TIA/EIA Standard Vocoders

IS-127

The algorithm implemented is the TIA/EIA recommendation IS-127 CDMA, a dynamically variable data rate speech coder. The encoder compresses speech input data in a 16-bit uniform Pulse Code Modulated (PCM) format, at a sample rate of 8kHz to full rate at 9 600, half rate at 4 800 and eighth rate at 1 200 bps. The recommendation also uses short-term and long-term post-filtering, and incorporates noise suppression procedures as part of the pre-processing.

At full and half rates, the 20ms speech frames are processed by a generalized AbS procedure (RCELP) to search the optimum indices of the adaptive codebook and the innovative ACELP (Algebraic Codebook Excited Linear Prediction) codebook. At eighth rate the compression is mainly characterised by the energy contour.

This product has been developed and shipped by SIGNALS+SOFTWARE on a number of platforms previously, both standalone and as part of a complete solution, and would be available customized  to meet specific requirements.

For more information please contact our sales team.

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