Linksys RTP300 User Guide - Page 22

Introducing Linksys Analog Telephone Adapters ATA Software Features ATA Software Features The Linksys ATA device is a full featured, fully programmable phone adapter that can be custom provisioned within a wide range of configuration parameters. This section contains a high-level overview of features to provide a basic understanding of the feature breadth and capabilities of the Linksys ATA device. The following sections describe the factors that contribute to voice quality: • "Voice Supported Codecs," on page 22 • "SIP Proxy Redundancy," on page 23 • "Other Linksys ATA Software Features," on page 23 Voice Supported Codecs Negotiation of the optimal voice codec sometimes depends on the ability of the Linksys ATA device to match a codec name with the codec used by the far-end device. The Linksys ATA device allows the network administrator to individually name the various codecs that are supported so that the Linksys ATA device can successfully negotiate the codec with the far-end equipment. The administrator can select which low-bit-rate codec is to be used for each line. G.711a and G.711u are always enabled. Configure your preferred codec in the (FXS) tab in the Administration Web Server. See "Linksys ATA Voice Field Reference," on page 94. See also "Supported Codecs," on page 44 for a list of which codecs are supported on each Linksys ATA device. Codec (Voice Compression Algorithm) G.711 (A-law and mμ-law) G.726 G.729a G.723.1 Description 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. 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 high voice quality. 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. The Linksys ATA device supports the use of ITU G.723.1 audio codec at 6.4 kbps. Up to two channels of G.723.1 can be used simultaneously. For example, Line 1 and Line 2 can be using G.723.1 simultaneously, or Line 1 or Line 2 can initiate a three-way conference with both call legs using G.723.1. Note: The WRP400 device does not support the G.723.1 audio codec. NOTE: When no static payload value is assigned per RFC 1890, the Linksys ATA device can support dynamic payloads for G.726. Linksys ATA Administration Guide 22