EP0149724B1 - Verfahren und Einrichtung zur Codierung von digitalen Signalen - Google Patents

Verfahren und Einrichtung zur Codierung von digitalen Signalen Download PDF

Info

Publication number
EP0149724B1
EP0149724B1 EP84112041A EP84112041A EP0149724B1 EP 0149724 B1 EP0149724 B1 EP 0149724B1 EP 84112041 A EP84112041 A EP 84112041A EP 84112041 A EP84112041 A EP 84112041A EP 0149724 B1 EP0149724 B1 EP 0149724B1
Authority
EP
European Patent Office
Prior art keywords
signal
coefficients
excitation
covariance
block
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP84112041A
Other languages
English (en)
French (fr)
Other versions
EP0149724A1 (de
Inventor
Michael George Beyrouti
Paul Mermelstein
Haim Garten
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nortel Networks Ltd
Original Assignee
Northern Telecom Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Northern Telecom Ltd filed Critical Northern Telecom Ltd
Priority to AT84112041T priority Critical patent/ATE42853T1/de
Publication of EP0149724A1 publication Critical patent/EP0149724A1/de
Application granted granted Critical
Publication of EP0149724B1 publication Critical patent/EP0149724B1/de
Expired legal-status Critical Current

Links

Images

Classifications

    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10L—SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; 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 TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; 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

