Generating the variable control parameters of a speech signal sy

Details Generating the variable control parameters of a speech signal sy Generating the variable control parameters of a speech signal sy

1993-07-27

2000-01-18

Knepper, David D.

Data processing: speech signal processing, linguistics, language

Speech signal processing

For storage or transmission

704223, G10L 914

Patent

active

060164689

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The present application relates to methods and apparatus for the coding of speech signals; particularly (though not exclusively) to code excited linear predictive coding (LPC) in which input speech is analysed to derive the parameters of an appropriate time-varying synthesis filter, and to select from a "codebook" of excitation signals those which, when (after appropriate scaling) supplied in succession to such a synthesis filter, produce the best approximation to the original speech. The filter parameters, codeword identifying codebook entries, and gains, can be sent to a receiver where they are used to synthesise received speech.
2. Related Art
Commonly in such systems a long-term predictor is employed in addition to the LPC filter. This is best illustrated by reference to FIG. 1 of the accompanying drawings, which shows a block diagram of a decoder. The coded signal includes a codeword identifying one of a number of stored excitation pulse sequences and a gain value; the codeword is employed at the decoder to read out the identified sequence from a codebook store 1, which is then multiplied by the gain value in a multiplier 2. Rather than being used directly to drive a synthesis filter, this signal is then added in an adder 3 to a predicted signal to form the desired composition excitation signal. The predicted signal is obtained by feeding back past values of the composite excitation via a variable delay line 4 and a multiplier 5, controlled by a delay parameter and further gain value included in the coded signal. Finally the composite excitation drives an LPC filter 6 having variable coefficients. The rationale behind the use of the long term predictor is to exploit the inherent periodicity of the required excitation (at least during voiced speech); an earlier portion of the excitation forms a prediction to which the codebook excitation is added. This reduces the amount of information that the codebook excitation has to carry, viz it carries information about changes to the excitation rather than its absolute value.
One difficulty with the apparatus of FIG. 1 is that the temporal resolution of the long term predictor is limited to an integer multiple of the sampling rate.
One prior proposal for alleviating this difficulty involves upsampling the speech signals prior to long-term prediction to increase the resolution of the prediction delay parameter, which however increases the complexity of the apparatus. Another approach is to provide the delay 4 with several taps, each with its own gain factor, a combination of gain factors being chosen from a codebook of gain combinations. This however involves a lengthy search procedure since each delay/gain combination must be tested in the coder to determine the optimum combination.


BRIEF SUMMARY OF THE INVENTION

According to the preset invention a method of speech coding is provided in which input speech is analyzed to determine the parameters of a synthesis filter and to determine parameters of an excitation signal which can be applied at a decoder to a filter having the determined filter parameters to produce an output resembling the input speech. The exemplary embodiment includes the steps or: excitation signal a part a excitation which would produce from the filter a signal resembling the input speech; partial excitation produces a total excitation which would produce from the filter a signal better resembling the input speech; and excitation samples delayed by a respective amount and (b) partial excitations each consisting of samples formed by weighted addition of at least two past excitation samples delayed by a respective amount; of the filter to each partial excitation, the partial excitation being scaled to minimise the said difference, and selecting that partial excitation producing the smallest difference; single or added past samples are employed, and a scaling factor.
Additionally, in code-excited LPC systems, substantial processing of the signals is required in order to identify the releva

REFERENCES:
patent: 3909533 (1975-09-01), Willimann
patent: 4787057 (1988-11-01), Hammond
patent: 4868867 (1989-09-01), Davidson et al.
patent: 4932061 (1990-06-01), Kroon et al.
patent: 5179594 (1993-01-01), Yip et al.
patent: 5187745 (1993-02-01), Yip et al.
patent: 5323486 (1994-06-01), Taniguchi et al.
patent: 5371853 (1994-12-01), Kao et al.
Lever et al, "RPCELP: A High Quality and Low Complexity Scheme for Narrow Band Coding for Speech", EUROCON 88, 8th European Conference on Electrotechnics, Stockholm, Jun. 13-17, 1988, pp. 24-27, IEEE, New York, US.
Kleijn et al, "An Efficient Stochastically Excited Linear Predictive Coding Algorithm For High Quality Low Bit Rate Transmission of Speech", Speech Communication, vol. 7, No. 3, Oct. 1988, pp. 305-316, Elsevier Science Publishers B.V. (North-Holland), Amsterdam, NL.
Davidson et al, "Real-Time Vector Excitation Coding of Speech at 4800 BPS", ICASSP '87, 1987 International Conference om Acoustics, Speech, and Signal Processing, Dallas, Texas, Apr. 6-9, 1987, vol. 4, pp. 2189-2192, IEEE, New York, US.
Adoul et al, "Fast CELP Coding Based on Algebraic Codes", ICASSP '87, 1987 International Conference on Acoustics, Speech, and Signal Processing, Dallas, Texas, Apr. 6-9, 1987, vol. 4, pp. 1957-1960, IEEE, New York, US.
Muller, "Improving Performance of Code Excited LPC-Coders by Joint Optimization", Speech Communication, vol. 8, No. 4, Dec. 1989, pp. 363-360, Elsevier Science Publishers B.V. (North-Holland), Amsterdam, NL.
Jayant et al, "Speech Coding with Time-Varying Bit Allocation to Excitation and LPC Parameters", ICASSP '89, 1989 International Conference on Acoustics, Speech and Signal Processing, Glasgow, May 23-26, 1989, vol. 1, pp. 65-68, IEEE, New York, US.
Bergstrom et al, "Code-Book Driven Glottal Pulse Analysis", ICASSP '89, 1989 International Conference on Acoustics, Speech and Signal Processing, Glasgow, May 23-26, 1989, vol. 1, pp. 53-56, IEEE, New York, US.
Menez et al, "A 2 ms-Delay Adaptive Code Excited Linear Predictive Coder", ICASSP '90, 1990 International Conference on Acoustics, Speech and Signal Processing, Albuquerque, New Mexico, Apr. 3-6, 1990, vol. 1, pp. 457-460, IEEE, New York, US.
"Pitch Prediction With Fractional Delays in CELP Coding", J.S. Marques, J.M. Tribolet, I.M. Trancoso, L.V. Almeida, EuroSpeech, 1989, pp. 509-512.
"Strategies for Improving the Performance of CELP Coders at Low Bit Rates", P. Kroon and B.S. Atai, ICASSP-88, vol. 1, pp. 151-154, 1988 (IEEE).
Proceedings of the 1988 International Conference on Parallel Processing, Aug. 15-19, 1988, vol. III, The Pennsylvania State University Press, University Park, USA; S.T. Peng et al.: A New VLSI 2-D Systolic Array For Matrix Multiplication and Its Applications:, pp. 169-172.
ICASSP 89 (1989 International Conference on Acoustics, Speech and Signal Processing, May 23-26, 1992, Glasgow, GB) vol. 1, IEEE, New York, US; Cellario et al.: "A 2 MS Delay CELP Coder", pp. 73-76.

Affiliated with

Also associated with

Rating

Generating the variable control parameters of a speech signal sy does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Generating the variable control parameters of a speech signal sy, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Generating the variable control parameters of a speech signal sy will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-569679