MXPA01003597A - Transmission of a digital information signal having m bit pcm samples - Google Patents

Abstract

A transmitter is disclosed for transmitting a digital information signal having M bit PCM samples via a transmission medium. The M bit PCM signal is split (8) into a P bit PCM signal, whereby P<M and a difference signal. The P bit PCM signal is a lower quality representation of the M bit PCM digital information signal and the difference signal is obtained by subtracting the P bit PCM signal from the M bit PCM signal. The difference signal is data compressed (16) so as to obtain a data compressed difference signal. The P bit PCM signal and the data compressed difference signal are combined (24) so as to obtain a transmission signal. The transmission signal is transmitted via the transmission medium (TRM).

Description

Transmission of a digital information signal that has M-bit PCM samples The invention relates to a transmitter that transmits a digital information signal having M-bit PCM samples to a receiver that receives a transmission signal that carries a digital information signal from a transmission medium and generates a bit PCM signal Q, said bit PCM signal Q is a representation of said digital information signal, for a recording bearer that was obtained with the transmitter, in the form of an apparatus for recording information in a recording bearer, and to a transmission method.

The transmitters and receivers described above are known, as in USP 5,479,168. Said document describes a method for encoding, transmitting and decoding a signal to provide an improved reproduction of the digital information signal having M-bit samples with a receiver having said decoding method, although they are still compatible with the standardized signals of the industry, the receivers do not incorporate the decoding characteristics of the invention. The transmitter analyzes and encodes the digital information signal to obtain a modified version of the digital information signal and control codes for transmission via a transmission medium. The control codes have a relationship with the characteristics of the digital information signal and the operations performed to encode the digital information signal. The control codes are used to control the operations of decoding and reconstructing the characteristics of the digital information signal.

The invention helps to provide transmitters and receivers having another less complicated transmission method and receiving a digital information signal having M-bit PCM samples, although the transmitted signal remains compatible with standardized reproducing signals that do not incorporate the method of receiving the invention, said digital information signal has a quality higher than that of the signal reproduced by said standardized player apparatus of the industry. The transmitter according to the invention is composed of: - input means for receiving the M-bit PCM signal; - dividing means for dividing the PCM signal of bit M into a representation of the digital information signal having PCM samples of bit P and a difference signal which is the difference between the PCM bit M signal and the bit PCM signal P, in which M > P; means for combining the first signal to combine the PCM bit signal P and the difference signal to obtain a transmission signal for transmission via the transmission means. The receiver according to the invention consists of: - recovery means for recovering the transmit signal from the transmission medium, - demultiplexing means for deriving a PCM representation of the P bit from the asid and a difference signal of the transmission signal , - signal combining means for combining the P-bit PCM signal and the difference signal to obtain a Q-bit PCM signal, wherein Q < P. The invention is based on the following recognition. The transmitter according to the invention divides the digital information signal having M-bit PCM samples into a representation of the digital information signal having PCM samples of bit P and a difference signal. The representation of the digital information signal and the difference signal are combined to obtain a transmission signal that can be transmitted. The transmission signal transmits via the transmission medium. In the preferred embodiment of the transmitter, the combining means of the first signal is adapted to obtain a transmission signal consisting of a bit PCM signal N which is a version of the P-bit signal P, wherein P < N. An advantage of such incorporation is that the transmission signal obtained in this manner can be received and processed by the receivers before they are able to receive., process and output a N-bit PCM signal. The data capacity needed to carry the difference signal is usually relatively small. The data compression can be carried out in this difference signal, as well as the subsequent reduction of the necessary data capacity. Accordingly, the transmitter is provided with data compression means to decrease the data capacity needed to carry the difference signal. The data compression means are preferably composed of a psycho-acoustic encoder, which removes irrelevance and redundancy in the difference signal. The division can be made by dividing the M-bit PCM samples of the digital information signal into more significant P bits to obtain the PCM signal of bit P, and less significant M-P bits to obtain the difference signal. In case P <; N, the least significant N-P bits may be used to store at least a part of the difference signal, which may be of compressed data. The hidden data techniques can be used to determine a hidden data channel in the P-bit PCM signal to carry at least a part of the difference signal. When using the hidden data techniques the perceived S / N ratio of the transmitted bit N-PCM signal is almost the same as the S / N ratio of the P-bit signal P. The receivers according to the invention are able to recover the two components of the transmitted signal and generates a reproduction of the M-bit PCM digital information.