Definitions

  • the invention relates to a method and apparatus for coding of digital signals and is especially, but not exclusively, applicable to coding of voice frequency signals to reduce bit rates for reduced transmission or storage requirements.
  • the invention concerns coding systems in which the input signal is encoded in discrete blocks. For each block an excitation signal is derived which, when applied to a synthesis filter having suitable coefficients, will generate an approximation to the input signal.
  • the excitation signal is a train of pulses having a period corresponding to the fundamental periodicity of the input signal. This is not entirely satisfactory becaus, the decoded signal from the synthesis filter is not usually an accurate reproduction of the input signal.
  • the excitation signal comprises a set of pulses having amplitudes and locations in the particular block determined according to the signal waveform.
  • Each set of pulses is derived using a linear predictive coding (LPC) filter which has reflection coefficients derived from the input signal.
  • LPC linear predictive coding
  • Each excitation pulse is derived by calculating the filter response for every possible pulse position and selecting the one which gives least weighted error between such response and the input signal.
  • the weighting of the error exploits the properties of human auditory perception.
  • the calculation of the excitation pulses can only begin when the LPC coefficients for the block are available. Consequently, there is a delay, equal to at least twice the period or frame over which the LPC coefficients are derived, between the synthesizer output and the encoder input.
  • Atal and Remde specify a frame period of about 20 milliseconds, equivalent to several blocks, which in their proposal, are 5 milliseconds long.
  • a delay could be intolerable because of exacerbated echo problems.
  • apparatus for processing a digital signal comprises an encoder having
  • the apparatus may further comprise:
  • the primary advantage of this arrangement is that the excitation signal calculations in the encoder are delayed by only the duration of the block. The delay therefore can be much shorter than in the previous known proposals.
  • the coefficients may be derived on a sample-by-sample or continuous basis and preferably are converted to LPC coefficients.
  • the coefficients generating means comprises an adaptive lattice.
  • the decoder synthesis filter may then comprise a lattice too, although other filters may also be used, for example, and preferably, a recursive filter with adaptable prediction coefficients.
  • a method of processing a digital signal comprises encoding the digital signal by:
  • the method may further comprise decoding the output signal by:
  • the first excitation pulse is derived by calculating the filter response for every possible pulse position in the block and selecting the one which gives the least weighted error when compared with the input signal. The procedure is then repeated, taking into account the contribution of the first excitation pulse, to find the next-best or second excitation pulse, and so on, until the complete set of excitation pulses have been selected.
  • a disadvantage of this approach is that it requires a considerable number of operations, i.e. multiplications and additions for each set of excitation pulses.
  • the encoder synthesis filter for which aid impulse response is computed is a modified synthesis filter i.e. a synthesis filter modified to take into account perceptual weighting additional to any preemphasis applied to the input signal.
  • the covariance and the cross-correlation are used to derive the location of the maximum cross-correlation, which is the position of the first excitation pulse, and the corresponding amplitude of that pulse.
  • the cross-correlation signal from the preceding pulse computation is used, having been stored in a buffer.
  • the general covariance matrix vector corresponding to the pulse location is multiplied by the corresponding amplitude and subtracted from the stored preceding cross-correlation signal.
  • the location of the maximum value of the difference a' m and corresponding pulse amplitude, are derived as before to give the parameters of the instant excitation pulse.
  • the general covariance signal may be derived by:
  • the general covariance matrix vector is then the matrix row corresponding to that of the maximum cross-correlation value.
  • the general covariance signal is the output of an auto- correlator.
  • the auto-correlation signal is used directly in computing the amplitude of the first excitation pulse.
  • the difference signal is derived by subtracting from the preceding value the product of the amplitude and the auto-correlation signal R h (i).
  • the transmitter/encoder comprises input means 10, to which an analogue speech input signal is applied and which provides a corresponding signal So in linear PCM format.
  • Each sample of the linear PCM formatted signal S " comprises 16 bits.
  • This signal S " is applied to storage means 12 and coefficient signal generating means 14, respectively.
  • the storage means 12 comprises a buffer which receives the signal S " serially and stores it in blocks of 32 samples. Each block has a duration of 4 ms.
  • the contents of the buffer 12 are accessed by excitation signal generating means 16 which uses them to generate an excitation signal (A), which is applied to a multiplexer 18.
  • This excitation signal (A) comprises a series of bits representing the amplitude and location of each of a set of pulses which, applied to a synthesis filter having suitable coefficients, will regenerate the block of the PCM input signal.
  • the excitation signal (A) also includes a gain factor, (G), which will be explained later.
  • the coefficient signal generating means 14 derives from the linear PCM signal S n a coefficient signal representing sets of reflection coefficients K 1 ⁇ K 8 . These coefficients are updated on a sample-by-sample basis.
  • the coefficient signal from the coefficient generating means 14 is applied to the multiplexer 18 and the excitation signal generating means 16, respectively.
  • the coefficient signal is updated continuously, only one set of coefficients K 1 ⁇ K 8 is used in calculating each set of excitation pulses.
  • the set of coefficients used are those pertaining to the last sample period of that block. In this specific example, therefore, the coefficients are subsampled or extracted every 32 samples coinciding with the end of each block.
  • the coefficient signal applied to the multiplexer 18 comprises a difference signal, specifically a series of bits which represent the difference between the instant coefficient values and those previously transmitted.
  • the output of multiplexer 18 is transmitted via channel 20 to the receiver/decoder 22.
  • the excitation signal A and coefficient signal K are segregated by means of a demultiplexer 24.
  • the three components of the excitation signal comprising amplitude component A m , location component m, and gain factor G, are applied to decoder input means 26 wherein they are decoded by amplitude decoder 21, location decoder 23, and gain factor or r.m.s. decoder 25, respectively.
  • the outputs of the amplitude decoder 21 and gain or r.m.s. decoder 25 are multiplied together by multiplier 27, the output of which is applied to excitation pulse generator 29.
