CA1236922A - Method and apparatus for coding digital signals - Google Patents
Method and apparatus for coding digital signalsInfo
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- CA1236922A CA1236922A CA000442281A CA442281A CA1236922A CA 1236922 A CA1236922 A CA 1236922A CA 000442281 A CA000442281 A CA 000442281A CA 442281 A CA442281 A CA 442281A CA 1236922 A CA1236922 A CA 1236922A
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- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10L—SPEECH ANALYSIS OR SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING; SPEECH OR AUDIO CODING OR DECODING
- G10L19/00—Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis
- G10L19/04—Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis using predictive techniques
- G10L19/08—Determination or coding of the excitation function; Determination or coding of the long-term prediction parameters
- G10L19/10—Determination or coding of the excitation function; Determination or coding of the long-term prediction parameters the excitation function being a multipulse excitation
-
- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10L—SPEECH ANALYSIS OR SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING; SPEECH OR AUDIO CODING OR DECODING
- G10L19/00—Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis
- G10L19/04—Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis using predictive techniques
- G10L19/06—Determination or coding of the spectral characteristics, e.g. of the short-term prediction coefficients
Abstract
METHOD AND APPARATUS FOR CODING DIGITAL SIGNALS
Abstract of the Disclosure In a method and apparatus for coding of digital signals, especially so-called "waveform" coding of voice frequency signals to reduce bit rates for reduced transmission or storage requirements, in which, for each block, an excitation signal is derived which, when applied to a synthesis filter having suitable LPC coefficients, will generate an approximation to the input signal, low signal delay is achieved by deriving such excitation signal using the LPC coefficients corresponding to the last sample period of the corresponding block. Thus the excitation signal calculations in the encoder need only be delayed by the duration of the block, which is shorter than the delay incurred by previous proposals. The LPC coefficients can be derived on a continuous or sample-by-sample basis using an adaptive lattice. Simplified computation of the excitation signal, which comprises a set of pulses fewer in number than the number of samples in the original block, may be achieved by cross-correlating the impulse response of the modified synthesis filter with the output of the filter and using the result, together with the covariance of the impulse response, to derive the parameters of the excitation pulses.
Further computation simplifications may be achieved by using an auto-correlation as the covariance signal.
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Abstract of the Disclosure In a method and apparatus for coding of digital signals, especially so-called "waveform" coding of voice frequency signals to reduce bit rates for reduced transmission or storage requirements, in which, for each block, an excitation signal is derived which, when applied to a synthesis filter having suitable LPC coefficients, will generate an approximation to the input signal, low signal delay is achieved by deriving such excitation signal using the LPC coefficients corresponding to the last sample period of the corresponding block. Thus the excitation signal calculations in the encoder need only be delayed by the duration of the block, which is shorter than the delay incurred by previous proposals. The LPC coefficients can be derived on a continuous or sample-by-sample basis using an adaptive lattice. Simplified computation of the excitation signal, which comprises a set of pulses fewer in number than the number of samples in the original block, may be achieved by cross-correlating the impulse response of the modified synthesis filter with the output of the filter and using the result, together with the covariance of the impulse response, to derive the parameters of the excitation pulses.
Further computation simplifications may be achieved by using an auto-correlation as the covariance signal.
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Claims (52)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. Apparatus for processing a digital signal comprising:
an encoder comprising:
(i) input means for providing a signal (Sn) in linear PCM format;
(ii) storage means for storing discrete blocks of said signal (Sn) individually and successively, each block comprising a predetermined number of samples;
(iii) coefficient driving means for deriving from said signal (Sn) a plurality of sets of coefficients, each set of coefficients defining a spectrum envelope of the block, said plurality of sets of coefficients being derived in succession during arrival of said predetermined number of samples in that block;
(iv) excitation signal generating means responsive to the waveform of said signal (Sn) and to the most-recently derived set of said plurality of sets of coefficients for generating an excitation signal A corresponding to each of said blocks. said excitation signal comprising a component representing amplitude and a component representing temporal location within said block for each of a set of excitation pulses less in number than the number of possible PCM samples in said block.
an encoder comprising:
(i) input means for providing a signal (Sn) in linear PCM format;
(ii) storage means for storing discrete blocks of said signal (Sn) individually and successively, each block comprising a predetermined number of samples;
(iii) coefficient driving means for deriving from said signal (Sn) a plurality of sets of coefficients, each set of coefficients defining a spectrum envelope of the block, said plurality of sets of coefficients being derived in succession during arrival of said predetermined number of samples in that block;
(iv) excitation signal generating means responsive to the waveform of said signal (Sn) and to the most-recently derived set of said plurality of sets of coefficients for generating an excitation signal A corresponding to each of said blocks. said excitation signal comprising a component representing amplitude and a component representing temporal location within said block for each of a set of excitation pulses less in number than the number of possible PCM samples in said block.
