Method and apparatus for modifying a video signal or for providing a copy protection signal by adding selected negative going and positive going pulses

Abstract

The horizontal blanking interval (HBI) of a normal video signal is modified to enhance the playability of the applied copy protected video signal while maintaining the copy protection effectiveness. As generally known, a copy protected video signal with positive-going pulses in a back porch region causes possible black level depression. The addition of a negative-going pulse and/or negative-going and positive-going pulse pair immediately prior to the H sync signal in the front porch region causes a reduction in such black level depression while resulting in enhanced playability. In other embodiments, an amplitude extending pulse is added to a latter portion of the H sync pulse or to a latter portion of a pseudo sync pulse, to increase the negative-going amplitude of the respective pulse. Various combinations of the added pulses also are possible.

Description

BACKGROUND OF THE INVENTION

The present invention relates to a video signal copy protection process and apparatus, and more particularly to a technique for providing or enhancing copy protection of video signals via the addition of special negative-going pulses as well as special positive-going pulses in some embodiments, within selected portions of front porch regions in the video signal horizontal blanking interval (HBI).

In the field of video signal copy protection, copy protection processes are well known for modifying a video signal so that a normal color picture may be produced by a television receiver receiving the copy protected video signal, but wherein videotape recording of the copy protected video signal is inhibited and/or is so degraded in quality as to be unwatchable. In addition, many processes have been developed which enhance or otherwise improve upon the many basic copy protection processes.

Typical of such processes is that disclosed in U.S. Pat. No. 4,631,603 issued to J. Ryan in Dec. 23, 1986, and herein incorporated by reference, which capitalizes on the fact that a typical video cassette recorder's (V7CR) automatic gain control (AGC) system cannot distinguish between the normal sync pulses of a conventional video signal (including equalizing or broad pulses) and added pseudo-sync pulses. Pseudo-sync pulses are defined here as any other pulses which extend down to a normal sync tip level and which have a duration of at least 0.5 microseconds. A plurality of such pseudo-sync pulses is added to the conventional video signal during the vertical blanking interval, and each of such pseudo-sync pulses is followed by a positive pulse of suitable amplitude and duration. As a result, the automatic gain control system in a videotape recorder will make a false measurement of video level which causes an improper recording of the video signal. The result is unacceptable picture quality during playback. However, this approach utilizes positive-going pulses which occur at a time not ordinarily used for black-level restoration in typical television receivers and therefore does not give rise to black level depression in such typical television sets, whereby a television set (TV) displays a picture of fully acceptable quality.

Another copy protection process is disclosed in U.S. Pat. No. 4,819,098 issued to J. Ryan on Apr. 4, 1989 and incorporated herein by reference, which capitalizes on the fact that VCRs include the AGC system which here measures the sync pulse level in a video signal and develops a gain correction signal for keeping the video level applied to an FM modulator in the VCR system at a fixed, predetermined value. A plurality of positive pulses are added to the video signal with each immediately following a respective trailing edge of a normally occurring sync pulse. These added pulses are clustered at the vertical blanking interval of each field to minimize the affect of the same on the watchability of the picture defined by the signal, but still cause the automatic level control circuit in a VCR to assess the video level at many times its actual value thereby providing a copy of unacceptable picture quality. The sync pulses themselves can also be at a reduced level, in order to enhance the effectiveness of the copy protection process.

A further copy protection process is disclosed in U.S. Pat. No. 4,163,253 issued to M. Morio et al. on Jul. 31, 1979, wherein the AGC circuit of a VCR again prevents recording an acceptable copy of a copy protected video signal. A pulse whose amplitude is substantially equal to the peak white level of the video signal is inserted into respective horizontal blanking intervals of the video signal. If this modified video signal is recorded on a conventional type of video signal recorder, the presence of the inserted pulse signal is detected by the AGC detector which, in turn, controls an AGC amplifier to substantially attenuate the modified video signal which then is recorded. The resulting recording is of unacceptable picture quality.

It has been found that the copy protection signals of various copy protection processes which employ positive-going pulses, such as AGC pulses, in the back porch region of the HBI, may experience various degrees of playability problems such as for example black level depression. In the field of copy protection, it obviously is necessary to maximize the effectiveness of the copy protection of a recorded video signal. However, it is equally necessary to maintain the playability of the copy protected video signal by reducing the amount of side effects such as darkening of the TV set monitor during playback of the video signal, playback of a legal copy of the video signal, etc. It follows that it would be advantageous to maximize not only the effectiveness of a copy protection process against illegal copying but also the playability of the video signal by a legitimate TV set.

SUMMARY OF THE INVENTION

The present invention provides a process and apparatus for maximizing video signal copy protection while also enhancing the playability of a legitimate playback of the copy protected video signal.

To this end, the various embodiments of the invention add selected special pulses to selected regions in the HBI of the video signal. In one embodiment, a modified horizontal sync (H sync) pulse is added in the front porch region of the HBI. The modified H sync pulse is a relatively narrow negative-going pulse, hereinafter also termed a “presync” pulse for ease of description. A positive-going pulse of even narrower width is added following the negative-going modified presync pulse within the front porch region. Both pulses are inserted immediately before the normal horizontal sync (H sync) signal of normal duration, for example, 4.7 microseconds (μs) width. The negative-going presync and positive-going pulses have a combined time duration about equal to the duration of the front porch.

