EP0372601B1
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Coder for incorporating extra information in a digital audio signal having a predetermined format, decoder for extracting such extra information from a digital signal, device for recording a digital signal on a record carrier, comprising such a coder, and record carrier obtained by means of such a device
Assignee: Koninklijke Philips NV
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Filing: 1989-11-08
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Granted: 1995-02-22
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Expires: 2009-11-08
Abstract
Abstract A coder for incorporating extra information in the form of an auxiliary signal in a digital audio signal having a predetermined format as well as a decoder for extracting this extra information from this digital signal, whilst the digital audio signal having the predetermined format is divided into frequency sub-bands, in which on the basis of psychoacoustic qualities of the human auditory system a relatively large amount of quantization noise is permissible, and the samples in each of these sub-bands are quantized relatively coarsely according to a preset criterion, whilst the quantized sub-band signals are summed with samples of the auxiliary signal, whose maximum amplitude is always smaller than a half quantization step of the relevant sample of the main signal; the summed sub-band signals are then reconstructed to a signal covering the entire frequency band, converted into a digital signal having the predetermined format and recorded or transmitted. In an unmodified receiver or reproducing device the original digital audio signal can be reproduced in a conventional way whereas the auxiliary signal remains masked. In a receiver or reproducing device comprising a decoder the signal is again divided into an equal number of frequency sub-hands in a way corresponding to that used in the coder and they are re-quantized according to the criterion applied in the coder. By subtracting per sub-band the quantized signal from the non-quantized signal, sub-bands of the auxiliary signal are formed, which are reconstructed into a replica of the complete original auxiliary signal. The coder can be employed in a device for recording a digital signal on the record carrier. Thus, record carriers can be obtained which are provided with a copy inhibit code and which are thus protected against unauthorized copying. If a signal containing such a copy inhibit code is to be recorded again this inhibit code is detected and recording can be inhibited, the signal to be recorded can be distorted seriously and/or the presence of the copy inhibit code can be signalled.
Inventors
- 👤 Willem Frederik Druyvesteyn
- 👤 Abraham Hoogendoorn
- 👤 Leon Maria Van De Kerkhof
- 👤 Raymond Nicolaas Johan Veldhuis
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 20:31
CPC Classifications
H; H03; H03M; H03M1/00; H03M1/02; G; G11; G11B; G11B20/00; G11B20/00086; G11B20/00884; G11B20/00891; G10; G10L; G10L19/00; G10L19/018; G11B20/10; G11B20/10527; H04; H04B; H04B1/00; H04B1/66; H04B1/665; H04B1/667; G06; G06F; G06F2211/00; G06F2211/007
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
107 words
A coder for incorporating extra information in the form of an auxiliary signal v(k) in a digital audio signal u(k) having a predetermined format, characterised in that the coder (7) comprises means (22, 28) for analysing the digital signal, means (24) for quantizing the analysed digital signal in an unequivocal manner and means (28′) for determining, on the basis of the acoustic properties of the human auditory system, the amount of extra information that can be added to the quantized digital signal without this extra information being audible with unmodified detection; means (26) for combining the extra information and the quantized digital signal to a compound signal.
Claim 2
Dependent Claim
27 words
A coder as claimed in Claim 1, characterized in that it comprises means (29) for reconverting the compound signal into a digital signal having the predetermined format.
Claim 3
Dependent Claim
103 words
A coder as claimed in Claim 1 or 2, characterised in that the means for analysing the digital signal comprise analysis filter means (22) for generating a number of P sub-band signals in response to the digital signal, which analysis filter means divide the frequency band of the digital signal into consecutive sub-bands having band numbers p (1 ≦ p ≦ P), whereas for each of the respective sub-bands (P) means (24(p)) are provided for quantizing the digital signal in an unequivocal manner and means (26) for combining the respective quantized sub-band signals and the auxiliary signal for constituting P compound sub-band signals.
Claim 4
Dependent Claim
62 words
A coder as claimed in Claim 3, where dependent on Claim 2, characterized in that synthesis filter means (27) are provided for constructing a replica of the compound signal in response to the compound sub-band signals, which synthesis filter means combine the sub-bands according to a filter method with sample frequency enhancement corresponding to the sub-division in the analysis filter means (22).
Claim 5
Dependent Claim
76 words
A coder as claimed in Claim 4, characterised in that the auxiliary signal v(k) is a digital audio signal and in that analysis filter means (23) are provided for generating a number of P sub-band signals in response to the auxiliary signal v(k), which analysis filter means divide the frequency band of the auxiliary signal into consecutive sub-bands having band numbers p (1 ≦ p ≦ P) according to a filter method with sample frequency reduction.
Claim 6
Dependent Claim
33 words
A coder as claimed in Claim 4 or 5, characterised in that the bandwidths of the sub-bands approximately correspond to the critical bandwidths of the human auditory system in the respective frequency ranges.
Claim 7
Dependent Claim
70 words
A coder as claimed in Claims 4, 5 or 6, characterised in that the means (24) for quantizing the digital signal in an unequivocal manner are arranged for adaptively quantizing this signal and in that for each sub-band the size of the quantization step depends on the amplitude of the digital signal sample, while there is an exponential relationship with a preset basic number a between the possible successive steps.
Claim 8
Dependent Claim
33 words
A coder as claimed in Claim 7, characterised in that the size of the quantization step of a sample to be quantized also depends on the size of at least a previous sample.
Claim 9
Dependent Claim
37 words
A coder as claimed in Claim 7 or 8, characterised in that means (25) are provided for attenuating each sub-band signal of the auxiliary signal by a factor G, for which holds G = 2a/(a - 1).