2. Apparatus as defined in claim 1, wherein said coefficient deriving means is arranged to derive said coefficients on a continuous basis.
3. Apparatus as defined in claim 2, wherein the coefficient deriving means comprises an adaptive lattice.
4. Apparatus as defined in claim 1, wherein said coefficients are linear prediction coefficients.
5. Apparatus as defined in claim 2, wherein said coefficients are linear prediction coefficients.
6. Apparatus as defined in claim 3, wherein said coefficients are linear prediction coefficients.
7. Apparatus as defined in claim 1, further comprising a decoder comprising:
a decoder synthesis filter having adjustable predictor coefficients;
decoder input means responsive to said excitation signal for providing said excitation pulses and applying them to the input of said synthesis filter; and coefficient means responsive to said coefficient signal for adjusting said filter predictor coefficients, whereby application to said decoder synthesis filter of each said set of excitation pulses, following adjustment of its coefficients to corresponding values, produces an output signal substantially identical to the corresponding block of the linear PCM
signal (Sn).
a decoder synthesis filter having adjustable predictor coefficients;
decoder input means responsive to said excitation signal for providing said excitation pulses and applying them to the input of said synthesis filter; and coefficient means responsive to said coefficient signal for adjusting said filter predictor coefficients, whereby application to said decoder synthesis filter of each said set of excitation pulses, following adjustment of its coefficients to corresponding values, produces an output signal substantially identical to the corresponding block of the linear PCM
signal (Sn).
8. Apparatus as defined in claim 7, wherein said encoder includes means for multiplexing said excitation signal and said coefficient signal, and said decoder includes means for demultiplexing said excitation signal and said coefficient signal.
9. Apparatus as defined in claim 7, wherein said coefficient deriving means is arranged to derive said coefficients on a continuous basis.
10. Apparatus as defined in claim 9, wherein said coefficient deriving means comprises an adaptive lattice.
11. Apparatus as defined in claim 8, wherein said coefficients are linear prediction coefficients.
12. Apparatus as defined in claim 9, wherein said coefficients are linear prediction coefficients.
13. Apparatus as defined in claim 10, wherein said coefficients are linear prediction coefficients.
14. Apparatus for processing a digital signal comprising:
an encoder comprising:
(i) input means for providing a signal (Sn) in linear PCM format;
(ii) storage means for storing discrete blocks of said signal (Sn) individually and successively, each block comprising a predetermined number of samples;
(iii) coefficient deriving means for deriving from said signal (Sn) a plurality of sets of coefficients, each set of coefficients defining a spectrum envelope of the block, said plurality of sets of coefficients being derived in succession during arrival of said predetermined number of samples in that block;
(iv) excitation signal generating means responsive to the waveform of said signal (Sn) and to the most-recently derived set of said plurality of sets of coefficients for generating an excitation signal A corresponding to each of said blocks, said excitation signal comprising a component representing amplitude and a component representing temporal location within said block for each of a set of excitation pulses less in number than the number of possible PCM samples in said block, wherein the excitation signal generating means comprises:
(v) filter means for generating from the linear PCM
signal a desired signal dn;
(vi) impulse response computer means for computing the impulse response hn of the filter means using the coefficients ai appropriate to that block;
(vii) cross-correlator means for computing cross-correlation .alpha.m between the impulse response hn and the output of the filter means;
(viii) covariance means for computing the general covariance 0(i,j) of the impulse response hn, in accordance with the general expression given in the equation 0(i,j) = ? hn-i hn-j;
(ix) location means responsive to the covariance means and the cross-correlation means for deriving the location of the maximum correlation, and generating therefrom an element of the said component representing temporal loction, such element being the position of the first excitation pulse, and (x) means responsive to the covariance means, the locating means and cross-correlation means for generating the corresponding amplitude of that pulse.
