Device for the digital recording and reproduction of speech signals
First Claim
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1. A process for the digital recording and reproduction in a single device of speech signals characterized by a spectral envelope and a periodicity, comprising:
- for the recording, combining digitized speech sampling values of the speech signal in a respective time frame, for each time frame, forming a digital overall code word which accommodates a first code word for the spectral envelope (Short Term Prediction, STP, code word), a second code word for the periodicity (Long Term Prediction, LTP, code word), and a third code word for a residual signal (Regular Pulse Excitation, RPE, code word), storing said digital overall code word in a memory, and reproducing the speech signals from the stored digital overall code word, and wherein the overall code word contains a STP parameter repetition symbol which indicates whether the overall code word contains an STP code word or not, said process further comprising;
forming the STP repetition symbol as a function of a comparison between speech sampling values of a first time frame and speech sampling values of a second, already encoded time frame.
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Abstract
Devices for the digital recording and reproduction of speech signals are used, for example in answering apparatus. In order to reduce the quantity of data to be stored without noticeably affecting the acoustic quality of the speech, it is proposed to encode speech signals by means of a residual signal speech encoder.
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Citations
31 Claims
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1. A process for the digital recording and reproduction in a single device of speech signals characterized by a spectral envelope and a periodicity, comprising:
- for the recording, combining digitized speech sampling values of the speech signal in a respective time frame, for each time frame, forming a digital overall code word which accommodates a first code word for the spectral envelope (Short Term Prediction, STP, code word), a second code word for the periodicity (Long Term Prediction, LTP, code word), and a third code word for a residual signal (Regular Pulse Excitation, RPE, code word), storing said digital overall code word in a memory, and reproducing the speech signals from the stored digital overall code word, and wherein the overall code word contains a STP parameter repetition symbol which indicates whether the overall code word contains an STP code word or not, said process further comprising;
forming the STP repetition symbol as a function of a comparison between speech sampling values of a first time frame and speech sampling values of a second, already encoded time frame. - View Dependent Claims (2, 3, 4, 5)
- for the recording, combining digitized speech sampling values of the speech signal in a respective time frame, for each time frame, forming a digital overall code word which accommodates a first code word for the spectral envelope (Short Term Prediction, STP, code word), a second code word for the periodicity (Long Term Prediction, LTP, code word), and a third code word for a residual signal (Regular Pulse Excitation, RPE, code word), storing said digital overall code word in a memory, and reproducing the speech signals from the stored digital overall code word, and wherein the overall code word contains a STP parameter repetition symbol which indicates whether the overall code word contains an STP code word or not, said process further comprising;
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6. A process for the digital recording and reproduction in a single device of speech signals characterized by a spectral envelope and a periodicity, comprising:
- for the recording, combining digitized speech sampling values of the speech signal in a respective time frame, for each time frame, forming a digital overall code word which accommodates a first code word for the spectral envelope (Short Term Prediction, STP, code word), a second code word for the periodicity (Long Term Prediction, LTP, code word), and a third code word for a residual signal (Regular Pulse Excitation, RPE, code word), storing said digital overall code word in a memory, and reproducing the speech signals from the stored digital overall code word, which process further comprises;
forming an LTP suppression symbol in the digital overall code word which symbol indicates whether the digital overall code word contains an LTP code word or not, the LTP suppression symbol being formed by comparing signals produced before and after an LTP analysis. - View Dependent Claims (7)
- for the recording, combining digitized speech sampling values of the speech signal in a respective time frame, for each time frame, forming a digital overall code word which accommodates a first code word for the spectral envelope (Short Term Prediction, STP, code word), a second code word for the periodicity (Long Term Prediction, LTP, code word), and a third code word for a residual signal (Regular Pulse Excitation, RPE, code word), storing said digital overall code word in a memory, and reproducing the speech signals from the stored digital overall code word, which process further comprises;
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8. A process for the digital recording and reproduction in a single device of speech signals characterized by a spectral envelope and a periodicity, comprising:
- for the recording, combining digitized speech sampling values of the speech signal in a respective time frame, for each time frame, forming a digital overall code word which accomodates a first code word for the spectral envelope (Short Term Prediction, STP, code word), a second code word for the periodicity (Long Term Prediction, LTP, code word), and a third code word for a residual signal (Regular Pulse Excitation, RPE, code word), storing said digital overall code word in a memory, and reproducing the speech signals from the stored digital overall code word, said process further comprising, forming as a part of the overall code word a symbol (unvoiced symbol) which indicates whether the overall code word comprises other code words besides the first (STP) code word, said symbol being formed as a function of a voiced/unvoiced decision.
