EP0855699B1 - Codeur/décodeur de parole à excitation par impulsions multiples - Google Patents

Codeur/décodeur de parole à excitation par impulsions multiples Download PDF

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Publication number
EP0855699B1
EP0855699B1 EP98101335A EP98101335A EP0855699B1 EP 0855699 B1 EP0855699 B1 EP 0855699B1 EP 98101335 A EP98101335 A EP 98101335A EP 98101335 A EP98101335 A EP 98101335A EP 0855699 B1 EP0855699 B1 EP 0855699B1
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Prior art keywords
speech
signal
input
circuit
coding
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German (de)
English (en)
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EP0855699A3 (fr
EP0855699A2 (fr
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Toshiyuki Nomura
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NEC Corp
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NEC Corp
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    • 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

Definitions

  • the present invention relates to a speech coder/decoder for high quality coding speech signal with designated parameters and corresponding speech coding/decoding methods according to the respective preamble of Claims 1, 5, 8 and 10.
  • CDMA Code Division Multiple Access
  • This system is disclosed in, for instance, "Enhanced Variable Rate Coded Speech Service Option 3 for Wideband Spread Spectrum Digital Systems", Standardization Recommendation Specifications, TIA/EIA/IS-127, committee TR45.5 published on 1.1.1997 by the Telecommunications Industry Association (Literature 1).
  • CELP code excited linear prediction
  • control parameters are set from a table, which is produced in advance from results of bit rate determination on the basis of input signal features, and the input signal is coded on the basis of the control parameters set in this way.
  • This system also has a function of forcibly setting a bit rate on the basis of an external signal.
  • the illustrated speech coder/decoder comprises a speech coder and a speech decoder.
  • the speech coder and speech decoder include respective coding parameter controllers 51 and 55.
  • a bit rate is given to the coding parameter controller 51.
  • the coding parameter controller 51 selects control parameters corresponding to the given bit rate with reference to a table (not shown, but for instance a ROM (read only memory) with bit rate addresses), in which a plurality of control parameters for controlling the operation of a CELP coder 52 are stored, and provides the selected control parameters to the CELP coder 52.
  • the control parameters are sub-frame length as a unit of excitation signal coding in CELP coding, and bit distribution.
  • An input signal (i.e., input speech signal) is supplied to a CELP coder 52.
  • the CELP coder 52 computes linear prediction coefficients, which represent a spectral envelope characteristic of the input signal, by linear prediction analysis thereof for each predetermined frame.
  • the CELP coder 52 also generates an excitation signal by driving a linear prediction synthesis filter corresponding to the spectral envelope characteristic, and codes the excitation signal on the basis of the bit distribution.
  • the excitation signal is coded for each of a plurality of sub-frames, into which each frame is divided.
  • the excitation signal noted above is constituted by a periodic component representing the pitch period of the input signal, a residue signal, and gains of these components.
  • the periodic component representing the pitch period of the input signal is expressed as an adaptive codevector stored in a codebook called adaptive codebook.
  • the residue component is expressed as a multi-pulse signal, which is disclosed in, for instance, J-P. Adoul et al, "Fast CELP Coding Based on Algebraic Coders" , Proc. ICASSP, pp. 1957-1960, 1987 (Literature 2).
  • the excitation signal is generated by weight imparting the adaptive codevector and the multi-pulse signal by gain data stored in a gain codebook and adding together the results of the weight imparting.
  • a reproduced signal can be synthesized by driving the linear prediction synthesis filter on the basis of the excitation signal.
  • the selection of the adaptive codevector, multi-pulse signal and gain is controlled such as to minimize error power as a result of acoustical weight imparting of an error signal, which represents an error between the reproduced signal and the input signal.
  • the CELP coder 52 outputs indexes corresponding to the adaptive codevector, multi-pulse signal and gain, and an index representing the linear prediction coefficients, to a multiplexer 53.
  • the multiplexer 53 provides a bit stream which is obtained by converting the indexes corresponding to the adaptive codevector, multi-pulse signal, gain index and linear prediction coefficients for each frame. Data representing the bit rate is stored in a bit stream header.
  • a multiplexer 54 receives the bit stream, extracts bit stream header data representing the bit rate, and provides the extracted bit rate data to the coding parameter controller 55. Then, the multiplexer 54 extracts the indexes corresponding to the adaptive codevector, multi-pulse signal, gain and linear prediction coefficients from the bit stream for each frame, and provides the extracted data to a CELP decoder 56.
