Process for compressing data relative to voice signals and device applying said process
First Claim
1. Process for compressing a digitally encoded voice signal, said compression resulting from a transcoding operation, characterized in that it includes the following steps:
- on a recuring basis splitting an epoch of the frequency bandwidth of said voice signal into a low frequency and a high frequency band, digitally coding and requantizing with dynamic bit allocation for each epoch the contents of said low frequency band for each epoch to generate SIGNAL information, processing the contents of said high frequency band for each epoch to generate a set of preemphasised parcor type coefficients (COEF), processing the contents of said high frequency band for each epoch to generate energy information (ENERG), said SIGNAL, COEF and ENERG data generated for each epoch providing the digital data characterizing the compressed voice signal.
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Abstract
A voice signal is transmitted digitally at reduced bit rate by use of data compression. The original frequency components of a telephone band width of the voice signal sampled at 8 KHz and quantized with 12 bits are transformed into three parameters: SIGNAL data representing adaptive quantization for lower frequency (300-800 Hz) sub-bands; COEF data representing pre-emphasized parcor type coefficients for the higher frequency (800-3000 Hz) band; and, ENERGY data representing higher frequency short term energy level. The three parameters are multiplexed for transmission in binary-code form, thereby representing a recoding of the original binary-coded voice signals.
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Citations
16 Claims
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1. Process for compressing a digitally encoded voice signal, said compression resulting from a transcoding operation, characterized in that it includes the following steps:
- on a recuring basis splitting an epoch of the frequency bandwidth of said voice signal into a low frequency and a high frequency band, digitally coding and requantizing with dynamic bit allocation for each epoch the contents of said low frequency band for each epoch to generate SIGNAL information, processing the contents of said high frequency band for each epoch to generate a set of preemphasised parcor type coefficients (COEF), processing the contents of said high frequency band for each epoch to generate energy information (ENERG), said SIGNAL, COEF and ENERG data generated for each epoch providing the digital data characterizing the compressed voice signal.
- View Dependent Claims (2)
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3. Process for transcoding a sampled and digitalized voice signal, characterized in that it includes the following steps:
- splitting the voice signal into blocks of samples;
splitting the frequency band of said voice signal into a low frequency band and a high frequency band, coding the information of said low frequency band by splitting the band thereof into several sub-bands and by requantizing each of said sub-bands with a bit rate determined for each block of samples in accordance with the energy contained in said sub-band, said coding of the whole low frequency band supplying SIGNAL information, processing the contents of said high frequency band to generate a set of preemphasized parcor type coefficients (COEF) for each block of samples being processed, determining an energy information (ENERG) about the high frequency portion of the bandwidth of the signal to be compressed considered by blocks, and multiplexing the said SIGNAL, COEF and ENERG data on a transmission line.
- splitting the voice signal into blocks of samples;
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4. A device for digitally compressing a voice signal, characterized in that it includes:
- an input, first means for applying to said input the samples of a telephone band of the voice signal taken by blocks of constant length, second means connected to said input for receiving and splitting the applied signal bandwidth into a high frequency band and a low frequency band, third means responsive to the information of said high frequency band and generating the preemphasized parcor type coefficients (COEF) of the signal it contains, periodic resampling means receiving the information of said low band, submitting it to a periodic resampling operation and quantizing it by splitting it into sub-bands and dynamically adapting the bit rate assigned to the quantization of each sub-band in accordance with the energy contained in said sub-band, so as to generate a SIGNAL information, means for determining the energy of the high frequency band connected to said input and to said periodic resampling means and generating information ENERG, means receiving said information COEF, SIGNAL and ENERG for multiplexing them on a transmission line.
- View Dependent Claims (5)
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11. A data compression process for compressing a voice signal extending over the telephone bandwidth, which has been sampled at a first given rate and quantized with a relatively high number of bits, said process including the following steps:
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splitting the frequency bandwidth of said sampled and quantized voice signal into a low frequency bandwidth and a high frequency bandwidth; periodically resampling said low frequency bandwidth at a rate lower than said first given rate; splitting the resampled low frequency bandwidth into p sub-bands; subjecting each of said p sub-bands to an adaptive sub-band block requantizing operation using a quantizing step dynamically adapted to the sub-band energy contained in said each sub-band; collecting the requantized information over the p sub-bands into a SIGNAL data information; measuring and quantizing the energy contained in said high frequency bandwidth for deriving ENERG data; processing the information contained in said telephone bandwidth for deriving COEF data representing preemphasized parcor type coefficients; and
,multiplexing said SIGNAL, COEF and ENERG data. - View Dependent Claims (6, 7, 8, 9, 10, 13, 14)
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12. A data compression process for compressing a voice signal extending over the telephone bandwidth, sampled at a first given rate and quantized with a relatively high number of bits, said process including the following steps:
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splitting the frequency bandwith of said sampled and quantized voice signal into a low frequency bandwidth and a high frequency bandwidth; periodically resampling said low frequency bandwith at a rate lower than said first given rate; splitting the resampled low frequency bandwidth into p sub-bands; subjecting each of said p sub-bands to an adaptive sub-band block requantizing operation using a quantizing step dynamically adapted to the sub-band energy contained in said each sub-band; collecting the requantized information over the p sub-bands into a SIGNAL data information; measuring and quantizing the energy contained in said high frequency bandwidth for deriving ENERG data; processing the information contained in said high frequency bandwidth for deriving COEF data representing preemphasized parcor type coefficients; and
, multiplexing said SIGNAL, COEF and ENERG data.
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15. A device for digitally compressing a voice signal extending over the telephone frequency bandwidth, said signal being sampled at a first given rate and quantized with a relatively high number of bits, said device including:
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filtering means for receiving said sampled and quantized voice signal and providing the high frequency components of said voice signal at an output thereof and the low frequency components of said voice signal at another output thereof; means for determining preemphasized parcor type coefficients receiving said low frequency components of said voice signal and providing preemphasized parcor type coefficients; first requantizing means for receiving said preemphasized parcor type coefficients and providing COEF data; periodic resampling means for receiving said high frequency components of said voice signal and for periodically resampling said high frequency components of said voice signal; adaptive sub-band block requentizing means for receiving the periodically resampled high frequency components of said voice signal and providing SIGNAL data; high band energy measuring means for receiving said high frequency components of said voice signal and providing information relative to the energy of said high frequency components of said voice signal; second requantizing means for receiving said information relative to the energy of said high frequency components of said voice signal and providing ENERG data; and multiplexing means for multiplexing said COEF, SIGNAL and ENERG data over a single output channel. - View Dependent Claims (16)
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Specification