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Echo Canceller: To remove acoustic echo from a voice
communication in order to improve the voice quality.
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VAD (Voice Activity Detection): Allow IP phone to detect
the presence or absence of human speech during a call.
When detecting period of “silence”, VAD replaces that
silence efficiently with special packets that indicate silen-
ce is occurring. It can facilitate speech processing, and
deactivate some processes during non-speech section
of an audio session. It can avoid unnecessary coding or
transmission of silence packets in VoIP applications,
saving on computation and network bandwidth.
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CNG (Comfort Noise Generation): Allow IP phone to
generate comfortable background noise for voice com-
munications during periods of silence in a conversation.
It is a part of the silence suppression or VAD handling for
VoIP technology. CNG, in conjunction with VAD algori-
thms, quickly responds when periods of silence occur
and inserts artificial noise until voice activity resumes. The
insertion of artificial noise gives the illusion of a constant
transmission stream, so that background sound is con-
sistent throughout the call and the listener does not think
the line has released.
Jitter buffer is a shared data area where voice packets
can be collected, stored, and sent to the voice processor
in even intervals. Jitter is a term indicating variations in
packet arrival time, which can occur because of network
congestion, timing drift or route changes. The jitter buffer,
located at the receiving end of the voice connection,
intentionally delays the arriving packets so that the end
user experiences a clear connection with very little sound
distortion.
IP phones support two types of jitter buffers: fixed and
adaptive.
Echo Canceller
Jitter Buffer
Description
Sections