  • the coding parameter controller 55 executes a similar process to that in the coding parameter controller 51, then selects the control parameters on the basis of the supplied bit rate data, and provides the selected control parameters to the CELP decoder 56.
  • the CELP decoder 56 executes a decoding process using the indexes corresponding to the adaptive codevector, multi-pulse signal, gain and linear prediction coefficients as well as the sub-frame length and bit rate data.
  • the excitation signal is obtained by weight imparting the adaptive codevector and multi-pulse signal with gain data held in the gain codebook and adding together the results of the weight imparting.
  • the reproduced signal is obtained by driving the linear prediction synthesis filter on the basis of the excitation signal.
  • the bit rate is controlled by controlling the sub-frame length as a unit of excitation signal coding and the bit distribution.
  • the frame length as a unit of coding is fixed. Therefore, it is impossible to control coding delay, which is defined as time from the instant when a first input signal sample is supplied till the instant of start of the coding.
  • ABREU-SERNANDEZ V ET AL 'A variable rate multipulse speech coder for CDMA cellular systems' WIRELESS PERSONAL COMMUNICATIONS, 1995, KLUWER ACADEMIC PUBLISHERS, NETHERLANDS, vol. 2, no. 3, pages 255-263 describes a variable rate speech coder with a variable bit rate, wherein the bit rate selection can be network-controlled and source-controlled, and a fixed frame length, and with a fixed frame length of 32 msec.
  • WO 97 15983 A describes a method and an apparatus which allow coding, manipulation and decoding of audio signals independently of the specific signal content.
  • EP 0 465 057 A1 describes an improved digital communication system which is improved for use with a wide-band signal by modifying the noise weighting filter.
  • the speech coder comprises a coding parameter control circuit for generating control parameters, i.e., frame length, sub-frame length and bit distribution that are necessary for the coding, from given bit rate and coding delay data.
  • the input speech signal is divided into frames on the basis of the given frame length.
  • a multi-pulse signal coding parameter setting circuit sets parameters, which are necessary for generating a multi-pulse signal from the given bit rate and coding delay.
  • the coding parameter control circuits Since the coding parameter control circuits generates the frame length, sub-frame length and.bit distribution data, and the input speech signal is divided into frames on the basis of the generated frame length, it is possible to vary the frame length which is a unit of processing for the coding. It is thus possible to control the coding delay in addition to the bit rate.
  • the multi-pulse signal coding parameter setting circuit sets parameters necessary for the multi-pulse signal generation, it is possible to increase the bit rate range. That is, it is not necessary to set a bit rate in advance.
  • a speech coder/decoder which comprises a speech coder and a speech decoder.
  • the speech coder includes a coding parameter control circuit 11, a CELP coding circuit 12 and a multiplexer 13.
  • the speech decoder includes a demultiplexer 14, a coding parameter control circuit 15 and a CELP decoding circuit 16.
  • bit rate and coding delay are given as control data to the coding parameter control circuit 11.
  • the coding parameter control circuit 11 calculates a frame length by subtracting an advance read length, which is necessary for an analytic processing in CELP coding, from the given bit rate and coding delay. For example, in a case where the coding delay is 25 ms and the advance read length of the linear prediction analysis is 5 ms, the frame length is 20 ms.
  • the coding parameter control circuit 11 selects, on the basis of the given bit rate, control parameters from a table, in which a plurality of control parameters for controlling the operation of the CELP coding circuit 12 are set on the basis of calculated frame length, and provides the selected control parameters to the CELP coding circuit 12.
  • the selected control parameters are frame length, sub-frame length (of 5 ms, for instance) and bit distribution.
  • the CELP coding circuit 12 codes the input signal (input speech signal) on the basis of frame length, sub-frame length and bit distribution that have been set.
  • the frame length F that has been set in the coding parameter control circuit 11, is supplied through an input terminal 213 to a frame dividing circuit 201 and a linear prediction coefficient quantizing circuit 204.
  • the sub-frame length S that has also been set in the coding parameter control circuit 11, is supplied through an input terminal 214 to a sub-frame dividing circuit 202, a linear prediction analysis circuit 203, the linear prediction coefficient quantizing circuit 204, an acoustical weight imparting signal generating circuit 205, an acoustical weight imparted reproduced signal generating circuit 206, a target signal generating circuit 208, an adaptive codebook retrieving circuit 209, a multi-pulse retrieving circuit 210 and a gain retrieving circuit 211.