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9. A device for the recording and reproduction of a speech signal comprising:
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short term prediction means for analyzing the speech signal in a first time frame so as to form a first code word that codes a spectral envelope of the speech signal in said first time frame, long term prediction means for forming a second code word which codes a periodicity of the speech signal in said first time frame and for forming a residual signal representing a residue of the speech signal, regular pulse excitation coding means for forming a third code word which codes the residual signal in said first time frame, overall code word forming means coupled to the short term prediction means, the long term prediction means and the regular pulse excitation coding means thereby to form an overall code word for the first time frame, which overall code word comprises the first, second and third code words, detection means fed by at least one of said short term prediction means, said long term prediction means and said regular pulse excitation coding means, the detection means detecting whether the speech signal in the first time frame meets a suppression condition and thereupon generating a suppression code, means included in said code word forming means and fed by said detection means for, under control of said suppression code, suppressing any code word signal meeting the suppression condition from the overall code word, any overall code word containing at least a distinctive part of said suppression code, storage means coupled to said overall code word forming means for storing the overall code word, and speech synthesizing means for reading the overall code word from said storage means and for, in a second time frame, regenerating the speech signal from the overall code word. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A process for the digital recording and reproduction in a single device of speech signals characterized by a spectral envelope and a periodicity, comprising:
- for the recording, combining digitized speech sampling values of the speech signal in a respective time frame, for each time frame, forming a digital overall code word which accommodates a first code word for the spectral envelope (Short Term Prediction, STP, code word), a second code word for the periodicity (Long Term Prediction, LTP, code word), and a third code word for a residual signal (Regular Pulse Excitation, RPE, code word), storing said digital overall code word in a memory, and reproducing the speech signals from the stored digital overall code word, said process further comprising;
forming an LTP suppression symbol as a part of the digital overall code word, said LTP suppression symbol indicating whether or not the digital overall code word contains an LTP code word, and in the reproduction of speech signals stored as digital overall code words, the performance of an LTP synthesis being determined by said LTP suppression symbol.
- for the recording, combining digitized speech sampling values of the speech signal in a respective time frame, for each time frame, forming a digital overall code word which accommodates a first code word for the spectral envelope (Short Term Prediction, STP, code word), a second code word for the periodicity (Long Term Prediction, LTP, code word), and a third code word for a residual signal (Regular Pulse Excitation, RPE, code word), storing said digital overall code word in a memory, and reproducing the speech signals from the stored digital overall code word, said process further comprising;
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22. A process for the digital recording and reproduction in a single device of speech signals characterized by a spectral envelope and a periodicity, comprising:
- for the recording, combining digitized speech sampling values of the speech signal in a respective time frame, for each time frame, forming a digital overall code word which accommodates a first code word for the spectral envelope (Short Term Prediction, STP, code word), a second code word for the periodicity (Long Term Prediction, LTP, code word), and a third code word for a residual signal (Regular Pulse Excitation, RPE, code word), storing said digital overall code word in a memory, and reproducing the speech signals from the stored digital overall code word, said process further comprising;
forming as a pary of the digital overall code word a symbol (unvoiced symbol) which indicates whether the overall code word comprises other code words besides the first (STP) code word, wherein for the reproduction of speech signals, stored as digital overall code words, the process further comprises;
bridging a device for synthesizing speech signals from the periodicity as a function of said unvoiced symbol in the digital overall code word so that the residual signal is reduced to a generated noise signal.