Claim 10
Dependent Claim
174 words
A decoder to be used in combination with a coder (7) as claimed in Claims 5 to 9, characterised in that the decoder (10) comprises analysis filter means (31) for generating a number of compound sub-band signals in response to the compound signal, which analysis filter means divide the frequency band of the compound signal into consecutive sub-bands having band numbers p (1 ≦ p ≦ P) according to a filter method with sample frequency reduction, while the bandwidths of the sub-bands correspond with those of the analysis filter means (22) in the coder; means (33) for quantizing compound sub-band signals in an unequivocal manner; means (34) for subtracting the respective quantized sub-band signals from the corresponding sub-band signals of the compound signals for constituting sub-band difference signals, and synthesis filter means (36) for constructing a replica of the auxiliary signal v′(k) in response to the sub-band difference signals, which synthesis filter means combine the sub-bands according to a filter method with sample frequency enhancement corresponding to the sub-division in the analysis filter means.
Claim 11
Dependent Claim
69 words
A decoder as claimed in Claim 10, characterised in that the means (33) for quantizing the digital signal in an unequivocal manner are arranged for adaptively quantizing this signal and in that per sub-band the size of the quantization step depends on the amplitude of the sample of the digital signal, whilst between the possible successive steps there is an exponential relationship with a predetermined basic number a .
Claim 12
Dependent Claim
32 words
A decoder as claimed in Claim 9, characterised in that means (35) are provided for amplifying each sub-band difference signal by a factor G, which complies with G = 2a/(a - 1).
Claim 13
Independent Claim
28 words
A device for recording a digital audio signal on a record carrier (48), comprising a coder (7) as claimed in any one of the claims 1 to 9.
Claim 14
Independent Claim
241 words
A device for recording a digital audio signal on a record carrier (48′), comprising a coder for sub-band coding of the digital audio signal of given sample frequency 1/T, the coder comprising: - analysis filter means (22) responsive to the audio signal to generate a plurality of P sub-band signals, which analysis filter means divide the frequency band of the audio signal in conformity with a filter method with sample frequency reduction into consecutive sub-bands having band numbers p(1 ≦ p ≦ P), which analysis filter means are further adapted to apply the P sub-band signals to P outputs, which outputs are coupled to P corresponding inputs of a - recording unit (47′) which is adapted to record the P sub-band signals on the record carrier, characterized in that the device further comprises a detection unit (50) coupled to the analysis filter means (22), in that the detection unit is adapted to detect the presence of an auxiliary signal in one or more of the sub-band signals and to generate a control signal upon detection of the auxiliary signal and to apply the control signal to an output (54), in that said output is coupled to a control signal input (55) of the recording unit (47′), and in that the recording unit is adapted to inhibit recording of the audio signal in the presence of the control signal and to record the audio signal in the absence of the control signal.
Claim 15
Independent Claim
234 words
A device for recording a digital audio signal on a record carrier (48′), comprising a coder for sub-band coding of the digital audio signal of given sample frequency 1/T, wherein the coder comprises: - analysis filter means (22) responsive to the audio signal to generate a plurality of P sub-band signals, which analysis filter means divide the frequency band of the audio signal into consecutive sub-bands having band numbers p(1 ≦ p ≦ P) in accordance with a filter method using sample frequency reduction, which analysis filter means are further adapted to apply the P sub-band signals to P outputs, which outputs are coupled to P corresponding inputs of a - recording unit (47′) which is adapted to record the P sub-band signals on the record carrier, characterized in that the device further comprises a detection unit (50) which is coupled to the analysis filter means (22), in that the detection unit is adapted to detect the presence of an auxiliary signal in one or more of the sub-band signals and to generate a control signal upon detection of the auxiliary signal and to apply the control signal to an output (54), in that said output is coupled to a signalling unit (56), and in that the signalling unit is constructed to signal that the audio signal to be recorded, when the control signal is present, is an audio signal containing an auxiliary signal.
Claim 16
Dependent Claim
94 words
A device as claimed in Claim 14 or 15, characterized in that the coder further comprises signal combination means (26, S1 to Sp) coupled to the analysis filter means, in that the signal combination means are adapted to selectively (via 60) add the auxiliary signal, in the absence of the control signal, to one or more of the sub-band signals to form P composite sub-band signals and to apply said P composite sub-band signals to P outputs, which P outputs are coupled to the P corresponding inputs of the recording unit (47′) (Fig 7).
Claim 17
Dependent Claim
88 words
A device as claimed in Claim 14 or 15, characterized in that the coder further comprises signal combination means (26) coupled to the analysis filter means (22), in that the signal combination means are adapted to add the auxiliary signal, in the absence of the control signal, to one or more of the sub-band signals to form P composite sub-band signals and to apply said P composite sub-band signals to P outputs, which P outputs are coupled to the P corresponding inputs of the recording unit (Fig 8).
Claim 18
Dependent Claim
28 words
A device as claimed in Claim 14, characterized in that the coder forms part of a coder as claimed in any one of the Claims 1 to 9.
Claim 19
Dependent Claim
113 words
A record carrier on which a digital audio signal has been recorded by means of a device as claimed in any one of the Claims 13, 16, 17 or 18, characterized in that the audio signal is divided into P sub-band signals and in that the audio signal is combined with an auxiliary signal in one or more of the sub-bands in order to obtain P composite sub-band signals recorded on the record carrier (48), and in that the auxiliary signal is selected in such a way that during reproduction of the composite audio signal recorded on the record carrier via a loudspeaker device said auxiliary signal is substantially imperceptable to a listener.
References Cited (Backward Citations)
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