In another embodiment, a latter portion of the amplitude of the H sync signal is increased to below its normal or clipped H sync tip level. For example, the H sync tip level of the latter portion can be extended by an amplitude of about 10 to 50 IRE. Thus, if normal H sync signals are 4.7 μs in width, the invention process provides an additional amplitude extending pulse of for example about 1.0 μs width and about −40 IRE, superimposed onto a latter 1.0 μs portion of the H sync signal to provide an amplitude augmented H sync signal of about −80 IRE during the last 1.0 μs of the pulse. The amplitude extending pulse can also be added to the latter portion of pseudo sync pulses as well. The H sync and/or pseudo sync signals also may be clipped. An example of the clipped H sync tip level and/or the pseudo sync level of previous mention is about −30 IRE.

In either of the above embodiments the sampling circuits of a VCR sample the signal in the HBI at other than the normal time thereby resulting in an erroneous AGC gain level that in turn will turn the gain down. Thus, a subsequent recording made by the VCR will be darkened and unacceptable for watching. However, the added pulses do not affect the determination of the black level in the TV set since the samples taken by the circuit in the TV set average out and cause the black level to be sampled at a preferred point in the back porch region.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating various embodiments of the invention wherein respective modifications are applied to a normal video signal or to a copy protected video signal.

FIG. 2A-2G is a chart illustrating waveforms generated via respective embodiments of the invention such as depicted for example in the block diagram of FIG. 1.

FIG. 3A-3D is a chart illustrating waveforms generated via other respective embodiments of the invention depicted in the block diagram of FIG. 1.

FIG. 4 is a block diagram illustrating an embodiment of the invention for generating and applying a negative-going presync and positive-going pulse pair to a normal or copy protected video signal.

FIG. 5 is a block diagram illustrating another embodiment of the invention for generating and applying amplitude extending pulses to the H sync and/or pseudo sync signals, time extending color burst signals and/or extra post H sync pulses to a normal or copy protected video signal.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a basic block diagram illustrating various modifications and associated apparatus corresponding to the several embodiments of the invention, and the manner of applying one, or a combination, of the modifications to an incoming video signal which may or may not be a copy protected video signal. That is, the input video signal may contain a basic copy protection signal such as automatic gain control, (AGC) pulses or pseudo sync/AGC pulses, as depicted in a block 12 of FIG. 1 which receives the input video signal. The output of the basic copy protection process 12 is supplied to one input of a jumper J1, while the input video signal is also supplied directly to a second input of the jumper J1. The output of jumper J1 then supplies several blocks each of which comprises a respective modification which can be applied to the normal or copy protected video signal supplied via the jumper J1. The several blocks are each coupled to a combining circuit 14 such as, for example, a summing amplifier, via respective jumpers J2 through J7, as further described below. The normal or copy protected video signal from the jumper J1 also is supplied to the combining circuit 14 via one input of the jumper J7.

More particularly, the different modifications are selectively supplied to the combining circuit 14, along with the video signal via the jumper J7, by closure of one or more of the respective jumpers J2-J6. One such modification, a process 16 for adding a special narrow negative-going presync and very narrow positive-going pulse pair prior to the normal horizontal sync (H sync), is illustrated by a respective block. This embodiment of the invention is supplied to the combining circuit 14 by closing jumper J2, whereupon the presync/positive-going pulse pair is combined with the normal or copy protected video signal in the combining circuit 14 by closure of jumper J7.

The video signal supplied via the jumper J7 may be the normal or copy protected video signal from the jumper J1, which, however, has the color bursts therein removed by a color burst blanker process 18 if the respective input to the jumper J7 is closed. The color burst blanker process 18 is activated for example in a modification, described hereinafter, in which a new extended color burst is to be added, to the video signal.

Another modification, a process 20 for extending an amplitude of a portion of an H sync signal whereby the AGC circuit in a respective VCR will be affected, is illustrated by a respective block. The resulting process 20 of an extended H sync amplitude portion is supplied to the combining circuit 14 by closure of the jumper J5, whereupon the extended H sync amplitude portion is combined with the video signal from the jumper J7 via the combining circuit 14.

A further modification, a process 22 for extending the amplitude of a portion of a pseudo sync pulse to affect the AGC circuit of respective VCRs, is illustrated by a respective block. Obviously, since a pseudo sync pulse is being extended, the basic copy protection process includes pseudo sync signals in the video signal, and is provided by the basic copy protection process 12 to the process 22. The process 22 supplies an amplitude extending pseudo sync portion to the combining circuit 14 via closure of the jumper J6, whereby the pseudo sync signal with the extended pseudo sync portion is combined with the video signal from jumper J7 via the combining circuit 14.

It is pointed out that the three modification processes 16, 20 and 22 of previous description provide enhanced effectiveness of the copy protection in a video signal when the signal is recorded illegally via a VCR and playback is attempted.

Another modification, a process 24 for adding a time extended color burst signal to a copy protected video signal, may be used to insure that a copy protection modification such as that of the process 16 of previous disclosure does not cause a color lock problem on some TV sets. The process 24 is supplied to the combining circuit 14 via closure of the jumper J3, wherein the extended color burst may be added to the video signal by the combining circuit 14 along with the presync/positive-going pulses provided by the process 16.

