Low bit rate vocoder means and method

Details Low bit rate vocoder means and method Low bit rate vocoder means and method

1991-07-19

1993-10-19

Fleming, Michael R.

G10L 904

Patent

active

052553396

ABSTRACT:
Efficient coding speech information for low rate (e.g., 600 bps) channels using a four frame superframe (SF) includes: (1) coding spectral information using alternative quantizers one of which is chosen for each superframe so that 3 bits/SF identify the optimal quantizer and 28-32 bits/SF contain the quantized spectral information; (2) coding pitch using 5 bits/SF if voiced and if unvoiced assigning the pitch bits to error correction; (3) coding energy using 9-12 bits/SF by a 4d vector quantizer (4dvQ); and (4) coding voicing using 3-4 bits/SF by a 4d VQ, for a total of 54 bits/SF including 1 sync bit and 0-1 error correction bits. When combined with a unique perceptual weighting scheme, output speech quality comparable to that of vocoders operating at almost four times the channel capacity is obtained.

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