- for the recording, combining digitized speech sampling values of the speech signal in a respective time frame, for each time frame, forming a digital overall code word which accommodates a first code word for the spectral envelope (Short Term Prediction, STP, code word), a second code word for the periodicity (Long Term Prediction, LTP, code word), and a third code word for a residual signal (Regular Pulse Excitation, RPE, code word), storing said digital overall code word in a memory, and reproducing the speech signals from the stored digital overall code word, said process further comprising;
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23. A process for the digital recording and reproduction in a single device of speech signals characterized by a spectral envelope and a periodicity, comprising:
- for the recording, combining digitized speech sampling values of the speech signal in a respective time frame, for each time frame, forming a digital overall code word which accommodates a first code word for the spectral envelope (Short Term Prediction, STP, code word), a second code word for the periodicity (Long Term Prediction, LTP, code word), and a third code word for a residual signal (Regular Pulse Excitation, RPE, code word), storing said digital overall code word in a memory, and reproducing the speech signals from the stored digital overall code word, which process further comprises;
recognizing a pause in the speech signal and in response forming a digital overall code word which includes a pause symbol, a time code word (T), a residual noise code word (N1) and a residual STP code word, and wherein for the reproduction of stored digital speech signals, a timer is reset in response to the pause signal in the digital overall code word, and via the time code word (T), and during a period of time thus defined forming the speech signal exclusively from the residual noise code word (N1) and the residual STP code word of the digital overall code word.
- for the recording, combining digitized speech sampling values of the speech signal in a respective time frame, for each time frame, forming a digital overall code word which accommodates a first code word for the spectral envelope (Short Term Prediction, STP, code word), a second code word for the periodicity (Long Term Prediction, LTP, code word), and a third code word for a residual signal (Regular Pulse Excitation, RPE, code word), storing said digital overall code word in a memory, and reproducing the speech signals from the stored digital overall code word, which process further comprises;
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24. A device for the recording and reproduction of a speech signal comprising:
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short term prediction means for analyzing the speech signal in a first time frame so as to form a first code word that codes a spectral envelope of the speech signal in said first time frame, long term prediction means for forming a second code word which codes a periodicity of the speech signal in said first time frame and forming a residual signal representing a residue of the speech signal, regular pulse excitation coding means for forming a third code word which codes the residual signal in said first time frame, overall code word forming means coupled to the short term prediction means, the long term prediction means and the regular pulse excitation coding means thereby to form an overall code word for the first time frame, which overall code word comprises the first, second and third code words, means responsive to a signal supplied by at least one of said short term prediction means, said long term prediction means and said regular pulse excitation coding means for detecting whether the speech signal in the first time frame meets a suppression condition and if met generating a suppression symbol, and said code word forming means being controlled by said suppression symbol to suppress from the overall code word formed any code word meeting said suppression condition thereby to reduce the length of the overall code word.
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25. A device for the recording and reproduction of a speech signal comprising:
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short term prediction means for analyzing the speech signal in a first time frame so as to form a first code word that codes a spectral envelope of the speech signal in said first time frame, long term prediction means for forming a second code word which codes a periodicity of the speech signal in said first time frame and for forming a residual signal representing a residue of the speech signal, regular pulse excitation coding means for forming a third code word which codes the residual signal in said first time frame, overall code word forming means coupled to the short term prediction means, the long term prediction means and the regular pulse excitation coding means thereby to form an overall code word for the first time frame, which overall code word comprises the first, second and third code words, and means responsive to signals supplied by said short term prediction means, said long term prediction means and said regular pulse excitation coding means for generating, as a part of the overall code word, suppression symbols indicating which, if any, of the first, second and third code words will be suppressed from the overall code word. - View Dependent Claims (26, 27, 28, 29, 30, 31)
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Specification