MXPA96005008A - Copy protection, installing a color synchronization signal displaced in phase, synchronism wires of an acolores analog video signal - Google Patents

Abstract

The present invention relates to a method for preventing an analog color video signal from being copied satisfactorily by an analog video recording apparatus, wherein the analog color video signal includes a color synchronization signal of the phase of reference placed in a range of color synchronism in respective line intervals, the method comprises the steps of: generating a phase-shifted color synchronism signal, and inserting the color synchronization signal shifted in phase at a predetermined location through of a predetermined duration in the collision synchronization interval

Description

"PROTECTION OF COPIES, INSTALLING A SYNCHRONIC SIGNAL OF COLOR DISPLACED IN PHASE, IN SYNCHRONOUS INTERVALS AN ANALOGUE COLOR VIDEO SIGNAL " BACKGROUND OF THE INVENTION This invention relates to preventing an analog color video signal from being copied satisfactorily and, more particularly, to a technique for modifying the usual color synchronization range of the analog color video signal such that when the signal of modified video is recorded and then reproduced, the reproduced color video image is seriously deteriorated. Copying protection techniques to prevent the unauthorized copying, or re-registration, of analog video signals are well known. These techniques, also known as copy-protecting processing, generally employ either or both of two separate processes. In a copy protection technique, the usual automatic gain control (AGC) circuit of an analog video recording apparatus is tricked into detecting a signal level that appears to be too high, thereby reducing the gain of the video signal that is recorded; as a result, the level of the recorded signal is too low to recover. This AGC copy protection process inserts pulses, referred to as pseudo-synchronous pulses, at predetermined line intervals of the usual vertical blanking interval of the analog video signal. Figure 10A schematically represents those line intervals of the vertical blanking interval into which the pseudo-synchronous pulses are inserted; and Figure 10B represents a number of cycles (e.g., 5 cycles) of these pseudo-synchronous pulses. Typically, the AGC circuit of a consumer-type analog video recording apparatus detects the difference between the level of the synchronization tip and the reference level of the video signal in the vertical blanking interval. This difference is known as the AGC reference level, shown in Figure 10C, and the differences in the AGC reference level are used to vary the gain of the registration circuit. However, when the pseudo-synchronous pulses are inserted in these line intervals, as shown in Figure 10B, the AGC reference level detected by the AGC circuit of the video recording apparatus now widens between the tip negative of the pseudo-synchronous impulses and the positive point of those impulses, the latter admitting a level P above the expected reference level. This deceptively large AGC reference level causes the AGC circuit of the video recording apparatus to reduce the gain of the registration circuit, thereby reducing to essentially zero, the regsitrated level of the video signal. Even though the use of these pseudo-synchronous pulses has proven to be effective in most consumer video recording devices, a number of video recording devices does not depend on the difference between the synchronization tip and the reference level. of the video signal in the horizontal blanking interval, in order to control the gain of the recording circuits. Examples of these video recording devices include beta-type recording apparatus, 8-millimeter video recording apparatus, and certain sophisticated VHS-type video recording devices. In an effort to prevent the unauthorized copying of color video signals in these analog video recorders, a so-called color strip copy protection technique has been introduced. In the process of color strips, the phase of the usual color sync signal is reversed on a generally repeatable basis. For example, the color sync signal in a block of two line intervals or in a block of four line intervals is inverted; and each frame is formed of a number of blocks having a repetitive inclination, for example of twenty lines. As a numerical example, the phase of the color synchronization signal can be reversed on lines 22 and 23, 42 and 43, 62 and 63, etc. Due to these phase reversals, when this analog video signal is recorded, the automatic phase control circuit (APC) of the registration circuit is subject to error; and the resulting video image that is finally reproduced from that recorded signal exhibits strips of unwanted colors, as shown in Figure 11. Since the color synchronism signal of a relatively small percentage of line intervals exhibit phase reversal , the phase-locked circuit (PLL) of the APC circuit in a conventional television receiver apparatus is not normally affected. This is because the time constant of this PLL circuit, and particularly the PLL circuit that generates the local subcarrier used to demodulate the color signal in the television receiver, exhibits a relatively high time constant. Consequently, the PLL circuit is unable to follow the relatively brief synchronization signal phase alterations, such as those phase inversions that occur during every two or four of twenty lines. But, since the APC circuit of the consumer analog video recorder exhibits a low time constant, this APC circuit is able to track these phase inversions, which are interpreted as phase errors and are used by the apparatus of video record to correct these nonexistent errors. Therefore, the inherently fast response time from the APC circuit of the video recording apparatus results in the recording of deteriorated video signals. However, when using color strip processing to record the video signal of pre-recorded video tapes, such as pre-registered tapes that can be obtained commercially for sale or lease, the fast response time of the APC circuit in the playback circuit allows the video recording apparatus to track and "correct" these phase inversions. Consequently, when a pre-recorded video tape having video signals processed in color strips registered therein is reproduced, the resulting video image frequently exhibits undesirable defects.

