MXPA00008915A - Embedding supplemental data in an encoded signal - Google Patents

Abstract

There are two different methods of embedding supplemental data, e.g. for watermarking into an encoded signal. I) For an encoder, requiring auxiliary information for encoding (=probability information here), the auxiliary information to encode the supplemental data is derived from other data used in the encoding process. Thus the derived auxiliary data needs not be stored, which makes embedding economical in terms of bit amount. II) In the encoding process used for super Audio CD, a set of parameters (e.g. filter coefficients) is used by the encoder, whereby these parameters have to be stored, as they are needed for decoding. To embed supplemental data, at least one of the chosen parameters (e.g. the LSB of the first coefficient) is set to a dedicated value in response to the value of the supplemental data to be embedded. Thus the bit rate will not be affected at all.

Description

INCLUSION DK SUPPLEMENTARY DATA IN A CODED SIGN FIELD OF THE INVENTION The invention relates to an arrangement for, and a method for including supplementary data in an encoded signal.

BACKGROUND OF THE INVENTION There is a growing need to accommodate supplementary data in encoded data, such as audio and video encoded signals, preferably without increasing the speed of the data, especially if the supplementary data are used as watermarks, they should They can be added in a perceptually invisible way.Watermarks include information, for example, on the source or copyright status of audiovisual documents and programs.They can be used to provide legal proof to the owner of the copyright, and allow piracy tracking and support intellectual property protection The Superaudio Compact Disc format (SACD), for example, specifies lossless encoding (LLC) to effectively allow approximately twice as much data on the disk. the lossless encoder allows up to 74 minutes of channel audio playback time multiple with SACD quality. As the words "lossless encoding" indicate, the required storage capacity of some data is reduced in such a way that after encoding, the original signal is reproduced with the identical bits. Such encoder / decoder is described, for example, in 1 Bit Audio Signal Coding, by Fons Bruers, Werner Oomen, Rene van der Vleuten, Leon van de Kerkhof, Audio Engineering Society, 103rd Convention, 1997, " September 26-29, in New York, 4563 (1-6) The coding is done by dividing a flow of input data into blocks and determining a set of parameters optimized for each frame, part of these parameters is issued by prediction, for Eliminate redundancies The difference between the original signal and the prediction signal, which is referred to as a residual signal, comprises much less relevant information, if good prediction parameters can be found.When the lossless coding is displayed, the residual signal can not be omitted, but if it comprises less relevant information, it can be encoded by entropy very efficiently, using some other part of the optimized parameters Since the redundant information is maintained in the parameter set, the set of parameters, as well as the residual signal encoded by entropy, are stored and needed for lossless encoding. If supplementary information is required, for example, for watermarking purposes, it can be added - as is widely known - by adding it to the original signal, in such a way, that the amendment of the signal will not be noticed by a listener. An altered signal like this can no longer be considered as an original signal (faithful bit). Additionally, this kind of watermarking suffers from the fact that it is not possible to detect watermarks present in the encoded signal without lossless decoding. For reasons of simplicity of the watermark decoder, it is desirable to have the option of detecting watermarks before decoding without loss.

BRIEF DESCRIPTION OF THE INVENTION It is an object of the invention to provide an arrangement for, and a method for including supplementary data in an encoded data signal, which allows the included supplementary data to be read without decoding the entire signal and does not influence the quality of music For this purpose, a method according to the invention is characterized by including supplementary data, supplementary information is inserted into the data, and the auxiliary information needed to encode the supplementary data is derived from the other data available in the coding process. The advantage of the invention is thatBy inserting the data into the data to be encoded, the supplementary information can not be eliminated without disturbing the content of the encoded signal. Since the auxiliary information needed to encode the supplementary information is derived from other data available in the process. coding, auxiliary information for coding supplementary data does not need to be recorded or stored for a subsequent decoding process. Thus, this method is very economical with respect to the speed of the bits. It is another object of the invention to provide an alternative for the first solution. For this purpose, an additional method according to the invention is characterized in that, to include the supplementary data in the encoded signal, the set of parameters is affected by the supplementary data. Thus, not all of the complete data has to be decoded to read a watermark, but only the part of the data where the parameters used to encode / decode are contained. As the supplementary information is included in the parameter set, additional bits do not have to be spent for this information.