  • the bit distribution to the parameters having been set in the coding parameter control circuit 11, is supplied through an input terminal 215 to the linear prediction coefficient quantizing circuit 204, adaptive codebook retrieving circuit 209, multi-pulse retrieving circuit 210 and gain retrieving circuit 211.
  • the frame dividing circuit 201 divides the input signal on the basis of the frame length F having been set, and provides each frame of input signal to the sub-frame dividing circuit 202.
  • the sub-frame dividing circuit 202 divides each frame on the basis of the sub-frame length S having been set, and provides each sub-frame of input signal to the linear prediction analysis circuit 203 and acoustical weight imparting signal providing circuit 205.
  • Np is the degree number of the linear prediction analysis, for instance 10.
  • the linear prediction analysis may be a self-correlation process or a covariance process, and is detailed in Furui, "Digital Speech Processing", Tokai University Publishing Association (Literature 3).
  • the linear prediction coefficient quantizing circuit 204 executes collective quantization of the linear prediction coefficients obtained for the individual sub-frames on the basis of the frame length F and sub-frame length S having been set for each frame. In order to reduce the bit rate, this quantization is executed for only the last sub-frame in the frame and using interpolated values of the quantized values of the pertinent and immediately preceding frames as the quantized values of the other sub-frames. This quantization and interpolation are executed after conversion of the linear prediction coefficient into corresponding line spectrum pair (LSP).
  • LSP line spectrum pair
  • LSP quantization may be executed in a well-known manner; for instance, it is disclosed in Japanese Laid-Open Patent Publication No. 4-171500 (Literature 5), and it is not described here.
  • Linear prediction synthesis filter Hs(z) is expressed by formula (1).
  • an acoustical weight imparting filter Hw(z) expressed by formula (2) is formed using the linear prediction coefficients, and is driven by sub-frame input signal to generate an acoustical weight imparted signal.
  • This acoustical weight imparted signal is provided to the target signal generating circuit 208.
  • the acoustical weight imparted reproduced signal generating circuit 206 drives the linear prediction synthesis filter and the acoustical weight imparting synthesis filter of the preceding frame with the excitation signal of the preceding sub-frame which is obtained through a sub-frame buffer 207, and provides data representing the states of the two filters after the driving to the target signal generating circuit 208.
  • the target signal generating circuit 208 receives the data representing the states of the linear prediction synthesis filter and acoustical weight imparting filter from the acoustical weight imparting reproduced signal generating circuit 206, generates a zero input response of a filter which is constituted by the two filters connected in cascade, subtracts the zero input response thus generated from the acoustical weight imparted signal, and provides the resultant difference as the target signal to the adaptive codebook retrieving circuit 209 and multi-pulse retrieving circuit 210 as well as to a gain retrieving circuit 211.
  • the adaptive codebook retrieving circuit 209 updates a codebook, called adaptive codebook and holding past excitation signals, on the basis of the excitation signal of the immediately preceding sub-frame that is obtained through the sub-frame buffer 207, and then selects an adaptive codevector corresponding to pitch d from the adaptive codebook.
  • a codebook called adaptive codebook and holding past excitation signals
  • an adaptive codevector is formed by repeatedly connecting excitation signal segments each corresponding to delay d, separated one after another from past excitation signal stored in the adaptive codebook, until reaching of the sub-frame length.
  • the reproduced signal SAd(n) is formed by driving the linear prediction synthesis filter and acoustical weight imparting filter in zero states thereof with the adaptive codevector Ad(n) thus formed, and selects pitch d which minimizes the error Ed between the target signal X(n) and the reproduced signal SAd(n), given by formula (3).
  • L is the sub-frame length set by the coding parameter control circuit 11.
  • the adaptive codebook retrieving circuit 209 further provides the selected pitch d through the output terminal 216 to the multiplexer 13, and also provides the selected adaptive codevector Ad(n) and the reproduced signal SAd(n) thereof to the gain retrieving circuit 211.
  • the adaptive codebook retrieving circuit 209 provides the reproduced signal SAd(n) to the gain retrieving circuit 211 and provides the reproduced signal SAd(n) to the multi-pulse retrieving circuit 210.
  • the multi-pulse retrieving circuit 210 forms a multi-pulse signal constituted by a plurality of non-zero pulses.