an encoder comprising:
(i) input means for providing a signal (Sn) in linear PCM format;
(ii) storage means for storing discrete blocks of said signal (Sn) individually and successively, each block comprising a predetermined number of samples;
(iii) coefficient deriving means for deriving from said signal (Sn) a plurality of sets of coefficients, each set of coefficients defining a spectrum envelope of the block, said plurality of sets of coefficients being derived in succession during arrival of said predetermined number of samples in that block;
(iv) excitation signal generating means responsive to the waveform of said signal (Sn) and to the most-recently derived set of said plurality of sets of coefficients for generating an excitation signal A corresponding to each of said blocks, said excitation signal comprising a component representing amplitude and a component representing temporal location within said block for each of a set of excitation pulses less in number than the number of possible PCM samples in said block, wherein the excitation signal generating means comprises:
(v) filter means for generating from the linear PCM
signal a desired signal dn;
(vi) impulse response computer means for computing the impulse response hn of the filter means using the coefficients ai appropriate to that block;
(vii) cross-correlator means for computing cross-correlation .alpha.m between the impulse response hn and the output of the filter means;
(viii) covariance means for computing the general covariance 0(i,j) of the impulse response hn, in accordance with the general expression given in the equation 0(i,j) = ? hn-i hn-j;
(ix) location means responsive to the covariance means and the cross-correlation means for deriving the location of the maximum correlation, and generating therefrom an element of the said component representing temporal loction, such element being the position of the first excitation pulse, and (x) means responsive to the covariance means, the locating means and cross-correlation means for generating the corresponding amplitude of that pulse.
15. Apparatus as defined in claim 14, further comprising:
(xi) buffer means for storing the output of the cross-correlator means, for each excitation pulse, (xii) subtraction means for subtracting from the buffer means output a signal representing the product of a covariance vector corresponding to the instant pulse and the corresponding amplitude parameter; and (xiii) switching means operative to select the output of the cross-correlator for application to said locating means for computation of said first pulse and to select the output of the subtraction means for application to said location means for computation of subsequent pulses in the same set.
(xi) buffer means for storing the output of the cross-correlator means, for each excitation pulse, (xii) subtraction means for subtracting from the buffer means output a signal representing the product of a covariance vector corresponding to the instant pulse and the corresponding amplitude parameter; and (xiii) switching means operative to select the output of the cross-correlator for application to said locating means for computation of said first pulse and to select the output of the subtraction means for application to said location means for computation of subsequent pulses in the same set.
16. Apparatus as defined in claim 15, wherein said covariance means comprises:
(xiv) matrix means for computing the covariance matrix in accordance with equation 0(i-l,j-1) = 0(i,j)-hN ihN-j;
(xv) squaring means for deriving the square of said cross-correlation signal; and (xvi) divider means responsive to the matrix means and the squaring means for dividing the diagonal of the covariance vector by the output of the squaring means; the output of the divider means being applied to said locating means for determination of the maximum thereof.
(xiv) matrix means for computing the covariance matrix in accordance with equation 0(i-l,j-1) = 0(i,j)-hN ihN-j;
(xv) squaring means for deriving the square of said cross-correlation signal; and (xvi) divider means responsive to the matrix means and the squaring means for dividing the diagonal of the covariance vector by the output of the squaring means; the output of the divider means being applied to said locating means for determination of the maximum thereof.
17. Apparatus for processing a digital signal comprising:
an encoder comprising:
(i) input means for providing a signal (Sn) in linear PCM format;
(ii) storage means for storing discrete blocks of said signal (Sn) individually and successively, each block comprising a predetermined number of samples;
(iii) coefficient deriving means for deriving from said signal (Sn) a plurality of sets of coefficients, each set of coefficients defining a spectrum envelope of the block, said plurality of sets of coefficients being derived in succession during arrival of said predetermined number of samples in that block;
(iv) excitation signal generating means responsive to the waveform of said signal (Sn) and to the most-recently derived set of said plurality of sets of coefficients for generating an excitation signal A corresponding to each of said blocks, said excitation signal comprising a component representing amplitude and a component representing temporal location within said block for each of a set of excitation pulses less in number than the number of possible PCM samples in said block, said apparatus further comprising a decoder comprising:
a decoder synthesis filter having adjustable predictor coefficients;
decoder input means responsive to said excitation signal for providing said excitation pulses and applying them to the input of said synthesis filter;
coefficient means responsive to said coefficient signal for adjusting said filter predictor coefficients, whereby application to said decoder synthesis filter of each said set of excitation pulses, following adjustment of its coefficients to corresponding values, produces an output signal substantially identical to the corresponding block of the linear PCM
signal (Sn), wherein the excitation signal generating means comprises:
(v) filter means for generating from the linear PCM
signal a desired signal dn;
(vi) impulse response computer means for computing the impulse response hn of the filter means using the coefficients ai appropriate to that block;
(vii) cross-correlator means for computing cross-correlation .alpha.m between the impulse response hn and the output of the filter means;
(viii) covariance means for computing the general covariance 0(i,j) of the impulse response hn, in accordance with the general expression given in the equation 0(i,j) = ? hn-i hn-j;
(ix) location means responsive to the covariance means and the cross-correlation means for deriving the location of the maximum correlation, and generating therefrom an element of the said component representing temporal location, such element being the position of the first excitation pulse, and (x) means responsive to the covariance means, the locating means and cross-correlation means for generating the corresponding amplitude of that pulse.
