Performance of a real time low rate voice codec

A real time low rate voice coder/decoder has been developed and is being tested using speakers in simulated operational environments. The unit uses the TMS32010 to perform the signal processing functions, and is packaged in a manner suitable for an office or benign field environment. The software implements the following algorithms: 2400 bps LPC using the United States Government standard LPC-10 algorithm. 800 bps using vector quantization. 400 bps using frame repeat vector quantization with trellis coding of gain and pitch. The hardware configuration is described, along with a brief explanation of the available test configurations and execution options. A review of the coding algorithms is presented, with a summary of the operational parameters. Test results include measured execution times, program and data memory sizes. Preliminary listening tests indicate that the voice quality at 800 bps is very close to that achieved at 2400 bps with the standard algorithms.