These and other objects of the invention will become apparent and will be clarified later with reference to the incipients described in the following description of the figures, in which: Figure 1 shows a first incoforation of the transmitter, Figure 2 shows a first embodiment of the receiver, Figure 3 shows a receiver of those before to receive the transmission signal generated by the transmitter of Figure 1, Figure 4 shows a first incorporation of a means of division of the transmitter, Figure 5 shows a third embodiment of the signal combining unit in the transmitter of Figure 1, Figure 6 shows a third inofofration of the demultiplexing unit in the receiver of Figure 2, Figure 7 shows a fourth embodiment of the signal combination unit in the transmitter of Figure 1, Figure 8 shows a fourth incoforation of the demultiplexing unit in the receiver of Fig. ura 2, Figure 9 shows a transmitter in the form of a recording apparatus, and Figure 10 shows a receiver in the form of a reproducing apparatus, Figure 11 shows another embodiment of a transmitter in the form of a recording apparatus, and Figure 12 shows another embodiment of a receptor in the form of a reproductive apparatus.

Figure 1 shows an incorporation of the transmitter. The transmitter has an input terminal 1 for receiving a digital information signal, such as a digital audio signal having PCM samples of M bits. This digital information could have been obtained by supplying an analogous version of the digital information signal to an input 2 of an A / D converter 4. The AD 4 converter exemplifies the signal applied to input 2 and supplies the digitalized M-bit samples to an input terminal 1 of the transmitter. The input terminal 1 is coupled to an input 6 of a division unit 8. The division unit is adapted to a division of the bit signal PCM applied to the input to the signal PCM of bit P which is a representation of the digital information signal having M-bit PCM samples, wherein P < M, and a difference signal, which is obtained by subtracting the PCM signal of bit P of the signal PCM of bit M applied to input 6. The signal PCM of bit P and the signal of difference are supplied to a first output 10 and to a second output 12 of the division unit, respectively. As an example, it can be chosen that M equals 24 and P equals 16, so that the representation can be saved in the form of an industry standardized signal, as in a CD. An output 12 of the division unit 8 is coupled to a first input 14 of a data compression unit 16. The data compression unit is optional and is not necessary for the invention. The data compression unit compresses the difference signal to the first input to obtain a compressed data difference signal to supply it to the output 18. The output 10 of the division unit 8 is coupled to a first input 22 of the unit signal combination 24. The output 18 of the data compression unit 16 is coupled to a second input 26 of the signal combining unit 24. The signal combining unit 24 combines the signals that are supplied to the inputs 22 and 26 in at least one series data stream, which is suitable for transmission via a TRM transmission means. The combination step of signals in the combination unit 24 may include a channel coding step, well known in this field. The data compression unit 16 may comprise a standard arithmetic encoder, such as the Huffmann encoder, well known in the art. The division unit 8 performs a quantization step to obtain the PCM bit-P signal. The quantization noise in the P-bit PCM signal results in the quantization noise in the difference signal. That is the reason why the difference signal has an almost white frequency spectrum. To improve data compression, unit 16 consists of a psycho-acoustic model, known in this area. Therefore, the data compression unit 16 is provided with a second input 20 which is coupled to the input terminal 1 to receive the digital bit information signal M. The improvement can be used to decrease the data capacity to carry the signal of difference or leg to increase the perception signal for the proportion of noise that can be obtained with a receiver having the characteristics of the invention. The transmitter described above works in the following manner. The digital information signal is supplied to an input terminal 1. The division unit separates the digital information having M-bit PCM samples into a P-bit PCM signal, which is a representation of low signal quality of the signal of digital information and a difference signal. The difference signal consists of the signal information of the M-bit PCM signal that is needed on the receiver side to reproduce a high-quality representation of the digital information signal in the form of a M-bit PCM signal, ai the PCM bit signal P and the difference signal. The PCM bit signal P and the difference signal, and thus the compressed data, are combined to obtain the transmission signal for the transmission via the transmission means TRM. The transmission signal carries the PCM bit signal P, so that the receiver that does not incorporate the features of the present invention can reproduce said signal. The transmission means TRM can be a transmission channel or a recording