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Polycom RealPresence Collaboration Server (RMX) 1500/2000/4000 Administrator’s Guide
4-36 Polycom, Inc.
The SirenLPR audio algorithm provides CD-quality audio for better clarity and less listener
fatigue with audio and visual communication applications.
In SVC conferences, the system supports SAC (Scalable Audio Coding) audio algorithm.
Guidelines
• Siren 22, G.719 and Siren 22Stereo are supported with MPM+ and MPMx cards.
• Siren 22 and G.719 are supported in both mono and stereo.
• Stereo is supported in H.323 calls only.
• Siren 22 is supported by Polycom HDX endpoints, version 2.0 and later.
• G.728 is supported with both MPM+ and MPMx cards and in H.323, SIP and ISDN
environments.
• SirenLPR is enabled by default and can be disabled by setting the system flag,
ENABLE_SIRENLPR, to NO.
• SirenLPR is supported:
— With MPMx Cards only.
— In IP (H.323, SIP) calls only.
— In CP and VSW conferences.
— With Polycom CMAD and HDX “Canyon 3.0.1”endpoints.
— For mono audio at audio line rates of 32Kbps, 48Kbps and 64Kbps.
— For stereo audio at audio line rates of 64Kbps, 96Kbps and 128Kbps.
SIP Encryption
The ENABLE_SIRENLPR_SIP_ENCRYPTION System Flag enables the SirenLPR audio
algorithm when using encryption with the SIP protocol.
The default value of this flag is NO meaning SirenLPR is disabled by default for SIP
participants in an encrypted conference. To enable SirenLPR the System Flag must be added
to system.cfg and its value set to YES.
Mono
The Siren 22, G.719 and SirenLPR mono audio algorithms are supported at the following bit
rates:
Table 4-11 Siren22, G.719 and SirenLPR Mono vs Bitrate
Audio Algorithm Minimum Bitrate (kbps)
Siren22 64k
384
Siren22 48K
Siren22_32k
G.719_64k
G.719_48k
G.719_32k
G.728 16K