Still another modification, a process 26 for adding an extra (post) sync pulse after the normal H sync signal, may be used to reduce any picture shifting effects which may be caused by a modification process of a copy protection process such as for example the process 16 of previous description. The post H sync pulse from process 26 is supplied to the combining circuit 14 via closure of the respective jumper J4, whereupon the extra post H sync pulse may be added along with the signals of the process 16 to the video signal.

It is noted that the two processes 24, 26 provide enhanced playability of a copy protected video signal in TV sets.

Thus, the output of the combining circuit 14 is the sum or combination of the normal or copy protected video signal plus one or more of the various modifications as selected by the various jumpers.

With regards now to FIG. 2A-2G, the waveform illustrated in FIG. 2A shows a standard video signal, particularly in the HBI region, with a normal H sync signal 30 but with the color burst signal blanked as would occur if the jumper J7 of FIG. 1 selected the video signal path through the color burst blanker process 18.

FIG. 2B illustrates a waveform of a negative-going presync (pseudo sync) pulse 32 of the invention such as that provided via the process 16 of FIG. 1, which presync pulse occurs in the front porch region at the end of active video and prior to the normal H sync signal. The negative-going presync pulse 32 is narrow, for example, about 1.0 microsecond (μs) and has an amplitude similar to the normal H sync signal, namely, about −40 IRE. However the width of the presync pulse 32 can vary from about 0.8 to 1.3 μs, while the amplitude of the extension can vary about the 40 IRE level.

FIG. 2C illustrates a waveform of a narrow positive-going pulse 34 such as that generated in the process 16 of FIG. 1, which also occurs in the front porch region at the trailing edge of the presync pulse 32 and prior to the normal H sync. Thus the positive-going pulse 34 is very narrow, for example, about 0.3 to about 0.8 μs and has an amplitude of about 30 to 130 IRE.

FIG. 2D illustrates a waveform of a conventional regenerated continuous wave (cw) color subcarrier signal which extends in time generally over the duration of the HBI.

FIG. 2E illustrates a waveform of a time extending color burst gate signal 36 that is used with the regenerated cw color subcarrier signal to extract a portion of the subcarrier signal to synthesize a time extended color burst envelope, such as provided via the process 24 of previous description in FIG. 1.

FIG. 2F illustrates a waveform of an alternative embodiment of the invention which includes a pulse 38 which is coincident with a latter portion of the H sync signal 30. In this embodiment, the pulse 38 is added to a latter portion of the H sync signal to extend the amplitude along the latter portion thereof. By way of example, the amplitude extending pulse has a duration of about 1.0 to 1.5 μs and an amplitude of about 10 to 50 IRE. The process corresponds to the process 20 in FIG. 1.

An amplitude extending pulse 42 also may be added to a latter portion of the presync pulse 32, such as depicted in phantom line in FIG. 2g.

FIG. 2G illustrates a waveform which is the result of combining the previous waveforms of FIGS. 2A-2F. The first portion of the front porch includes the negative-going presync pulse 32 shown in FIG. 2B. Pulse 32 is followed by the positive-going pulse 34 of FIG. 2C, wherein both pulses 32, 34 are inserted in the front porch region prior to the normal H sync signal 30. An amplitude extending pulse 38 is added to the latter portion of the H sync signal to provide the extended amplitude H sync signal such as that generated via the process 20 in FIG. 1. In addition, FIG. 2G may include a signal 40 corresponding to the extended color burst signal synthesized from the cw color subcarrier signal of FIG. 2D via the time extending burst gate signal 36 of FIG. 2E, and previously depicted as the process 24 disclosed in FIG. 1. It is understood that the time extending burst gate signal 36 and thus the time extended color burst signal 40 may coincide with any portion of the H sync signal 30 as well.

FIG. 3A-3D illustrate further modifications of additional embodiments in accordance with the invention. Thus, FIG. 3A illustrates a waveform of a video signal HBI including the H sync signal 30, but further including a known copy protection signal of an AGC pulse 44 in a back porch region of the HBI. Alternatively, a pseudo sync pulse 46 and an AGC pulse 48 may be added as pseudo sync/AGC pulse pairs to the back porch region. Pulse pair 46, 48 may exemplify the basic copy protection process 12 of FIG. 1.

FIG. 3B illustrates a waveform of the amplitude extending pulse 38, previously shown in FIG. 2F, which is coincident with the latter portion of the H sync signal 30. The addition of pulse 38 to them sync signal provides-an amplitude extension of the corresponding latter portion of the H sync signal.

In a further embodiment, FIG. 3C illustrates a waveform of a pulse 50 which is coincident with a latter portion of the pseudo sync pulse 46 of FIG. 3A and, in the manner of the pulse 38 added to the H sync signal 30, extends the amplitude of the latter portion of the pseudo sync pulse 46. This modification corresponds to the process 22 previously disclosed with reference to FIG. 1.

FIG. 3D illustrates a waveform which is a result of combining the waveforms of FIGS. 3A-3C. As may be seen, the amplitude extending pulse 38 is added to the level of the normal H sync signal 30 to provide an amplitude extended H sync signal. The AGC pulse 44 is added to the waveform in the back porch region. Alternatively, the amplitude extending pulse 50 may be added to respective pseudo sync pulses 46 to provide amplitude extended pseudo sync pulses. The amplitude extending pulse 38 can be added alone or in combination with the addition of the amplitude extending pulses 50.

