User's Manual
Avaya B179 SIP Conference Phone Installation and Administration Guide
30
Codec
Codecs are used to convert an analog voice signal to a digitally encoded version and vice
versa. Codecs vary in the sound quality they deliver and the bandwidth required. The Avaya
B179 supports the most common codecs and each codec can be given a precedence depend-
ing on your requirements for high quality audio or low bandwidth use.
The priority can be set to from 4 (high) to 1 (low) or 0 (disabled)
G722 G.722 is an ITU-T standard codec that provides 7 kHz wideband audio at
a data rate within 64 kbit/s. It oers greately improved speech quality
compared with older narrowband codecs such as G.711, but requires
a high quality network connection between the devices.
G711 Alaw G.711 is an ITU-T standard codec that uses audio companding.
Companding algorithms reduce the dynamic range of an audio
signal. In analog systems, this can increase the signal-to-noise ratio
achieved during transmission and, in the digital domain, can reduce
the quantization error.
Two main compression algorithms are dened in the standard,
the µ-law algorithm (used in North America and Japan) and A-law
algorithm (used in Europe and the rest of the world).
G711 Ulaw See G711 A-law above.
G729 G.729 is an ITU-T standard codec that operates at 8 kbit/s. It is mostly
used in VoIP applications with low bandwidth requirement.
On phone: > SETTINGS > ADVANCED > (PIN) > MEDIA > CODEC (6,2,4,1).
Security
The media in VoIP calls is usually sent using the RTP protocol (Real-time Transport Protocol).
RTP is a standardized packet format for delivering audio and video over the Internet.
SRTP (Secure Real-time Transport Protocol) is an extension of RTP to provide encryption,
message authentication and integrity for the audio and video streams.
All devices must support SRTP to establish a connection. It is therefore possible to set SRTP as
disabled, optional or mandatory.
RTCP can be used to control the RTP session. When using SRTP, the same security-related
features are added to the control protocol. SRTCP (Secure Real Time Control Protocol) can be
either encrypted or not encrypted.