Cisco SPA112 Administration Manual page 36

Configuring Voice
Getting Started with Voice Services
Cisco SPA100 Series Phone Adapters Administration Guide
Supported Codecs
The ATA voice ports support the following codecs:
Codec
G.711 (A-law and mu-law)
G.726-32
G.729a
The administrator can select the preferred codecs to be used for each line. See
Audio Configuration, page
In addition, negotiation of the optimal voice codec sometimes depends on the
ability of a device to match a codec name with the codec used by the far-end
device. You can individually name the various codecs so that the ATA can
successfully negotiate the codec with the far-end equipment. For more
information, see Audio Configuration, page
SIP Proxy Redundancy
In typical commercial IP Telephony deployments, all calls are established through
a SIP proxy server. A typical SIP proxy server can handle thousands of
subscribers. It is important that a backup server be available so that an active
server can be temporarily switched out for maintenance. The ATA supports the
use of backup SIP proxy servers (through DNS SRV) so that service disruption is
minimized.
Description
Very low complexity codecs that support
uncompressed 64 kbps digitized voice
transmissions at one through ten 5 ms voice frames
per packet. These codecs provide the highest
narrow-band voice quality and uses the most
bandwidth of any of the available codecs.
Low complexity codec that supports compressed
32 kbps digitized voice transmission at one through
ten 10 ms voice frames per packet. This codec
provides high voice quality.
ITU G.729 voice coding algorithm used to
compress digitized speech. G.729a is a reduced
complexity version of G.729 requiring about half
the processing power of G.729. The G.729 and
G.729a bit streams are compatible and
interoperable, but not identical.
104.
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