  • the output of the location decoder 23 is also applied to excitation pulse generator 29, which produces therefrom a train of excitation pulses P, having the appropriate amplitudes and locations. In each 4 mS period only 8 pulses will be generated. It has been found that a mere 8 pulses are sufficient to reconstruct accurately each 32 sample block of the input signal.
  • the excitation pulses are applied to the input of a synthesis filter 28, which has adjustable predictor coefficients a 1 ⁇ a 8 .
  • the coefficient signal K, from the demultiplexer 24 is applied to coefficient decoding means 30 which produces therefrom the reflection coefficients K 1 ⁇ K 8 .
  • the adjustment of the synthesis filter coefficients is synchronised to the beginning of the 4 millisecond period during which the corresponding set of excitation pulses are applied to the input of the synthesis filter 28.
  • the resulting output signal from the synthesis filter 28, following its excitation by the set of excitation pulses, is a close approximation to the corresponding 4 millisecond block of the linear PCM input signal S n from which the set of excitation pulses were derived.
  • the input means 10 comprises sampling means 40 for sampling and digitizing the analogue voice signal into 8-bit ⁇ -law samples, p-law to linear conversion means 42, and pre-emphasis means 44 for emphasizing the high frequencies for perceptual reasons.
  • sampling means 40 for sampling and digitizing the analogue voice signal into 8-bit ⁇ -law samples
  • p-law to linear conversion means 42 for linear conversion
  • pre-emphasis means 44 for emphasizing the high frequencies for perceptual reasons.
  • the input means 10 could be modified readily to accommodate inputs other than analogue speech.
  • the A/D sampling means 40 could be omitted if the input signal were already in PCM form.
  • conversion from A-law could be used instead of p-law if the signal required it, and other weighting could be applied.
  • the coefficient signal generating means 14 comprises an adaptive lattice 46 and coefficient encoder 48.
  • the lattice 46 is shown in detail in Figure 4 and is of the kind disclosed by J. I. Makhoul and L. K. Cosell in a paper entitled "Adaptive Lattice Analysis of Speech". IEEE Transactions of Acoustics, Speech and Signal Processing, Vol. ASSP-29, No. 3, June 1981.
  • the adaptive lattice illustrated in Figure 4 has eight stages. Its output is discarded, its prime purpose being to vary continually its coefficients K 1 ⁇ K 8 in dependence upon the linear PCM input signal S " applied to its input.
  • the adaptive estimate of K m (n+1) for each stage m, where 1 ⁇ m ⁇ 8, is derived generally in accordance with equation 1, (see Figure 6) where:
  • w is the impulse response of a recursive filter of finite order.
  • the coefficient encoder 48 encodes the set of coefficient values (actually the difference between each set and the previously-transmitted set) every 4 milliseconds to provide the coefficient signal K, which is applied to both the multiplexer 18 and the excitation signal generating means 16.
  • the coefficient signal K i is decoded by a decoder 52 which extracts the original set of reflection coefficients K 1 ⁇ K 8 .
  • Conversion means 54 then transforms the reflection coefficients K 1 ⁇ K 8 into the corresponding set of predictor coefficients a 1 ⁇ a 8 , using the recursive formulae specified as equations 4 and 5 in Figure 6.
  • the set of predictor coefficients a 1 ⁇ a 8 are applied to impulse response computation means 56, and "desired” signal computation means 58, respectively.
  • the "desired” signal computation means 58 comprises an inverse filter 60, which is in all-zero filter, and a modified synthesis filter 62, which is an all-pole filter.
  • the modification of the synthesis filter 62, respresented by the symbol y, results in additional perceptual weighting being applied to the linear PCM signal S n as it is encoded.
  • the value of y is between 0 and 1, preferably 0.75.
  • the predictor coefficients of both filters 60 and 62 are updated every 4 milliseconds in response to the predictor coefficient signal a,.
  • the input to the inverse filter 60 is derived from the block of thirty-two 16-bit words stored in the storage means 12 at the instant the coefficient signals K i , and hence a,, are derived or sub-sampled.
  • the output of the inverse filter 60 is a linear prediction residual signal r o , derived in accordance with equation 6 of Figure 6.
  • the signal r n still comprising thirty-two 16-bit words, is applied by way of an adder 61 to the modified synthesis filter 62, which provides the "desired" signal d n , in accordance with equation 7 of Figure 6.
  • the residual prediction signal r n is also applied to RMS-computing means 63, which computes its root-mean-square value G which is then differentially encoded into a 3-bit word by RMS encoding means 65, the output of which is applied to multiplexer 18 and RMS-decoding means 67.
  • the adder 61 subtracts from the residual signal r o the output of an encoder excitation pulse generator 69 which is connected to the adder 61 by a switch 71.
  • the output of the pulse generator 69 is a set of excitation pulses P corresponding to those which will be generated in the decoder for that block of the input signal.
  • the excitation pulse generator 69 computes the pulses using the location component m and amplitude component A m derived from the excitation signal A, as will be described later.
  • Closure of switch 71 is controlled by means of a counter 73 which counts the number of excitation pulses and closes the switch 71 after the last pulse in each block, reopening it before the first pulse of the next block.
  • the output of adder 61 is used by the modified synthesis filter 62 to compute the desired signal d n twice.
  • the first time uses the data from the inverse filter 60 directly and is the basis for the set of excitation pulses P used for the second computation.
  • the value for d n calculated the second time around, however, is discarded, the object of the second computation being merely to refresh the memory of the recursive modified synthesis filter.
  • the impulse response computation means 56 computes, for each 4 millisecond block, the impulse response h n of the modified synthesis filter 62.
  • the impulse response h n comprises a corresponding block of thirty-two 16-bit words.
  • the impulse response h n , and output d n of the modified synthesis filter 62, are both applied to pulse-computation means, which computes the amplitude and location of each of the set of excitation pulses corresponding to that block or 4 millisecond period.
  • the impulse response h n is applied to a cross-correlator 80, together with the "desired" signal d n from the modified synthesis filter 62.
  • the cross-correlator 80 correlates the two signals h n and d n in thirty-two steps over the entire 4 milliseconds block and produces a cross-correlation signal a m , which is also a block of thirty-two 16-bit words.
  • the cross-correlation signal a m is applied by way of switch 82 to squaring means 84, which generates (a m ) 2.
  • the switch 82 is controlled by counter 73 so as to select the output of cross-correlator 82 for application to the squaring means 84 for computation of only the first excitation pulse. Thereafter switch 82 selects the output of an adder 86.
  • One input of adder 86 is connected to the common or output of switch 82, by way of a buffer/delay 88, its other input being connected to the output of a multiplier 90.
  • the impulse response h n is also applied to covariance computation means 92 which derives the covariance matrix (32x32 elements, each 16 bits), generally according to equation 8 (see Figure 6) and specifically, and preferably, equation 9 (see Figure 6).
