Abstract:
A small-sized and low-cost receiving apparatus receives digital television broadcasts and reproduces DVD video discs. A receiving circuit receives a digital television broadcast wave via an antenna and supplies it to a demultiplexer (DMUX). A reproducing circuit reads a signal recorded on a DVD and supplies it to another demultiplexer (DMUX). Each demultiplexer separates the input signal into a video signal coded in a compressed form, an audio signal coded in a compressed form, and copyright protection information and supplies the separated signals to a switching circuit. A video signal decoding circuit decodes the video signal coded in the compressed form as received from the switching circuit. An audio signal decoding circuit decodes the audio signal coded in the compressed form as received from the switching circuit.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a receiving apparatus, a receiving method, and a supplying medium, and more particularly to a receiving apparatus, a receiving medium, and a supplying medium having the capability of reproducing DVD (digital versatile disc) video data. 
     2. Description of the Related Art 
     In recent years, DVD players for reproducing DVD videos have become commercially available. Audio Visual (AV) data recorded on DVD video discs is coded in a compressed form according to the MPEG (Moving Picture Experts Group)-2 standard. Therefore, DVD players have the capability of decoding the AV data into a decompressed form. 
     Receiving apparatus for receiving satellite digital broadcasts (such as Sky Perfect TV (trademark)) are now becoming popular. AV data of satellite digital broadcasts is supplied also in the compressed form according to the MPEG-2 standard. Therefore, receiving apparatus for receiving broadcast programs have the capability of decompressing compressed AV data. 
     The MPEG-2 standard will be adopted in terrestrial digital broadcasting which will begin in the near future, and receiving apparatus therefor will also have the capability of decoding AV data into a decompressed form. 
     However, if a certain user wants to enjoy both AV data recorded on DVD video discs and digital broadcast programs (satellite or terrestrial digital broadcasts), the user has to have both a DVD player and a set top box (apparatus for receiving digital broadcasts). Thus, the cost and the installation space become large because two devices are required. 
     Furthermore, to display the outputs of both the DVD player and the set top box on the same television receiver, complicated connections and operations are required. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a technique for realizing a small-sized low-cost receiving apparatus capable of receiving digital television broadcasts and also capable of reproducing DVD video discs using the same means for decoding data compressed in accordance with the MPEG-2 standard. 
     According to an aspect of the present invention, there is provided a receiving apparatus comprising: an inputting device operable to input an operation command given by a user; a receiver operable to receive a digital television broadcast signal in response to the operation command; a reproducing device operable to reproduce, in response to the operation command, an AV signal coded in a compressed form according to a predetermined method and recorded on a recording medium; a decoder operable to decode the television broadcast signal received by the receiver or the AV signal reproduced by the reproducing device; and an adder operable to add information to the television broadcast signal or the AV signal decoded by the decoder, thereby limiting the copying of the decoded signal. 
     According to another aspect of the present invention, there is provided a receiving method comprising the steps of: inputting an operation command given by a user; receiving a digital television broadcast signal in response to the operation command; reproducing, in response to the operation command, an AV signal coded in a compressed form according to a predetermined method and recorded on a recording medium; decoding the television broadcast signal received in the receiving step or the AV signal reproduced in the reproducing step; and adding information to the television broadcast signal or the AV signal decoded in the decoding step, thereby limiting the copying of the decoded signal. 
     According to still another aspect of the present invention, there is provided a supplying medium operable to supply a computer-readable program executed by a receiving apparatus, wherein the computer-readable program comprises: inputting an operation command given by a user; receiving a digital television broadcast signal in response to the operation command; reproducing, in response to the operation command, an AV signal coded in a compressed form according to a predetermined method and recorded on a recording medium; decoding the television broadcast signal received in the receiving step or the AV signal reproduced in the reproducing step; and adding information to the television broadcast signal or the AV signal decoded in the decoding step, thereby limiting the copying of the decoded signal. 
     In the receiving apparatus, the receiving method, and the supplying medium according to the present invention, the inputting device is operable to input an operation command given by a user; the receiver is operable to receive a digital television broadcast signal in response to the operation command; the reproducing device is operable to reproduce, in response to the operation command, an AV signal coded in a compressed form according to a predetermined method and recorded on a recording medium; the decoder is operable to decode the television broadcast signal received by the receiver or the AV signal reproduced by the reproducing device; and the adder is operable to add information to the television broadcast signal or the AV signal decoded by the decoder, thereby limiting the copying of the decoded signal. 
     In the receiving apparatus, the receiving method, and the supplying medium according to the present invention, as described above, the decoder is used in common for both a television broadcast signal and an AV signal reproduced from a DVD video disc, and thus it becomes possible to reduce the cost and the installation space of the receiving apparatus which is also capable of reproducing DVD videos. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram illustrating an example of a configuration of a digital television receiver including a DVD drive according to the present invention; 
         FIG. 2  is a block diagram illustrating an example of a configuration of the copyright protection circuit shown in  FIG. 1 ; and 
         FIG. 3  is a flow chart illustrating the operation of the digital television receiver including the DVD drive. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIG. 1 , an example of a configuration of a digital television receiver including a built-in DVD drive according to the present invention is shown. In the digital television receiver  1  having the built-in DVD drive, a receiving circuit  3  receives a digital television broadcast wave (satellite or terrestrial digital broadcast wave) via an antenna  2  and extracts a signal (AV data coded in a compressed form according to the MPEG-2 standard) corresponding to a selection command given by a control circuit  18 . The resultant signal is supplied to a demultiplexer (DMUX)  4 . The demultiplexer  4  separates the signal received from the receiving circuit  3  into a video signal coded in the compressed form, an audio signal coded in the compressed form, and copyright protection information (waveform information and an APS (analog protection system) signal). These resultant signals are supplied to a switching circuit  8 . 