an encoder comprising:
(i) input means for providing a signal (Sn) in linear PCM format;
(ii) storage means for storing discrete blocks of said signal (Sn) individually and successively, each block comprising a predetermined number of samples;
(iii) coefficient deriving means for deriving from said signal (Sn) a plurality of sets of coefficients, each set of coefficients defining a spectrum envelope of the block, said plurality of sets of coefficients being derived in succession during arrival of said predetermined number of samples in that block;
(iv) excitation signal generating means responsive to the waveform of said signal (Sn) and to the most-recently derived set of said plurality of sets of coefficients for generating an excitation signal A corresponding to each of said blocks, said excitation signal comprising a component representing amplitude and a component representing temporal location within said block for each of a set of excitation pulses less in number than the number of possible PCM samples in said block, said apparatus further comprising a decoder comprising:
a decoder synthesis filter having adjustable predictor coefficients;
decoder input means responsive to said excitation signal for providing said excitation pulses and applying them to the input of said synthesis filter;
coefficient means responsive to said coefficient signal for adjusting said filter predictor coefficients, whereby application to said decoder synthesis filter of each said set of excitation pulses, following adjustment of its coefficients to corresponding values, produces an output signal substantially identical to the corresponding block of the linear PCM
signal (Sn), wherein the excitation signal generating means comprises:
(v) filter means for generating from the linear PCM
signal a desired signal dn;
(vi) impulse response computer means for computing the impulse response hn of the filter means using the coefficients ai appropriate to that block;
(vii) cross-correlator means for computing cross-correlation .alpha.m between the impulse response hn and the output of the filter means;
(viii) covariance means for computing the general covariance 0(i,j) of the impulse response hn, in accordance with the general expression given in the equation 0(i,j) = ? hn-i hn-j;
(ix) location means responsive to the covariance means and the cross-correlation means for deriving the location of the maximum correlation, and generating therefrom an element of the said component representing temporal location, such element being the position of the first excitation pulse, and (x) means responsive to the covariance means, the locating means and cross-correlation means for generating the corresponding amplitude of that pulse.
18. Apparatus as defined in claim 17, further comprising:
(xi) buffer means for storing the output of the cross-correlator means, for each excitation pulse;
(xii) subtraction means for subtracting from the buffer means output a signal representing the product of a covariance vector corresponding to the instant pulse and the corresponding amplitude parameter; and (xiii) switching means operative to select the output of the cross-correlator for application to said locating means for computation of said first pulse and to select the output of the subtraction means for application to said location means for computation of subsequent pulses in the same set.
(xi) buffer means for storing the output of the cross-correlator means, for each excitation pulse;
(xii) subtraction means for subtracting from the buffer means output a signal representing the product of a covariance vector corresponding to the instant pulse and the corresponding amplitude parameter; and (xiii) switching means operative to select the output of the cross-correlator for application to said locating means for computation of said first pulse and to select the output of the subtraction means for application to said location means for computation of subsequent pulses in the same set.
19. Apparatus as defined in claim 18, wherein said covariance means comprises:
(xiv) matrix means for computing the covariance matrix in accordance with equation 0(i-1,j-1) = 0(i,j)-hN-i hN-j;
(xv) squaring means for deriving the square of said cross-correlation signal; and (xvi) divider means responsive to the matrix means and the squaring means for dividing the diagonal of the covariance vector by the output of the squaring means; the output of the divider means being applied to said locating means for determination of the maximum thereof.
(xiv) matrix means for computing the covariance matrix in accordance with equation 0(i-1,j-1) = 0(i,j)-hN-i hN-j;
(xv) squaring means for deriving the square of said cross-correlation signal; and (xvi) divider means responsive to the matrix means and the squaring means for dividing the diagonal of the covariance vector by the output of the squaring means; the output of the divider means being applied to said locating means for determination of the maximum thereof.
20. Apparatus as defined in claim 19, further comprising:
(xvii) row selection means responsive to the matrix means and the output of the locating means for selecting as said covariance vector the row of the covariance matrix corresponding to the location represented by such locating means output, such row being applied to multiplier means for providing said product.
(xvii) row selection means responsive to the matrix means and the output of the locating means for selecting as said covariance vector the row of the covariance matrix corresponding to the location represented by such locating means output, such row being applied to multiplier means for providing said product.