  • One output of covariance means 92 comprises the diagonal terms 0(m,m) and is applied to one input of a divider 94, the output of squaring means 84 being applied to the second input of the divider 94.
  • the output of the divider 94 representing the term (a m ) 2 /0(m,m), is applied to pulse-maximum-locating means 98 which compares the values of all thirty-two samples thereof and selects the maximum.
  • the temporal location of that maximum is m 1 the location of the first excitation pulse. This location signal is encoded by encoder 100 and supplied to the multiplexer 18.
  • the output of divider 94 is also supplied to amplitude-computing means 102, together with the location signal m, from the locating means 98, and the output of switch 82 which, for calculation of the first excitation pulse is a and for subsequent pulses of the set, a' m .
  • the output of amplitude-computation means 102 is the amplitude component A m (see equation 10 of Figure 6), which is applied to one input of a divider 104.
  • the output of decoder 67 i.e. the gain factor G, is applied to the other input of the divider 104.
  • the output of divider 104 is encoded by means of amplitude encoder 108 and applied to the multiplexer 18.
  • the output of the encoder 108 is also decoded by decoder 110 and multiplied, by means of multiplier 112, by the output of the RMS decoder 67, i.e. the gain factor G, and applied to one input of multiplier 90.
  • the other input of the multiplier 90 is connected to the output of row-selection means 114. As previously mentioned, the output of the multiplier 90 is applied to the negative input of adder 86.
  • Row-selection means 114 has one input derived from the covariance computation means 92, to receive the entire matrix (O i,j ), and a second input connected to the max-location means 98 to receive the location of the maximum value i.e. pulse position m. The row-selection means 114 determines to which row of the matrix the maximum pulse corresponds and supplies that row to the multiplier 90.
  • switch 82 selects the output a m of cross-correlator 80 for application to squaring means 84.
  • the maximum value of a m 2 /0 ⁇ (m,m) is selected by location means 98 as the position m, of the first excitation pulse for that block.
  • Amplitude computing means 102 derives the corresponding amplitude Am ⁇ , for that first pulse according to equation 10 ( Figure 6).
  • Signal A m1 constitutes one element of the excitation signal component A m , which comprises eight 4-bit words, one for each pulse.
  • the amplitude A m1 is divided, by the divider 104, by the r.m.s./ gain factor. This division process normalizes the amplitudes for different blocks of the signal.
  • the counter 73 which counts the excitation pulses located by location means 98, is arranged so that it resets the switch 82 to disconnect the cross-correlator 80 once the parameters, i.e. amplitude and location, of the first excitation pulse have been generated.
  • the switch 82 applies to the squaring means 84, and amplitude-computing means 102, the output of adder 86, which is the different a' m between the previous cross-correlation signal, stored in buffer/delay 88, and the output of multiplier 90.
  • the output of multiplier 90 is the product of the maximum amplitude vector and the row of the covariance matrix which contains the maximum value.
  • the parameters of the second excitation pulse are computed in the same way as the first, using a' m instead of a m .
  • the cycle repeates for the third and each subsequent pulse until a total set of eight have been generated, whereupon counter 73 restores switch 82 to its position, selecting the cross-correlator output, and momentarily closes switch 71 to refresh the memory of synthesis filter 62.
  • FIG. 5 A second embodiment of the invention is illustrated in Figure 5, wherein parts corresponding to the first embodiment have the same reference numerals.
  • the computation of the covariance in the general sense, is simplified by using an auto-correlator 120 in place of covariance computation means 92 and row- selector 114.
  • Other modifications are that the output of switch 82 is taken to location means 122 as well as amplitude computing means 102.
  • the locating means 122 differs from locating means 98 in Figure 3 because, although it computes the same output, it uses different input, namely a m direct rather than the signal a m 2 /0 ⁇ (m, m) .
  • the auto-correlator 120 supplies the first auto-correlation value, directly to the amplitude-computing means 132, as indicated by the line 124.
  • Amplitude-computing means 132 differs from amplitude-computing means 102 of Figure 3 because, although it supplies the same output, it uses different input signals.
  • the impulse response signal h n is applied to the auto-correlator 120, which auto-correlates it in thirty-two steps over the entire 4 millisecond period to provide an auto-correlation signal R h (i) which then comprises a block of thirty-two 16-bit words.
  • the impulse response signal h n is applied to the cross-correlator 80, together with the desired signal d n from the modified synthesis filter 62.
  • the cross-correlator again cross-correlates the two signals h n and d n in thirty-two steps over the 4 millisecond period and produces a cross-correlation signal a m , which is also a block of thirty-two 16-bit words.
  • cross correlation signal a m is applied by way of one pole of a switch 82 to pulse-location means 122.
  • the pulse-location means 122 compares the absolute values of the thirty-two 16 bit words of the cross-correlation signal a m and selects the maximum. The location of this maximum within the block is coded as a binary word m 1 which represents the location of the first excitation pulse.
  • This binary word is applied to encoder 100, as are binary words for locations of subsequent excitation pulses. Encoder 100 encodes them to produce location component m of the excitation signal A and is applied to the multiplexer 18.
  • the position of the maximum value from pulse-location means 122 is applied to amplitude-computing means 132, which receives also, direct from the autocorrelator 102 (as indicated by line 124) the value R h (O), which is the first of the thirty-two words of the auto-correlation signal R h .
  • the amplitude-computing means 132 derives the ratio a mi /R h (O) to provide a signal A m1 which represents the amplitude of the first excitation pulse.
  • Signal A m1 is divided by gain factor G, by means of divider 104, and is then supplied to the multiplexer 18 as a 4-bit binary word by means of a pulse-amplitude encoder 118.
  • the amplitude signal A m1 constitutes one element of the excitation signal component A m , which comprises eight 4-bit words, one for each excitation pulse.
  • the output of the auto- correlator 120 i.e. R h (i) is applied directly to multiplier 90.
  • the output of multiplier 90 is applied, as before, to the adder 86.
  • the second and subsequent excitation pulses are generated in a similar manner to the first with switch 82 operated to select the output of adder 86 for application to the locating means 98, i.e. disconnecting the cross-correlation signal a m .
  • the signal a' m is applied to the maximum locating means 122 is then the difference between a m , the previous input to means 122, and the output of multiplier 90.
  • the cycle is repeated, with counter 73 being incremented each time, until eight excitation pulses have been computed, whereupon switch 82 resets to apply the cross-correlation signal for the next block to the pulse-maximum locating means 122.