OBJECTS OF THE INVENTION Therefore, an object of the present invention is to provide an improved color strip processing technique that prevents an analog color video signal from being copied satisfactorily, but which nevertheless allows an acceptable video image reproduce of it. Another object of this invention is to provide an improved color strip processing technique that can be applied to pre-recorded video tapes, without introducing defects or deteriorations in the reproduced video image of those tapes. A further object of this invention is to provide an improved color stripe processing technique that can be used to prevent the pre-registered video tape from being copied but, nevertheless, allows an acceptable video image to be reproduced from this video tape. pre-registered video. A still further object is to provide a copy protection recording medium which has not been copied satisfactorily but which allows a suitable video image to be reproduced therefrom. Various other objects, advantages and features of the present invention will become readily apparent from the following detailed description, and novel features will be pointed out with particularity in the appended claims.

COMPENDIUM OF THE INVENTION In accordance with this invention, a copy protection technique is provided wherein a copy protection signal formed from a color synchronization signal shifted in phase of predetermined duration is inserted into a predetermined location of the color synchronization signal usual of an analog video signal. Preferably, the phase shifted color sync signal exhibits a phase shift of 90 ° or 180 ° relative to the phase of the normal color sync signal. In accordance with one aspect of this invention, the phase shifted color sync signal is inserted at a location in the color sync range that precedes the normal color sync signal. As a particularity of this aspect, the duration of the phase shifted color sync signal begins before the color sync interval begins and ends during an initial portion of the color sync interval.

As another aspect of the invention, the phase shifted color sync signal is inserted into a color sync range at a site or location that follows the normal color sync signal. As a particularity of this aspect, the color synchronization signal shifted in inserted phase begins at the moment when the normal color synchronization interval ends. Alternatively, and as another feature, the phase shifted color sync signal begins before the normal color sync interval ends and ends after the color sync interval ends, such as a number of signal cycles. Color synchronism after the end of the color synchronization interval. As a still further aspect of this invention, the color synchronization signal inverted in phase both precedes and follows the normal color synchronization signal.Also as another aspect, the phase shifted color synchronization signal is inserted in the portion of the normal color synchronization interval According to another embodiment of this invention, the amplitude of a portion of the color synchronization signal shifted in phase is increased relative to the amplitude of the normal color synchronization signal. still another feature of this invention, the phase shifted color sync signal is inserted into a predetermined number of successive line intervals of the analog color video signal, such as in intervals of two or four successive lines, constituting this way a block, and these blocks exhibit a repetitive tilt in each field or in the alternative fields of each frame of the video signals. Alternatively, the line interval block containing the phase shifted color sync signal can be provided only in the vertical suppression range of the video signal. According to a further aspect, an improved recording medium is protected against copies by recording therein the information which, when reproduced, causes the color synchronization signal shifted in phase and described above to be generated and inserted in the video signal produced.

BRIEF DESCRIPTION OF THE DRAWINGS The following detailed description which is provided by way of example and is not intended to limit the present invention solely to the same, will be understood in conjunction with the accompanying drawings, in which: Figures IA and IB schematically represent the synchronization signal of color that is recorded and produced respectively by a consumer video recording apparatus; Figures 2A to 2D are waveforms representing the embodiments of the present invention; Figures 3A and 3B are waveforms representing the color synchronization signal, modified in accordance with the present invention, which is recorded and produced respectively, by a consumer video recording apparatus. Figure 4 is a functional diagram of the apparatus carrying out the present invention; Figures 5A to 5D are waveform diagrams illustrating the different embodiments of the present invention; Figures 6A and 6B are waveform diagrams representing the copy protection technique in accordance with an aspect of the present invention; Figures 7A and 7B schematically represent blocks of copy protection signals, produced in accordance with one embodiment of the present invention; Figure 8 schematically represents the location in a normal color synchronization range of color shifted signals synchronized in phase according to the different embodiments of the present invention; Figure 9 schematically depicts yet another embodiment of the manner in which the phase shifted color sync signals are inserted in the color synchronization range of a copy protected video signal; Figures 10A to 10C are timing or synchronization diagrams schematically representing a prior art copy protection technique using AGC processing; Figure 11 schematically represents a video image produced of a copy-protected video signal that has been subjected to color strip processing.