carrier, such as a magnetic or optical engraving carrier. The transmission signal is transmitted via the TRM transmission medium to a receiver. Figure 2 shows an embodiment of a receiver to redirect the transmission signal and regenerate from there a reproduction of the original digital information signal. The transmission signal TRM is received via the input 60 of a demultiplexing unit 62. The demultiplexing unit 62 is capable of recovering the PCM bit signal P from the transmission signal and supplying said signal to a first input 68 of a unit signal combining 70. Another input 66 of the demultiplexing unit 62 is coupled to an input 72 of a data expansion unit 74. The demultiplexing unit 62 is capable of recovering the difference signal from the transmission signal and for supplying the signal thus recovered to the output 66 which is coupled to a second input 76 of the signal combining unit 70. The signal combining unit 70 combines the signals received at the first and second inputs in order to obtain a PCM reproduction of Q bit of the original digital information signal. An output 78 of the signal combining unit 70 is coupled to an output 80 of the receiver, if required via a D / A converter 82. In addition, the receiver may have a second D / A converter, which is not shown, the which has an input which is coupled to an output 64 of the demultiplexing unit 62 and an output is coupled to another output terminal, which is not shown. The operation of the receiver of Figure 2 is as follows. The demultiplexing unit 62 recovers the PCM bit signal P which is a signal representation of inferior quality of the transmitted digital information signal and supplies said signal to the output 64. The demultiplexing unit 62 is also capable of recovering, if there is compressed data, the difference signal and supplies said signal to the output 66. If necessary, the data expansion unit 74 retrieves the compressed data difference signal to the input 72, expands this signal to obtain the difference signal and it supplies said difference signal to the second input 76 of the signal combining unit 76. The difference signal refers to the signals of the digital information signal below a certain level, which are not presented in the PCM signal bit P representing the M-bit PCM digital information signal, and the quantization noise that was introduced by means of the division unit in the transmitter. The data expansion unit 84 is composed of a psycho-acoustic decoder, which is a dissipative decoder, or an entropy decoder, which is a lossless decoder, such as the Huffmann decoder. These decoders are well known in this field. The signal combining unit 70 combines the PCM bit signal P and the difference signal to obtain the Q bit PCM signal which is a reproduction of the original digital information signal and supplies the Q bit PCM to the output 78. The value of Q is related to the data expansion unit 84 that is used. Depending on the complexity of the data expansion unit 84, which is capable of reconstructing the signal with superior quality. The Q value of the Q-bit PCM signal generated by the signal combining unit has a relation to the signal quality of the reconstructed difference signal that was received at the input 76. To generate a reproduction signal with a signal quality higher than the PCM signal of bit P, at least the value of Q is increased. Therefore, Q >; P. The D / A converter 82, which may be present, converts the reproduction of the digital information signal into a similar signal. Figure 4 shows an embodiment of the division unit in the transmitter of figure 1. The input 6 of the division unit 8 receives the digital information signal having bit-PCM samples. The quantizer 4.2 performs a quantization in the PCM signal of bit M to obtain the PCM signal of bit P which is a representation of the digital information signal and supplies the PCM signal of bit P to the output 10 of the division unit 8. The quantization step that is carried out can be be an ordinary function of rounding or truncation but any other method of quantification may also be adequate, including the use of noise formation or hesitation. The division unit is also provided with a subtraction unit 4.4 to subtract the PCM signal from bit P of the PCM signal from bit M to thereby obtain the difference signal. The difference signal is supplied to the output 12 of the division unit 8. The division unit can also be adapted to perform the truncation function by supplying the most significant P bits of the M-bit PCM samples to the output 10 and supplying the least significant bit MP to the output 12. Preferably, the transmitter is compatible with the standardized signal players of the industry, such as CD players. Therefore, the signal combining unit 24 is adapted to generate a transmission signal having an N bit PCM signal. To be compatible with the standard CD, N must be equal to 16. Therefore, the division 8 supplies a PCM signal of bit P, where P = N. A receiver of those before, such as that shown in figure 3, is provided with a demultiplexing unit 62 'which is capable of recovering the PCM signal bit N, which is a representation of the bit representation P of the