21. Apparatus as defined in claim 14, wherein the filter means comprises a synthesis filter having coefficients which are modified relative to those of the decoder synthesis filter.
22. Apparatus as claimed in claim 21, wherein the filter means coefficients a? are related to the decoder synthesis filter coefficients ai by the expression a?=yi.ai where 1 ? i ? 8 and 0 ? .gamma. ? 1.
23. Apparatus as defined in claim 15, wherein said covariance means comprises:
(xviii) auto-correlator means for providing the auto-correlation Rh(i) of the impulse response hn, said subtraction means being arranged to subtract from the buffer output the product of the auto-correlation Rh(i) and said amplitude parameter.
(xviii) auto-correlator means for providing the auto-correlation Rh(i) of the impulse response hn, said subtraction means being arranged to subtract from the buffer output the product of the auto-correlation Rh(i) and said amplitude parameter.
24. Apparatus as defined in claim 23, wherein means for computing the amplitude is responsive to the output of the auto-correlator, at least for computing the amplitude of the first excitation pulse.
25. A method of processing a digital signal comprising the steps of:
encoding the signal by:
(i) providing a signal (Sn), in linear PCM format;
(ii) storing discrete blocks of said signal (Sn) individually and successively, each block comprising a predetermined number of samples;
(iii) deriving from said signal (Sn) a plurality of sets of coefficients, each set of coefficients defining a spectrum envelope of the block, said plurality of sets of coefficients being derived in succession during arrival of said predetermined number of samples in that block; and (iv) from the waveform of signal (Sn), and the most-recently derived set of said plurality of sets of coefficients generating an excitation signal (A) corresponding to each of said blocks, said excitation signal comprising a component representing amplitude and a component representing temporal location within said block for each of a set of excitation pulses less in number than the number of possible PCM samples in said block.
encoding the signal by:
(i) providing a signal (Sn), in linear PCM format;
(ii) storing discrete blocks of said signal (Sn) individually and successively, each block comprising a predetermined number of samples;
(iii) deriving from said signal (Sn) a plurality of sets of coefficients, each set of coefficients defining a spectrum envelope of the block, said plurality of sets of coefficients being derived in succession during arrival of said predetermined number of samples in that block; and (iv) from the waveform of signal (Sn), and the most-recently derived set of said plurality of sets of coefficients generating an excitation signal (A) corresponding to each of said blocks, said excitation signal comprising a component representing amplitude and a component representing temporal location within said block for each of a set of excitation pulses less in number than the number of possible PCM samples in said block.
26. A method as defined in claim 25, wherein said coefficients are derived on a continuous basis.
27. A method as defined in claim 26, wherein the coefficients are derived using an adaptive lattice.
28. A method as defined in claim 25, wherein said coefficients are linear prediction coefficients.
29. A method as defined in claim 26, wherein said coefficients are linear prediction coefficients.
30. A method as defined in claim 27, wherein said coefficients are linear prediction coefficients.
31. A method of processing a digital signal as defined in claim 25, further comprising decoding the output signal by:
deriving from said excitation signal said excitation pulses and applying them to the input of a synthesis filter having adjustable predictor coefficients; and adjusting said filter predictor coefficients, in response to said coefficient signal;
wherein each said set of excitation pulses is applied to said filter following corresponding adjustment of its coefficients, to produce an output signal substantially identical to the corresponding block of the linear PCM signal (Sn).
deriving from said excitation signal said excitation pulses and applying them to the input of a synthesis filter having adjustable predictor coefficients; and adjusting said filter predictor coefficients, in response to said coefficient signal;
wherein each said set of excitation pulses is applied to said filter following corresponding adjustment of its coefficients, to produce an output signal substantially identical to the corresponding block of the linear PCM signal (Sn).
32. A method as defined in in claim 31, wherein said coefficients are derived on a continuous basis.
33. A method as defined in claim 32, wherein the coefficients are derived using an adaptive lattice.
34. A method as defined in claim 31, wherein said coefficients are linear prediction coefficients.
35. A method as defined in claim 32, wherein said coefficients are linear prediction coefficients.
36. A method as defined in claim 32, 33 or 34, wherein said encoding includes the step of multiplexing said excitation signal and said coefficient signal, and said decoding includes the step of demultiplexing said excitation signal and said coefficient signal.