DETAILED DESCRIPTION OF THE PREFERRED MODALITIES Referring now to Figure IA, a waveform of a portion of the horizontal blanking interval of each line of an analog color signal is illustrated. As is conventional, the horizontal blanking interval includes the horizontal synchronizing pulse h followed by the color synchronizing interval a, the latter including a predetermined number of cycles of the chrominance subcarrier which, in the NTSC system is about 9. cycles at a frequency of about 3.58 MHz. Figure IA illustrates that the envelope of the color synchronization signal increases and decreases gradually, ie the envelope thereof does not change instantaneously from its suppression level (10 IR) to its level of reference (30 IRÉ). As is known, when the analog color video signal is recorded in a conventional analog video recording apparatus, the components of the video signal, including the color synchronization signal, are converted down to a frequency band below. of the frequency band of the luminance components; and when the recorded color video signal is reproduced, the components of the color signal including the color synchronization signal are converted back to their original frequency band. As a result of the downconversion and upconversion of the color sync signal, the range of the color sync signals shown in Figure IA tends to expand in order to exhibit the waveform shown in Figure IB. This expansion, which is referred to herein as expansion of the time axis, tends to "lengthen" the range of color synchronism, thereby considerably eliminating the separation between the end of the horizontal synchronization pulse and the beginning of the color synchronization signal. The present invention depends on this inherent time axis expansion of the color synchronization signal to down-convert and up-convert the components of the color signal into a video recording apparatus to impart copy protection to both a video signal to pre-registered colors and as an "active" color video signal, (e.g., a color signal received in real time). In particular, the present invention inserts in the color synchronization range a phase shifted version of the color synchronization signal. In one embodiment, the phase shifted color sync signal is placed immediately after the usual normal (or reference) phase color sync signal, as shown by the shaded area in Figure 2D, or immediately before to the normal color sync signal, as shown by the shaded area in Figure 2C, or both in the previous one and in the next normal color sync signal as shown by the shaded area in Figure 2D. Here, the color shifted signal in phase which acts as the copy protection signal is designated by the reference number b, when the color synchronization signal shifted in phase follows the normal color sync signal, and by the reference number c, when the color synchronization signal shifted in phase precedes the normal color sync signal. In Figures 2A to 2D, the normal color sync signal, i.e., the synchronism signal exhibiting the reference phase, is identified by the reference number a. Assuming that the normal color sync signal is formed of 9 cycles of the chrominance subcarrier, the phase shifted color synchronization signal b is formed of two cycles of the chrominance subcarrier shifted in phase and the sync signal c of color displaced in phase is formed of 2 cycles asismimo. In one embodiment, the color synchronization signal displaced in phase is 180 ° out of phase with respect to the reference color synchronization signal; and in another embodiment, the color synchronization signal displaced in phase is 90 ° out of phase. Although other phase shifts can be used, phase shifts of 180 ° and 90 ° are preferred.

Figures 2A to 2D illustrate the envelopes of the color synchronization signal, including the insertion in the color synchronization range of the phase shifted color sync signal, before registration thereof. That is, the frequency of the chrominance subcarrier illustrated in Figures 2A to 2D is approximately 3.58 MHz. Of course, the color synchronization signal and the phase shifted color sync signal are converted down to register in the apparatus of analog video recording; and when the video signal is reproduced, this color synchronization signal and the phase shifted color sync signal becomes upward. As a result, and as described with reference to Figures IA and IB, the reproduced color sync signal and the phase shifted color sync signal exhibit time axis expansion. Figure 3A illustrates the copy-protected color sync signal before registration (ie, before the color sync signal is converted downward) and the Figure 3B illustrates the envelope of the color synchronization signal protected against copying after reproduction (ie, after the copy-protected color synchronization signal has been converted downward and then converted upwardly.) It will be seen from Figure 3B that the color synchronization signal b 'shifted in reproduced phase exhibits a duration greater than the duration the original occupied by the phase shifted color synchronization signal b, and, similarly, the shifted color synchronized signal c 'exhibits a duration that exceeds the original duration of the color synchronization signal c shifted by In addition, due to the expansion of the time axis, the reproduced "phase shifted" color synchronization signals b 'and e "leak" towards the interval originally occupied only by the normal color synchronism signal of the reference phase This leakage tends to compress the duration of the color synchronization signal of the reference phase, however, the PLL circuit of the circuit or APC of the conventional television receiver is too slow (i.e., its inherent time constant is too large) to latch onto the phase shifted color sync signal. Consequently, this PLL circuit with the relatively high time constant can not follow the phase shifted color sync signal, and the insertion of the color shifted signal in phase is not sufficient to interfere with the PLL circuit of the conventional television receiver.