FIG. 3E illustrates a waveform of an extra (post) sync pulse 51 such as provided via the process 26 of FIG. 1 and which is added to the video signal following the H sync signal in the back porch region, to reduce any picture shifting effects which may be caused by the presync/positive-going pulse pairs 32/34 of FIGS. 2B, 2C and 2G.

FIG. 4 illustrates an embodiment of circuitry for adding the negative-going presync pulse 32 and the positive-going pulse 34 as a presync/positive-going pulse pair. The FIG. 4 also-illustrates how the positive-going pulse 34 may be paired with each respective presync pulse 32 or may be paired with only some selected presync pulses 32. Generally, the presync pulses 32 are applied to video lines in the active TV field. However, if there a are residual darkening effects or for any other reason, the positive-going pulses may be spread out over the active field in clusters, or may be spread out over a-percentage of the active field video lines. For example, the percentage of positive-going pulses added to the lines containing negative-going pulses(presync pulses) may be about 10% to 30%. Also some or all of the positive-going AGC pulses may be amplitude, width, or position modulated.

Referring to FIG. 4, a normal or copy protected video signal is input into a sync separator circuit 54. A first output of circuit composite sync signal which is coupled to an H timing, circuit 56, which can be a horizontal PLL (phase lock loop) circuit, that is preferably timed to the HBI vicinity via a phase control 58. The output of H timing circuit 56 then is coupled to a presync timing generator 60 that creates the presync pulse 32 of FIGS. 2B and 2G prior to the H sync signal 30. Such a pulse 32 may start at the beginning of the front porch or, alternatively, may start near or within the end of the active video line. The output of presync timing generator 60 then is coupled to a positive-going pulse generator 62 and to an AND gate 64. The pulse generator 62 may comprise another timing circuit, which generates the pulse 34 of FIGS. 2C and 2G prior to the H sync signal 30 and after the presync pulse 32. The pulse generator 62 also has provision for applying pulse width modulation to the pulse 34 via a Vwidth voltage source 66. The output of the pulse generator 62 then is coupled to an AND gate 68.

It is preferable to provide means for selecting specific video lines in which the presync and/or the positive-going pulses 32, 34 are to be inserted. To this end, a line selection circuit is formed of the sync separator circuit 54, the H timing circuit 56 and further includes a counter circuit 70 and an EPROM circuit 72. The sync separator circuit 54 provides a second output of a vertical rate or frame rate signal to-reset the counter circuit 70. The H timing circuit 56 supplies an H rate signal to clock the counter circuit 70 at a horizontal frequency rate. The counter circuit in turn supplies selected pulses to the EPROM circuit 72. For example, sync separator circuit 54 may output a frame rate signal whereupon the counter circuit 70 counts from 1 to 525 (for a 525 TV line NTSC standard). The counts are supplied to the EPROM circuit 72 whose data output then assigns a logic level to each video line. A first output, line select 1, is coupled to the AND gate 64. The signal, line select 1, determines the line location of the presync pulse 32 and is supplied to AND gate 64, which is coupled to inverting scaling amplifier 74. A negative-going pulse is supplied from the amplifier 74 to a combining circuit 76 which synthesizes the presync pulse 34 on the video signal which it also receives via the input line 52. Typically, line select 1 is logic level high on the active field video lines, which may include at least a video line in the vertical blanking interval (VBI).

Another EPROM data output, line select 2, determines the video line location of the positive-going pulses 34. In one example, line select 2 is substantially identical to line select 1, so that each presync pulse 32 is paired with a positive-going pulse 34. In another example, line select 2 may be logic level high at a smaller group or groups of video lines in the active field. It follows that the positive-going pulse 34 is supplied to an AND gate 68 and is selected by the data output, line select 2, of the EPROM circuit 72. Also, the amplitude of the pulse 34 is determined by a Vampl voltage source 78 coupled to control an amplifier 80 which may be a voltage control amplifier. Since the control voltage Vampl may be fixed or dynamic, the resulting pulse 34 added to the video signal via the combiner circuit 76, may be of fixed level or of a selectable amplitude modulated level.

The output of the combiner circuit 76 is a video signal on line 82 modified to contain the pulses 32 in a first set (set 1) of selected video lines, and has positive-going pulses 34 inserted prior to the H sync pulse 30 in a second set (set 2) of selected video lines. As previously described, the positive-going pulses may be amplitude modulated or fixed.

The incoming video signal on input line 52 also is supplied to a color subcarrier regenerator 84, which also receives the composite sync signal (to form a color burst gate signal) from the sync separator circuit 54. The color subcarrier regenerator 84 may comprise phase-block loop (PLL) and supplies, on an output line 86, the regenerated cw color subcarrier signal previously described in FIG. 2, and provided via the process 24 in FIG. 1. Other output signals from the circuit of FIG. 4 include the line select 1 on an output line 88, and line select 3, 4 and 5 on output lines 90, 92 and 93. In addition, the H rate signal and the composite sync signal are provided on output lines 94 and 96, respectively. Various signals of FIG. 4 are supplied to the embodiment of the invention illustrated in FIG. 5, as is described hereinafter.