digital information signal, which has bit samples N, from the transmission signal transmitted via the transmission means TRM. The receiver has a D / A converter 82 ', so that the analog version of the representation of the digital information signal is for output 84. In a receiver of the above, a D / A converter with a range is sufficient less dynamic, where N < M. A first embodiment of the signal combining unit 24 may be used in case P < N. The signal combining unit receives the PCM signal of bit P in the first input 22. The samples of the PCM signal of bit P are used to generate the most significant bits P of the samples of the bit PCM signal N in the transmission signal. The least significant N-P bits in the N-bit PCM signal are used to carry at least a part of the difference signal, if there is compressed data, which was received in the second input 26 of the signal combining unit 24. A receiver of the above will reproduce the N-bit PCM signal having a bit P-PCM signal which is a reproduction of a lower quality of the digital information signal. The least significant N P bits in the N-bit PCM signal will be reproduced as low signal noise added to the P-bit PCM signal. When the N-bit PCM signal has a small amplitude, said low signal noise may be audible. . A first embodiment of the demultiplexing unit 62 in the receiver of Figure 2 is adapted to receive a transmission signal having a bit N PCM signal. The demultiplexing unit extracts the most significant P bits of the bit N PCM signal to obtain the PCM bit signal P and supply the output 64. In addition, the demultiplexing unit extracts the least significant N-P bits of the N bit PCM signal to obtain the difference signal, if there is compressed data to supply the output 66. In the following embodiment of the signal combining unit 24 in the transmitter of Figure 1 and the demultiplexing unit 62 in the receiver of Figure 2, the units are adapted to transmit and receive, respectively, a transmission signal having a bit PCM signal N, where N is equal to P. A second embodiment of the signal combining unit 24 in the transmitter of the Figure 1, makes use of the hidden data techniques, well known in this area, to combine the P-bit signal P with the difference signal, if there is compressed data to obtain the transmission signal. The signal combinator unit determines a hidden data channel in the PCB signal of .bit P. This hidden data channel is used to carry the difference signal. In the previous receiver, the transmission signal reproduces the representation of the digital signal that has the hidden data channel, but the data of the hidden data channel is not perceptive this time. A second incorporation of the demultiplexing unit 62 in the receiver of Fig. 2 is adapted to derive a PCM signal of bit P having a hidden data channel and to derive the difference signal, if there is compressed data, from the channel of data. data hidden in said P-bit signal P. FIG. 5 shows a third embodiment of the signal combining unit 24 in the transmitter of FIG. 1. A channel modulation unit 5.2 receives the P-bit PCM signal received in the first input 22 of the signal combining unit 24 and processes the composite signal to obtain a sequence of m-bit channel words. Preferably, the channel modulation unit consists of an n-m channel modulator. A generating unit 5.4 receives the difference signal received at the second input 26 of the signal combining unit 24 and generates pop-up bits p in response to said remaining portion. A unit 5.6 receives the sequence of m-bit channel words and the emergent bits p, and inserts the emerging bits p between the adjacent m-bit channel word to obtain the transmission signal and supplies it to the output 28 of the unit. signal combination 24 for transmission via the transmission means TRM 32. The emergent bits p are normally used to prevent (d, k) coercion violatons between the words of the adjacent channel and for the additional task of the DC control. After doing this, there is still space to choose one or more of those emerging bits in response to the information content of the difference signal. The generating unit to generate the emerging bits uses this space. Figure 6 shows a third embodiment of the demultiplexing unit 62 in the receiver of Figure 2. A unit 6.2 redistributes the transmission signal supplied to the input 60 of the demultiplexing unit 62. The transmission signal is composed of a sequence of m-bit channel words with bits emerging p between each time of the m-bit channel words. The unit 6.2 separates said transmission signal into a sequence of words of channel m-brt and said emerging bits p. The m-bit channel word sequence is supplied to a prearranged channel 6.4 demodulator unit for the modulation of the m-n channel to obtain the representation of the digital information signal. The representation signal in the form of a standard digital stereo signal having PCM samples of bit P is supplied to the output terminal 64. The emerging bits p are supplied to a processing unit 6.6. The processing unit 6.6 is arranged to process the emerging bits p so as to obtain the difference signal, if there is compressed data, to supply the output terminal 66.