But, due to the low time constant of the PLL circuit in the video recording apparatus, this PLL circuit is fast enough to follow the color synchronization signal shifted in the expanded phase on the time axis as well as the signal of normal color synchronism. Therefore, the oscillator included in the PLL circuit is engaged in the phase-shifted color synchronization signal so that when the line interval containing the phase-shifted color synchronization signal is demodulated in color, the phase The color signal differs from the phase of the demodulation signal to distort the hue of that line. That is, the resulting color signal that is sent from the video recording apparatus during upconversion causes a seriously distorted hue for those lines that contain the phase shifted color sync signal. Referring now to Figure 4, there is illustrated a functional diagram of the apparatus used to insert at a predetermined location in the color synchronization range of the color video signal, the color synchronization signal shifted in phase over a duration default Here, the color synchronization signal shifted in phase, that is, the copy protection signal is inserted into the color video signal that is reproduced by the video signal reproduction device 1, although it will be appreciated that the copy protection signal may be inserted in a signal of "active" color video. Examples of the video signal reproducing device include a digital video recording apparatus, an analog video recording apparatus, a laser disc player apparatus, a digital video disc player apparatus, a signal reproducing apparatus computer generated video, a CD-ROM video signal, a video signal receiver or the like. Preferably and in accordance with the best way to carry out this invention, the digital apparatus is used as or with the device for reproducing the video signal, and it will be appreciated that the resulting digital video signal obtained therefrom becomes analog form. The video signal reproduction device 1 generates from a recording medium loaded thereon a luminance signal Y and a signal C to colors as the respective outputs at the separated output terminals. The video signal reproduction device also generates, as individual outputs, a horizontally synchronized HD signal, a vertical synchronization VD signal, and a clock CLK signal, the latter being a high frequency system clock. For example, the clock signal CLK can be generated by a PLL circuit included in the video signal reproduction device 1 in order to synchronize the chrominance subcarrier. The video signal reproduction device is also adapted to generate a copy control signal which determines that the reproduced color video signal must be modified to include a copy protection signal (e.g., to be included in the color synchronization signal shifted in phase). In its simplest form, the copy control signal can be a "1" when the color video signal will be modified with a copy protection signal and a "0" when the color video signal is not going to Modify in this way; and is generated in response to the copy control information that can be recorded in and therefore reproduced from the recording medium. A time generator 2 is coupled with the video signal reproduction device 1 to receive the HD and VD signals of horizontal and vertical synchronization and also the clock signal CLK, in order to generate the time control or synchronization pulses that they are used to control the insertion of the color synchronization signal shifted in phase in the color synchronization interval of the color video signal. These time control or synchronization pulses establish the duration of the color synchronization signal shifted in phase and the time in which it occurs; the latter being used to select the predetermined location or locations of the color sync interval where the color shifted signal is inserted in phase. These time control or synchronization pulses are also used to determine the phase shift (e.g., 90 °, 180 ° or other) of the color shifted signal in phase and ensure that the signal frequency color shifted in phase sync is identical to the frequency of the normal color sync signal (or reference phase). The construction of the time or synchronization generator 2 to achieve the aforementioned functions is within the skill of a person skilled in the art. A color synchronization signal generator 3 is coupled to the time or synchronization generator 2 and responds to the timing or synchronization control pulses generated by the time or synchronization generator in order to generate the phased color synchronization signal in phase of duration, phase and time that is determined by the synchronization control pulses. As used herein, the term "synchronization" of the phase shifted color sync signal is intended to imply the specific location or locations of the color sync interval where the shifted color sync signal is inserted. in phase. In this regard, the synchronization control pulses include a phase control pulse which, as will be described below in relation to FIGS. 5B to 5D, establishes the synchronization of the color shifted signal in phase. Also, as will be described in conjunction with Figure 5D, the generator 3 of the color synchronization signal is adapted to change the amplitude of a predetermined portion (or portions) of the color shifted signal in phase. For example, assuming that the amplitude of the color shifted signal in phase is equal to the amplitude of the normal color or reference phase sync signal, the color sync signal generator is adapted to increase the amplitude of the color synchronization signal shifted in phase in a predetermined portion thereof. In this way, only a portion of the phase shifted color sync signal can exhibit a higher gain than the rest of the phase shifted color sync signal. Therefore, the synchronization control pulses generated by the synchronization generator 2 may include, in addition to the phase control pulse, a gain control pulse which controls the gain of the color shifted signal in phase. A color synchronization positioning circuit 4 is coupled to the video signal reproduction device 1 and the color synchronization generator 3 and is adapted to insert the copy protection signal produced by the synchronization signal generator color in the component of the color signal of the video signal. More particularly, the color synchronization positioning circuit 4 receives the component C of the color signal and the copy control signal produced by the video signal reproduction device and functions to insert in the color synchronism range of the component of the color signal, the color synchronization signal shifted in phase produced by the color synchronization signal generator, depending on the state of the copy control signal. In the example discussed above, if the copy control signal is a "1", the color synchronization placement circuit 4 inserts the phase shifted color synchronism signal produced by the color synchronization signal generator 3 in color synchronism interval of the color C signal. On the other hand, if the copy control signal is a "0", the color synchronization setting circuit does not insert the color synchronization signal shifted in phase in the color synchronization range. A 5 Y / C mixer is coupled to the video signal reproduction device 1 and the color synchronization positioning circuit 4 to mix the luminance component Y and the color signal C, the latter being modified by the signal of copy protection, to produce a composite video signal protected against copying at its output terminal 7. The output terminal 7 can be coupled with a video recording apparatus and / or with a monitor. If a monitor is supplied, it will be appreciated that the color video signal can be presented visually appropriately as a video image without distortion or noticeadeterioration. If an analog video recording apparatus is coupled to the output terminal 7, the modified color video signal is subjected to downconversion and then to upconversion of the color C signal, resulting in time axis expansion of the modified color sync interval (as shown in Figure 3B); and as a result, when the reproduced color video signal is presented visually, considerable distortions and deteriorations will be present, thus canceling the viewer's acceptance of the copy-protected video signal.

