Video-signal output apparatus, video-signal input apparatus, and scramble method, and descramble method6819765Abstract A system, which includes a video-signal output apparatus and a video-signal input apparatus, has a construction in which scrambling or descrambling is performed with a scramble key generated using copy-control information. If the copy-control information has been falsified, a scramble key for a scrambling mode will not coincide with a scramble key for a descrambling mode, whereby appropriate descrambling is not performed. By performing no scrambling in a vertical blanking interval, the copy-control information can be easily detected from a scrambled video signal. Claims What is claimed is: Description BACKGROUND OF THE INVENTION
CGMS Definition
00 Copy freely
01 One-generation copying possible
11 Copying prohibited
The CGMS is, for example, 2-bit information. When the two bits are noon, the information represents "copy freely", which means that the number of copies is not limited. When the CGMS is "01", the information indicates that only-one-generation copy is possible. When the CGMS is "11", the information represents prohibition of copying. Referring back to FIG. 1, in a scramble method according to an embodiment of the present invention, scrambling is performed corresponding to an effective screen interval. In the vertical blanking interval, no scrambling is performed. This is a preparation for easily detecting the CGMS with arbitrary timing without performing descrambling, after at least the CGMS inserted in the vertical blanking interval is not scrambled. In practice, there is no particular limitation in superimposition of the CGMS on which of horizontal scanning intervals in the vertical blanking interval. The superimposition may be in accordance with an actually defined standard or the like. 2. Basic Structures of Video-Signal Output Apparatus and Video-Signal Input Apparatus FIG. 3 shows conceptual basic structures of a video-signal output apparatus 1 and a video-signal input apparatus 2 according to embodiments of the present invention, which comply with the scramble method. The output apparatus 1, shown in FIG. 3, may be one of various apparatuses such as videocassette recorders or the like, television broadcast tuners, and television receivers, as described below. Similarly, the input apparatus 2 may be one of various apparatuses such as videocassette recorders and display units (monitors). In FIG. 3 only a processing system for the CGMS, and signal scramble and descramble processing systems, are extracted and shown. The output apparatus 1 adapted for the scramble method treats component video signals in analog form (hereinafter referred to as "analog component signals"). Accordingly, analog component signals, for example, a luminance (Y) signal, a color-difference (R-Y) signal, and a color-difference (B-Y) signal, are input to a signal scrambler 11 for performing scrambling. The signal scrambler 11 generates scramble patterns based on a scramble key generated by a scramble-key generator, scrambles the analog component signals input in accordance with a predetermined scramble method, and outputs the scrambled signals via three signal lines corresponding to the Y signal, the R-Y signal, and the B-Y signal. Here, the Y signal is output to the exterior via a combining unit 13 (described later), and the R-Y signal and the B-Y signal are output to the exterior. As described above with reference to FIG. 1, the signal scrambler 11 executes signal processing so that scrambling in only the effective screen interval is executed without performing scrambling in the vertical blanking interval. This type of operation can be easily achieved by providing, for example, a counter, or the like, which counts horizontal scanning intervals in one field interval. The CGMS, which should be set corresponding to a video source (video signals) output from the output apparatus 1, is input to the scramble-key generator 10, and the scramble-arm key generator 10 uses the input CGMS to generate a scramble key. By way of example, a scramble key to be used for performing actual scrambling is represented by the following expression: Sk=f(Sk, CGFMS) where Sk represents a scramble key, and f represents a function having a predetermined computational expression for generating the scramble key. The scramble-key generator 10 generates the scramble key by performing computation represented by the expression. This means that the scramble key is determined so as to be correlated with the copy-control information. In the output apparatus 1, a vertical blanking interval (VBI) generator 12 is provided. When, for example, CGMS data is input to the VBI generator 12, the VBI generator 12 generates a video-signal waveform in the vertical blanking interval, in which the CGMS waveform is superimposed in the predetermined one horizontal scanning interval, as described with reference to FIG. 2. This video-signal waveform is output to the combining unit 13 with timing that the Y signal output from the signal scrambler 11 is used as a vertical blanking interval. The combining unit 13 combines the video-signal waveform