Digital signal processor: Sub-band coding

This paper explores the use of the Bell Laboratories digital signal processing integrated circuit for digitally encoding speech or audio signals based on the sub-band coding technique. Sub-band coding represents a next level in algorithmic complexity over that of adaptive differential pulse-code modulation, discussed in a companion paper, and it has a corresponding advantage in performance. We discuss the details of a real-time, two-band sub-band coding implementation on the digital signal processor. We then comment on how this approach can be extended to more than two band designs for greater bit rate compression capability. In connection with this, we also consider some general issues involved in implementing multirate signal processing algorithms of this type on the digital signal processor.