Source: http://www.google.com/patents/US5488663?dq=4,923,986
Timestamp: 2017-06-29 06:32:28
Document Index: 141181967

Matched Legal Cases: ['Application No. 04', 'Application No. 04', 'Application No. 04', 'Application No. 04', 'Application No. 04', 'Application No. 04']

Patent US5488663 - Encoding methods for generating a digital signal containing modulated bit ... - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inPatentsTransmission system for transmitting and receiving, and subband encoding methods for generating for transmission, digital signals containing modulated bit allocation information; and record carriers containing such a signal. The transmission system include a transmitter which encodes in accordance with...http://www.google.com/patents/US5488663?utm_source=gb-gplus-sharePatent US5488663 - Encoding methods for generating a digital signal containing modulated bit allocation information, and record carriers containing that signalAdvanced Patent SearchTry the new Google Patents, with machine-classified Google Scholar results, and Japanese and South Korean patents.Publication numberUS5488663 APublication typeGrantApplication numberUS 08/285,870Publication dateJan 30, 1996Filing dateAug 4, 1994Priority dateFeb 3, 1992Fee statusLapsedAlso published asDE69331166D1, DE69331166T2, US5375171Publication number08285870, 285870, US 5488663 A, US 5488663A, US-A-5488663, US5488663 A, US5488663AInventorsJan Dewolf, Gerardus C. P. Lokhoff, Abraham HoogendoornOriginal AssigneeU.S. Philips CorporationExport CitationBiBTeX, EndNote, RefManPatent Citations (16), Non-Patent Citations (14), Referenced by (14), Classifications (17), Legal Events (4) External Links: USPTO, USPTO Assignment, EspacenetEncoding methods for generating a digital signal containing modulated bit allocation information, and record carriers containing that signal
US 5488663 AAbstract
Transmission system for transmitting and receiving, and subband encoding methods for generating for transmission, digital signals containing modulated bit allocation information; and record carriers containing such a signal. The transmission system include a transmitter which encodes in accordance with the subband encoding method a wide-band digital signal into subband signals which are each made up of successive signal blocks having a predetermined number of samples of that subband signal. The samples in the signal blocks of the subband signals are quantized to produce quantized samples in the signal blocks, and bit allocation information denoting how many bits the samples in the signal blocks are to be quantized by is generated. The bit allocation information (or a portion thereof) is modulated to obtain modulated bit allocation information. The quantized samples in the signal blocks and the modulated bit allocation information are included in a digital signal applied by the transmitter to a transmission medium. The transmission system also includes a receiver for receiving a replica of the digital signal applied to the transmission medium. The modulated bit allocation information is demodulated to obtain the bit allocation information. The quantized samples in the signal blocks and the bit allocation information are used to obtain replicated samples in the signal blocks which substantially correspond to the original samples in the signal blocks of the subband signals. The replicated samples are used to produce a replica of the original wide-band digital signal.
1. A method of subband encoding a wide-band digital signal, the method comprising:generating a plurality of subband signal from the wide-band digital signal, each of the subband signals being made up of consecutive signal blocks with each contain a predetermined number of samples of that subband signal; quantizing the samples in the signal blocks of the subbands signals to produce quantized samples in the signal blocks; generating bit allocation information denoting how many bits the samples in the signal blocks are to be quantized by; modulating the bit allocation information or a portion thereof to produce modulated bit allocation information; and generating a digital transmission signal including the quantized samples and the modulated bit allocation information. 2. The method as claimed in claim 1, wherein said modulating is performed by a self synchronizing modulator.
3. The method as claimed in claim 1, wherein said modulating is performed by a non-self synchronizing modulator.
4. The method as claimed in claim 1, wherein said modulating includes selective scrambling of the bit allocation information or the portion thereof which is to be modulated.
5. The method as claimed in claim 1, wherein the bit allocation information or the portion thereof which is to be modulated has a bit sequence, and said modulating includes changing the order of the bit sequence.
6. The method as claimed in claim 1, wherein the bit allocation information or the portion thereof which is to be modulated comprises y-bit words having a word sequence, and said modulating includes changing the order of the word sequence.
7. The method as claimed in claim 1, wherein further comprising applying the digital transmission signal to a transmission medium.