The luminance signal Y produced by the video signal reproduction device 1 and the copy protected color signal C produced by the copy synchronization positioning circuit 4, are coupled to a terminal block 6 which constitutes the output called S As is known, the output S includes separate luminance and chrominance signals which can be supplied to the input S of a higher quality video display device. However, even when the color signal C has been modified with the copy protection signal, as mentioned above, the color video image presented visually therefrom will not exhibit noticeable deterioration; but if the color signals at the output S of the terminal block 6 are subsequently recorded and reproduced by a consumer-type video recording apparatus, the resulting image that is displayed visually of the reproduced video signal will not be satisfactory. Figures 5A to 5D illustrate the signals provided in the horizontal blanking interval of the color video signal, as a result of the operation of the apparatus shown in Figure 4. Figure 5A is a waveform illustrating the blanking interval "normal" horizontal and illustrates the horizontal synchronization signal h followed by the color synchronization signal a, the latter being provided in the color signal C supplied to the color synchronization positioning circuit 4 by the reproduction device 1 of the video signal. Figure 5B illustrates the phase control pulse included in the synchronization control pulses generated by the synchronization generator 2; and it will be seen that the color chrominance signal generator 3 responds to the phase control pulse to generate the color synchronization signal b phase shifted during the synchronization that follows the reference phase color synchronization signal. The color synchronization positioning circuit 4 inserts the phase shifted color synchronization signal generated by the color synchronization signal generator 3 in the color synchronization range resulting in the modified color synchronism range shown in FIG. Figure 5B. Figure 5C illustrates two phase control pulses included in the synchronization control pulses whereby the color synchronization generator 3 generates two durations of the color shifted signals b and c shifted in phase. The color synchronization positioning circuit 4 inserts the color synchronization signals b and c shifted in phase in the color synchronization range and as seen in Figure 5C, the duration of the reference phase color synchronization signal is compress Figure 5D illustrates a phase control pulse similar to that shown in Figure 5B and, in addition, illustrates the gain control pulse that can be included in the timing control pulses supplied to the color sync signal generator 3. As discussed above, the generator of the color synchronization signal responds to the gain control pulse to increase the gain or amplitude level of a portion of the color shifted signal in phase, as shown. It will be appreciated that the width of the gain control pulse determines the width of that portion of the phase shifted color sync signal whose gain is increased. The color synchronization positioning circuit 4 inserts in the color synchronization range and the phase shifted color sync signal in gain generated by the color synchronization signal generator 3 resulting in the color synchronization interval modified shown in Figure 5D. Turning now to FIGS. 6A and 6D, an explanation will now be provided for the implementation of one embodiment of the present invention. Figure 6A illustrates the waveform of the relevant portions of the horizontal blanking interval with the following synchronization annotations: t ^ -t2 is the conventional color synchronization range; t5 ~ t] _ is referred to as the color pre-synchronism interval because it is placed immediately before the conventional color synchronization interval t] _-t2. ] _- t3 is referred to as the beginning of the color sync interval; and t_j-t2 is referred to as the end of the color synchronization interval. It will be appreciated that t3 ~ t.j is smaller than the normal color sync interval; and this occurs because the color synchronization signal displaced in phase b and c "shows leaks" towards the normal color synchronization interval. Finally, reference is made to t2 ~ tß as the color skew interval because it occurs immediately after and outside the normal color sync interval. Figure 6B illuses a plurality of successive horizontal line intervals, for example, four line intervals, wherein the copy protection signal of the present invention, i.e. the first signal shifted in phase,. it is inserted in the color synchronization interval of the color video signal. It will be seen that the precise locations of the color synchronization signal shifted in phase in the color sync range on each line changes slightly from line to line. Of course, the shaded portions shown in Figures 6A and 6B represent those portions of the color sync range where the phase shifted color sync signal is inserted. In one embodiment, the line intervals of the video signal containing the phase shifted color sync signal, i.e., those line intervals that are subject to copy protection, are included in the vertical blanking interval. In other embodiments to be described, the line intervals included in the visual presentation portion of the video image contain the copy protection signal, (i.e., the color synchronized signal shifted in phase). In the mode in which the copy protection signal is placed in those line intervals that are visually presented in the video image, it is preferred to generate a pattern of lines protected against copies. Here, the phase shifted color sync signal is inserted into a predetermined number of successive line intervals of the video signal, for example, in two successive line intervals or, alternatively, in four successive line intervals constituting this way a block. A field of the video signal is formed of multiple blocks exhibiting a repetitive tilt. For example, successive blocks can be separated by intervals of 20 unmodified lines or by intervals of thirty unmodified lines or intervals of forty unmodified lines, etc. As another example, the successive blocks can be separated by intervals of one hundred modified lines. In another example, instead of forming multiple blocks exhibiting a repetitive tilt in only one field of the video signal, multiple blocks may be provided that exhibit the repetitive tilt mentioned above in a frame of the video signal. Of course, in this alternative, a "block" is formed of intervals of two or four successive lines where the color synchronization signal shifted in phase has been inserted. From Figure 6B, it will be seen that the phase shifted color sync signal can be inserted in the color sync range in one or more of the following sites or locations: t5 ~ t3, t_j-t2 / 2 ~ tg and tj -tg. Of course due to the downconversion and upconversion processing of the color sync signal and the phase shifted color sync signal when a copy-protected color video signal is recorded and reproduced as discussed above , the color synchronization signal displaced in phase and "presents leaks" towards the reference phase color synchronization signal and, in addition, exhibits expansion of the time axis, thus increasing the opportunity for the PLL circuit and the conventional television receiver follows the phase alterations of the color synchronization signal, resulting in significant defects and deteriorations of the reproduced video image. The selection of the number of successive line intervals that contain the copy protection signal (i.e., the phase shifted color sync signal) in accordance with the present invention depends, in part, on the susceptibility of conventional television receivers to latch onto the phase shift color synchronization signal that does not exhibit expansion of the time axis. For example, if a copy-protected video signal is an "active" signal or a pre-registered signal, the intervals of four (or more) successive lines may include the color synchronization signal shifted in phase if the PLL circuit of the television receivers admits a high time constant, and a smaller number of successive line intervals may contain the color synchronized signal shifted in phase if the time constant is lower.