  • the position of each pulse is selected from a plurality of pulse position candidates predetermined for each pulse.
  • Each pulse is a polarity pulse.
  • the multi-pulse excitation signal is constituted by P (for instance 5) pulses.
  • the multi-pulse retrieving circuit 210 is holding a plurality of combinations of pulse number P and M(p) pulse position candidates, and selects a combination of pulse number P and M(p) pulse position candidates on the basis of a bit distribution designated by a coding parameter control circuit 11.
  • the multi-pulse retrieving circuit 210 also forms multi-pulse signal Cj(n) by using the selected pulse number P (equal to the number of channels) and M pulse position candidates of each channel, and selects a multi-pulse signal Cj(n) which minimizes formula (4).
  • X'(n) is a subtracted signal of the reproduced signal SA(n) of the adaptive codevector from the target signal X(n) and given by formula (5).
  • the multi-pulse retrieving circuit 210 provides the selected multi-pulse signal Cj(n) and reproduced signal SCj(n) thereof to the gain retrieving circuit 211, and provides corresponding index j through the output terminal 216 to the multiplexer 13.
  • the gain retrieving circuit 211 quantizes the gains GA and GC by using the reproduced signal SAd(n) of the adaptive codevector, reproduced signal SCj(n) of the multi-pulse signal and target signal X(n) such as to minimize formula (6).
  • the gain retrieving circuit 211 further forms an excitation signal by using the quantized gain, adaptive codevector and multi-pulse signal, provides the excitation signal thus formed through the sub-frame buffer 207 to the acoustical weight imparted reproduced signal generating circuit 206 and adaptive codebook retrieving circuit 209, and an index corresponding to the gain through the output terminal 216 to the multiplexer 13.
  • the multiplexer 13 provides a bit stream obtained by conversion from the indexes representing the quantized LSP, pitch, multi-pulse signal and quantized gains for each signal.
  • the bit rate and coding delay data are provided in a header of the bit stream.
  • the bit stream is supplied to the demultiplexer 14.
  • the demultiplexer 14 provides the bit rate and coding delay data present in the bit stream header to the coding parameter control circuit 15, and then it extracts the indexes of the quantized LSP, pitch, multi-pulse signal and quantized gains from the bit stream for each frame, and provides them to the CELP decoding circuit 16.
  • the coding parameter control circuit 15 executes an operation similar to that in the coder side coding parameter control circuit 11; i.e., it selects control parameters on the basis of the input bit rate and coding delay data, and provides the selected control parameters to the CELP decoding circuit 16.
  • the indexes representing the quantized LSP, pitch, multi-pulse signal and quantized gains are supplied through an input terminal 227 to a linear prediction coefficient decoding circuit 221, an adaptive codebook decoding circuit 222, a multi-pulse signal decoding circuit 223 and a gain decoding circuit 224.
  • the frame length data set by the coding parameter control circuit 15 is supplied through an input terminal 228 to the linear prediction coefficient decoding circuit 221 and a frame unifying circuit 226.
  • the sub-frame length data set by the coding parameter control circuit 15 is supplied through an input terminal 229 to the linear prediction coefficient decoding circuit 221, adaptive codebook decoding circuit 222, multi-pulse signal decoding circuit 223 and gain decoding circuit 224 and also to a reproduced signal synthesizing circuit 225 and the frame unifying circuit 226.
  • the bit distribution data set by the coding parameter control circuit 15 is supplied through an input terminal 230 to the linear prediction coefficient decoding circuit 221, adaptive codebook decoding circuit 222, multi-pulse signal decoding circuit 223 and gain decoding circuit 224.
  • the adaptive codebook decoding circuit 222 restores the adaptive codevector by decoding from the pitch data supplied for each sub-frame.
  • the multi-pulse decoding circuit 223 provides the multi-pulse signal restored by decoding from the indexes supplied for each sub-frame to the gain decoder 224.
  • the gain decoding circuit 224 restores the gains by decoding from the indexes supplied for each sub-frame, forms an excitation signal by using the adaptive codevector, multi-pulse signal and gains, and provides the excitation signal thus formed to the reproduced signal synthesizing circuit 225.
  • the reproduced signal synthesizing circuit 225 forms a reproduced signal by driving the linear prediction synthesis filter Hs(z) with the excitation signal for each sub-frame, and provides the reproduced signal thus formed to the frame unifying circuit 226.
