for playback on a Pocket PC, and is a higher quality recording format than MP3.
G.711 and G.729a usually are not compatible with hand-held computers.
Interoperability Among Multiple Voice-Messaging Systems
If multiple Cisco Unity servers will communicate with one another via Cisco Unity Digital Networking
or VPIM, or if Cisco
Unity will communicate with other voice-messaging systems by using AMIS, the
Cisco
Unity Bridge, or VPIM, you must choose a compatible codec. Table 3-2 shows a summary of
codec considerations for Cisco Unity networking options.
Table 3-1 Voice Message File Sizes and Audio Quality Ratings
Audio Codec Approximate File Size, 1-Minute Message Quality Rating
G.711 Mu-Law and A-Law 480 KB Excellent
G.726 32 Kbps 240 KB Fine
OKI ADPCM 8 kHz 240 KB Fine
OKI ADPCM 6 kHz 180 KB Fine
GSM 6.10 98 KB Good
G.729a 60 KB Good
Table 3-2 Networking Interoperability Comparison for Audio Codecs
Networking Option Supported Codecs
AMIS The AMIS protocol is not dependent on audio format.
The Cisco Unity servers can use any of the supported codecs.
Cisco Unity Bridge Octel Analog Networking is not dependent on audio format.
The Cisco Unity servers must use either G.711 or G.729a in order to
communicate with the Cisco
Unity Bridge servers.
VPIM For inbound messages, Cisco Unity can convert voice messages to any codec
that Cisco
Unity supports.
For outbound voice messages, Cisco Unity can either convert voice messages
to G.726 format or not convert at all. Not converting is useful when you are
using VPIM to send voice messages between Cisco
Unity servers.