16kbps Real time QMF sub-band coding implementation

The availability of medium performance microprocessors, in conjunction with different concepts to generate real time efficient signal processing software on microprocessors without hardwired multipliers, allows the real time implementation of sub-band voice compression algorithms. This paper deals with the implementation of a 16kbps (8kHz, 2 bits per sample) 8 sub-band coder assuming a bank of 40 tap QMF decimator and interpolator filters, an adaptive allocation of the bits resource based on channels activity and a straigth block PCM coding of the decimated samples. The paper focuses on the implementation and software techniques which were used to achieve a complete sub-band coder with about 1.3 million of instructions per second on a processor with a 16 bits instruction and data flow.