Multirate digital transmission method and device for implementing said method

Claim 2

A digital transmission method for transmitting a speech-originating signal at different predetermined rates, comprising the steps of: sampling said speech signal at a predetermined frequency and subband coding it, said subband coding being made with dynamic allocation of coding bits to the subbands, and the rate of said coding bits of all subbands being chosen so as to be the highest one in a set of prede-termined bit rates chosen as a function of said dif-ferent transmission rates; generating a so-called macro-sample format for regroup-ing the bits obtained by coding all samples of the different subbands considered at the same sampling instant, said format being split into a number of prede-termined fields as a function of said set of coding bit rates; generating a so-called multirate macro sample by dis-tributing the bits obtained by coding each macro sample over the different fields, considering the order of said bits and their distribution over the subbands for coding at each rate of said set of rates; selecting a transmission rate among the predetermined rates; and selecting a given portion of said multirate macro sample for transmission, said portion being obtained by even-tually truncating said multirate macro-sample by drop-ping one or several predetermined fields depending on the selected transmission rate.

Claim 3

A digital transmission method for transmitting a speech-originating signal at different predetermined rates, comprising: sampling said speech signal at a predetermined rate and subband coding it using Block Companded PCM type techniques, said subband coding being made by dynamically allocating the coding bits to the subbands during a given time interval, the rate of said coding bits being chosen so as to be the highest one among a set of bit rates derived from said predetermined transmission rates after subtracting a given number of bits reserved for coding the so-called characteristic terms of the Block Companded PCM technique for the group of said subbands; generating a so-called macro sample format to regroup the bits obtained by coding the samples of the different subbands considered at the same sampling instant, said format being split into a number of predetermined fields depending on said set of coding bit rates; generating a multirate macro sample by distributing the bits obtained by coding each macro sample over said fields, considering the order of said bits and their distribution over the subbands for coding at each of said rates; selecting a transmission rate; generating a truncated multirate macro sample obtained by selecting a given portion of said multirate macro sample, said portion being obtained by eventually truncating said multirate macro sample and by possibly dropping one or several predetermined fields depending on the transmission rate selected; constructing a bit block to be transmitted during each of the given time intervals as a function of said selected rate, each of said blocks providing a portion containing said Block Companded PCM characteristic terms for said given time interval and a portion containing the eventually truncated multirate macro samples; and, transmitting the bit blocks.

Claim 4

A digital transmission method for transmitting a speech-originating signal at different predetermined rates, comprising: sampling said speech signal at a predetermined rate and subband coding it using Block Companded PCM type techniques, said subband coding being made by dynamically allocating the coding bits to the subbands during a given time interval, the rate of said coding bits being chosen so as to be the highest one among a set of bit rates derived from said predetermined transmission rates after subtracting a given number of bits reserved for coding the so-called characteristic terms of the Block Companded PCM technique for the group of said subbands; generating a so-called macro sample format to regroup the bits obtained by coding the samples of the different subbands considered at the same sampling instant, said format being split into a number of predetermined fields depending on said set of coding bit rates; generating a multirate macro sample by distributing the bits obtained by coding each macro sample over said fields, considering the order of said bits and their distribution over the subbands for coding at each of said rates; selecting a transmission rate; generating a truncated multirate macro sample obtained by selecting a given portion of said multirate macro sample, said portion being obtained by eventually truncating said multirate macro sample and by possibly dropping one or several predetermined fields depending on the transmission rate selected; constructing a bit block to be transmitted during each of the given time intervals as a function of said selected rate, each of said blocks providing a portion containing said Block Companded PCM characteristic terms for said given time interval and a portion containing the eventually truncated multirate macro samples; and, transmitting the bit blocks.

Claim 5

A digital transmission method according to claim 2, wherein said bit block to be transmitted is built up according to a format regrouping the bits of similar fields of all macro samples of the same sample block.

Claim 6

A digital transmission method according to claim 2 or 3, wherein said Block Companded PCM subband coding covers the whole frequency range of the speech signal to be transmitted.

Claim 7

A digital transmission method according to claim 2, wherein said subband coding covers a portion of the frequency spectrum of the speech signal portion defined for the predictive coding of the speech signal.

Claim 8

A digital transmission method according to claim 5, wherein said portion of the spectrum corresponds to the so-called speech signal base band.

Claim 9

A digital transmission device for transmitting at a rate chosen in a set of predetermined rates over a transmission path, comprising: sampling means for sampling the speech signal at its Nyquist frequency and coding means for coding the samples thus obtained at a relatively high bit rate; subband coding means connected to the sampling means and using Block Companded PCM techniques for coding the signal by segments of a given duration after filtering over p frequency subbands; formatting means connected to the subband coding means for formatting multirate macro-samples by controlling the distribution of the bits obtained by coding of so-called macro samples formed by the samples of the p subbands obtained at the same sampling instant according to a format providing a given number of fields as a function of the possible transmission rates; transmission rate selecting means for selecting a transmission rate among said predetermined rates; constructing means connected to said formatting means and to said subband coding means for building bit blocks to be transmitted by eventually truncating the multirate macro-samples by dropping one or several given fields depending on the selected rate; and, transmission means connected to said constructing means for transmitting the bit blocks over the transmission path.

