Transmission process and device for implementing the so-improved process
First Claim
1. A method of transmitting a voice signal, the spectrum of which extends within a given frequency band, said method including the following steps:
- at the transmitter;
sampling said voice signal;
digitally coding the sample stream at a relatively high bit rate;
filtering the digitally-coded signal into p frequency sub-bands;
dividing the sample stream of the p sub-band filtered signals into consecutive blocks of samples of a given time duration;
sequentially requantizing each of said blocks, said requantizing including a dynamic allocation of the bits allocated to the requantizing of the samples of the voice signal of each of said sub-bands, and including for the processing of each of the blocks to be requantized, the following operations;
determining requantizing parameters of the sub-band, for each of said sub-bands, from the energy of the voice signal within said sub-band derived from the filtering and dividing operation of a given block of samples;
quasi simultaneous requantizing the samples, upon said parameter determination, which samples are contained in each sub-band and derived from said given block of samples, using the requantizing parameters determined from the previous block of samples in the same sub-bands; and
,transmitting in multiplex format the requantized signal samples over the p sub-bands together with requantizing parameters, for each block of samples.
1 Assignment
0 Petitions
Accused Products
Abstract
An improved split-band coder reduces signal-processing time, thereby reducing echo delay time and listener confusion. The voice-originated signal to be transmitted over a transmission line is sampled and digitally coded at a relatively high bit rate; the spectrum of said signal is then partitioned into p sub-bands. The sample stream of the signal so-filtered and partitioned into p sub-bands is split into blocks of samples, or portions, of a given time duration. A requantizing device proceeds for each block to the requantizing of the samples in each sub-band by means of requantizing parameters derived from the samples of the preceding sample block, whereas new requantizing parameters are determined and stored with a view to requantizing the following sample block. The requantized samples in the different sub-bands are multiplexed, and transmitted over the transmission line, together with the values of the highest amplitude samples in each sub-band.
24 Citations
5 Claims
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1. A method of transmitting a voice signal, the spectrum of which extends within a given frequency band, said method including the following steps:
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at the transmitter; sampling said voice signal; digitally coding the sample stream at a relatively high bit rate; filtering the digitally-coded signal into p frequency sub-bands; dividing the sample stream of the p sub-band filtered signals into consecutive blocks of samples of a given time duration; sequentially requantizing each of said blocks, said requantizing including a dynamic allocation of the bits allocated to the requantizing of the samples of the voice signal of each of said sub-bands, and including for the processing of each of the blocks to be requantized, the following operations; determining requantizing parameters of the sub-band, for each of said sub-bands, from the energy of the voice signal within said sub-band derived from the filtering and dividing operation of a given block of samples; quasi simultaneous requantizing the samples, upon said parameter determination, which samples are contained in each sub-band and derived from said given block of samples, using the requantizing parameters determined from the previous block of samples in the same sub-bands; and
,transmitting in multiplex format the requantized signal samples over the p sub-bands together with requantizing parameters, for each block of samples.
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2. A method of transmitting a voice signal the spectrum of which extends within a given frequency band, said method including the following steps:
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at the transmitter; sampling said voice signal substantially at Nyquist frequency; digitally coding the sample stream at a relatively high bit rate; filtering the digitally-coded signal into p frequency sub-bands; dividing the sample stream of the p sub-band filtered signals into consecutive blocks of samples of a given time duration; sequentially BCPCM block requantizing each of the sample blocks, said requantizing including, for each block; (a) determining the amplitude M of the largest sample contained within each of said sub-bands for the considered block; (b) determining a requantizing step for each sub-band, said step satisfying the relation;
##EQU13## wherein i=1, 2, 3, . . . , p is indicative of the order of the considered sub-band over the p sub-band assembly,ni is representative of the requantizing bit rate associated with said sub-band of order i, N is the total number of the bits to be allocated to the requantization of the p sub-bands;
##EQU14## Mi, is the value of the amplitude of the largest sample for the sub-band of order i and for the considered block;(c) requantizing the samples of each sub-band which samples are derived from the filtering of said considered block, by using the requantizing step determined for said sub-band by the processing of the samples belonging to the preceding block; and transmitting in multiplex format the requantized samples appearing in the p sub-bands, together with the requantizing parameters for each sample block. - View Dependent Claims (3)
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4. A transmission system for transmitting over a transmission line a voice signal the frequency spectrum of which extends within a given frequency band, said system including:
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sampling and coding means for sampling and coding said voice signal into a digital signal coded at a relatively high bit rate; means connected to said sampling and coding means for filtering the digitized voice signal spectrum into p sub-bands; means connected to said filtering means for dividing the sample stream of digitally coded signal into blocks of samples of a given time duration;
requantizing means connected to said filtering means and including;energy measuring means connected to said filtering means for sorting on each sub-band the largest signal sample within each of said blocks of samples; logarithm generating means connected to said energy measuring means; adding means connected to said logarithm generating means; storing means connected to said energy measuring means to said logarithm generating means and to said adding means for storing data used to determine the requantizing parameters of each block of samples; a requantizer connected to said storing means and said filtering means for requantizing the samples provided on each of said sub-bands and derived from the filtering of a given block of samples, using the parameters provided by said storing means and derived from the preceding block of samples; and multiplexing means connected to said requantizer and to said filtering means, for multiplexing the requantized sample blocks with the requantizing parameters, over said transmission line.
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5. A transmission system for transmitting over a digital transmission line a voice signal the spectrum of which extends within a given frequency band, said system including:
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sampling and converting means for sampling said voice-signal and for digitally encoding the samples; a tree type filter means connected to said sampling and converting means for filtering said spectrum into p sub-bands; divider means for dividing the sample stream into blocks of a given time duration; means connected to said filter means for measuring the amplitude of the largest amplitude sample M which appears in each sub-band within each sample block; means connected to said amplitude measuring means for calculating the base-two logarithm of the samples M in each sub-band for each sample block; first adding means connected to said logarithm calculating means for calculating;
##EQU15## where N is a predetermined value indicative of the total number of the bits to be used in requantifying the signal samples over the p sub-bands;i=1,2, . . . , p defines the order of the considered sub-band at the output of said filtering means; second adding means connected to the outputs of said logarithm calculating means and said first adding means; quantizing step generating means connected to said second adding means and said amplitude measuring means; storing means connected to said amplitude measuring means and to said quantizing step generating means; sub-band requantizing devices connected to said storing means and to said tree-shaped filtering means; and multiplexing means connected to said sub-band requantizing means and to said storing means.
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Specification