Case study-speech terminal interface

Describes the design of a digital interface for a CCITT High Quality Speech Terminal using DSP techniques to compress 7 kHz bandwidth audio signals into 64 kbit/s. The decision process involved in choosing between two different solutions is described and reasons given for the final compromise. CCITT Recommendation G722 defines the characteristics of an audio coding system which may be used for a wide variety of high quality speech and data applications. The algorithm has been implemented using Digital Signal Processors (DSPs) to compress 7 kHz audio signals and up to 16 kbit/s of auxiliary data into a single 64 kbit/s digital bitstream. This is the basic channel for the Integrated Services Digital Network (ISDN) and most private digital circuits