Landscapes

  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Audiology, Speech & Language Pathology (AREA)
  • Computational Linguistics (AREA)
  • Signal Processing (AREA)
  • Health & Medical Sciences (AREA)
  • Human Computer Interaction (AREA)
  • Acoustics & Sound (AREA)
  • Multimedia (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Compression, Expansion, Code Conversion, And Decoders (AREA)
  • Analogue/Digital Conversion (AREA)
  • Transmission Systems Not Characterized By The Medium Used For Transmission (AREA)

Claims (29)

1. Vorrichtung zum Bearbeiten eines Digitalsignals, welche einen Kodierer enthält mit:
Eingangsmitteln (10) zur Schaffung eines Signales (Sn) in linearem PCM-Format;
Speichermitteln (12) zum einzelnen aufeinanderfolgenden Speichern diskreter Blöcke des linearen PCM-Signals (Sn), wobei jeder Block eine vorbestimmte Anzahl von Abtastungen umfaßt;
Koeffizienten-Generatormitteln (14, 46, 48) zum Ableiten einer Vielzahl von Reihen von Reflexionskoeffizienten aus dem Signal (Sn), und
Anregungssignal-Generatormitteln (15, 52, 54) zur Erzeugung eines dem Block entsprechenden Anregungssignals (A), wobei das Anregungssignal eines Komponente umfaßt, welche die Amplitude repräsentiert, und eine Komponente, welche den zeitlichen Ort für jeden aus einer Reihe von Anregungsimpulsen innerhalb des Blockes repräsentiert, die eine kleinere Zahl bilden als die Anzahl möglicher PCM-Abtastungen in dem Block,
dadurch gekennzeichnet, daß die Vielzahl von Koeffizientenreihen kontinuierlich auf Grundlage Abtastung um Abtastung aufgefrischt werden während der Ankunft der vorbestimmten Anzahl von Abtastungen in dem Block, und daß das Anregungssignal-Generatormittel (16, 52, 54) das Anregungssignal (A) in Reaktion auf die Wellenform der Signale (Sn) und die zuletzt abgeleitete Reihe aus der Vielzahl von Koeffizientenreihen erzeugt, die bis zu der letzten Abtastung aufgefrischt worden sind.
2. Vorrichtung nach Anspruch 1, weiter gekennzeichnet durch:
einen Dekoder mit:
einem Dekodier-Synthesefilter (28) mit einstellbaren Ziel-Koeffizienten;
von dem Erregungssignal abhängige Dekoder-Eingangsmitteln (26), um die Anregungsimpulse zu schaffen und sie an den Eingang des Synthesefilters (28) anzulegen;
auf das Koeffizientensignal zur Einstellung der Filter-Zielkoeffizienten reagierende Koeffizientenmittel (30, 32),
wodurch Anwendung jeder Reihe von Anregungsimpulsen auf das Dekodier-Synthesefilter nach Einstellung seiner Koeffizienten auf entsprechende Werte ein im wesentlichen mit dem entsprechenden Block des linearen PCM-Signals Sn identisches Ausgangssignal erzeugt.
3. Vorrichtung nach Anspruch 2, bei der der Kodierer Mittel (18) zum Multiplexen des Anregungssignales (A) und des Koeffizientensignales enthält, und der Dekoder Mittel (24) zum Demultiplexen des Anregungssignales und des Koeffizientensignales enthält.
4. Vorrichtung nach Anspruch 1 oder 2, bei der das Koeffizienten-Generatormittel (14; 46, 48) zum Ableiten der Koeffizienten auf einer kontinuierlichen Grundlage ausgelegt ist.
5. Vorrichtung nach Anspruch 4, bei der das Koeffizienten-Generatormittel (14; 46, 48) ein adaptives Gitter (46) umfaßt.
6. Vorrichtung nach einem der vorangehenden Ansprüche, bei der die Reflexions-Koeffizienten in lineare Ziel-Koeffizienten gewandelt werden.
7. Vorrichtung nach Anspruch 6, bei der das Anregungssignal-Generatormittel (16) umfaßt:
Filtermittel (62) zur Erzeugung eines gewünschten Signales dn aus dem linearen PCM-Signal,
auf Impulse ansprechendes Computermittel (56) zum Errechnen der Impuls-Reaktion hn des Filtermittels (62) unter Benutzung der für den Block zuständigen Koeffizienten al;
Quer-Korrelatormittel (80) zum Errechnen der Quer-korrelation am der Impulsreaktion hn mit dem Ausgangssignal dn des Filtermittels (62);
Kovarianz-Mittel (92) zum Errechnen der allgemeinen Kovarianz 0(i, j) der Impulsreaktion hn gemäß dem in Gleichung 8 der beigefügten Figur 6 gegebenen allgemeinen Ausdruck;
Lokalisierungsmittel (98) in Abhängigkeit von den Kovarianz-Mitteln (92) und den Querkorrelationsmitteln (80) zum Ableiten der Lokalisierung der maximalen Korrelation und zum Erzeugen eines Elementes der die zeitliche Lokalisierung repräsentierenden Komponente daraus, wobei dieses Element die Lage des ersten Anregungsimpulses ist, und
