Variable frame rate, fixed bit rate vocoding method

Details Variable frame rate, fixed bit rate vocoding method Variable frame rate, fixed bit rate vocoding method

1987-10-05

1989-07-25

Salce, Patrick R.

Electrical audio signal processing systems and devices

Binaural and stereophonic

Hearing aid

381 51, 3645135, G10L 500

Patent

active

048521795

ABSTRACT:
A method of operating a vocoder so that a variable frame rate results while maintaining a constant bit rate is disclosed. A base frame rate remains constant. However, spectral change is measured to determine an appropriate subframe rate within the base frame. Only one of a plurality of separate vector quantization processes is selected in response to spectral change for performance of a vector quantization operation on LPC spectrum coefficients. Each of the plurality of vector quantization operations utilizes its own codebook that contains a different quantity of reference patterns from that contained in the other codebooks. Each vector quantization operation produces a reference pattern descriptor code that contains a different number of bits from that produced by the other vector quantization processes. Vector quantization operations producing smaller, less spectrally accurate outputs are selected when more subframes are included with a base frame, and vector quantization operations producing larger, more spectrally accurate outputs are selected when fewer subframes are included within a base frame.

REFERENCES:
patent: 4701955 (1987-10-01), Taguchi
"The Application of a Functional Perceptual Model of Speech to Variable-Rate LPC System", Viswanathan et al., IEEE, A.S.S.P. Conference, 1977, pp. 219-222.
"Vector Quantization in Speech Coding", Makhoul et al., Proceedings of the IEEE, vol. 73, No. 11, Nov. 1985, pp. 1551-1588.
"Vector Quantization: A Pattern-Matching Technique for Speech Coding", Gevsho et al., Proceedings of the IEEE, Dec. 1983, pp. 87-105.

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