FIG. 5 illustrates other embodiments of the invention one of which extends the amplitude of the latter portion of the H sync pulses, and another which extends the amplitude of the latter portion of pseudo sync pulse. FIG. 5 also illustrates further embodiments for modifying a video signal by adding an extra negative-going (post sync) pulse after a H sync signal, and/or for modifying a video signal by extending a color burst envelope, which is useful for example in reducing picture shifting effects which may be caused by the process 16 described in FIG. 1.

Referring to FIG. 5, the horizontal blanking signal, H, generated in FIG. 4 and supplied on line 94, is coupled to an inverter 100 and thence to AND gates 102 and 104. The composite sync signal on line 96 of FIG. 4 is coupled to the AND gate 102 and the resulting pseudo sync pulses therefrom are supplied to the AND gate 104. AND gate 104 also receives an output from the EPROM circuit 72, viz, line select 3, whereby the pseudo sync pulses on video lines selected by line select 3 are converted to a logic level and are supplied to timing circuits formed of one-shots 106 and 108. One-shot 106 forms a time delay extending from the leading edge of the pseudo sync pulse, and one-shot 108 forms a pulse whose width is coincident with a latter portion of the pseudo sync pulse. The coincident pulse corresponds to the amplitude extending pulse 50 of FIGS. 3C, 3D as provided via a process 22 of FIG. 1.

Similarly, an AND gate 110 receives the signal H, the composite sync signal and a signal, line select 5 on lines 94, 96 and 93, respectively, from FIG. 4, and supplies pulses coincident with the H sync signal only on video lines selected by line select 5 signal. The output of AND gate 110 is coupled to timing circuits formed of one-shots 112 and 114. One shot 112 forms a time delay extending from the leading edge of the pulse of the selected H sync signal, while the one-shot 114 forms a H sync coincident pulse during a latter portion of the H sync signal. The H sync coincident pulse corresponds to the amplitude extending pulse 38 of FIGS. 2F, 2G as provided via a process 20 of FIG. 1.

The resulting amplitude extended H sync pulse 30, 38 and amplitude extended pseudo sync pulse 46, 50 are supplied to an OR gate 116, are OR'd together and selectively supplied to an inverting scaling amplifier 118. One input of a combining circuit 120 is coupled to the output of amplifier 118 and a second input thereof is coupled via a line 122 to either the original video signal on line 52 or the video signal on line 82 of FIG. 4, as directed by a jumper J8. The output of the combining circuit 120 is coupled to an input of a jumper J9, and adds the amplitude extended pseudo sync pulse 50 or the amplitude extended H sync pulse 38 to the respective pseudo sync pulse or H sync signal, in the modified or original video signal. The original video signal is supplied via the line 122 to a second input of the jumper J9, while the output of jumper J9 is coupled to an input of a switch 124. The other input of the switch 124 is grounded.

In another embodiment, if it is desirous to modify the video signal with an extended color burst (process 24 of FIG. 1 and waveforms of FIGS. 2D, 2E and 2G), the original color burst is substantially removed via a switch 124. The switch 124 is controlled by a burst blanking signal from an AND gate 126, which supplies a signal coincident with a portion of the back porch region. In turn, the AND gate 126 is responsive to a timing circuit formed of a one-shot 128, as is determined by a line select 4 signal on line 92 from the EPROM circuit 72 in FIG. 4. It follows that the output of switch 124 has the color burst signal removed in the video lines by line select 4.

An extended color subcarrier color burst 40 such as depicted in FIG. 2G and the process 24 of FIG. 1, is generated in FIG. 5 via an AND gate 130 which is coupled at one input to the signal, line select 4, on line 92 of FIG 4. In addition, the H rate signal on line 94 is supplied to timing circuits formed of one-shots 132, 134 which in turn are coupled to a second input of AND gate 130. The color subcarrier cw signal on the line 86 from FIG. 4 is supplied to a third input of AND gate 130. The one-shot 132 forms a time delay extending from the beginning of the HBI, and the one-shot 134 produces a pulse in the HBI, preferably in latter half of the HBI. The resulting time extended subcarrier color burst signal from the AND gate 130 is supplied to a band pass filter 136 (of 3.58 megahertz (MHz) for NTSC and 4.43 MHz for PAL color standards). The filtered signal is supplied to a phase shifting circuit 138 which is controlled by a phase adjusting device 140. The output of phase shifting, circuit 138 is a time extended color burst signal applied only to those video lines selected by the line select 4 signal, which output is supplied to a combining circuit 142.

The combining circuit 142 receives the output from the switch 124, and in one embodiment combines the time extended color burst signal with the video signal that has had the color burst signal blanked via the circuits 124, 126, 128. The resulting, output on line. 144 from combining circuit 142 is a video signal with a time extended color burst such as burst 40 in FIG. 2G. The video signal may contain in addition basic copy protection signals, the negative-going presync and positive-going pulse pairs of the invention and/or the amplitude extended latter portions of the H sync signal or the pseudo sync pulse of the invention, as determined by the positions of the jumpers J8, J9 and switch 124.

