DRAFT
© 2003 - 2005 Linksys, a Division of Cisco Systems Proprietary (See Copyright Notice on Page 2)
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individually name the various codecs that are supported such that the correct codec successfully
negotiates with the far end the equipment.
Voice Algorithms:
The SPA941 supports the following voice algorithms.
G.711 (A-law and mµ-law)
This very low complexity codec supports uncompressed 64 kbps digitized voice transmission at one
through ten 5 ms voice frames per packet. This codec provides the highest voice quality and uses the
most bandwidth of any of the available codecs.
G.726
This low complexity codec supports compressed 16, 24, 32 and 40 kbps digitized voice transmission at
one through ten 10 ms voice frames per packet. This codec provides the high voice quality.
G.729A
The ITU G.729 voice coding algorithm is used to compress digitized speech. Linksys supports G.729.
G.729A is a reduced complexity version of G.729. It requires about half the processing power to code
G.729. The G.729 and G.729A bit streams are compatible and interoperable, but not identical.
G.723.1
The SPA supports the use of ITU G.723.1 audio codec at 6.4 kbps.
Codec Selection
The administrator can select which low-bit-rate codec to be used for each line. G711a and G711u are
always enabled.
Dynamic Payload
When no static payload value is assigned per RFC 1890, the SPA can support dynamic payloads for
G.726.
Adjustable Audio Frames Per Packet
This feature allows the user to set the number of audio frames contained in one RTP packet. Packets can
be adjusted to contain from 1 – 10 audio frames. Increasing the number of packets decreases the
bandwidth utilized – but it also increases delay and may affect voice quality.
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