  • the linear prediction synthesis filter Hs(z) is expressed by formula (1) noted above.
  • the frame unifying circuit 226 connects together successively supplied sub-frame reproduced signals for the frame length, and provides the resultant reproduced signal for each frame to be output at terminal 231.
  • the illustrated coder/decoder comprises a speech coder and a speech decoder.
  • the speech coder includes a coding parameter control circuit 31, a CELP coding circuit 32, a multi-pulse signal coding parameter setting circuit 33 and a multiplexer 13.
  • the speech decoder includes a demultiplexer 14, a coding parameter setting circuit 34, a CELP decoding circuit 35 and a multi-pulse signal coding parameter setting circuit 36.
  • the coding parameter control circuit 31 receives the bit rate and coding delay as control data, and calculates the frame length by subtracting advance read length, which is necessary for an analysis process in CELP coding, from the given bit rate and coding delay. On the basis of the calculated frame length, the coding parameter control circuit 31 selects control parameters from a table, in which a plurality of control parameters for controlling the operation of the CELP coding circuit 32 are stored, on the basis of the supplied bit rate, and provides the selected control parameters to the CELP coding circuit 32. The coding parameter control circuit 31 further provides the bit number distributed to the sub-frame length and multi-pulse signal to the multi-pulse signal coding parameter setting circuit 33.
  • the multi-pulse signal coding parameter setting circuit 33 computes pulse number P, pulse position candidate number M(p) of each pulse and position candidates thereof, necessary for the multi-pulse excitation signal coding, from supplied sub-frame length N and bit number Y of the multi-pulse signal.
  • the pulse position candidates of each pulse are set such that a sequence of 0, 2, 3, ..., N-1 is interleaved with the pulse number P, as disclosed in Literature 2 noted above. For example, in a case where the sub-frame length is set to 40 (i.e., a sample number N of 40) and the bit number Y of the multi-pulse signal is set to 20, the pulse number P is 5 and the pulse position candidate number M(p) is 8.
  • the CELP coding circuit 32 codes the input signal on the basis of the frame length, sub-frame length and bit distribution that are set by the coding parameter control circuit 31, and also the pulse number P, pulse position candidate number M(p) of each pulse and position candidates thereof that are set by the multi-pulse signal coding parameter setting circuit 33.
  • the CELP coding circuit 32 is the same as the CELP coding circuit described before in connection with Fig. 2 except for the operation of the multi-pulse retrieving circuit. For this reason, only the operation of the multi-pulse retrieving circuit 401 will be described.
  • the multi-pulse retrieving circuit designated at 401 in Fig. 5, generates the multi-pulse signal Cj(n) on the basis of the pulse number P and M(p) pulse position candidates of each pulse, set by the multi-pulse generation parameter setting circuit 33 and supplied through an input terminal 217, and selects a multi-pulse signal Cj(n) that minimizes formula (4) noted above.
  • the computational effort extent can be reduced by using the manner described in Literature 6.
  • the multi-pulse retrieving circuit 401 provides the selected multi-pulse signal Cj(n) and reproduced signal SCj(n) thereof to the gain retrieving circuit 211 and also provides corresponding index j through the output terminal 216 to the multiplexer 13. As described before in connection with Fig. 1, the multiplexer 13 provides a bit stream.
  • the bit stream is received by the demultiplexer 14.
  • the demultiplexer 14 provides the bit rate and coding delay data present in the bit stream header to the coding parameter control circuit 34, then extracts the indexes representing the quantized LSP, pitch and multi-pulse signal from the bit stream for each frame, and provides the extracted indexes to the CELP decoding circuit 35.
  • the coding parameter setting circuit 34 executes an operation similar to that in the coding parameter control circuit 31, thus selecting the control parameters and providing the same to the CELP decoding circuit 35.
  • the multi-pulse coding parameter setting circuit 36 executes an operation similar to that in the coding side multi-pulse generation parameter setting circuit 33, thus computing the pulse number representing the multi-pulse excitation signal, pulse position candidate number of each pulse and position candidates thereof, and providing the computed data to the CELP decoding circuit 35.
  • the CELP decoding circuit 35 is the same as the CELP decoding circuit described before in connection with Fig. 3 except for the operation of the multi-pulse decoding circuit. For this reason, only the operation of the multi-pulse decoding circuit 402 will be described.
