Chapter 4-Additional Conferencing Information
Polycom, Inc. 4-45
Audio Algorithm Support
The Collaboration Server supports the following audio algorithms: G.711, G.722, G.722.1,
G.722.1C, G.729A, Polycom Siren 7 (in mono), Siren14, Siren 22 (in mono or stereo) and
SirenLPR.
Polycom’s proprietary Siren 22 is supported for participants connecting with Polycom
endpoints.
The Siren 22 audio algorithm provides CD-quality audio for better clarity and less listener
fatigue with audio and visual communication applications. Siren 22 requires less computing
power and has much lower latency than alternative wideband audio technologies.
The SirenLPR audio algorithm provides CD-quality audio for better clarity and less listener
fatigue with audio and visual communication applications.
Guidelines
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 and Group series endpoints.
SirenLPR is enabled by default and can be disabled by setting the system flag,
ENABLE_SIRENLPR, to NO.
SirenLPR is supported:
In IP (H.323, SIP) calls only.
With Polycom CMAD and HDXCanyon” and Group series 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 22and SirenLPR mono audio algorithms are supported at the following bit rates:
Table 4-14 Siren22 and SirenLPR Mono vs Bitrate
Audio Algorithm Minimum Bitrate (kbps)
Siren22 64k
Siren22 48K
Siren22_32k
Siren22_48K
G.7221C_48k
Siren14_48k