in the vertical blanking interval, which is input from the VBI generator 12, with the vertical blanking interval of the Y signal input from the signal scrambler 11. As a result, the analog component signals, output from the output apparatus 1, are in a scrambled state, as described with reference to FIG. 1. The input apparatus 2, shown in FIG. 3, includes a VBI detector 22, a scramble-key reproducer 20, and a signal descrambler 21, which are formally adapted for the scramble method according to the embodiment. The analog component signals input to the input apparatus 2 are input to the signal descrambler 21. Among the input analog component signals, the Y signal is split and input to the VBI detector 22. The VBI detector 22 detects the waveform of the vertical blanking interval of the input Y signal, whereby the CGMS, superimposed on the Y signal when it is sent from the output apparatus 1, is detected and obtained as data. The CGMS data is supplied to the scramble-key reproducer 20. The scramble-key reproducer 20 uses the input CGMS to perform computation using a function similar to the above-described expression, thereby reproducing and outputting the scramble key to the signal descrambler 21. The signal descrambler 21 executes descrambling on the analog component signals in accordance with descramble patterns obtained based on the input scramble key, and outputs the descrambled signals to a predetermined function circuit unit (not shown). At this stage, if the CGMS superimposed in the vertical blanking interval of the video signal has not been falsified until the analog component signals are input from the output apparatus 1 to the input apparatus 2, the value of the CGMS which is used for generating the scramble key by the output apparatus 1 must be equal to the value of the CGMS which is used for reproducing the scramble key by the output apparatus 1. Thus, the scramble key generated by the output apparatus 1 and the scramble key reproduced by the input apparatus 2 must be the same. Accordingly, the output apparatus 1 and the input apparatus 2 use a common scramble key, whereby the input apparatus 2 can obtain appropriately descrambled video signals. Conversely, in the case where the value of the CGMS, which is superimposed on the Y signal when it is sent from the output apparatus 1, differs from the value of the CGMS which is detected by the input apparatus 2 by inserting a falsifying unit 3 in the channels for the analog component signals between the output apparatus 1 and the input apparatus 2 so that the CGMS is falsified or deleted, the in scramble key generated by the output apparatus 1 and the scramble key detected by the input apparatus 2 do not have the same scramble key. Accordingly, even if descrambling is performed by the input apparatus 2, it is not appropriately executed, so that irregular video signals are obtained. By way of example, it is assumed that CGMS "11" representing copy prohibition is superimposed on the Y signal in the output apparatus 1. It is also assumed that the Y signal is input to the input apparatus 2, with the CGMS falsified into CGMS "00" representing "copy freely". In this case, the output apparatus 1 uses the CGMS "11" to generate a scramble key, and the input apparatus 2 uses the CGMS "00" to reproduce the scramble key. Accordingly, the scramble keys differ. As a result, the video-signal waveform cannot be appropriately reproduced, even if descrambling is performed in the input apparatus 2. This means that determination of whether the CGMS has been falsified is performed based on the descramble result. Basically, in the present invention, by correlating the CGMS with the scramble key, as described above, copy control is performed in which appropriate descrambling cannot be performed if the CGMS has been falsified. In other words, this copes with falsification of the CGMS. In the present invention, when the CGMS, set for the analog component signals processed by the output apparatus 1, is "00" representing "copy freely", the signals are output without being scrambled. Accordingly, also when the CGMS, inserted for the analog component signals input to the input apparatus 2, is detected as "00", descrambling is not performed. 3. Actual Examples of Copy Protection With reference to FIGS. 4 to 7 copy control is described below, using actual examples. In FIGS. 4 to 7, blocks identical to those shown in FIG. 3 are denoted by identical reference numerals, and a description of their operations is omitted. FIG. 4 shows an output apparatus 1 as shown in FIG. 3, which is adapted for the scramble method, and a recording apparatus 2A (as an input apparatus) which records video signals on a magnetic tape. The output apparatus 1 uses CGMS "01" to perform signal scrambling. Also, the output apparatus 1 superimposes CGMS "01" on a scrambled Y signal, and outputs the resultant signal. The recording apparatus 2A reproduces the descramble key, as described referring to FIG. 3, and performs signal descrambling, thereby obtaining appropriately restored analog component signals. The recording apparatus 2A records the appropriately restored analog component signals on a