Claim 10

A digital transmission device for transmitting at a rate chosen in a set of predetermined rates over a transmission path, comprising: sampling means for sampling the speech signal at its Nyquist frequency and coding means for coding the samples thus obtained at a relatively high bit rate; subband coding means connected to the sampling means and using Block Companded PCM techniques for coding the signal by segments of a given duration after filtering over p frequency subbands; formatting means connected to the subband coding means for formatting multirate macro-samples by controlling the distribution of the bits obtained by coding of so-called macro samples formed by the samples of the p subbands obtained at the same sampling instant according to a format providing a given number of fields as a function of the possible transmission rates; transmission rate selecting means for selecting a transmission rate among said predetermined rates; constructing means connected to said formatting means and to said subband coding means for building bit blocks to be transmitted by eventually truncating the multirate macro-samples by dropping one or several given fields depending on the selected rate; and, transmission means connected to said constructing means for transmitting the bit blocks over the transmission path.

Claim 11

A transmission device according to claim 7, wherein said formatting means comprise: means for determining the bit rate to be allocated to each subband for each of the possible transmission rates; and, means for distributing over said fields the bits of each sample forming a macro sample depending on its rank in the subband sample to which it belongs and on its contribution to the coding at each of the coding rates corresponding to each of the possible transmission rates.

Claim 12

A digital transmission method for concentrating the speech signals originating from different sources on the same path, said method comprising : sampling each of said speech signals at a predetermined frequency and subband coding it, the subband coding being made by dynamic distribution of the available coding bits, and the bit rate being chosen so as to be the highest one in a set of predetermined bit rates; creating a socalled multirate macro sample format for regrouping the bits obtained by coding the samples of the different subbands considered at the same sampling instant, said multirate macro sample format being split into a number of predetermined fields; distributing the bits obtained by coding each macro sample over said fields, taking into account the order of each bit in the sample to which it belongs and the distribution of said bits over the subbands for each of the predetermined bit rates; measuring the relative activity of each of said sources with respect to the other sources; selecting the bit rate to be allocated to the coding signal supplied by each source as a function of said relative activity measured; building macro-samples by possibly dropping bits of predetermined fields of the multirate macro samples as a function of said bit rate selected for each source; and, multiplexing the macro-samples for transmitting them over said transmission path.

Claim 13

A digital transmission method for concentrating the speech signals originating from different sources on the same path, said method comprising : sampling each of said speech signals at a predetermined frequency and subband coding it, the subband coding being made by dynamic distribution of the available coding bits, and the bit rate being chosen so as to be the highest one in a set of predetermined bit rates; creating a socalled multirate macro sample format for regrouping the bits obtained by coding the samples of the different subbands considered at the same sampling instant, said multirate macro sample format being split into a number of predetermined fields; distributing the bits obtained by coding each macro sample over said fields, taking into account the order of each bit in the sample to which it belongs and the distribution of said bits over the subbands for each of the predetermined bit rates; measuring the relative activity of each of said sources with respect to the other sources; selecting the bit rate to be allocated to the coding signal supplied by each source as a function of said relative activity measured; building macro-samples by possibly dropping bits of predetermined fields of the multirate macro samples as a function of said bit rate selected for each source; and, multiplexing the macro-samples for transmitting them over said transmission path.

Claim 14

A digital transmission method according to claim 9, wherein the bit rate to be allocated to coding the signal of each source is dynamically defined as a function of the relative activity of said source in such a way that the sum of the bit rates allocated to the different sources is equal to a predetermined portion of the transmission capacity of said path.

Claim 15

A digital transmission method according to claim 10, wherein said subband coding uses the so-called Block Companded PCM techniques.

Claim 16

A digital transmission method according to claim 11, wherein said relative activity measurement is based on a comparison of the Block Companded PCM characteristic terms.

Claim 17

A digital transmission method according to claim 11, wherein said relative activity of the speech signal sources is measured about the highest absolute values of the characteristic terms for each signal segment.

Claim 18

A digital transmission method according to claim 11, wherein the coding is of the so-called predictive type which supplies an information on the energy contained in at least one portion of the covered speech signal spectrum.

Claim 19

A digital transmission method according to claim 14, wherein said relative activity measurement of the speech signal sources is based on information combining the energies in a portion of the speech signal spectrum with the characteristic terms of Block Companded PCM coding.