  • the multi-pulse decoding circuit designated at 402 in Fig. 6, receives the sub-frame length set by the coding parameter control circuit 34 through the input terminal 229, receives the pulse number, pulse position candidate number of each pulse and position candidates thereof set by the multi-pulse coding parameter setting circuit 36 through an input terminal 232, and restores the multi-pulse signal by decoding from the indexes supplied for each sub-frame.
  • the illustrated speech coder includes a coding parameter control circuit 61, a CELP coding circuit 62 and a multiplexer 13.
  • the coding parameter control circuit 61 executes an operation similar to that in the coding parameter control circuit 11 described before in connection with Fig. 1, thus setting the frame length, sub-frame length and bit distribution from the supplied bit rate and coding delay data.
  • the coding parameter control circuit 61 computes permissible multi-pulse signal coding computational effort extent, to which computational effort can be paid for the multi-pulse signal coding, from the supplied computational effort extent data. This computation can be executed by storing in advance data of computational effort extents necessary for the coding of other parameters and subtracting these stored computational effort extents frcm the supplied computational effort extent.
  • the coding parameter control circuit 61 provides frame length, sub-frame length, bit distribution and permissible multi-pulse coding computational effort extent as control parameters to the CELP coding circuit 62.
  • the CDLP coding circuit 62 codes the input signal on the basis of the supplied frame length, sub-frame length, bit distribution and permissible multi-pulse signal coding computational effort extent data.
  • the CELP coding circuit 62 is the same as the CELP coding circuit described before in connection with Fig. 2 except for the operation of the multi-pulse retrieving circuit. For this reason, only the multi-pulse retrieving circuit will be described.
  • the multi-pulse retrieving circuit designated at 301 in Fig. 8, executes an operation similar to that in the multi-pulse retrieving circuit 210 described before in connection with Fig. 2, thus selecting a multi-pulse signal Cj(n) that minimizes formula (4) noted above.
  • the computational effort paid for the coding of the multi-pulse signal is preliminarily selected such that it does not exceed the permissible multi-pulse coding computational effort extent data supplied through an input terminal 218.
  • This preliminary selection can be realized by selection of a high value of E1 given by formula (9).
  • the multi-pulse retrieving circuit 301 provides the selected multi-pulse signal Cj(n) and reproduced signal SCj(n) thereof to the gain retrieving circuit 211, and also provides corresponding index j through the output terminal 216 to the multiplexer 13.
  • the illustrated speech coder includes a coding parameter control circuit 71, a multi-pulse generation parameter setting circuit 33, a CELP coding circuit 72 and a multiplexer 13.
  • the coding parameter control circuit 71 executes an operation similar to that in the coding parameter control circuit 31 described before in connection with Fig. 4, thus setting frame length, sub-frame length and bit distribution from the supplied bit rate and coding delay data.
  • the coding parameter control circuit 71 computes permissible multi-pulse signal coding computational effort extent, which is paid for the coding of multi-pulse signal, from the supplied computational effort extent data.
  • the coding parameter control circuit 71 provides the frame length, sub-frame length, bit distribution and permissible multi-pulse signal coding computational effort extent to the CELP coding circuit 72.
  • the coding parameter control circuit 71 provides sub-frame length and bit number distributed to the multi-pulse signal to the multi-pulse generation parameter setting circuit 33.
  • the CELP coding circuit 72 codes the input signal on the basis of the frame length, sub-frame length, bit distribution and permissible multi-pulse signal coding computational effort extent set by the coding parameter setting circuit 71 and the pulse number P, pulse position candidate number M(p) of each pulse and position candidates thereof set by the multi-pulse signal generation parameter setting circuit 33.
  • the CELP coding circuit 72 is the same as the CELP coding circuit described before in connection with Fig. 5 except for the operation of the multi-pulse retrieving circuit. For this reason, only the operation for the multi-pulse retrieving circuit 501 will be described.
  • the multi-pulse retrieving circuit designated at 501 in Fig. 10, executes an operation similar to that in the multi-pulse retrieving circuit 401 described before in connection with Fig. 5, thus selecting a multi-pulse signal Cj(n) that minimizes Formula (4) noted above.
  • the computational effort paid for the coding of multi-pulse signal is preliminarily set such that it does not exceed permissible multi-pulse signal coding computational effort extent supplied through an input terminal 218.
  • the multi-pulse retrieving circuit 501 also provides the selected multi-pulse signal Cj(n) and reproduced signal SCj(n) thereof to the gain retrieving circuit 211, and also provide corresponding index j through the output terminal 216 to the multiplexer 13.
