Frame-Fill Techniques for Reducing Vocoder Data Rates.
MASSACHUSETTS INST OF TECH LEXINGTON LINCOLN LAB
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Two experimental vocoder systems are described which exploit the frame-fill concept described by McLarnon to achieve data rates in the range of 800 to 1200 bps. One is based on a well-known 2400 bps channel vocoder design, the second is based on a form of the Lincoln 2400 bps linear predictive coder LPC-10 algorithm. Both systems were found to perform well at the 1200 bps rate representing a 21 savings in transmission bandwidth at very little additional algorithm complexity. At 800 bps both systems were judged usable but not wholly satisfactory. Performance of the channel vocoder was considered marginally better than LPC at 800 bps. Author
- Voice Communications