Figure 7 shows a fourth incorporation of the signal combining unit 24 in the transmitter of Figure 1. A processing unit 7.2 receives the PCM signal of bit P at the output 22 of the signal combining unit 24 and processes the PCM bit signal P to obtain a block sequence of bytes q. The processing unit may have a Reed-Solomon time division multiplexing cross-coder. The value of q is 32 for the standard CD format. A subcode encoder 7.4 receives the difference signal, if there is compressed data, supplied to its input and generates a byte subcode r in response to said difference signal. The subcode in the standard CD format is essentially an auxiliary data stream. At least a part of said byte subcode r, like subcode U, is obtained in response to the difference signal. A unit 7.6 receives the sequence of byte blocks q and said byte subcode r, and inserts the byte subcode r between the adjacent m-bit channel word to obtain a signal that can be written to the record carrier 32. Before transmitting said signal in a transmission medium in the form of the recording carrier, the signal is encoded to the channel, for example by means of an EFM encoder. Figure 8 shows a fourth embodiment of the demultiplexing unit in the receiver of Figure 2. A unit 8.2 redistributes the transmission signal supplied to the input 60 of the demuxing unit 6. The transmission signal consists of a sequence of blocks byte q with sub-codes of byte r between each time there are byte blocks q. The unit 8.2 separates said transmission signal in a sequence of byte blocks q and said byte sub-codes r. The separation is based on the physical position of the byte blocks q and the subcodes in the transmission signal. The byte block sequence q is supplied to a processing unit 8.4 arranged to process the sequence of byte blocks q to obtain the P-bit signal P. The process unit 8.4 can perform the functions of Reed-Solomon decoding and demultiplexing by division of time. The transmission signal, which is in the form of a standard digital stereo signal, is supplied to the output terminal 64. The byte sub-codes r are supplied to a processing unit 8.6. The processing unit 8.6 is arranged to process the byte sub-codes r to obtain the difference signal, if there is compressed data, of at least a part of the byte sub-codes r. The difference signal is supplied to the output terminal 66 of the demultiplexing unit 62. Figure 9 shows the transmitter in the form of an apparatus for recording the digital information signal on a recording carrier. The block of the circuit denoted 9.2 in Figure 9 replaces the circuit diagram of Figure 1. The input terminal 1 of the engraving apparatus of Figure 9 is equivalent to the input terminal 1 of Figure 1, and the terminal 28 of Figure 9 is equivalent to the output 28 of the signal combining unit 24 of Figure 1. The recording apparatus further comprises writing means 9.4 for writing the output signal present in the terminal 28 of the recording carrier 9.8 . The recording carrier 9.8 may be of the magnetic type. In that case, the writing means 9.4 is composed of one or more magnetic heads 9.6 for writing the information on a track of the recording carrier 9.8. In another incoforation, the gravure carrier 9.8 is an optical engraving carrier. The writing means 9.4 consists of an optical writing head for writing the information in an optical recording carrier track. In general, before the recording, the signal to be recorded is encoded to the channel, depending on the fact that in the incorporation of the circuit block 9.2 the recording means 9.4 consists of a channel coding unit. Figure 10 shows the receiver in the form of an apparatus for reproducing the digital information signal of the engraving bearer. The circuit block denoted 10.4 in Figure 10 replaces the circuit diagram of Figure 2. The terminal 60 of the reproducing apparatus of Figure 10 is equivalent to the input 60 of the demultiplexing unit 62 of Figure 2, and the output terminal 80 of Figure 10 is equivalent to the output terminal 80 of the receiver of Figure 2. The reproducing apparatus further comprises reading means 10.2 for reading the recorded signal on the recording carrier 9.8 and for supplying the signal read at the input 60. The recording carrier 9.8 can be of the magnetic type. In that case, the reading means 10.2 is composed of one or more magnetic heads 10.6 for reading the information on a track of the engraving bearer 9.8. In another embodiment, the recording carrier 9.8 is an optical recording carrier. The reading means 10.2 consists of an optical reading head for reading the information in a track of the optical recording carrier. In general, before processing said signal, the signal that is read in the recording carrier is encoded to the channel. Depending on the incorporation of the receiver, the reading means 10.2 consist of a channel decoding unit for decoding the channel of the signal read on the engraving carrier. Figure 11 shows the transmitter in the form of an apparatus for recording the digital information signal in an optical recording carrier. The transmitter of Figure 11 shows a great resemblance to the Figure of the transmitter of Figure 1. An optical recording carrier replaces the transmission means. The signal combination unit 24 of FIG. 1 is composed of a first write unit 11.2 and a second write unit 11.4. The first write unit 11.2 is adapted to receive the P-bit PCM supplied by the division unit 8 to the input and to write the bit PCM P on a first channel of the engraving bearer. The recording carrier thus obtained is compatible with a standard audio CD, wherein the PCM bit P signal can be played with a conventional CD player.