37. A method of processing a digital signal comprising the steps of:
encoding the signal by:
(i) providing a signal (Sn), in linear PCM format;
(ii) storing discrete blocks of said signal (Sn) individually and successively, each block comprising a predetermined number of samples;
(iii) deriving from said signal (Sn) a plurality of sets of coefficients, each set of coefficients defining a spectrum envelope of the block, said plurality of sets of coefficients being derived in succession during arrival of said predetermined number of samples in that block;
(iv) from the waveform of signal (Sn), and the most-recently derived set of said plurality of sets of coefficients, generating an excitation signal (A) corresponding to each of said blocks, said excitation signal comprising a component representing amplitude and a component representing temporal location within said block for each of a set of excitation pulses less in number than the number of possible PCM samples in said block, wherein the generation of said excitation signal comprises the steps of:
(v) generating from the linear PCM signal a desired signal dn;
(vi) computing the impulse response hn of encoder filter means using the coefficients ai appropriate to that block;
(vii) computing cross-correlation .alpha.m between the impulse response hn and the desired signal dn;
(viii) computing the general covariance 0(i,j) of the impulse response hn, in accordance with the general expression given in the equation 0(i,j) = ? hn-i hn-j:
(ix) in response to the covariance and the cross-correlation deriving the location of the maximum correlation, and generating therefrom an element of said component representing temporal location, such element being the position of the first excitation pulse; and (x) responsive to the covariance, the maximum location and cross-correlation, generating the corresponding amplitude of that pulse in accordance with the equation .
encoding the signal by:
(i) providing a signal (Sn), in linear PCM format;
(ii) storing discrete blocks of said signal (Sn) individually and successively, each block comprising a predetermined number of samples;
(iii) deriving from said signal (Sn) a plurality of sets of coefficients, each set of coefficients defining a spectrum envelope of the block, said plurality of sets of coefficients being derived in succession during arrival of said predetermined number of samples in that block;
(iv) from the waveform of signal (Sn), and the most-recently derived set of said plurality of sets of coefficients, generating an excitation signal (A) corresponding to each of said blocks, said excitation signal comprising a component representing amplitude and a component representing temporal location within said block for each of a set of excitation pulses less in number than the number of possible PCM samples in said block, wherein the generation of said excitation signal comprises the steps of:
(v) generating from the linear PCM signal a desired signal dn;
(vi) computing the impulse response hn of encoder filter means using the coefficients ai appropriate to that block;
(vii) computing cross-correlation .alpha.m between the impulse response hn and the desired signal dn;
(viii) computing the general covariance 0(i,j) of the impulse response hn, in accordance with the general expression given in the equation 0(i,j) = ? hn-i hn-j:
(ix) in response to the covariance and the cross-correlation deriving the location of the maximum correlation, and generating therefrom an element of said component representing temporal location, such element being the position of the first excitation pulse; and (x) responsive to the covariance, the maximum location and cross-correlation, generating the corresponding amplitude of that pulse in accordance with the equation .
38. A method as defined in claim 37, further comprising:
(xi) storing the output of the cross-correlator means, for each excitation pulse;
(xii) subtracting from the said stored output a signal representing the product of a covariance vector corresponding to the instant pulse and the corresponding amplitude parameter; and (xiii) selecting the cross-correlation signal for computation of said first pulse and the product of the subtraction step for computation of subsequent pulses in the same set.
(xi) storing the output of the cross-correlator means, for each excitation pulse;
(xii) subtracting from the said stored output a signal representing the product of a covariance vector corresponding to the instant pulse and the corresponding amplitude parameter; and (xiii) selecting the cross-correlation signal for computation of said first pulse and the product of the subtraction step for computation of subsequent pulses in the same set.
39. A method as defined in claim 38, further comprising:
(xiv) computing the covariance matrix in accordance with the equation 0(i-1)(j-1) = 0(i,j) + hn-i hn-j;
(xv) deriving the square of said cross-correlation signal; and (xvi) in response to the covariance matrix and the squared signal dividing the diagonal of the covariance vector by the squared signal; the result of such division being used in determination of the maximum thereof.
(xiv) computing the covariance matrix in accordance with the equation 0(i-1)(j-1) = 0(i,j) + hn-i hn-j;
(xv) deriving the square of said cross-correlation signal; and (xvi) in response to the covariance matrix and the squared signal dividing the diagonal of the covariance vector by the squared signal; the result of such division being used in determination of the maximum thereof.
40. A method as defined in claim 39, further comprising:
(xvii) responsive to the covariance matrix and the pulse location, selecting as said covariance vector the row of the covariance matrix corresponding to such location, such row being applied to multiplier means for providing said product.
(xvii) responsive to the covariance matrix and the pulse location, selecting as said covariance vector the row of the covariance matrix corresponding to such location, such row being applied to multiplier means for providing said product.
