ITU-T Standard Vocoders
G.728
The algorithm implemented is the
ITU-T G.728 recommendation, fixed rate speech coder. The encoder compresses
linear-PCM (Pulse Code Modulated), narrowband speech data, at a sample rate
of 8kHz, to 16 000 bps. G.728 is a complex coder using a Low-Delay Code-Excited
Linear Prediction (LD-CELP) algorithm that employs backward-adaptive Linear
Predictive Coding (LPC) analysis in order to achieve a low transcoding delay.
The decoder also incorporates an adaptive post-filter to enhance performance
for multiple transcodings.
The post-filter function can be omitted for single
coder-decoder operation to reduce the processing power required on the DSP.
G.728 is an essential addition to all video conferencing systems and is increasingly
being used in Voice and DSL applications.
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