von den Kovarianz-Mitteln, den Lokalisierungs-Mitteln und den Querkorrelations-Mitteln abhängige Mittel (84, 86, 88, 90) zur Erzeugung der entsprechenden Amplitude jenes Impulses.
8. Vorrichtung nach Anspruch 7, die weiter enthält:
Puffermittel (88) zum Speichern des Ausgangssignales der Querkorrelatormittel für jeden Anregungsimpuls;
Subtraktionsmittel (86) zum Subtrahieren eines das Produkt eines dem augenblicklichen Impuls entsprechenden Kovarianzvektors mit dem entsprechenden Amplitudenparameter repräsentierenden Signales von dem Ausgangssignal des Puffermittels; und
Schaltmittel (82), die zum Auswählen des Ausgangssignales des Quer-Korreiators (80) zum Anlegen an das Lokalisierungsmittel (98) wirksam sind zur Errechnung des ersten Impulses und zum Auswählen des Ausgangssignales des Subtraktionsmittels zum Anlegen an das Lokalisierungsmittel zur Errechnung der folgenden Impulse der gleichen Reihe.
9. Vorrichtung nach Anspruch 8, bei der das Kovarianzmittel (92) umfaßt:
Matrix-Mittel zum Errechnen der Kovarianz- Matrix entsprechend Gleichung 9 der Figur 6;
Quadrierungsmittel zum Ableiten des Quadrates des Querkorrelationssignales; und
Dividiermittel in Abhängigkeit von den Matrix-Mitteln und dem Quadrierungsmittel zum Dividieren der Diagonale des Kovarianz-Vektors durch das Ausgangssignal des Quadrierungsmittels, wobei das Ausgangssignal des Dividiermittels an das Lokalisiermittel zur Bestimmung von dessen Maximum angelegt wird.
10. Vorrichtung nach Anspruch 9, die weiter enthält:
Zeilenwahl-Mittel in Abhängigkeit von den Matrix-Mitteln und dem Ausgangssignal der Lokalisierungsmittel zum Auswählen der Zeile der Kovarianz-Matrix, die dem durch solches Lokalisierungsmittel-Ausgangssignal dargestellten Ort entspricht, als den Kovarianzvektor, wobei diese Zeile zur Schaffung des Produktes dem Multiplikator-Mittel angelegt wird.
11. Vorrichtung nach Anspruch 7, bei dem das Filtermittel (62) ein Synthesefilter-Mittel umfaßt mit Koeffizienten, die relativ zu denen des Dekodier-Synthesefilters modifiziert sind.
12. Vorrichtung nach Anspruch 11, bei der die Filtermittel-Koeffizienten a'; auf die Dekodier-Synthesekoeffizienten a durch den Ausdruck a'i=yi · ai bezogen sind, wobei 1≦i≦8 und 0̸≦y≦1.
13. Vorrichtung nach Anspruch 8, bei der das Kovarianz-Mittel (92) umfaßt:
Auto-Korrelator-Mittel zum Schaffen der Auto- Korrelation Rh(i) der Impuls-Reaktion hn, wobei das Subtraktionsmittel ausgelegt ist, von dem Puffer-Ausgangssignal das Produkt der Autokorrelation rh(i) mit dem Amplitudenparameter zu subtrahieren.
14. Vorrichtung nach Anspruch 13, bei der das Mittel zum Errechnen der Amplitude auf das Ausgangssignal des Autokorrelators reagiert, mindestens zum Errechnen der Amplitude des ersten Anregungsimpules.
15. Verfahren zur Bearbeitung eines Digitalsignales mit Kodierung des Digitalsignales durch: Schaffung eines Signals S" in linearem PCM-Format;
einzelnes und aufeinanderfolgendes Speichern diskreter Blöcke des Signales Sn, wobei jeder Block eine vorbestimmte Anzahl von Abtastungen umfaßt;
Ableiten einer Vielzahl von Reihen von Reflexionskoeffizienten aus dem Signal Sn, und
Erzeugen eines Anregungssignales (A) entsprechend dem Block, wobei das Anregungssignal eine die Amplitude repräsentierende Komponente und eine den zeitlichen Ort innerhalb des Blockes repräsentierende Komponente für jeden Anregungsimpuls einer Reihe von Anregungsimpulsen umfaßt mit einer Anzahl kleiner als der Anzahl der möglichen PCM-Abtastungen in dem Block,
dadurch gekennzeichnet,
daß die Vielzahl von Reihen von Koeffizienten kontinuierlich auf Basis Abtastung um Abtastung während der Ankunft der vorbestimmten Anzahl von Abtastungen in dem Block aufgefrischt werden, und daß das Anregungssignal (A) in Abhängigkeit von den Wellenform des Signals (Sn) und der zuletzt abgeleiteten Reihe aus der Vielzahl von Reihen von Koeffizienten erzeugt wird, die bis zur letzten Abtastung aufgefrischt wurde.
16. Verfahren nach Anspruch 15, das weiter die Schritte umfaßt:
Dekodieren des Ausgangssignales durch:
Ableiten der Anregungsimpulse von dem Anregungssignal und Anlegen derselben an den Eingang eines Synthesefilters mit einstellbarem Ziel- Koeffizienten-Signal;
Einstellen der Filter-Ziel-Koeffizienten in Abhängigkeit von dem Koeffizienten-Signal;
