EP0145332A2
Expired / Lapsed
EP
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Digital audio transmission
Assignee: British Telecommunications PLC
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Filing: 1984-11-15
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Granted: —
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Expires: 2004-11-15
Abstract
Abstract @ A digital sub-band coder for audio signals provides for adaptive allocation of bits to (eg) two sub-bands. Estimation of the relative energy content of the bands is determined by reference only to those bits which are always transmitted, so that decoding can take place without the need for transmission of side information. Accompanying data may be transmitted in a fixed bit position, or may be by insertion of the data into the lower energy band. In the latter case, the data may optionally be duplicated in both bands when their energy contents are random. The invention can be applied to embedded ADPCM coders.
Inventors
- 👤 Frederick Arthur Westall
- 👤 Ian Ross Cameron
- 👤 Robert William Mclintock
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-30 23:16
CPC Classifications
H; H04; H04M; H04M11/00; H04M11/06; H04M11/064; H04B; H04B1/00; H04B1/66; H04B1/667
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
47 words
A method of coding a digital sub-band coded signal, in which the number of bits allocated to the respective sub-bands is adaptively determined as a function of those bits which are always transmitted, whereby the coded signal may be decoded by reference only to the transmitted bits.
Claim 2
Independent Claim
47 words
A method of coding a digital sub-band coded signal, in which the number of bits allocated to the respective sub-bands is adaptively determined as a function of those bits which are always transmitted, whereby the coded signal may be decoded by reference only to the transmitted bits.
Claim 3
Dependent Claim
18 words
A method as claimed in claim 1 wherein the sub-band coded signal is a digitally coded voice signal.
Claim 4
Dependent Claim
28 words
A method as claimed in claim 1 or 2 in which data bits are inserted into the coded signal, the data bits being inserted in predetermined bit positions.
Claim 5
Dependent Claim
33 words
A method as claimed in claim 1 or 2 in which data bits are inserted into the coded signal, the data bits being inserted adaptively into a sub-band with a low energy content.
Claim 6
Independent Claim
19 words
A method as claimed in any preceding claim in which the energy content of two adjacent sub-bands is compared.
Claim 7
Dependent Claim
25 words
A method as claimed in claim 5 in which the comparison of the energy contents of the sub-bands is effected by taking the ratio thereof.
Claim 8
Dependent Claim
51 words
A method as claimed in claim 5 or 6 when dependent on claim 4 in which the data bits are inserted in both sub-bands if the comparison indicating that the difference of the energies in the sub-bands, or the difference between their ratio and unity, is less than a predetermined amount.
Claim 9
Independent Claim
46 words
A method as claimed in anyone of the preceding claims in which each sub-band is coded by an embedded adaptive differential pulse code modulation (ADPCM) encoder and the comparison of the energy content of the sub-bands is effected by comparing the stepsizes of the ADPCM encoders.
Claim 10
Independent Claim
52 words
A method as claimed in any preceding claim in which the sub-bands are two adjoining half-bands of 64kbit/s voice transmission system of a 7kHz speech bandwidth, the total transmission capacity is 8 bits, the lower sub-band is encoded by 4 or 5 bits and the upper sub-band by 2 or 3 bits.
Claim 11
Independent Claim
36 words
A method of transmitting a digital data signal together with a digital sub-band coded signal which comprises comparing the energy contents different sub-bands and adaptively inserting data bits into a sub-band with a low energy content.
Claim 12
Independent Claim
36 words
A method of transmitting a digital data signal together with a digital sub-band coded signal which comprises comparing the energy contents different sub-bands and adaptively inserting data bits into a sub-band with a low energy content.
Claim 13
Dependent Claim
67 words
A digital sub-band coder comprising filter means for dividing the input signal into two or more frequency sub-bands, and adaptive bit allocation means for adaptively determining the number of bits to be used for encoding each sub-band in dependence on the relative energy content of the sub-bands, characterised in that the bit allocation means is responsive only to those bits of each sub-band which are always transmitted.
Claim 14
Dependent Claim
67 words
A digital sub-band coder comprising filter means for dividing the input signal into two or more frequency sub-bands, and adaptive bit allocation means for adaptively determining the number of bits to be used for encoding each sub-band in dependence on the relative energy content of the sub-bands, characterised in that the bit allocation means is responsive only to those bits of each sub-band which are always transmitted.
Claim 15
Dependent Claim
28 words
Apparatus as claimed in claim 11 including embedded ADPCM encoders for encoding the sub-bands, in which the relative energy contents are assessed by comparing the respective quantisation stepsizes.
Claim 16
Dependent Claim
21 words
Apparatus as claimed in claim 11 or 12 including means to measure and compare the energy content of two adjacent sub-bands.
Claim 17
Dependent Claim
22 words
Apparatus as claimed in claim 13 wherein the means for comparing is arranged to derive the ratio of the measured energy contents.
Claim 18
Dependent Claim
25 words
Apparatus as claimed in any one of claims 11 to 14 including means for inserting data bits into predetermined bit positions of the coded signal.
Claim 19
Dependent Claim
40 words
Apparatus as claimed in any one of claims 11 to 14 including means for inserting data bits into the coded signal, the insertion means being arranged to selectively insert the data bits into a sub-band having a low energy content.
Claim 20
Dependent Claim
41 words
Apparatus as claimed in claim 16, when dependent on claim 14 in which the insertion means is arranged to insert data bits into both bands in the event that the energy contents thereof are dissimilar to less than a predetermined extent.
Claim 21
Dependent Claim
24 words
Apparatus as claimed in any one of claims 11 to 17 employing digital filters to divide an incoming signal into said plurality of sub-bands.
Claim 22
Dependent Claim
62 words
Apparatus to transmit digital sub-band encoded signals and digital data signals, comprising means to divide an incoming frequency band into a plurality of sub-bands and means for encoding each sub-band separately, characterised in that the apparatus further comprises means to measure and compare the energy contents of the sub-bands and selectively insert data bits into a sub-band having a low energy envelope.
Claim 23
Dependent Claim
62 words
Apparatus to transmit digital sub-band encoded signals and digital data signals, comprising means to divide an incoming frequency band into a plurality of sub-bands and means for encoding each sub-band separately, characterised in that the apparatus further comprises means to measure and compare the energy contents of the sub-bands and selectively insert data bits into a sub-band having a low energy envelope.
References Cited (Backward Citations)
No citation records indexed.
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