In another embodiment, the extra post H sync pulse 51 of FIG. 3E is added in the back porch region of the HBI to offset a possible picture shift caused by the addition of for example, the presync/positive-going pulses in the front porch region. To this end, timing circuits formed of one-shots 146, 148 receive the composite sync signal on the line 96 from FIG. 4, and an AND gate 150 receives the line select 1 signal from FIG. 4 on line 88 as well as the output from the timing circuits. The one-shots 146, 148 generate a pulse coincident with a selected portion of the back porch region. The AND gate 150 supplies this pulse in the lines selected by the line select 1 signal to an inverting amplifier 152 which in turn supplies the negative-going pulse 51 of previous mention to the combiner circuit 142. With jumper J10 closed, the extra sync pulse 51 is added to the back porch region in the video signal supplied on an output line 144.

It should be noted that in certain embodiments the jumper J10 is kept open circuit so as to not add the pulse 51 in the back porch region, for example, when amplitude extending H sync signal modifications are generated (i.e., by circuits 110, 112, 114). The reason is that an extended latter portion of the H sync signal combined with an extra negative-going pulse in a back porch region may cause less copy protection effectiveness in a VCR.

Although the present invention has been described and illustrated in detail, it to be understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of the present invention being, limited only by the terms of the appended claims and their equivalents.

Claims

1-48. (canceled)

49. A method of modifying a video signal having video lines with at least one horizontal blanking interval (HBI), horizontal (H) sync having a sync tip level, pseudo sync, automatic gain control (AGC) signal, and/or color burst signal to provide, modify, and/or enhance copy protection, wherein the copy protected video signal is viewable or watchable, the method comprising the application of two or more of the following steps:

adding a negative-going presync pulse of substantially said sync tip level and/or adding a positive-going pulse following the negative-going presync pulse, in a front porch region of the HBI prior to the H sync signal;

blanking one or more color bursts from the video signal;

blanking a portion or one or more back porch regions in one or more video lines;

extending an amplitude of a portion of the H sync signal;

extending an amplitude of a portion of the pseudo sync signal;

adding a time extended color burst signal to the video signal; and or

adding an extra sync pulse of substantially said sync tip level after the H sync signal.

50. Apparatus for modifying a video signal having video lines with at least one horizontal blanking interval (HBI), pseudo sync signal, automatic gain control (AGC) signal, color burst signal, and/or horizontal (H) sync signal having a sync tip level, to provide, modify, and/or enhance copy protection, wherein the copy protected video signal is viewable or watchable, the apparatus comprising two or more of the following elements:

a generating circuit for adding a negative-going presync pulse of substantially said sync tip level and/or adding a positive-going pulse following the negative-going pulse in a front porch region of the HBI prior to the H sync signal;

a circuit for removing one or more color bursts from the video signal and or for blanking a portion or one or more back porch regions in one or more video lines;

a circuit for extending the amplitude of a portion of the H sync signal and/or of the pseudo sync signal;

a circuit including a color subcarrier regenerator circuit for adding and/or inserting a time extended color burst signal to the video signal; and/or

a generating circuit for adding an extra sync pulse of substantially said sync tip level after the H sync signal.

51. A method of modifying a video signal and or copy protected video signal having video lines, horizontal blanking intervals, and horizontal sync signals, to provide a reduction in black level depression and or an enhanced playability, wherein the copy protected video signal is viewable or watchable, the method comprising:

modifying at least one horizontal sync signal by extending or increasing a horizontal sync amplitude portion of the video signal, to provide the enhanced playability or reduced black level depression when the video signal is viewed on a television set.

52. The method of claim 51 wherein at least one of the H sync or pseudo sync signal is reduced in amplitude.

53. Apparatus for modifying a video signal and or copy protected video signal having video lines, horizontal blanking intervals, and horizontal (H) sync signals, to provide a reduction in black level depression and or enhanced playability, wherein the copy protected video signal is viewable or watchable, the apparatus comprising:

a circuit for extending or increasing the amplitude of a portion of at least one of the horizontal sync signals to provide the enhanced playability or reduced black level depression when the video signal is viewed.

54. The apparatus of claim 53 further including pseudo sync signals, wherein an H sync or pseudo sync signal is reduced in amplitude.

55. A method of modifying a video signal and or copy protected video signal having video lines, horizontal blanking intervals, pseudo sync signals, AGC signals, horizontal (H) sync signals, and/or color burst signals, to provide copy protection effectiveness or copy protection enhancement, wherein the copy protected video signal is viewable or watchable, the method comprising:

adding or inserting a time extended phase shifted color burst signal to at least one line of the video signal; and

modifying at least one horizontal sync or pseudo sync signal by extending or increasing a horizontal sync or pseudo sync amplitude portion of the video signal;

thereby providing a video signal with copy protection effectiveness or copy protection enhancement.

56. The method of claim 55 wherein the H sync or pseudo sync signal is reduced in amplitude.

57. Apparatus for modifying a video signal and or copy protected video signal having video lines, horizontal blanking intervals, pseudo sync signals, AGC signals, horizontal (H) sync signals, and/or color burst envelopes, to provide copy protection effectiveness or enhanced copy protection, wherein the copy protected video signal is viewable or watchable, the apparatus comprising:

a generating circuit for providing a time extended color burst signal;

a phase shifting circuit for adding or inserting a time extended phase shifted color burst signal to at least one line of the video signal; and

a circuit for extending or increasing the horizontal sync or pseudo sync amplitude portion of the video signal;

to provide the copy protection effectiveness or the enhanced copy protection.