wobei jede Reihe von Anregungsimpulsen nach entsprechender Einstellung der Koeffizienten an das Filter angelegt wird zur Erzeugung eines im wesentlichen mit dem entsprechenden Block des linearen PCM-Signals Sn identischen Ausgangssignals.
17. Verfahren nach Anspruch 16, bei dem das Kodieren das Multiplexen des Anregungssignales und des Koeffizienten-Signales einschließt und das Dekodieren das Demultiplexen des Anregungssignales und des Koeffizientensignales einschließt.
18. Verfahren nach Ansprüchen 15 und 16, bei dem die Koeffizienten auf kontinuierlicher Grundlage abgeleitet werden.
19. Verfahren nach Anspruch 18, bei dem die Koeffizienten unter Benutzung eines adaptiven Gitters abgeleitet werden.
20. Verfahren nach einem der Ansprüche 15 bis 19, bei dem die Reflexionskoeffizienten in lineare Ziel-Koeffizienten gewandelt werden.
21. Verfahren nach Anspruch 20, bei dem die Erzeugung des Anregungssignales folgende Schritte umfaßt:
Erzeugen eines gewünschten Signals dn aus dem linearen PCM-Signal;
Errechnen der Impulsreaktion hn des Kodier-Filtermittels unter Benutzung der diesem Block angemessenen Koeffizienten al;
Errechnen der Querkorrelation am zwischen der Impulsreaktion hn und dem gewünschten Signal dn;
Errechnen der allgemeinen Kovarianz 0(i, j) der Impulsreaktion hn entsprechend dem allgemeinen Ausdruck Gleichung 8 der beigefügten Figur 6;
Ableiten des Ortes der maximalen Korrelation in Abhängigkeit von der Kovarianz und der Quer- korrelation und Erzeugen eines Elementes der den zeitlichen Ort repräsentierenden Komponente daraus, wobei dieses Element die Position des ersten Anregungsimpulses ist; und
Erzeugen der entsprechenden Amplitude dieses Impulses entsprechend Gleichung 10 aus Figur 6 in Abhängigkeit von der Kovarianz, dem Maximum-Ort und der Querkorrelation.
22. Verfahren nach Anspruch 2, das weiter enthält:
Speichern des Ausgangssignales des Quer-Korrelatormittels für jeden Anregungsimpuls;
Subtrahieren eines das Produkt eines dem augenblicklichen Impuls entsprechenden Kovarianzvektors mit dem entsprechenden Amplitudenparameter darstellenden Signales von dem gespeicherten Ausgangssignal; und
Auswählen des Quer-Korrelationssignales zur Berechnung des ersten Impulses und des Produktes des Subtraktionsmittels zur Berechnung nachfolgender Impulse in der gleichen Reihe.
23. Verfahren nach Anspruch 22, das weiter enthält:
Errechnen der Kovarianz-Matrix nach Gleichung 9 der Figur 6;
Ableiten des Quadrates des Korrelationssignales; und
Dividieren der Diagonale des Kovarianzvektors durch das quadrierte Signal in Abhängigkeit von der Kovarianzmatrix und dem quadriertem Signal; wobei das Ergebnis einer solchen Division bei der Bestimmung des Maximums derselben benutzt wird.
24. Verfahren nach Anspruch 23, das weiter umfaßt:
in Abhängigkeit von der Kovarianzmatrix und dem Impulsort, Auswählen der Zeile der Kovarianzmatrix als den Kovarianzvektor, die diesem Ort entspricht, wobei eine solche Zeile an das Multiplikatormittel zur Schaffung des Produktes angelegt wird.
25. Verfahren nach Anspruch 22, bei dem die Kovarianz abgeleitet wird durch:
Schaffen der Autokorrelation Rh(i) der Impulsreaktion hn, wobei die Subtraktion das Produkt der Auto-Korrelation Rh(i) mit dem Amplitudenparameter von dem gespeicherten Signal subtrahiert.
26. Verfahren nach Anspruch 25, bei dem die Berechnung der Amplitude in Abhängigkeit von dem Auto-Korrelationssignal geschieht, mindestens zur Errechnung der Amplitude des ersten Anregungsimpulses.
27. Verfahren nach Anspruch 21, bei dem das Kodierfiltermittel ein Synthesefilter mit relativ zu denen des Dekodier-Synthesefilters modifizierten Koeffizienten umfaßt.
28. Verfahren nach Anspruch 27, bei dem das Kodierfiltermittel Koeffizienten a', besitzt, die auf die Koeffizienten a, des Dekodier-Synthesefilters durch den Ausdruck
Figure imgb0002
bezogen sind, wobei
Figure imgb0003
EP84112041A 1983-11-30 1984-10-08 Verfahren und Einrichtung zur Codierung von digitalen Signalen Expired EP0149724B1 (de)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT84112041T ATE42853T1 (de) 1983-11-30 1984-10-08 Verfahren und einrichtung zur codierung von digitalen signalen.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CA442281 1983-11-30
CA000442281A CA1236922A (en) 1983-11-30 1983-11-30 Method and apparatus for coding digital signals

