Telephony Products
VAD and CNG
The implemented algorithms are stand-alone Voice Activity Detection (VAD) and Comfort
Noise Generation (CNG). These modules are based on the Full Rate-GSM speech processor
standard, which uses silence compression techniques to reduce the transmitted bit rate
during the silent intervals of speech. Discontinuous transmission (DTX) systems are based
on VAD and CNG algorithms, which insert Silence Insertion Descriptor (SID) frames during
the silence intervals. The VAD module makes speech/silence decisions and analyses silence
to produce SID frames.
During silence, SID's are periodically sent to the CNG module, which generates comfort
noise. This also provides the additional advantage of using lower processing loads and
DSP bandwidth resource during silence frames.
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