An 8 kbit/s transform coder for noisy channels

The design of a speech transform coder which is robust against channel errors is presented. The bit rate is 8 kb/s including 1.3 kb/s redundancy bits for bit-selective error correction. The coder is based on transform coding with weighted vector quantization and two-channel conjugate vector quantization. Each scheme improves the robustness against channel errors without sacrificing the performance of the error-free case. Real-time operation can be achieved with 10 MIPS DSP and 8-kword memory with a 80-ms coding delay. The mean opinion score of the coded speech is comparable to that of 5-bit log PCM even at a 1% burst error rate