In that case, the value of P is preferably equal to 16. The first channel is formed in this case by optical marks detectable in a track, where the optically detectable marks are in the form of pits. The second writing unit 11.4 is adapted to receive the difference signal supplied by the division unit 14, via the data compression unit 16, and to write the difference signal, if there is compressed data, in a second channel of the CD recording bearer. The second channel can be written in the form of variations of detectable optical marks transverse to the direction of the track, as variations of the width of the marks. In USP 5,724,327 some incorporations of the second channel are disclosed. Said document reveals the variation in position of a track in the recording carrier, variations in the width or depth of the holes in the track or variations in the frequency of the recovered data clock. An advantage of this embodiment is that it produces recording carriers, for example, CDs that can be used in CD players according to the current standard CD to play the P-bit PCM signal which is a lower quality representation of the signal of M-bit PCM digital information. Even CD recorders available today are only able to read the first channel. A copy made by said CD recorders only contains the data in the first channel and, therefore, only the lower quality representation of the M-bit PCM digital information signal. The incorporation of the transmitter pres a recording carrier that has a copy protection to copy the high-resolution M-bit PCM signal. Opdonally, the first write unit 11.2 may be adapted to insert a first portion of the difference signal, if there is compressed data, into the bit signal P PCM to be written on the first channel of the record carrier. This insertion can be done with hidden data techniques. In that case, the second writing unit is adapted to write the remaining portion of the difference signal on the second channel of the recording carrier. This opponon increases the data capacity in the engraver carrier to carry the differend signal. Figure 12 shows another embodiment of the receiver in the form of an apparatus for reproducing an M-bit PCM signal written on the recording carrier. The receiver of Figure 12 shows a great resemblance to the receiver of Figure 2. The demultiplexing unit 62 is composed of a first reading unit 12.2 and a second reading unit 12.4. The first reading unit 12.2 reads the data written on the first channel of a recording carrier to obtain the PCM signal of bit P written on the first channel and supplies said PCM signal of bit P to the first input 68 of the combining unit of signal. Said first preferential channel is in the form of a channel carrying the N-bit PCM signal on a standard CD, where N = 16. The second reading unit 12.4 reads the data written on a second channel of the recording carrier for obtain the difference signal, if there is compressed data, to supply a second input 76 of the signal combining unit 70. If the second channel consists of a compressed data difference signal, said compressed signal is expanded before supplying the second input 76 of the signal combining unit 70. The incuborations of said second channel have already been given. Opdonally, the first reading unit can be adapted to read a first portion of the difference signal, if there is compressed data of the signal read from the first channel of the engraving-holding CD, by using hidden data techniques. In that case, the second reading unit 12.4 is adapted to write the remaining portion of the difference signal of the second channel of the recording carrier. This second reading unit is also adapted to combine the first portion and the remaining portion to obtain the difference signal, if there is compressed data.