58. The apparatus of claim 57 wherein the H sync or pseudo sync signal is reduced in amplitude.

59. A method of providing a copy protection signal wherein the copy protection signal includes horizontal sync signals, pseudo sync signals, color burst envelopes, and/or automatic gain control (AGC) pulses, wherein the horizontal sync signals may be of reduced amplitude or of substantially normal amplitude, wherein the AGC pulses cause a copy protection effect on a recorder, and wherein the copy protected video signal is viewable or watchable, the method comprising:

extending at least a portion of the amplitude of at least one horizontal sync signal and/or at least one pseudo sync signal, thereby increasing the effectiveness of the copy protection in a recorder.

60. The method of claim 59 wherein at least one color burst envelope is extended in duration.

61. The method of claim 60 wherein the extended color burst envelope includes phase shifting in at least a portion of the extended color burst envelope.

62. The method of claim 59 wherein some or all of the AGC pulses may be amplitude, pulse width, or position modulated.

63. The method of claim 60 wherein some or all of the AGC pulses may be amplitude, pulse width, or position modulated.

64. The method of claim 61 wherein some or all of the AGC pulses may be amplitude, pulse width, or position modulated.

65. Apparatus for providing a copy protection signal, wherein the copy protection signal includes horizontal sync signals, pseudo sync signals, color burst envelopes, and/or automatic gain control(AGC) pulses, wherein the horizontal sync signals may be of reduced amplitude or of substantially normal amplitude, wherein the AGC pulses cause a copy protection effect on a recorder, wherein the copy protected video signal is viewable or watchable, the apparatus comprising:

a circuit for extending at least a portion of the amplitude of at least one horizontal sync signal and/or at least one pseudo sync signal, thereby increasing the effectiveness of the copy protection in a recorder.

66. The apparatus of claim 65 including:

an AGC pulse circuit for providing the AGC pulses; and

a color burst circuit for providing at least one color burst envelope that is extended in duration.

67. The apparatus of claim 66 wherein the extended color burst circuit a provides one or more phase shifted cycles of color burst signal.

68. The apparatus of claim 65 wherein the AGC pulse circuit provides amplitude, pulse width, or position modulation of some or all of the AGC pulses.

69. The apparatus of claim 66 wherein the AGC pulse circuit provides amplitude, pulse width, or position modulation of some or all of the AGC pulses.

70. The apparatus of claim 67 wherein the AGC pulse circuit provides amplitude, pulse width, or position modulation of some or all of the AGC pulses.

71. A method of synthesizing a video copy protection signal having horizontal blanking intervals, video lines, synchronizing pulse tips, and color burst signals, comprising:

adding in a horizontal blanking interval a negative going pulse whose pulse tip level is lower than the tip level immediately following a leading edge of a synchronizing pulse; and

adding a positive going pulse in the horizontal blanking interval to cause an automatic gain control (AGC) effect on a video cassette recorder.

72. Apparatus for synthesizing a video copy protection signal having horizontal blanking intervals, video lines, synchronizing pulse tips, and color burst signals, comprising:

a circuit for adding in a horizontal blanking interval a negative going pulse whose pulse tip level is lower than the tip level immediately following a leading edge of a synchronizing pulse; and

a circuit for adding a positive going pulse in the horizontal blanking interval to cause an automatic gain control (AGC) effect on a video cassette recorder.

73. Method of synthesizing a copy protection signal having horizontal blanking intervals, comprising:

generating or providing a first and/or a second negative going pulse in a horizontal blanking interval;

wherein the first negative going pulse has a first sync tip level, and the second negative going pulse has a second sync tip level; and

whereby the second sync tip level is lower or more negative than the first sync tip level.

74. The method of claim 73 wherein the first sync tip level is a substantially normal sync tip level and the second sync tip level is lower or more negative than the substantially normal first sync tip level.

75. The method of claim 74 wherein a positive going pulse is inserted or added after the second negative going pulse or after the second sync tip level.

76. Apparatus for synthesizing a copy protection signal having horizontal blanking intervals, comprising:

a circuit for generating or providing a first and/or a second negative going pulse in a horizontal blanking interval;

wherein the first negative going pulse has a first sync tip level, and the second negative going pulse has a second sync tip level; and

wherein the second sync tip level is lower or more negative than the first sync tip level.

77. The apparatus of claim 76 wherein the first sync tip level is a substantially normal sync tip level and the second sync tip level is lower or more negative than the substantially normal first sync tip level.

78. The apparatus of claim 77 including:

a circuit for inserting or adding a positive going pulse after the second negative going pulse or after the second sync tip level.

79. A method of modifying a video signal and/or synthesizing a video copy protection signal having video lines, a sync pulse tip level, and horizontal blanking intervals, comprising:

providing, inserting or adding a negative going pulse in a portion of the horizontal blanking interval;

wherein the negative going pulse has a lower or more negative level than the sync pulse tip level; and

wherein a positive going pulse is inserted or added immediately after the negative going pulse.

80. The method of claim 79 wherein the negative going pulse has a duration in the range of about 0.8 microsecond to about 1.3 microseconds.

81. The method of claim 79 wherein the negative going pulse is a pseudo sync pulse and the positive going pulse is an automatic gain control (AGC) pulse.