Supplementary information can be included by choosing an odd or even number of parameters, or by loading the least significant bit of, for example, the first parameter. As an example, an even number of parameters represents the_value "1" of a bit of the watermark and an odd number of parameters represents the value "0" of the bit of the watermark. The invention benefits from the fact that, for practical reasons (computing power, costs, ...), not the best set of parameters, but a reasonably good set of parameters, is determined for the coding. Therefore, these algorithms have been designed to work with a suboptimal set of parameters, such as a rule. Small changes in the parameter set, such as changing the least significant bit of a parameter, adding a false parameter in order to achieve an even or odd number of parameters, when it is necessary to include a bit of a watermark or even omit a parameter in order to achieve an odd number or pair of parameters, normally will not have a big impact on the efficiency of the coding. Sometimes, such small variations of the parameter set will even marginally improve the coding process. An advantage of the invention is that, if the data is to be maintained in a lossless coded form, the watermarks can not be removed without decoding the signal and coding without repeated loss of the data with an altered set of parameters. Since the lossless decoder requires all the coefficients, a missing or incorrect coefficient, which has been removed or changed to erase the watermark, will result in a loss of the signal, for the duration of a block or table for all the channels.

DETAILED DESCRIPTION OF THE INVENTION Figure 1 shows an array for including two independent supplementary data, x, y in a coded signal without loss. The first data x is used to include a watermark information w. Since the length of the watermark w is greater than the information that could be stored by the supplementary data, the water-laden mark w is packaged by a packet generator 1 to a transport packet, which allows to include the bits of the watermark. data packet as a serial signal. Through the synchronization pattern included in the header of the transport packet, the start of the transport packet can be easily recovered. The x bits of the transport packet are included bit by bit in the encoded signal without losses, such as the so-called X DST bits.

The second data and are included in the so-called Bits_DST_Y. A Bit_DST_Y is set to a value of "1", to indicate that the encoded signal without loss is applied to the current format. If there is a future need to have an indicator, Bit_DST_Y can be used. It will be obvious to those skilled in the art that Bit_DST_Y in other registration systems can also be used in the form of a structured data stream, to include information, which is longer than a single bit. In order to encode n parallel data streams, which are referred to as the data channels C0 ... Cn_ ?, the stereo or multi-channel DSD registers divide into frames. In the embodiment of the invention, seventy-five frames per second are used for each C-channel. Although the data rate of the watermark signal w depends on the frame rate, the invention is not limited to a special frame rate. For each block, a control arrangement, which is not shown since it is not part of the invention, discriminates which mode is used for coding: LLC mode Simple or LLC mode Coded. LLC Simple mode is used in exceptional cases, if the compression ratio of a table is insufficient, and actually contains simple DSD.

The chosen LLC algorithm is based on a prediction filter and a probability table. To optimize the compression ratio of LLC Mode Coded, a parameter control unit 4 analyzes each channel separately from card frame, again. The parameter control unit 4 calculates, for each Cx channel, a set of coefficients of the prediction filter (1) ... ai (kj.) For each prediction filter, and a set of coefficients of the probability table. Tlx = p (l). . . p (mx), for each probability table. In the embodiment of the invention, the length of a probability filter coefficient a? it is nine bits, while the number k of the prediction filter coefficients is variable, but it is limited to a maximum value of 128. Each coefficient of probability table px has a length of feels bits. The number n of the coefficients of the px probability table is also variable, but is limited by a maximum value of sixty-four. Typically, it's between thirty-two and sixty-four. These numbers are given as examples and represent the numbers that have been found to give the best results for audio signals, but should not be construed as limiting the invention to these numbers. The numbers, of course, depend on the speed of the frame, the algorithm of the prediction filter and the content of the source signal. However, other numbers can be found that allow a better compression ratio. The determination of the optimum coefficients a, p is difficult and requires considerable computing power. Therefore, a commitment is made to select only a reasonably good set of coefficients. As a separate set of coefficients? X, Tl ^ is calculated for each Cx channel, the sets of coefficients used for each channel will differ from each other, but do not need to differ in each case. To insert a Bit_DST_Y in each frame, an indicator generator 3 alters the least significant bit LSB of the first filter coefficient ao (l). As already mentioned above, there should not be a substantial decrease in the performance of the coding by slightly altering the filter coefficients. All the coefficients of sets A and p, including the modified coefficient ao (l), are substantial for the encoded signal, and therefore, must be recorded for a later reading or decoding process.