Although the invention is described with reference to the preferred embodiments, it is understood that these examples are not limiting. Therefore, various modifications may be made apparent to those skilled in the art, without departing from the scope of the invention, as defined in the claims. As an example, the difference signal, if there is compressed data can be divided into a first portion and a remaining portion, the first portion can be saved in the hidden data channel, while the remaining portion can be saved in the emerging bits or in the user's bits. A protection copy can be made easily. Therefore, the differend signal can be mixed with a key. The mixed signal can be inserted into the hidden data signal and stored on the first channel of the recording bearer, while the mixing key is stored on the second channel of the engraving bearer. By doing this, the mixed key can be read and copied with the current recording devices, but the key can not be read and, therefore, can not be copied either. The copied tape players carry the mixed signal, but they do not carry the mixer key. In the absence of said mixing key, a reproducing apparatus according to the invention will not be able to undo the mixing of the mixed signal bearing the difference signal and, therefore, is not able to reproduce a reproduction signal of superior quality of the PCM. bit M of the digital information signal of the read P-bit PCM signal. In addition, the difference signal may be in the form of a scalabte signal.

This has the advantage that the digital information signal can be recovered from the transmission signal with the receivers having a different complexity. The complexity of the means for recovering the difference signal determines the quality of the reproduced digital information signal. For example, if a compressed data difference signal is transmitted, some portions of said digital signal can not be used by a less complex decoder to generate the difference signal. This will eventually result in a reproduced digital information signal having a signal quality lower than the signal quality of the original digital M-bit information signal. The phrase 'consists of' does not exclude the presence of other elements or steps other than those listed in a claim. Any sign of referenda does not limit the area of the claims. The invention can be implemented by means of hardware or software. Several "media" can be represented by the same hardware element. In addition, the invendón relies on each novel feature or combination of characteristics.

Claims (29)

CHAPTER CLAIMING Having described the invention, it is considered as a novelty and, therefore, what is contained in the following is redacted: CLAIMS

1. The transmitter for transmitting a digital information signal having M-bit PCM samples via a transmission means, the transmitter is composed of: input means for receiving the M-bit PCM signal; - dividing means for dividing the PCM signal of bit M into a representation of the digital information signal having PCM samples of bit P and a difference signal which is the difference between the PCM bit M signal and the bit PCM signal P, in which M > P; - first signal combining means for combining the P-bit PCM signal and the difference signal to obtain a transmission signal for transmission via the transmission medium.

2. The transmitter according to claim 1, characterized in that data compression means are provided for the compression of data of the signal of difference to obtain a signal of difference of compressed data, the first means of signal combination are adapted to combine the P-bit PCM signal and the compressed data difference signal to obtain said transmission signal for transmission via the transmission medium.

3. The transmitter according to claim 1 or 2, characterized in that the first signal combining means are adapted to obtain a transmission signal that is composed of a bit PCM signal N which is a version of the PCM signal of bit P, where P < N.

4. The transmitter according to claim 1, 2 or 3, characterized in that the dividing means are adapted to divide the M-bit PCM signal into more significant P-bits (MSB) of said PCM signal. of bit M to obtain the PCM signal of bit P and the least significant bits M-P (LSB, for its acronym in English) of said PCM signal of bit M to obtain the difference signal.

5. The transmitter according to claim 3 or 4, wherein N > P, characterized in that the signal combining means is adapted to insert at least a part of the difference signal (if there is compressed data) into the least significant N-P bits of the Bit N PCM signal.

6. The transmitter according to any of the preceding claims, characterized in that the first signal combining means are adapted to insert at least a part of the difference signal (if there is compressed data) into a data channel hidden in the signal of bit P to obtain said transmission signal for the transmission via the transmission medium.

7. The transmitter according to any of the claims of the 2 a fa 6, characterized in that the data compression means consist of a psycho-acoustic encoder, in which the psycho-acoustic encoder is adapted for the compression of the difference signal data in dependence on the digital information signal in order to get the compressed data difference signal.

8. The transmitter according to any of claims 2 to 6, wherein the data compression means are composed of entropy coding means.