Figures 7A and 7B schematically represent those fields of a frame containing the copy protected video signal shown in Figure 6B. It will be seen that each field or alternative fields may contain a number of lines having in them the color synchronization signal shifted in phase. Alternatively, the copy protection signal may be inserted in the color synchronization range of a predetermined number in lines in each other frame. Still additionally, those lines containing the copy protection signal may exhibit a so-called network or mesh form. Figure 8 automatically represents different configurations in which the color shifted synchronism signal in phase can be inserted in the color synchronization interval. Each shaded area is intended to identify the color synchronization signal shifted in phase. In a real implementation, one or more of the configurations may be adapted. It will be seen, then, that the phase shifted color synchronism signal may exhibit different durations as illustrated in Figure 8 mediated by the reference numbers e, i, j, k and 1. Therefore, the shifted color sync signal in phase e, it can be placed in color post-synchronization intervals and it is seen to start when the normal color sync interval ends and a number of cycles (eg, 2 cycles of the subcarrier) end later. The phase shifted color sync signal i is provided at the end of the color synchronization interval t_j-t2 and is seen to follow the reference phase color sync signal. The phase shifted color synchronization signals e and i can be combined. The phase shifted color synchronization signal j is placed in a central portion of the color synchronization range and is preceded and followed by the reference phase color synchronization signal. The phase shifted color synchronization signal k is provided at the beginning of the color synchronization interval t] .- t3 and simply precedes the reference phase color sync signal. The color synchronization signal 1 shifted in phase is placed in the color pre-synchronism interval of t5 at ^ and also at the beginning of the color synchronism interval t] .- t3 and it is seen to begin before it starts and terminate the synchronism interval in phase in the phase synchronization interval but before the color synchronization signal of the reference phase begins. Since the circuit used in the consumer-type analog video recording apparatus, it may differ from one manufacturer to another and from one model to another, when different combinations are used, of the phase-shifted color synchronization signal shown in FIG. Figure 8 virtually ensures success to prevent the video recording apparatus from successfully copying the copy-protected video signal. Alternatively, the different line ranges of the copy-protected video signal may contain different phase-shifted color sync signals shown in Figure 8. For example, one line may contain the phase-shifted color synchronization signal e, another may contain the phase-shifted color synchronization signal i, another may contain the phase-shifted color sync signal j, and so on. It is possible that the oscillation in the visually reproduced video image reproduced from a pre-recorded or "active" copy-protected video signal may be present in the boundary between the line interval containing the color synchronization signal e displaced in phase and the next line interval that does not contain the phase shifted color sync signal. For example, if a block of 4 successive lines contains the color synchronization signal e shifted in phase, this oscillation may be present. To avoid this possibility, the duration of the phase shifted color synchronism signal is gradually increased from line to line in the beginning portion of the block and gradually decreased from line to line in the final portion of the block, as illustrated. schematically in Figure 9. Here, the portion m of the phase shifted color synchronization signal represents the gradual increase in the duration of the same, i.e., a gradual increase in the duration of the displaced color synchronism signal e in phase, and portion n represents the gradual decrease in the duration of the phase shifted color synchronism signal. Although the invention has been shown and described with particularity with reference to the preferred embodiments, it will be readily appreciated by those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. Some of these changes have been discussed and suggested in the foregoing. Furthermore, even when the color synchronization signal generator 3 and the color synchronization positioning circuit 4 (Figure 4) insert the color synchronization signal shifted in phase in the color synchronization interval, it will be appreciated that the signal of reference phase color synchronization in case it can be modulated in phase to achieve the same effect. That is, by phase modulation, the phase of the predetermined portions of the color sync signal can be changed. It is intended that the appended claims be construed as including those embodiments that have been specifically described herein as well as all equivalents thereof, some of which have been described above and others will be apparent to those skilled in the art. of the technique.