Since the sets of coefficients A, as well as p still have some redundancy, a first and second compressors 5, 6 are used to generate compressed data words A ', p'. Preferably, a compression algorithm is used, which will allow corresponding decompression of A ', 11' in an easier way, so that the reading of Bit_DST_Y included, can be done without great effort. It is important that the coefficients, the values of which have been modified, are also used for lossless coding, instead of the coefficients originally evaluated. Otherwise, the coding process fails. In this embodiment of the invention, the function of the lossless encoder is to divide a coding prediction unit 7 for each C channel and an arithmetic encoder 9, which is common for all coding prediction units 7. The structure xle a encoding prediction unit 7 is shown in Figure 2. An encoding prediction unit 7 comprises a prediction filter 71, which is initialized with the corresponding filter parameter set _, _. By means of a level 72 converter, a binary "0" of the input signal xx becomes the numerical value "-1" and a binary value of "1" becomes a numerical value of "+1" before of inputting the input signal to the prediction filter 71. The output signal of the prediction filter 71 is quantized by the first quantizer 73, 74. The first signal of the first quantizer 73 is exorated with the input signal x by means of a gate EXOR 75, and forms the signal "residual eL, which is the first of two output signals of the coding prediction unit 7. The output signal of the second quantizer 74 serves as an Index ax for a stored probability table in an arrangement 76. The probability table consists of a set of probability parameter IT, .. The output signal of the array 76 forms the second output signal of the coding prediction unit 7, the probability signal px. use of the p table Robotability is described in more detail in the document cited in the opening paragraph. A multiplexer 8 gathers the residual signals e0 ... en-? in e and the probability signals p0 ... pn-? in P. The output of the watermark generator 2 is also fed to an input of the multiplexer 8. To include the Bits_DST_X of the watermark information, the multiplexer 8 inserts the Bit_DST_X in front of e. Due to the design of the arithmetic coder 9, a probability coefficient for coding the Bit_DST_X, hereinafter referred to as the probability coefficient of the watermark pw, is indispensable. To save storage space in the embodiment of the invention, the probability coefficient of the watermark pw is derived from the first coefficient of the prediction filter a0 (l). For this purpose, the first prediction filter a0 (l) of the first channel is fed to a probability module of the watermark 10. By means of this module, the first seven bits of the coefficient a0 (l) are interpreted in the reverse order as an unsigned integral number D, to which a value of 1 has been added. Using a value derived from the probability coefficient of the watermark, a record of the probability coefficient of the watermark is not necessary and does not require a supplementary bit in the encoded data block. In this way, including the Bit_DST_X will lengthen the encoded LLC block only marginally. The arithmetic coder 9 generates the encoded DSD signal of the signal e and the probability signal p. When the Bit_DST_X is inserted as the first bit of each block to be encoded by the arithmetic encoder 9, the Bit_DST_X may not be located as a single bit in the encoded DSD signal. Therefore, it can not be eliminated without decoding the encoded DSD signal. The deletion or change of one or some bits will inevitably cause a loss of data from the complete frame. On the other hand, a "rudimentary" arithmetic decoder is enough to read a watermark, therefore, it fulfills the ideal of a watermark in a perfect way: difficult to eliminate, but easy to read. "However, it is not mandatory to insert Bit_DST_X in front of signal e, but it will simplify the process of decoding the watermark slightly, since only the start of the encoded DSD signal has to be evaluated. The following table shows the approximate syntax of a frame encoded in the Coded LLC Mode: In this case, the LLC bit has the value "1" to indicate a data block of the Coded LLC mode. The bits of the subblock CNTRL contain some control information, such as, for example, the number kx of the coefficients of the prediction filter and the number x of the probability coefficients of a channel Chj. dice. The following two subblocks A 'and IV contain _ the sets _ of the prediction filter coefficients A and the probability coefficients TI in a compressed form. The last DSD block CODED finally contains the encoded DSD signal. As explained hereinabove, the length of the CODED data blocks A, P and DSD varies from one frame to another. The encoded LLC data blocks are written to a data bearer, such as, for example, an SACD or a DVD. As the process of writing on a data carrier and the process for reading the data carrier are not part of the invention, but many appropriate means are known to those skilled in the art, not described here, but are symbolized by the dotted line 11 and are referred to as a disk interface. In the reading device, here in the embodiment of the invention, for example, an SACD or a DVD player, a data block is detected as being an LLC block encoded if the first bit, the LLC bit, has the value of "1". In this case, the data block is divided into its sub-blocks A ', IV and CODED DSD by means of the data contained in the CNTRL data control block. The subblocks A 'and IV are decompressed by a first and second decompressor 12, 13 to recover the sets of coefficients? X, TIX. For each channel, a separate decoding prediction unit 14 is provided, each coding prediction unit 14 comprising a prediction filter and a probability table. At the beginning of the decoding of an encoded LLC block, the sets of coefficients i, IV are loaded onto the appropriate prediction filters and the probability tables of the decoding prediction units 14. The prediction units of coding 14 also reconstruct the probability signals po ... pn- ?, which are combined to the signal p by a multiplexer _15 of the reading device. The signal p is fed to an arithmetic decoder 16, which, by means of the probability signal p, decompresses the data contained in the CODED DSD sub-block, to a data stream e. By means of a demultiplexer 17, the data stream e is divided into the residual signals different eo ... en-? of the individual channels and fed to the prediction units 14. The structure of the decoding prediction unit 14 is shown in Figure 3. The residual signal ex of each channel is fed to a first input of an EXOR gate of a decoding subunit. The output of the EXOR gate forms the output signal of each Chx channel. The output is also fed to a level converter, which performs the same operation as the level converter in the recording device described here above. The output of the level converter is fed to the prediction filter. The output of the prediction filter is fed to two quantifiers. The output of the first quantizer is connected to the second output of the EXOR gate, the other output of the quantizer is used as an Index, for the probability table stored in an array. The px values of everything that is selected by the ot index are fed via the multiplexer to an arithmetic decoder. An indicator 18 detector is used to reconstruct the included Bit_DST_Y. Since the Bit_DST_Y is stored in the first coefficient, only - the start of the compressed block A has to be examined by the detector of the indicator 18. The detector of the indicator 18 decompresses only the beginning of the block A 'and collects the coefficients ao ( l) of the first "filter of the first channel, and analyze its least significant bit to decide the value of Bits_DST_Y. Since the decompression algorithm for blocks A and p was chosen to allow easy decompression, the watermark detector can be designed very primitive, when compared to the total decoder. To extract the watermark w, the coefficient a0 (l) determined by the detector of the watermark indicator 18 is fed to a probability module of the watermark 19 of the reading device. The probability module of the watermark calculates, as described for the 'recording device, the probability coefficient of the watermark p ". The probability coefficient of the watermark pw is fed to an arithmetic decoder to decode the Bit_DTS_X.