9. The transmitter according to claim 8, wherein said entropy coding means is in the form of a Huffmann encoder.

10. AND! transmitter according to any of the preceding claims, the transmitter is in the form of an apparatus for recording the digital information signal in a recording carrier.

11. The transmitter according to any of the preceding claims, characterized in that the transmitter is also composed of channel coding means for a channel to encode the transmission signal before transmission.

12. Bearer of engraving obtained with the transmitter according to claim 10 or 11.

13. The recording carrier according to claim 12, wherein the engraving carrier is of optical or magnetic recording type.

14. A receiver for receiving a transmission signal carrying a digital information signal from a transmission means and generating a Q-bit PCM signal, said Q-bit PCM signal is a representation of said digital information signal, the receiver is composed of : - recovery means for recovering the transmission signal from the transmission medium, - demultiplexing means for deriving the PCM representation of bit P of the digital information signal and a signal of difference of the transmission signal, - combination means of signal to combine the P-bit signal PCM and the difference signal to obtain the Q-bit PCM signal, where Q > P, - output means for supplying the Q bit PCM signal.

15. The receiver according to claim 14, the demultiplexing means is adapted to recover a difference signal which are compressed data of the transmission signal, the receiver is further provided with data expansion means to thereby obtain a difference signal which they are expanded data.

16. The receiver according to claim 14 or 15, characterized in that the demultiplexing means is adapted to extract the PCM representation of bit P from the bit representation N of the digital information signal, wherein P < N.

17. Ef receiver according to claim 16, wherein N > P, is characterized in that the demultiplexing means is adapted to extract the least significant N-P bits of the N-bit PCM signal to thereby obtain at least a part of the difference signal (if there is compressed data).

18. The receiver according to claim 15, 16 or 17, characterized in that the demultiplexing means is adapted to recover at least one part of the difference signal (if there is compressed data) of the data channel hidden in the signal P. bit PCM

19. The receiver according to any of claims 15 to 18, wherein the data expansion means consist of psychoacoustic decoding means.

20. The receiver according to any of claims 15 to 18, wherein the data expansion means consist of entropy decoding means.

21. The receiver according to claim 20, wherein said decoding means is composed of a Huffman decoder.

22. The receiver according to any of the claims of ia 14 to fa 21, characterized in that it also consists of channel decoding means arranged between the recovery means and the demultipfexion means.

23. Method for transmitting a digital information signal having M-bit PCM samples via a transmission medium, the transmitter is composed of the following steps: reception of the M-bit PCM signal; - division of the PCM signal of bit M into a PCM signal of bit P which is a representation of the PCM signal of bit M and a difference signal which is a difference between the PCM signal of bit M and the signal PCM of bit P , wherein M > P; - combination of the P-bit PCM signal and the difference signal to obtain a transmission signal for transmission via the transmission medium.

24. The method according to claim 23, characterized in that the method also comprises the step of compressing data of the difference signal to obtain a compressed data difference signal, and wherein the combination step it is adapted to combine the PCM bit signal P and the compressed data difference signal to thereby obtain said transmission signal for transmission via the transmission medium.

25. The method according to claim 23 or 24, characterized in that the combination step obtains a transmission signal that is composed of a bit PCM signal N which is a version of the P-bit signal P, in which P < N.

26. The method according to claim 23, 24 or 25, characterized in that the division step divides the M-PCM signal into more significant P bits (MSB) of said M-bit PCM signal to thereby obtain the PCM signal. of bit P, and in least significant bits M - P (LSB) to obtain the signal of diferenda.

27. The method according to claim 25 or 26 wherein N > P, characterized in that the combining step inserts at least a part of the difference signal (if there is compressed data) in the least significant NP bits of the N-bit PCM signal to thereby obtain said transmission signal for the transmission via the transmission medium.

28. The method according to claim 23 to 27, characterized in that the combinadon step inserts at least a part of the difference signal (if there is compressed data) into a hidden data channel in the bit PCM signal. P to obtain the transmission signal.

29. The method according to any of the claims of the 24 to 28, characterized in that the step of data compression is composed of the pscio-acoustic coding step of the difference signal in dependence on the digital information signal to obtain the signal of different compressed data.