     A reproducing circuit  6  reads a signal (AV data coded in a compressed form according to the MPEG-2 standard) recorded on a DVD  5  in response to a reproducing command given by the control circuit  18 . The resultant signal is sent to a demultiplexer (DMUX)  7 . The demultiplexer  7  separates the signal received from the reproducing circuit  6  into a video signal coded in the compressed form, an audio signal coded in the compressed form, and copyright protection information. These resultant signals are supplied to the switching circuit  8 . 
     Under the control of the control circuit  18 , the switching circuit  8  selects a video signal coded in the compressed form, an audio signal coded in the compressed form, and copyright protection information output from either the demultiplexer  4  or  7 , and outputs them to a video signal decoding circuit  12 , an audio signal decoding circuit  13 , and a copyright protection circuit  9 , respectively. 
     In accordance with the copyright protection information received from the switching circuit  8 , the copyright protection circuit  9  generates a signal which allows the copyright of the AV data to be protected (that is, which limits the copying of the AV data). 
       FIG. 2  illustrates an example of a detailed configuration of the copyright protection circuit  9 . In  FIG. 2 , a CGMS signal generator  21  generates a CGMS (copy generation management system) signal in accordance with the wave information contained in the copyright protection information and outputs it to an insertion circuit  10 . The CGMS signal refers to a 2-bit signal which controls a DV (digital video) recorder so as to limit the number of times that the AV data including the CGMS signal is copied. The CMGS signal can have one of four values: 00, 10, 01, and 11, which indicate “Copyfree”, “Copyonce”, “Already Copied”, and “Never Copy”, respectively. 
     An AGC pulse output circuit  22  generates an AGC (automatic gain control) pulse signal in accordance with an APS (a signal indicating whether or not analog copying is allowed) contained in the copyright protection information and outputs the resultant signal to the insertion circuit  10 . The AGC pulse signal refers to a signal which controls a VHS video cassette recorder so as to prevent AGC processing (prevent the AV data from being copied in a normal fashion). 
     A color stripe output circuit  23  generates a color stripe signal in accordance with the APS signal contained in the copyright protection information and outputs it to the insertion circuit  10 . The color stripe signal refers to a signal which controls a VHS video cassette recorder so as to insert color stripes into a recorded image (thereby preventing the image from being copied in a normal fashion). 
     Referring again to  FIG. 1 , the insertion circuit  10  inserts the CGMS signal, the AGC pulse signal, and the color stripe signal supplied from the copyright protection circuit  9  into the video signal decoded by the video signal decoding circuit  12 , within a V blank period thereof, and outputs the resultant video signal to an external output terminal  11 a, a display  14 , and a recording circuit  16 . The external output terminal  11  is connected to, for example, a VHS video cassette recorder (not shown). 
     The video signal decoding circuit  12  decodes the video signal coded in the compressed form, supplied from the switching circuit  8 , and outputs the decoded video signal to the insertion circuit  10 . The audio signal decoding circuit  13  decodes the audio signal coded in the compressed form, supplied from the switching circuit  8 , and outputs the decoded audio signal to the external output terminal  11 b, a loudspeaker  15 , and the recording circuit  16 . 
     The display  14  displays the image of the decoded video signal supplied from the insertion circuit  10 . Although the decoded video signal output from the insertion circuit  10  includes the CGMS signal and other protection control signals, those protection control signals do not act upon the display  14  and thus do not affect the image displayed thereon. 
     The loudspeaker  15  emits an audio signal decoded by the audio signal decoding circuit  13 . 
     In accordance with the control signal output from the control circuit  18 , the recording circuit  16  codes the video signal received from the insertion circuit  10  (that is, the video signal received, decoded, and added with the CGMS signal in the V blank period by the antenna  2 ) and the audio signal received from the audio signal decoding circuit  13  (that is, the audio signal received and decoded by the antennal  2 ) in accordance with the MPEG-2 standard and records them on the DVD  5 . 
     A remote controller  17  includes a plurality of buttons (not shown) used by a user to issue commands to receive and select a digital television broadcast station and to reproduce or record data from or onto the DVD  5 . The operation performed by the user upon a button is detected, and a corresponding operation command is applied to the control circuit  18 . In response to the operation command given from the remote controller  17 , the control circuit  18  outputs control commands to various circuit parts as required. 
     The displaying operation of the digital television receiver including the built-in DVD drive is described below with reference to FIG.  3 . In step S 1 , if a user issues a command to select a digital television broadcast channel or a command to reproduce a DVD  5  by pressing a button provided on the remote controller  17 , the remote controller  17  supplies a corresponding operation command to the control circuit  18 . 