8. The method as claimed in claim 7, wherein said transmission medium is a magnetic record carrier.
9. A record carrier produced by the method of claim 7.
10. The record carrier as claimed in claim 9, wherein the record carrier is a magnetic record carrier.
11. A method of subband encoding a wide-band digital signal, the method comprising:generating a plurality of subband signal from the wide-band digital signal, each of the subband signals being made up of consecutive signal blocks with each contain a predetermined number of samples of that subband signal; quantizing the samples in the signal blocks of the subbands signals to produce quantized samples in the signal blocks; generating bit allocation information denoting how many bits the samples in the signal blocks are to be quantized by; combining the quantized samples in the signal blocks and the bit allocation information relating thereto in successive frames of a second digital signal; modulating the bit allocation information or a portion thereof in a frame of the second digital signal thereby producing an intermediate digital signal including modulated bit allocation information in a frame thereof; and converting the intermediate digital signal into a digital transmission signal for transmission to a transmission medium. 12. The method as claimed in claim 11, wherein said modulating is performed by a self synchronizing modulator.
13. The method as claimed in claim 11, wherein said modulating is performed by a non-self synchronizing modulator.
14. The method as claimed in claim 11, wherein said modulating includes selective scrambling of the bit allocation information or the portion thereof which is to be modulated.
15. The method as claimed in claim 11, wherein the bit allocation information or the portion thereof which is to be modulated has a bit sequence, and said modulating includes changing the order of the bit sequence.
16. The method as claimed in claim 11, wherein the bit allocation information or the portion thereof which is to be modulated comprises y-bit words having a word sequence, and said modulating includes changing the order of the word sequence.
17. The method as claimed in claim 11, wherein further comprising applying the digital transmission signal to a transmission medium.
18. The method as claimed in claim 17, wherein said transmission medium is a magnetic record carrier.
19. A record carrier produced by the method of claim 17.
20. The record carrier as claimed in claim 19, wherein the record carrier is a magnetic record carrier.
This is a continuation of application Ser. No. 08/011,938, filed Feb. 1, 1993, U.S. Pat. No. 5,375,171 issued Dec. 20, 1994.
The invention relates to encoding methods for use by a digital transmission system in generating for transmission via a transmission medium, a digital signal representing a wide-band digital signal, for example, a digital audio signal sampled with a specific sample frequency FS. Such a system includes a transmitter having an input terminal for receiving the wide-band digital signal, which input terminal is coupled to an input of a first encoder. The first encoder includes a subband coder responsive to the wide-band digital signal to generate a plurality of M subband signals with sample frequency reduction, for which purpose the subband coder divides the wide-band digital signal into successive subbands having band numbers m which increase as the frequency increases, where 1≦m≦M; a quantization unit for the blockwise quantization of the respective subband signals to produce quantized samples in the signal blocks, a subband signal being composed of consecutive signal blocks, each signal block comprising q samples; and a bit allocation unit for generating bit allocation information specifying the number of bits representative of each of the q samples in a signal block. The transmitter further comprises a scale-factor information determiner for determining information related to a scale factor belonging to each signal block of a subband signal; a combining unit for combining the quantized samples in the signal blocks, the scale factor information and the bit allocation information in a frame of a second digital signal formed by successive frames; a second encoder for converting the second digital signal into a third digital signal so as to enable the third digital signal to be transmitted via the transmission medium; and an application unit for applying the third digital signal to the transmission medium.
The invention also relates to record carriers containing the signal produced by the transmission system.
It is an object of the invention to provide an encoding method for use by a transmission system in producing a digital signal for transmission in which the information therein is protected from being used by unauthorized persons. To this end, the method in accordance with the invention is characterized in that the bit allocation information in a frame (of the second digital signal) is selectively subjected to a signal processing step involving modulation of the bit allocation information, thereby providing an intermediate digital signal having modulated bit allocation information.
Since the bit allocation information is subjected to an additional signal processing step, the bit allocation information is changed (i.e., mutilated) in such a manner that the bit allocation information cannot be derived correctly from the transmitted signal received by a receiver. As is described with reference to FIG. 12 in European Patent Application No. 04.02.973, the bit allocation information is needed to derive from a serial data stream of a replicated second digital (which substantially corresponds to the second digital signal) signal derived from the transmitted signal received by a receiver the quantized samples in the signal blocks of the subband signals in the different subbands. If the bit allocation information in the replicated second digital signal no longer complies with the standard as described in European Patent Application No. 04.02.973, it is, in fact, no longer possible to determine how many bits represent the quantized samples in the corresponding (i.e., time equivalent) signal blocks of the subband signals in the subbands, so that decoding of the audio information is not possible. A replica of the original wide-band signal can be constructed only if a receiver is capable of processing the bit allocation information it receives in an inverse manner.