Publications (2)

Publication Number Publication Date
EP0149724A1 EP0149724A1 (de) 1985-07-31
EP0149724B1 true EP0149724B1 (de) 1989-05-03

Family

ID=4126639

Family Applications (1)

Application Number Title Priority Date Filing Date
EP84112041A Expired EP0149724B1 (de) 1983-11-30 1984-10-08 Verfahren und Einrichtung zur Codierung von digitalen Signalen

Country Status (5)

Country Link
EP (1) EP0149724B1 (de)
JP (1) JPS60185432A (de)
AT (1) ATE42853T1 (de)
CA (1) CA1236922A (de)
DE (1) DE3478065D1 (de)

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA1328509C (en) * 1988-03-28 1994-04-12 Tetsu Taguchi 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 (ko) 2003-05-10 2006-06-07 엘지전자 주식회사 사이클론 방식 진공 청소기의 집진 유니트

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4472832A (en) * 1981-12-01 1984-09-18 At&T Bell Laboratories Digital speech coder

Also Published As

Publication number Publication date
ATE42853T1 (de) 1989-05-15
EP0149724A1 (de) 1985-07-31
CA1236922A (en) 1988-05-17
JPS60185432A (ja) 1985-09-20
DE3478065D1 (en) 1989-06-08

Similar Documents

Publication Publication Date Title
US3624302A (en) Speech analysis and synthesis by the use of the linear prediction of a speech wave
US4184049A (en) Transform speech signal coding with pitch controlled adaptive quantizing
US6484140B2 (en) Apparatus and method for encoding a signal as well as apparatus and method for decoding signal
US4821324A (en) Low bit-rate pattern encoding and decoding capable of reducing an information transmission rate
US5265190A (en) CELP vocoder with efficient adaptive codebook search
US5457783A (en) Adaptive speech coder having code excited linear prediction
US7013270B2 (en) Determining linear predictive coding filter parameters for encoding a voice signal
WO1992016930A1 (en) Speech coder and method having spectral interpolation and fast codebook search
EP0342687B1 (de) Überträgungssystem für codierte Sprache mit Codebüchern zur Synthetisierung von Komponenten mit niedriger Amplitude
WO1980002211A1 (en) Residual excited predictive speech coding system
CA2178073A1 (en) Adaptive speech coder having code excited linear prediction with multiple codebook searches
EP0477960B1 (de) Sprachcodierung durch lineare Prädiktion mit Anhebung der Hochfrequenzen
JPH0668680B2 (ja) 改善された多パルス線形予測符号化音声処理装置
US4945565A (en) Low bit-rate pattern encoding and decoding with a reduced number of excitation pulses
EP0374941B1 (de) Sprachübertragungssystem unter Anwendung von Mehrimpulsanregung
JPH02249000A (ja) 音声符号化方式
EP0149724B1 (de) Verfahren und Einrichtung zur Codierung von digitalen Signalen
EP0379296A2 (de) Linearer Prädiktivkodierer mit Code-Anregung für Sprach- oder Audiosignale mit niedriger Verzögerung
JPH11504733A (ja) 聴覚モデルによる量子化を伴う予測残余信号の変形符号化による多段音声符号器
US4908863A (en) Multi-pulse coding system
EP0162585B1 (de) Codierer, welcher die Unterdrückung der Wechselwirkung zwischen angrenzenden Rahmen ermöglicht
US5708756A (en) Low delay, middle bit rate speech coder
US5905970A (en) Speech coding device for estimating an error of power envelopes of synthetic and input speech signals
CA2127483C (en) Speech signal encoding system capable of transmitting a speech signal at a low bit rate without carrying out a large volume of calculation
EP0333425A2 (de) Sprachcodierung

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Designated state(s): AT DE FR GB IT NL SE

17P Request for examination filed

Effective date: 19850708

17Q First examination report despatched

Effective date: 19861006

D17Q First examination report despatched (deleted)
GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): AT DE FR GB IT NL SE

REF Corresponds to:

Ref document number: 42853

Country of ref document: AT

Date of ref document: 19890515

Kind code of ref document: T

ITF It: translation for a ep patent filed
REF Corresponds to:

Ref document number: 3478065

Country of ref document: DE

Date of ref document: 19890608

ET Fr: translation filed
PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: GB

Effective date: 19891008

Ref country code: AT

Effective date: 19891008

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: SE

Effective date: 19891009

PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT

26N No opposition filed
PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: NL

Effective date: 19900501

GBPC Gb: european patent ceased through non-payment of renewal fee
NLV4 Nl: lapsed or anulled due to non-payment of the annual fee
PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: FR

Effective date: 19900629

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: DE

Effective date: 19900703

REG Reference to a national code

Ref country code: FR

Ref legal event code: ST

EUG Se: european patent has lapsed

Ref document number: 84112041.3

Effective date: 19900706