Hardware implementation of a 16 kbps subband coder using vector quantization

A real-time 16 kb/s waveform coder which uses a combination of subband analysis/synthesis and vector quantization (VQ) to achieve a one-way communication delay of 20 ms is described. Gain-shape decomposition is used to vector-quantize the outputs of a generalized quadrature mirror filter bank. The short-time filter bank energy (gain) is used to dynamically allocate bits for coding the gain-normalized filter outputs (shape). The coder-decoder, implemented on a single AT&T DSP32 signal processing chip with 256 kB of off-chip memory for codebook storage, has a typical segmental SNR of 20.44 dB for sentences outside the training set