Cisco Systems OL-14619-01 manual TTS, TTY, Pocket PCs, and Hand-Held Computers, Audio Codec

Chapter 3 Network Infrastructure Requirements

Audio Codecs

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

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 3-2shows a summary of codec considerations for Cisco Unity networking options.

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.

Design Guide for Cisco Unity Release 5.x

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