magnetic tape. At this time, the CGMS "01" superimposed in the output apparatus 1 is detected by a VBI detector 22 in the recording apparatus 2A, and is changed into "11" by a converter 23. In other words, in order that the video signals having permission of one-generation copy may be recorded on the tape, the CGMS is changed into "11" representing copy prohibition. Actually, the CGMS "11" is superimposed on the Y signal, and is recorded on the tape. The following description also uses the tape containing the video signals that are descrambled (as described above) by the recording apparatus 2A in the construction shown in FIG. 4 and that include the CGMS "11". Accordingly, for convenience, the tape is denoted by "TP-A". Next, the present invention is described below with reference to FIG. 5. FIG. 5 shows an output apparatus 1 as shown in FIG. 3, which is adapted for the scramble method of the present invention, and a recording apparatus 2B (as an input apparatus) which is not adapted for the scramble method of the present invention. Although the recording apparatus 2B includes a VBI detector 22 and a converter 23, it does not include processing units corresponding to the scramble-key reproducer 20 and the signal descrambler 21 shown in FIG. 3 or 4. Here, similarly to the construction shown in FIG. 4, it is assumed that the output apparatus 1 uses the CGMS "01" to perform signal scrambling. It is also assumed that the output apparatus 1 superimposes the CGMS "01" on a scrambled Y signal. In this construction, without performing descrambling, the recording apparatus 2B records, on a magnetic tape, scrambled video signals which are input from the output apparatus 1 and on which the CGMS "01" is superimposed. The above-described tape that contains the video signals which are not descrambled and on which the CGMS "01" is superimposed is denoted by "TP-B". FIG. 6 shows a construction in which a player apparatus 1A which is not adapted for the scramble method is used as an output apparatus and a display apparatus 2C adapted for the scramble method is used as an input apparatus. The player apparatus 1A includes a VBI generator 12 in which when the CGMS superimposed in the Y signal of video signals recorded on a magnetic tape is, for example, "Ol", the VBI generator 12 changes the CGMS into "11" for superimposing the CGMS on the read Y signal and outputs it. The display apparatus 2C also includes a cathode-ray tube (CRT) 24 for displaying the video signals descrambled by a construction as in the above-described embodiments. Other than the CRT, the display apparatus 2C may be, for example, a liquid crystal device, etc. There is no particular limitation in the type of the display apparatus 2C. It is assumed that the tape TP-B described referring to FIG. 5 is played by the player apparatus 1A in the above-described construction. In this case, video signals recorded on the tape TP-B remain scrambled, and the video signals, which includes the CGMS "11", are output to the display apparatus 2C. Since a construction adapted for the scramble method in the above-described embodiments is employed in the display apparatus 2C, the display apparatus 2C descrambles the scrambled video signals. The video signals read from the tape TP-B are signals scrambled by a scramble key using the CGMS "11", as can be understood from the description using FIG. 5. The display apparatus 2C reproduces the scramble key, using the CGMS "11". Thus, appropriate descrambling is not performed. This means that as long as video signals are recorded on the tape TP-B by an apparatus which is not adapted for the scramble method in the above-described embodiments, it is impossible to perform the reading of the video signals, and descrambling by the input apparatus having a descramble function to restore the video signals. If the tape TP-A described using FIG. 4 is played in the construction shown in FIG. 6, a scramble key reproduced using the CGMS "11" is used to scramble input video signals by the display apparatus 2C. Accordingly, appropriately video signals cannot be obtained from the tape TP-A, and a picture based on the video signals is not displayed in its original condition. In other words, to descramble unscrambled video signals is consequently the scrambling of the video signals. This means that if a magnetic tape on which video signals are recorded after being scrambled and descrambled is played by an apparatus which is not adapted for the scramble method in the above-described embodiments, appropriate video signals cannot be obtained and that appropriate video signals can be obtained by, for example, only a display apparatus having no descramble function. FIG. 7 shows the case where a player apparatus 1B adapted for the scramble method in the above-described embodiment is used as an output apparatus and a display apparatus 2C is used as an input apparatus similarly to the case shown in FIG. 6. Blocks identical to those shown in FIG. 6 are denoted by identical reference numerals, for omitting descriptions. The player apparatus 1B is designed to scramble video signals read from a magnetic tape. Similarly to the player apparatus 1A