The signal processing step may, for example, be such that the third encoder operates so as to aselectively modulate (i.e., scramble) the bit allocation information in a frame.
The third encoder may operate in either a non-self-synchronize manner. Self-synchronizing modulators (i.e., scramblers) are known per se, for example, from J. E. Savage, "Some simple self-synchronizing digital data scramblers" The Bell System Technical Jrnl., February, 1967, pp. 449-487. Non-self-synchronizing modulators are also known per se from the literature. Non-self-synchronizing modulators are preferred over self-synchronizing modulators because error propagation is not possible with the first type of modulation, while it is with the second type.
The third encoder may operate so as to modulate (i.e., scramble) the bit allocation information before that information has been combined with the scale factor information and the quantized samples in the signal blocks in order to obtain the second digital signal. Another possibility is that the third encoder operate so as to modulate the bit allocation information after it is included in the second digital signal.
Another signal processing possibility for the bit allocation information is to change the sequence of the bit allocation information in a frame. The bit allocation information may then, for example, be subjected to a kind of interleaving. The sequence of the bit allocation information may be changed on a word basis. This means that y-bit code words, which are related to the number of bits representing the quantized samples in corresponding (i.e., time equivalent) signal blocks of the subband signals in the subbands and which the bit allocation information is composed, are not affected themselves, but rather, merely the code word sequence is changed. Interleaving as a possibility of changing the sequence is a step which is known per se and, for example, in the Compact Disc Digital Audio System it is applied to the audio information to be recorded, see Philips Technical Review, Vol. 40, 1982, no. 6, pp. 162-170.
Dutch Patent Application Nos. 90.01.127 and 90.01.128, which correspond to U.S. patent application Ser. Nos. 08/144,092 and 08/144,093, respectively, filed Oct. 27, 1993, and which are incorporated herein by reference, extensively discuss the operations of the bit-need determining unit 6 and the bit allocation unit 7.
The quantized samples in the signal blocks of the subband signals are subsequently applied to inputs 4.1 to 4.M of a signal combining unit 14. Likewise, bit allocation information formed generally from conversion of the numbers n1 to nM, is applied to inputs 12.1 to 12.M of the combining unit 14. European Patent Application No. 04.02,973 indicates that the numbers in the bit allocation information which represent the number of bits by which the samples have been represented are converted to y-bit code words, where y is 4, see FIG. 9 in European Patent Application No. 04.02,973. Similarly, scale factor information, formed generally from conversion of the scale factors SF1 to SFM is applied, to inputs 11.1 to 11.M of the combining unit 14.
FIG. 2 shows the format of the second digital signal. This format is described extensively in European Patent Application No. 04.02.973. FIG. 2 shows the second digital signal comprising successive frames j-1, j, j+1 and the format of those frames. The frame j, for example, comprises a first frame portion FD1 in which sync information may be contained, a second frame portion FD2 in which the bit allocation information may be contained and a third frame portion FD3 in which the scale factor information followed by the quantized samples of the subband signals in the subbands may be contained. For a further description reference is made to European Patent Application No. 04.02,973.
Additional modulation and demodulation are illustrated below for an arbitrary data byte D.M is the number with which the data block D is modulated to form the data block D and is subsequently demodulated. ##EQU1## The final result after demodulation is identical to the data byte D.
Instead of non-self-synchronizing modulators/demodulators, it is possible to employ self-synchronizing modulators/demodulators. These are generally known from the literature, (see the previously mentioned Bell System Technical Journal of February, 1967), and therefore they are not discussed in more detail.
It is to be noted that the invention has been described primarily in terms of coding and transmission of a monophonic signal. However, the invention is not restricted to such a signal. The invention may, as suggested throughout, be applied to coding of a stereophonic signal, in which case each subband has two signal portions, i.e. a left-channel signal portion and a right-channel signal portion. The invention may also be applied to coding arrangements in which one or more of the subband signals can be coded in a stereo intensity mode. For an explanation of the stereo intensity mode coding reference is made to European Patent Applications 04.02,973 and 91.00.173. The latter of which corresponds to U.S. application Ser. No. 07/829,789, filed Jan. 31, 1994 and is incorporated by reference herein.
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