Since Bit_DTS X is the first bit that comes out of the arithmetic decoder, it can be easily extracted by the watermark detector 20. However, with a more sophisticated detector, it can be extracted from any place in the signal, wherever it may be. It has been decided to insert it. A formatter 21 extracts the watermark information w from the Bits_DST_X, which are converted from a_ serial bit stream to a data block, with the help of the synchronization pattern. Although the function of detecting the watermark can be integrated into other decoding means, this structure shows that a detection of the watermark can be done in an isolated situation. There is no need to decode the entire encoded DSD signal. Therefore, the watermark indicator detector 18, the watermark probability module 19, the watermark detector 20 and the formatter 21, can be integrated into a device by itself, and run without the more complicated functions incorporated in the encoding prediction units 14. The LLC encoded mode has been described so far. As described above, if sometimes the coding fails to reduce the bit rate, the signal can be stored as a simple SDS. This data mode is referred to as the LLC Simple mode and is shown later.

Bit LLC Bit X DTS DSD Simple The LLC bit is set to the value of "0" to indicate that the table contains Simple DSD. The next bit to the LLC Bit is used to store the Bit_DTS_X of the watermark in the simple format. The Bit_DTS_X is followed by the Simple DSD data. This ensures that each coded block contains a Bit_DTS_X, regardless of whether it is a Coded DSD block or Simple DSD. This has the advantage that the serial data flow of Bit_DTS_X does not depend on the format used. On the other hand, it is true that the simple Bit_DTS_X of a Simple DSD can be changed without any damage to the signal content of a block in Simple DSD. However, since a simple DSD block is the exception in the vast majority, there will be Encoded DSD blocks that are interrupted enough to carry the watermark along its entire length. In a further embodiment of the invention, more than one bit; supplementary is included in the encoded signal without loss, loading more than one LSB of the parameters. To include two bits per frame, for example, the first and second coefficients of the prediction filters a? (0), a2 (0) of the first audio channel are not used.

These two bits can be used to present the following information: Since only one watermark bit is provided for use in each frame, the watermark information has to be written in a serial data format. Therefore, the synchronization symbol "10" serves to detect the start of the watermark information.

Claims (9)

CHAPTER CLAIMEDICATORÍO Having described the invention, it is considered as a novelty and, therefore, the content is claimed in the following CLAIMS:

1. "A method for encoding data (e) by means of auxiliary information (p), characterized in that, to include supplementary data (x), supplementary information (x) is inserted into the data (e), and auxiliary information (pw) necessary to encode the supplementary data is derived from other data (a0 (l))

2. The method for extracting supplementary data from coded data in accordance with claim 1.

3. A method for encoding input data by dividing the data data in tables, determining a set of parameters for each frame, reducing the speed of the data of the input signal by applying an algorithm, which is controlled by a set of parameters, where the encoded data comprise a set of parameters or less data, which can be used to derive the set of parameters and the signal with reduced data rate, characterized in that, to include supplementary data (and) in the encoded signal a, the parameter set is affected by the supplementary data (y).

4. The method for extracting information that is included in the parameter set of an encoded signal, according to claim 3.

5. A signal, characterized in that it comprises encoded data according to claim 1 or 3.

6. A carrier data with a registered signal, according to claim 5.

7. An arrangement, for performing a method according to claim 1, 2, 3 or 4.

8. A reproduction device, with an arrangement in accordance with the claim 2 and / or 4.

9. A device according to claim 7, characterized in that it is a disc player for an audio and audiovisual media, respectively.