shown in FIG. 6, the player apparatus 1B has a function in which if the CGMS superimposed on the Y signal of video signals recorded on the tape is "01", the function changes it into "11" and uses a VBI generator 12 to perform superimposition of the CGMS "11" on the scrambled Y signal and outputting the signal. When the player apparatus 1B plays, for example, the TP-A, video signals on the tape TP-A are scrambled by a scramble key using the CGMS "11", and the signals are output. In this case, the CGMS "11" is superimposed on the scrambled Y signal. In this case, in the display apparatus 2C, the read video signals are descrambled by the scramble key reproduced using the CGMS "11", and the signals are output on the CRT 24. The player apparatus 1B and the display apparatus 2C obtain the same scramble key. Thus, in the display apparatus 2C, the video signals are appropriately descrambled and the restored picture is displayed. When the tape TP-B is played by the player apparatus 1B in the construction shown in FIG. 7, the scrambled video signals recorded on the tape TP-B are scrambled with the scramble key generated using the CGMS "11" by the player 13 apparatus 1B because the video signals on the tape TP-B remains scrambled by the scramble key using the CGMS "00". If the video signals output from the player apparatus 1B are descrambled with the scramble key reproduced using the same CGMS "11", the video signals simply return to earlier video signals scrambled with the CGMS "Ol", and an appropriate picture is not displayed. This means that video signals falsely recorded cannot be appropriately played and displayed in a system adapted for the scramble method in the above-described embodiments. As can be understood from the foregoing description, in the present invention, a system in which the scramble method in the above-described embodiments cannot perform display depending on, for example, a display apparatus unless recording is performed by a proper recording apparatus adapted for the scramble method in the above-described embodiments. In other words, in this respect, it is possible to determine whether any false act has been performed. In the following description, no illustration is used. When in order that video signals which are scrambled with the scramble key generated using the CGMS "11" and are output may be recorded, the CGMS "11" is rewritten into "00" or "01", recording using correct video signals cannot be performed by, for example, a recording apparatus 2A (shown in FIG. 4), as can be clear from the description of the basic construction shown in FIG. 3. In other words, if the CGMS is falsified into "00", the recording apparatus 2A does not execute descrambling by detecting the falsified CGMS "00" whereby video signals, which are unchanged in a scrambled form with the scramble key generated using the CGMS "11", are recorded. When the CGMS is falsified into "01", video signals scrambled with the scramble key using the CGMS "11" are descrambled (for recording) with the scramble key reproduced using the CGMS "01", whereby the recorded video signals are not appropriately descrambled, which are irregular. The relationships between CGMS values and actual scramble states, and determination results corresponding to the relationships are shown as a summary of the foregoing description in the following table.
CGMS Scramble State Determination Result
00 Not scrambled Copy freely
01 Scrambled with a key One-generation copying possible
corresponding to "01"
11 Scrambled with a key Copying prohibited
corresponding to "11"
00, 01 Scrambled with a key CGMS "11" falsified into "00"
corresponding to "11" or "01"
11 Scrambled with a key Recorded by an apparatus not
corresponding to "01" adapted for scrambling
(on medium)
11 Unscrambled signal output Read by an apparatus not
adapted for scrambling
11 Scrambled so that Output from a medium containing
descrambling is possible contents recorded by an
apparatus not adapted for
scrambling
01 Scrambled with a key Recorded by an apparatus not
corresponding to "01" adapted for CGMS
(on medium)
In this table, the three upper lines correspond to cases where no falsification is performed, and the five lower lines correspond to cases where recording or playing is performed using apparatuses which are not adapted for the scramble/copying-protection method in the foregoing embodiments and where the CGMS is falsified. In the forgoing embodiments, analog component signals are scrambled or descrambled. However, the type of signal to be processed may be a composite signal. Definitely, a video-signal output apparatus and a video-signal input apparatus of the present invention are not limited to the foregoing illustrated embodiments, but may be applied to various types of apparatuses capable of processing video signals. By way of example, any type of video signal output apparatus and any type of video-signal input apparatus may be used, such as videocassette recorders (using a digital or analog recording method) which perform tape recording, and recording/playing apparatuses adapted for, for example, recordable disk media.
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