82. Apparatus for modifying a video signal and/or synthesizing a video copy protection signal having video lines, a sync pulse tip level, and horizontal blanking intervals, comprising:

a circuit for providing, inserting or adding a negative going pulse in a portion of the horizontal blanking interval;

wherein the negative going pulse has a lower or more negative level than the sync pulse tip level; and

wherein a positive going pulse is inserted or added immediately after the negative going pulse.

83. The apparatus of claim 82 wherein the negative going pulse has a duration in the range of about 0.8 microsecond to about 1.3 microseconds.

84. The apparatus of claim 82 wherein the negative going pulse is a pseudo sync pulse and the positive going pulse is an automatic gain control (AGC) pulse.

85. A method of providing or synthesizing an enhanced automatic gain control (AGC) copy protection effect in a video signal having video lines and horizontal blanking intervals, comprising:

adding or inserting a negative going pulse followed by a positive going pulse in a horizontal blanking interval in one or more selected video lines;

wherein the negative going pulse extends below any other negative going pulse in the horizontal blanking interval of the one or more selected video lines; and

wherein the copy protection effect is enhanced by the negative going pulse extension.

86. Apparatus for providing or synthesizing an enhanced automatic gain control (AGC) copy protection effect in a video signal having video lines and horizontal blanking intervals, comprising:

a circuit for adding or inserting a negative going pulse followed by a positive going pulse in a horizontal blanking interval in one or more selected video lines;

wherein the negative going pulse extends below any other negative going pulse in the horizontal blanking interval of the one or more selected video lines; and

wherein the copy protection effect is enhanced by the negative going pulse extension.

87. A method of providing or synthesizing a video copy protection signal, comprising:

forming a negative going waveform in a horizontal blanking interval, wherein the negative going waveform includes a leading or negative going edge, a first sync tip level and a second sync tip level;

wherein the second sync tip level is more negative or of a lower level than the first sync tip level; and

inserting or adding a positive going pulse immediately following the second sync tip level.

88. The method of claim 87 wherein the first sync tip level is the sync tip level of a horizontal sync pulse and wherein the positive going pulse is an automatic gain control (AGC) pulse.

89. Apparatus for providing or synthesizing a video copy protection signal, comprising:

a circuit for forming a negative going waveform in a horizontal blanking interval, wherein the negative going waveform includes a leading or negative going edge, a first sync tip level and a second sync tip level;

wherein the second sync tip level is more negative or of a lower level than the first sync tip level; and

a circuit for inserting or adding a positive going pulse immediately following the second sync tip level.

90. The apparatus of claim 89 wherein the first sync tip level is the sync tip level of a horizontal sync pulse and wherein the positive going pulse is an automatic gain control (AGC) pulse.

91. A method of providing or synthesizing a video copy protection signal, comprising:

inserting or adding an amplitude extending pulse in the latter portion of a horizontal sync pulse interval, wherein the amplitude extending pulse is more negative in level than a normal sync pulse tip level; and

adding or inserting a positive going pulse after the amplitude extending pulse to provide or to synthesize the video copy protection signal.

92. Apparatus for providing or synthesizing a video copy protection signal, comprising:

a circuit for inserting or adding an amplitude extending pulse in the latter portion of a horizontal sync pulse interval, wherein the amplitude extending pulse is more negative in level than a normal sync pulse tip level; and

a circuit for adding or inserting a positive going pulse after the amplitude extending pulse to provide or to synthesize the video copy protection signal.

93. A method of providing or synthesizing a video copy protection signal in a video signal having a first negative going pulse in a horizontal blanking interval, wherein the first negative going pulse has a leading edge followed by a negative sync tip level referenced to a blanking or black level, comprising:

inserting a second negative going pulse of lower negative sync tip level than the sync tip level of the first negative going pulse, whereby the sync tip voltage or level of the first negative going pulse is higher than the sync tip voltage or level of the second negative going pulse, and wherein the second negative going pulse is added or inserted after the leading edge of the first negative going pulse; and

inserting a positive going pulse after the second negative going pulse to provide or synthesize the video copy protection signal.

94. Apparatus for providing or synthesizing a video copy protection signal in a video signal having a first negative going pulse in a horizontal blanking interval, wherein the first negative going pulse has a leading edge followed by a negative sync tip level referenced to a blanking or black level, comprising:

a circuit for inserting a second negative going pulse of lower negative sync tip level than the sync tip level of the first negative going pulse, whereby the sync tip voltage or level of the first negative going pulse is higher or greater than the sync tip voltage or level of the second negative going pulse and wherein the second negative going pulse is added or inserted after the leading edge of the first negative going pulse; and

a circuit for inserting a positive going pulse after the second negative going pulse to provide or synthesize the video copy protection signal.

95. Apparatus for inserting or providing extended negative going pulses in one or more horizontal blanking intervals of a video signal, comprising:

a circuit for inserting or providing the extended negative going pulses such that the extended negative going pulses have a lower tip level than the tip level of a normal sync tip, comprising:

an input for receiving the video signal;

a generator circuit coupled to the video signal, wherein the generator circuit generates, adds, and/or inserts an extended negative going pulse in one or more horizontal blanking interval(s) of selected video lines, and wherein the tip level of the extended negative going pulse is lower than a normal sync tip level of a horizontal blanking interval.

96. The apparatus of claim 95 further comprising:

a circuit for adding, inserting or combining a positive going pulse after the leading edge of the extended negative going pulse to form a pulse pair.