ETSI Standard Vocoders
ETSI FR-GSM
The algorithm implemented is the
ETSI Full-Rate (FR) GSM recommendation, digital mobile telephone system. The
encoder compresses linear-PCM (Pulse Code Modulated), narrowband speech input
data, at a sample rate of 8kHz, to 13 000 bps, and uses a Regular Pulse Excitation
with Long-Term Prediction (RPE-LTP) algorithm. The software includes voice
activity detection, error concealment, and discontinuous transmission facilities.
The FR-GSM algorithm implements
silence compression techniques to reduce the transmitted bit rate during the
silent intervals of speech. Systems allowing discontinuous transmission (DTX)
are based on Voice Activity Detection (VAD) algorithms and Comfort Noise Generator
(CNG) algorithms that allows the insertion of Silence Insertion Descriptor
(SID) frames during the silence intervals. This also provides the additional
advantage of using lower processing loads and DSP bandwidth resource during
silence frames.
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