System for wideband speech coding based on recursive filterbanks
Ralf Th. Pietsch, Arild Lacroix · The Journal of the Acoustical Society of America · 1999
Wideband speech coding becomes increasingly important because of the enhanced quality due to the extended frequency range. Possible applications are in various fields partly with fixed and partly with variable data rates: synchronous and asynchronous transmission over digital networks, mobile telephony, and multimedia systems. In this context a system is presented which is well suited for dialog communication. The signal analysis and synthesis is done by filterbanks based on recursive filters. The use of recursive filters implies short system delays in the filterbank. However, phase distortions are present and have to be considered carefully. Different methods were implemented to reduce phase distortions and to compensate group delay peaks. Coding is based on redundance and irrelevance reduction. The irrelevance reduction is implemented by the exploitation of psychoacoustical masking effects. Encoder and decoder are running on a single DSP32C signal processor in real time. The achieved data rate for good speech quality is 32 kbit/s and below.