Mandatory Speech Codec speech processing functions; Adaptive Multi-Rate (AMR) speech codec; Transcoding functions
The present document describes the detailed mapping from input blocks of 160 speech samples in 13‑bit uniform PCM format to encoded blocks of 95, 103, 118, 134, 148, 159, 204, and 244 bits and from encoded blocks of 95, 103, 118, 134, 148, 159, 204, and 244 bits to output blocks of 160 reconstructed speech samples. The sampling rate is 8 000 samples/s leading to a bit rate for the encoded bit stream of 4.75, 5.15, 5.90, 6.70, 7.40, 7.95, 10.2 or 12.2 kbit/s. The coding scheme for the multi-rate coding modes is the so‑called Algebraic Code Excited Linear Prediction Coder, hereafter referred to as ACELP. The multi-rate ACELP coder is referred to as MR-ACELP.
In the case of discrepancy between the requirements described in the present document and the fixed point computational description (ANSI‑C code) of these requirements contained in [4], the description in [4] will prevail. The ANSI‑C code is not described in the present document, see [4] for a description of the ANSI‑C code.
The transcoding procedure specified in the present document is mandatory for systems using the AMR speech codec.