Claims (47)

CLAIMS:

1. A method for preventing an analog color video signal from being copied satisfactorily by an analog video recording apparatus, wherein the analog color video signal includes a color synchronization signal of the reference phase placed in a range of color synchronism in respective line intervals, the method comprises the steps of: generating a color synchronism signal shifted in phase; and inserting the color synchronization signal shifted in phase to a predetermined location through a predetermined duration in the color sync interval.

The method according to claim 1, wherein the predetermined location precedes the color synchronization signal of the reference phase.

3. The method according to claim 2, wherein the predetermined duration begins before the color sync interval in the color synchronization interval begins and ends.

4. The method according to claim 1, wherein the predetermined location follows the color synchronization signal of the reference phase.

5. The method according to claim 4, wherein the predetermined duration begins when the color synchronization interval ends.

The method according to claim 4, wherein the predetermined duration begins before the color synchronization interval ends, and ends at a number of color synchronization signal cycles after the synchronization interval of the color is terminated. color.

The method according to claim 1, wherein the predetermined location both precedes and follows the color synchronization signal of the reference phase.

The method according to claim 1, wherein the predetermined location is in a central portion of the color synchronization range.

The method according to claim 1, wherein the phase shifted color sync signal exhibits an amplitude essentially equal to that of the color sync signal of the reference phase; and further comprising the step of changing the amplitude only a portion of the color synchronized signal shifted in phase.

The method according to claim 9, wherein the amplitidu is only the portion of the phase shifted color sync signal is increased.

The method according to claim 1, wherein the phase shifted color synchronization signal is inserted into a predetermined number of successive line intervals of the analog color video signal, thereby constituting an interval block. of line, and a predetermined field of the analog color video signal is formed of multiple blocks exhibiting a repetitive tilt.

The method according to claim 1, wherein the phase shifted color sync signal is inserted into a predetermined number of successive line intervals of the analog color video signal, thereby constituting an interval block. line and a frame of the analog color video signal is formed of multiple blocks that exhibit a repetitive tilt.

The method according to claim 1, wherein the analog color video signal includes a vertical blanking interval; and wherein the phase shifted color sync signal is inserted into predetermined line intervals of the vertical blanking interval.

The method according to claim 4, wherein the phase shifted color sync signal is inserted at a predetermined number into line intervals constituting a block, and wherein the predetermined duration gradually increases from line to line those lines that constitute a beginning portion of the block and gradually decrease from line to line in those lines that constitute a termination portion of the block.

15. The method according to claim 1, wherein the color synchronization signal displaced in phase shifts in phase by 180 ° relative to the reference phase.

The method according to claim 1, wherein the phase shifted color synchronization signal is shifted in phase by 90 ° relative to the reference phase.

17. The apparatus for preventing an analog color video signal from being successfully copied by an analog video recording apparatus, wherein the analog color video signal includes a color synchronization signal of the reference phase placed on a color synchronization interval in respective line intervals, the apparatus comprises: a copy protection generating means for generating a phased color synchronization signal in phase; and an insertion means for inserting the color synchronization signal shifted in phase to a predetermined location through a predetermined duration in the color sync interval.

18. The apparatus according to claim 17, wherein the predetermined location precedes the reference phase color sync signal.

19. The apparatus according to claim 18, wherein the predetermined duration begins before the color synchronism interval in the color synchronization interval begins and ends.

20. The apparatus according to claim 17, wherein the predetermined location follows the color synchronization signal of the reference phase.

21. The apparatus according to claim 20, wherein the predetermined duration begins when the color synchronization interval ends.