41. A method as defined in claim 37, wherein said covariance is derived by:
(xviii) providing the auto-correlation Rh(i) of the impulse response hn, said subtraction step subtracting from the stored signal the product of the auto-correlation Rh(i) and said amplitude parameter.
(xviii) providing the auto-correlation Rh(i) of the impulse response hn, said subtraction step subtracting from the stored signal the product of the auto-correlation Rh(i) and said amplitude parameter.
42. A method as defined in claim 41, wherein computation of the amplitude is responsive to the auto-correlation signal, at least for computing the amplitude of the first excitation pulse.
43. A method as defined in claim 37, wherein the encoder filter means comprises a synthesis filter having coefficients modified relative to those of the decoder synthesis filter.
44. A method as claimed in claim 43, wherein the encoder filter means has coefficients ai related to the coefficients ai of the decoder synthesis filter by the expression ai = .gamma.i.ai where 1 ? i ? 8 and 0 ? .gamma. ? 1.
45. A method as defined in claim 25, further comprising decoding the output signal by:
deriving from said excitation signal said excitation pulses and applying them to the input of a synthesis filter having adjustable predictor coefficients; and adjusting said filter predictor coefficients, in response to said coefficient signal;
wherein each said set of excitation pulses is applied to said filter following corresponding adjustment of its coefficients, to produce an output signal substantially identical to the corresponding block of the linear PCM signal (Sn), and wherein the generation of said excitation signal comprises the steps of:
(v) generating from the linear PCM signal a desired signal dn;
(vi) computing the impulse response hn of encoder filter means using the coefficients ai appropriate to that block;
(vii) computing cross-correlation .alpha.m between the impulse response hn and the desired signal dn;
(viii) computing the general covariance 0(i,j) of the impulse response hn, in accordance with the general expression given in the equation 0(i,j) = ? hn-i hn-j;
(ix) in response to the covariance and the cross-correlation deriving the location of the maximum correlation, and generating therefrom an element of said component representing temporal location, such element being the position of the first excitation pulse; and (x) responsive to the covariance, the maximum location and cross-correlation generating the corresponding amplitude of that pulse in accordance with the equation .
deriving from said excitation signal said excitation pulses and applying them to the input of a synthesis filter having adjustable predictor coefficients; and adjusting said filter predictor coefficients, in response to said coefficient signal;
wherein each said set of excitation pulses is applied to said filter following corresponding adjustment of its coefficients, to produce an output signal substantially identical to the corresponding block of the linear PCM signal (Sn), and wherein the generation of said excitation signal comprises the steps of:
(v) generating from the linear PCM signal a desired signal dn;
(vi) computing the impulse response hn of encoder filter means using the coefficients ai appropriate to that block;
(vii) computing cross-correlation .alpha.m between the impulse response hn and the desired signal dn;
(viii) computing the general covariance 0(i,j) of the impulse response hn, in accordance with the general expression given in the equation 0(i,j) = ? hn-i hn-j;
(ix) in response to the covariance and the cross-correlation deriving the location of the maximum correlation, and generating therefrom an element of said component representing temporal location, such element being the position of the first excitation pulse; and (x) responsive to the covariance, the maximum location and cross-correlation generating the corresponding amplitude of that pulse in accordance with the equation .
46. A method as defined in claim 45, further comprising:
(xi) storing the output of the cross-correlator means, for each excitation pulse;
(xii) subtracting from the said stored output a signal representing the product of a covariance vector corresponding to the instant pulse and the corresponding amplitude parameter; and (xiii) selecting the cross-correlation signal for computation of said first pulse and the product of the subtraction means for computation of subsequent pulses in the same set.
(xi) storing the output of the cross-correlator means, for each excitation pulse;
(xii) subtracting from the said stored output a signal representing the product of a covariance vector corresponding to the instant pulse and the corresponding amplitude parameter; and (xiii) selecting the cross-correlation signal for computation of said first pulse and the product of the subtraction means for computation of subsequent pulses in the same set.
47. A method as defined in claim 46, further comprising:
(xiv) computing the covariance matrix in accordance with the equation 0(i-1)(j-1) = 0(i,j) + hN-i hN-j;
(xv) deriving the square of said cross-correlation signal; and (xvi) in response to the covariance matrix and the squared signal dividing the diagonal of the covariance vector by the squared signal; the result of such division being used in determination of the maximum thereof.
(xiv) computing the covariance matrix in accordance with the equation 0(i-1)(j-1) = 0(i,j) + hN-i hN-j;
(xv) deriving the square of said cross-correlation signal; and (xvi) in response to the covariance matrix and the squared signal dividing the diagonal of the covariance vector by the squared signal; the result of such division being used in determination of the maximum thereof.
