Design of uniform DFT filter banks optimized for subband coding of speech

Abstract

A new approach for designing uniform DFT analysis/synthesis filter banks, optimized for subband coding (SBC) of speech, is presented. A spectral-domain distortion measure, which consists of a weighted sum of error terms due to filtering, rate conversion, and quantization, is derived. The quantization is embedded by means of a statistical model. For the case of 'fine' quantization, a simpler, deterministic distortion function is derived. The optimal filters are designed using an iterative algorithm in which two sets of linear equations are solved in each iteration, aiming at minimizing the distortion function. A 16-kb/s SBC is simulated using a filter bank designed by the new approach, and is found to achieve subjective and objective (SNR) performance similar to that of a conventional QMF-based SBC, with only about half the amount of computation.< >