Real-time implementation of sub-band coding on a programmable integrated circuit

In this paper we discuss the implementation of sub-band coding (SBC) on a programmable digital signal processing (DSP) integrated circuit developed at Bell Laboratories. A two-band SBC has been developed for use in 7 kHz bandwidth transmission (AM broadcast quality) at a bit-rate of 56 kb/s. A four-band SBC has been developed for use in speech coding (3.2 kHz bandwidth) at bit rates ranging from 16 kb/s to 24 kb/s. We first review the capabilities of the DSP integrated circuit. We then discuss the hardware and software development environment used for programming real-time SBC on the DSP. Next we discuss block diagrams of the SBC algorithms that were implemented. Finally, we discuss aspects of how these algorithms were programmed in real-time on the DSP and features of the DSP that are utilized.