48. A method as defined in claim 47, further comprising:
(xvii) responsive to the covariance matrix and the pulse location selecting as said covariance vector the row of the covariance matrix corresponding to such location, such row being applied to multiplier means for providing said product.
(xvii) responsive to the covariance matrix and the pulse location selecting as said covariance vector the row of the covariance matrix corresponding to such location, such row being applied to multiplier means for providing said product.
49. A method as defined in claim 37 or 46, wherein said covariance is derived by:
(xviii) providing the auto-correlation Rh(i) of the impulse response hn, said subtraction subtracting from the stored signal the product of the auto-correlation Rh(i) and said amplitude parameter.
(xviii) providing the auto-correlation Rh(i) of the impulse response hn, said subtraction subtracting from the stored signal the product of the auto-correlation Rh(i) and said amplitude parameter.
50. A method as defined in claim 49, wherein computation of the amplitude is responsive to the auto-correlation signal, at least for computing the amplitude of the first excitation pulse.
51. A method as defined in claim 45, wherein the encoder filter means comprises a synthesis filter having coefficients modified relative to those of the decoder synthesis filter.
52. A method as claimed in claim 51, wherein the encoder filter means has coefficients ai related to the coefficients ai of the decoder synthesis filter by the expression ai = .gamma.i.ai where 1 ? i ? 8 and 0 ? .gamma. ? 1.
Priority Applications (5)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000442281A CA1236922A (en) | 1983-11-30 | 1983-11-30 | Method and apparatus for coding digital signals |
| EP84112041A EP0149724B1 (en) | 1983-11-30 | 1984-10-08 | Method and apparatus for coding digital signals |
| AT84112041T ATE42853T1 (en) | 1983-11-30 | 1984-10-08 | METHOD AND DEVICE FOR ENCODING DIGITAL SIGNALS. |
| DE8484112041T DE3478065D1 (en) | 1983-11-30 | 1984-10-08 | Method and apparatus for coding digital signals |
| JP59250655A JPS60185432A (en) | 1983-11-30 | 1984-11-29 | Digital signal encoding and decoding device and method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000442281A CA1236922A (en) | 1983-11-30 | 1983-11-30 | Method and apparatus for coding digital signals |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1236922A true CA1236922A (en) | 1988-05-17 |
Family
ID=4126639
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000442281A Expired CA1236922A (en) | 1983-11-30 | 1983-11-30 | Method and apparatus for coding digital signals |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0149724B1 (en) |
| JP (1) | JPS60185432A (en) |
| AT (1) | ATE42853T1 (en) |
| CA (1) | CA1236922A (en) |
| DE (1) | DE3478065D1 (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5048088A (en) * | 1988-03-28 | 1991-09-10 | Nec Corporation | Linear predictive speech analysis-synthesis apparatus |
| US5701392A (en) * | 1990-02-23 | 1997-12-23 | Universite De Sherbrooke | Depth-first algebraic-codebook search for fast coding of speech |
| US5754976A (en) * | 1990-02-23 | 1998-05-19 | Universite De Sherbrooke | Algebraic codebook with signal-selected pulse amplitude/position combinations for fast coding of speech |
| WO1995001673A1 (en) * | 1993-06-30 | 1995-01-12 | Royal Melbourne Institute Of Technology | Filter windows for fourier transform signal compression |
| WO1999041737A1 (en) * | 1998-02-17 | 1999-08-19 | Motorola Inc. | Method and apparatus for high speed determination of an optimum vector in a fixed codebook |
| KR100587099B1 (en) | 2003-05-10 | 2006-06-07 | 엘지전자 주식회사 | Dust removing unit of cyclone cleaner |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4472832A (en) * | 1981-12-01 | 1984-09-18 | At&T Bell Laboratories | Digital speech coder |
-
1983
- 1983-11-30 CA CA000442281A patent/CA1236922A/en not_active Expired
-
1984
- 1984-10-08 EP EP84112041A patent/EP0149724B1/en not_active Expired
- 1984-10-08 AT AT84112041T patent/ATE42853T1/en not_active IP Right Cessation
- 1984-10-08 DE DE8484112041T patent/DE3478065D1/en not_active Expired
- 1984-11-29 JP JP59250655A patent/JPS60185432A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| JPS60185432A (en) | 1985-09-20 |
| EP0149724A1 (en) | 1985-07-31 |
| EP0149724B1 (en) | 1989-05-03 |
| DE3478065D1 (en) | 1989-06-08 |
| ATE42853T1 (en) | 1989-05-15 |
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