  • the frame length as a unit of processing for coding is made variable, permitting generation of parameters necessary for the coding of multi-pulse signal from given bit rate and coding delay data.

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

Claims (10)

  1. Codeur vocal pour coder un signal vocal d'entrée, comprenant des moyens de codage vocal (12 ; 32 ; 62 ; 72) incluant
    un diviseur de trame (201) divisant un signal vocal d'entrée en des trames ayant une longueur de trame F,
    des moyens (203, 204) générant des coefficients de prédiction linéaire du signal vocal d'entrée divisé,
    des moyens (209, 210 ; 301 ; 401 ; 501) générant un signal vocal reproduit en pilotant un filtre de synthèse de prédiction linéaire sur la base d'un signal d'excitation de signal vocal d'entrée, le filtre de synthèse de prédiction linéaire recevant le signal de sortie des moyens générateurs de coefficients de prédiction linéaire (203, 204),
    des moyens (211) générant, à partir du signal de sortie des moyens générateurs de signal vocal reproduit (209, 210 ; 301 ; 401 ; 501), ledit signal d'excitation de signal vocal d'entrée, exprimé sous la forme d'une pluralité d'impulsions,
       caractérisé en ce que
       le codeur vocal comprend un circuit de commande (11 ; 31 ; 61 ; 71), dont l'entrée sont des données de commande désignées et dont la sortie sont au moins un paramètre de commande variable incluant la longueur variable F, de trame générée sur la base des données de commande désignées, et
       les paramètres de commande générés sont entrés dans les moyens de codage vocal (12 ; 32 ; 62 ; 72), en particulier la longueur F de trame est entrée dans le diviseur de trame (201).
  2. Codeur vocal selon la revendication 1, dans lequel les données de commande entrées dans le circuit de commande (11 ; 31 ; 61 ; 71) comprennent un débit de bits désigné et un délai de codage.
  3. Codeur vocal selon la revendication 2, dans lequel les données de commande entrées dans le circuit de commande (11 ; 31 ; 61 ; 71) comprennent une ampleur de difficultés de calcul / un volume de calculs.
  4. Codeur vocal selon la revendication 2 ou 3, comprenant un circuit (33) de fixation de paramètres, dont le signal d'entrée est donné par les paramètres de commande délivrés par le circuit de commande (11 ; 71), et dont la sortie sont des paramètres de fixation calculés qui sont entrés dans au moins une borne d'entrée (217, 218) des moyens de codage vocal (32 ; 72).
  5. Décodeur vocal pour restaurer un signal vocal reproduit à partir de données vocales codées reçues, comprenant des moyens de décodage vocal (16 ; 35) incluant
    des moyens (221) restaurant des coefficients de prédiction linéaire à partir des données vocales codées reçues,
    des moyens (225) restaurant un signal vocal reproduit en pilotant un filtre de synthèse de prédiction linéaire sur la base d'un signal d'excitation, le filtre de synthèse de prédiction linéaire recevant le signal de sortie des moyens restaurateurs de coefficients de prédiction linéaire (221),
    des moyens (224) générant, à partir de la sortie des moyens (225) restaurateurs de signal vocal reproduit, ledit signal d'excitation,
    un circuit (226) unificateur de trame générant le signal vocal décodé en réassemblant le signal vocal reproduit,
       caractérisé en ce que
       le décodeur vocal comprend un circuit de commande (15 ; 34), dont le signal d'entrée est des données de commande désignées et dont le signal de sortie est au moins un paramètre de commande variable incluant la longueur de trame variable F, généré sur la base des données de commande désignées, et
       les paramètres de commande générés sont entrés dans les moyens de décodage vocal (16 ; 35), en particulier la longueur F de trame est entrée dans le circuit (226) unificateur de trame.
  6. Décodeur vocal selon la revendication 5, dans lequel les données de commande entrées dans le circuit de commande (15 ; 34) comprennent un débit désigné de bits et un délai de codage.
  7. Codeur vocal selon la revendication 6, dans lequel les données de commande entrées dans le circuit de commande (15 ; 34) comprennent une ampleur de difficultés de calcul / un volume de calculs.