     In step S 2 , the control circuit  18  determines whether the operation command input from the remote controller  17  is a command to select a digital television broadcast channel or a command to reproduce the DVD  5 . If it is determined that the input command is a command to select a digital television broadcast channel, then the operation goes to step S 3 . 
     In step S 3 , the control circuit  18  outputs a control command to the receiving circuit  3  to control the switching circuit  8  such that the signals output from the demultiplexer  4  are transferred to the circuit parts following the switching circuit  8 . In response to this control command, the receiving circuit  3  extracts a signal (AV data coded in the compressed form according to the MPEG-2 standard) of the selected channel of digital television broadcast waves input via the antenna  2 , and outputs the extracted signal to the demultiplexer  4 . The demultiplexer  4  separates the signal received from the receiving circuit  3  into a video signal coded in the compressed form, an audio signal coded in the compressed form, and copyright protection information, and outputs these signals to the switching circuit  8 . Under the control of the control circuit  18 , the switching circuit  8  outputs the video signal coded in the compressed form, input from the demultiplexer  4 , to the video signal decoding circuit  12 , the audio signal coded in the compressed form to the audio signal decoding circuit  13 , and the copyright protection information to the copyright protection circuit  9 . 
     In step S 5 , the video signal decoding circuit  12  decodes the video signal coded in the compressed form, received from the switching circuit  8 , and outputs the decoded video signal to the insertion circuit  10 . The audio signal decoding circuit  13  decodes the audio signal coded in the compressed form, applied from the switching circuit  8 . 
     In step S 6 , the CGMS signal generator  21  generates a CGMS signal in accordance with the wave information contained in the copyright protection information and outputs it to the insertion circuit  10 . The AGC pulse output circuit  22  generates an AGC pulse signal in accordance with the APS contained in the copyright protection information and outputs the resultant signal to the insertion circuit  10 . The color stripe output circuit  23  generates a color stripe signal in accordance with the APS signal and outputs it to the insertion circuit  10 . The insertion circuit  10  inserts the CGMS signal, the AGC pulse signal, and the color stripe signal received from the copyright protection circuit  9  into the video signal decoded by the video signal decoding circuit  12 , within the V blank period thereof, and outputs the resultant video signal to the external output terminal  11 a and the recording circuit  16 . In synchronization with the output of the video signal, the audio signal decoding circuit  13  outputs the audio signal, decoded in step S 5 , to the external output terminal  11 b, the loudspeaker  15 , and the recording circuit  16 . 
     In step S 7 , the display  14  displays the image of the video signal decoded by the video signal decoding circuit  12 . The loudspeaker  15  emits the audio signal decoded by the audio signal decoding circuit  13 . 
     If it is determined in step S 2  that the input command is a command to reproduce the DVD  5 , then the operation goes to step S 4 . 
     In step S 4 , the control circuit  18  outputs a control command to the reproducing circuit  6  to control the switching circuit  8  such that the signals output from the demultiplexer  7  are transferred to the circuit parts following the switching circuit  8 . In response to this control command, the reproducing circuit  6  reads a signal (AV data or the like coded in the compressed form according to the MPEG-2 standard) from the DVD  5  and outputs it to the demultiplexer  7 . The demultiplexer  7  separates the signal received from the reproducing circuit  6  into a video signal coded in the compressed form, an audio signal coded in the compressed form, and copyright protection information, and outputs these resultant signals to the switching circuit  8 . Under the control of the control circuit  18 , the switching circuit  8  outputs the video signal coded in the compressed form, input from the demultiplexer  7 , to the video signal decoding circuit  12 , the audio signal coded in the compressed form to the audio signal decoding circuit  13 , and the copyright protection information to the copyright protection circuit  9 . 
     Thereafter, step S 5  and the following steps are performed. 
     In the digital television receiver  1  including the built-in DVD drive according to the preferred embodiment described above, unlike the case where a set top box for receiving a digital television broadcast and a DVD player are separately connected to a display, the MPEG decoder (including the video signal decoding circuit  12  and other parts) having a relatively large circuit size, the power supply, and the housing are used in common, and thus reductions in the installation space and the cost are achieved and an increase in reliability is also achieved. Furthermore, users are not required to connect cables for transmitting signals such as a video signal. 
     Furthermore, in the preferred embodiment, because the digital AV data can be processed without needing conversion into analog form, degradation in the bandwidth of data and occurrences of cross-color and dot interference are suppressed, and thus the image quality is improved. 
     In the embodiment described above, when AV data of a digital television broadcast is recorded on the DVD  5 , the received AV data is first decoded into the decompressed form and then coded again into the compressed form. Alternatively, the received AV data in the compressed form may be directly recorded, or the decoded AV data (in analog form) may be recorded. 
     The present invention may also be applied to other devices such as a set top box for digital cable television. 
     The computer program for performing the above-described process may be supplied to a user via an information recording medium such as a magnetic disk or a CD-ROM and also via a network medium such as the Internet and a digital satellite. 
     Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.