22. The apparatus according to claim 20, wherein the predetermined duration begins before the color synchronization interval ends, and ends during a number of cycles of the color synchronization signal after the synchronization interval ends. color.

23. The apparatus of. according to claim 17, wherein the predetermined location precedes as much as follows the color synchronization signal of the reference phase.

24. The apparatus according to claim 17, wherein the predetermined location is in a central portion of the color synchronization range.

The apparatus according to claim 17, wherein the phase shifted color sync signal exhibits an amplitude substantially equal to that of the reference phase color sync signal; and the copy protection generating means is capable of operating to change the amplitude of only a portion of the color shifted signal in phase.

26. The apparatus according to claim 25, wherein the copy protection generating means increases the amplitude of only the portion of the synchronism signal of the color shifted in phase.

The apparatus according to claim 17, wherein the insertion means is operable to insert the color synchronization signal shifted in phase at a predetermined number of successive line intervals of the analog color video signal, thereby constituting a block of line intervals, and for constructing a predetermined field of the analog color video signal with multiple blocks exhibiting a repetitive tilt.

The apparatus according to claim 17, wherein the insertion means is operable to insert the phase shifted color sync signal at a predetermined number of successive line intervals of the analog color video signal , thereby constituting a block of line intervals, and for constructing a frame of the analog color video signal with multiple blocks exhibiting a repetitive tilt.

29. The apparatus according to claim 17, wherein the analog color video signal includes a vertical blanking interval; and wherein the insertion means is operable to insert the phase shifted color sync signal and predetermined line intervals of the vertical blanking interval.

30. The apparatus according to claim 20, wherein the insertion means is operable to insert the color synchronization signal shifted in phase at a predetermined number of line intervals constituting a block and to gradually increase the duration line line default in those lines that constitute a block start portion and to gradually decrease the predetermined duration of line in line in those lines that constitute the termination portion of the block.

31. The apparatus according to claim 17, wherein the phase-shifted color synchronization signal is shifted in phase by 180 ° relative to the reference phase.

32. The apparatus according to claim 17, wherein the phase-shifted color synchronization signal is shifted in phase by 90 ° relative to the reference phase.

33. A means of recording protected against copies in which a color video signal is recorded that is not capable of being copied satisfactorily by an analog video recording device, the color video signal includes a copy control signal and when it is recovered for analog recording includes a color synchronism signal of the reference phase placed in a color synchronization interval in the respective line intervals with the color synchronization interval having a predetermined location where during playback, a signal is inserted of color synchronization shifted in phase through a predetermined duration, in response to the copy control signal.

34. The medium according to claim 33, wherein the predetermined location precedes the color synchronization signal of the reference phase.

35. The medium according to claim 34, wherein the predetermined duration begins before the color sync interval begins and ends in the color sync interval.

36. The medium according to claim 33, wherein the predetermined location follows the color synchronism signals of the reference phase.

37. The medium according to claim 36, wherein the predetermined duration begins when the color synchronization interval ends.

38. The medium according to claim 36, wherein the predetermined duration begins before the color synchronization interval ends and a number of color synchronization signal cycles ends after the synchronization interval of the color has expired. color.

39. The medium according to claim 33, wherein the predetermined location both precedes and follows the color synchronization signal of the reference phase.

40. The medium according to claim 33, wherein the predetermined location is in a central portion of the color synchronization range.

41. The medium according to claim 33, wherein the phase shifted color synchronization signal exhibits an amplitude essentially equal to that of the color synchronization signal of the reference phase; the amplitude is only a portion of the color synchronized signal shifted in phase has a greater amplitude.

42. The medium according to claim 33, wherein the phase shifted color sync signal is inserted into a predetermined number of successive line intervals of the recovered color video signal, thereby constituting a block of intervals. of line, and a predetermined field of the recovered color video signal is formed of multiple blocks - exhibiting a repetitive tilt.

43. The medium according to claim 33, wherein the phase shifted color synchronization signal is inserted into a predetermined number of successive line intervals of the recovered color video signal, thereby constituting an interval block. of line, and a box of color video signal recovered, in the form of multiple blocks that exhibit a repetitive tilt.

44. The medium according to claim 33, wherein the recovered color video signal includes a vertical blanking interval; and wherein the phase shifted color sync signal is inserted at predetermined line intervals at the vertical blanking interval.

45. The means according to claim 36, wherein the phase shifted color synchronization signal is inserted at a predetermined number at line intervals of the recovered color video signal, constituting a block; and wherein the predetermined duration gradually increases from line in line in those lines that constitute a portion of the beginning of the block, and gradually decreases from line to line in those lines that constitute a portion of the termination of the block.

46. The medium according to claim 33, wherein the phase-shifted color synchronization signal is shifted by 180 ° relative to the reference phase.

47. The medium according to claim 33, wherein the phase-shifted color synchronization signal is shifted in phase by 90 ° relative to the reference phase.