  8. Procédé de codage vocal pour coder un signal vocal d'entrée, comprenant les étapes consistant :
    à diviser le signal vocal d'entrée en des trames ayant une longueur de trame F,
    à générer des coefficients de prédiction linéaire du signal vocal d'entrée divisé,
    à générer un signal vocal reproduit en pilotant un filtre de synthèse de prédiction linéaire sur la base d'un signal d'excitation de signal vocal d'entrée, le filtre de synthèse de prédiction linéaire recevant les coefficients de prédiction linéaire générés,
    à générer, à partir du signal vocal reproduit généré, ledit signal d'excitation de signal vocal d'entrée, exprimé sous la forme d'une pluralité d'impulsions,
    à délivrer les données vocales codées,
       caractérisé par
       la génération d'au moins un paramètre de commande variable incluant la longueur variable F de trame sur la base des données de commande désignées, et
       l'utilisation de la longueur générée F de trame au cours de l'étape de partition du signal vocal d'entrée.
  9. Procédé de codage vocal selon la revendication 8, dans lequel les données de commande utilisées pour calculer les paramètres de commande comprennent un débit désigné de bits et un délai de codage.
  10. Procédé de décodage vocal pour restaurer un signal vocal reproduit à partir de données vocales codées reçues, comprenant les étapes consistant
    à restaurer des coefficients de prédiction linéaire à partir des données vocales codées reçues,
    à restaurer un signal vocal reproduit en pilotant un filtre de synthèse de prédiction linéaire sur la base d'un signal d'excitation, le filtre de synthèse de prédiction linéaire recevant les coefficients de prédiction linéaire restaurés,
    à générer, à partir du signal vocal reproduit, ledit signal d'excitation,
    à réassembler le signal vocal reproduit,
    à délivrer le signal vocal décodé,
       caractérisé par
       la génération d'au moins un paramètre de commande variable incluant la longueur variable F de trame, généré sur la base de données de commande désignées, et
       l'utilisation de la longueur générée F de trame au cours de l'étape de réassemblage du signal vocal reproduit.
EP98101335A 1997-01-27 1998-01-27 Codeur/décodeur de parole à excitation par impulsions multiples Expired - Lifetime EP0855699B1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
JP01247797A JP3329216B2 (ja) 1997-01-27 1997-01-27 音声符号化装置及び音声復号装置
JP12477/97 1997-01-27
JP1247797 1997-01-27

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EP0855699A2 EP0855699A2 (fr) 1998-07-29
EP0855699A3 EP0855699A3 (fr) 1999-04-07
EP0855699B1 true EP0855699B1 (fr) 2004-04-28

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JP3166697B2 (ja) 1998-01-14 2001-05-14 日本電気株式会社 音声符号化・復号装置及びシステム
US6721280B1 (en) 2000-04-19 2004-04-13 Qualcomm Incorporated Method and apparatus for voice latency reduction in a voice-over-data wireless communication system
JP3881943B2 (ja) * 2002-09-06 2007-02-14 松下電器産業株式会社 音響符号化装置及び音響符号化方法
WO2006085586A1 (fr) * 2005-02-10 2006-08-17 Matsushita Electric Industrial Co., Ltd. Procédé d’affectation d’impulsions dans le codage vocal
KR101235425B1 (ko) * 2005-03-09 2013-02-20 텔레폰악티에볼라겟엘엠에릭슨(펍) 저-복잡성 코드 여기 선형 예측 인코딩
US8000967B2 (en) 2005-03-09 2011-08-16 Telefonaktiebolaget Lm Ericsson (Publ) Low-complexity code excited linear prediction encoding
AU2018338424B2 (en) * 2017-09-20 2023-03-02 Voiceage Corporation Method and device for efficiently distributing a bit-budget in a CELP codec

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US5235669A (en) * 1990-06-29 1993-08-10 At&T Laboratories Low-delay code-excited linear-predictive coding of wideband speech at 32 kbits/sec
IT1281001B1 (it) * 1995-10-27 1998-02-11 Cselt Centro Studi Lab Telecom Procedimento e apparecchiatura per codificare, manipolare e decodificare segnali audio.

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JP3329216B2 (ja) 2002-09-30
EP0855699A3 (fr) 1999-04-07
DE69823398T2 (de) 2005-01-13
EP0855699A2 (fr) 1998-07-29
CA2228183C (fr) 2001-05-29
JPH10207496A (ja) 1998-08-07
DE69823398D1 (de) 2004-06-03
CA2228183A1 (fr) 1998-07-27

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