Universal Vocoder Using Variable Data Rate Vocoding.

摘要

To help achieve universal secure communications interoperability in the Department of Defense (DoD), one intermediate goal has been the development of a universal voice encoder (vocoder) that can seamlessly encode speech at a wide range of variable and fixed data rates to suit a wide range of DoD communication equipment. This report describes the most recent advancements in achieving this goal. Four of the most important areas of improvements presented are: (1) Significant improvements were made to the variable data rate (VDR) vocoder that make it much more robust in less than ideal environments. (2) Error control coding is now extended to all VDR modes. (3) Fixed rate vocoding modes based directly on the VDR encoding method were designed so that transcoding between these options can be done directly and with very little degradation in voice quality. (4) Heavily error protected, fixed rate modes were designed. These modes can be used as fail-safe modes to ensure communicability when channels deteriorate to previously unusable levels.