WO2000005894A1 - Procede et appareil permettant d'emettre un signal qui rend inoperants les decodeurs de cable illegaux - Google Patents

Procede et appareil permettant d'emettre un signal qui rend inoperants les decodeurs de cable illegaux Download PDF

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Publication number
WO2000005894A1
WO2000005894A1 PCT/US1999/012387 US9912387W WO0005894A1 WO 2000005894 A1 WO2000005894 A1 WO 2000005894A1 US 9912387 W US9912387 W US 9912387W WO 0005894 A1 WO0005894 A1 WO 0005894A1
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WIPO (PCT)
Prior art keywords
signal
vertical
color burst
circuit
responsive
Prior art date
Application number
PCT/US1999/012387
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English (en)
Inventor
Ronald Quan
Original Assignee
Macrovision Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Macrovision Corporation filed Critical Macrovision Corporation
Priority to BR9912312-6A priority Critical patent/BR9912312A/pt
Priority to AU52033/99A priority patent/AU5203399A/en
Publication of WO2000005894A1 publication Critical patent/WO2000005894A1/fr

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N7/00—Television systems
    • H04N7/16—Analogue secrecy systems; Analogue subscription systems
    • H04N7/167—Systems rendering the television signal unintelligible and subsequently intelligible
    • H04N7/169—Systems operating in the time domain of the television signal
    • H04N7/1693—Systems operating in the time domain of the television signal by displacing synchronisation signals relative to active picture signals or vice versa

Definitions

  • This invention relates to video cable scrambling systems, and more particularly relates to a method and apparatus for inserting or otherwise adding a jamming signal in a video signal to defeat the illegal video cable decoders also known as cable "black boxes”.
  • the video level is adjusted via an amplifier 12, and then supplied to a low pass filter 14 and a comparator 16.
  • the comparator then generates a vertical timing signal V reset for a television sync generator circuit 18 which also receives a horizontal timing signal from a filter/slicer circuit 20.
  • V reset a vertical timing signal
  • the sync generator circuit 18 delivers composite sync for a viewable picture via a switcher 22.
  • the comparator 16 picks out the normally blanked lines in the vertical interval and generates a suitable vertical reset signal.
  • the color burst of the video signal is used for illegal decoding.
  • the lack of color burst in some lines of the vertical blanking interval identifies the vertical sync area.
  • the color burst is relied upon to provide the illegal decoding process.
  • the lack of burst in the vertical blanking interval (VBI) allows for the illegal generation of a reliable vertical rate reset signal. The fact is that in most video signals, scrambled or not, burst is not present for about 9 lines in the VBI.
  • the scrambled video signal is bandpass filtered in a filter 24 to provide a burst envelope signal which is supplied to a detection amplifier 26 and a phase lock loop (PLL) circuit 28.
  • the detection amplifier senses the burst envelope.
  • a one shot 30 triggers off the burst envelope leading edge and supplies a pulse which extends into the next video line (e.g., is 50 microseconds) and thus is referenced to the color burst, not the video signal.
  • a one shot 32 provides a short pulse (of about 2 to 3 microseconds) as a burst gate to the PLL circuit 28, which also receives the burst envelope signal.
  • the PLL circuit 28 supplies a burst signal and a clock reference to a sync regenerator circuit 36.
  • a retriggerable one shot 34 is triggered by the one shot 30 pulse and provides a pulse which is slightly longer than one video line, and which thus extends through the active video field so that the one shot 30 no longer sees the burst envelope. At this point the retriggerable one shot 34 turns off during most of the VBI (e.g., for about 20 video lines).
  • the output of one shot 34 comprises a regenerated vertical rate pulse, which is supplied to the sync regenerator circuit 36.
  • the latter circuit 36 supplies new sync/burst signals as well as an insert control signal to a switch circuit 38.
  • the switch circuit 38 also receives the scrambled video signal and, in response to the insert control signal, inserts the new sync/burst signals to descramble the signal sufficiently to provide a viewable video signal to an unauthorized user via an amplifier 40.
  • the present invention provides an added signal which jams or disrupts the illegal operation of the black box.
  • a key to creating the added signal is to cause the comparator, e.g., comparator 16, to generate an erroneous vertical reset signal.
  • lines near and within the vertical blanking interval are modified. This modification can consist of removing the broad vertical pulses of the vertical sync and then adding and/or inserting a jamming, i.e., unreliable, vertical signal in lines near the bottom and top portions of the active field.
  • This jamming signal is also added or inserted to lines in the vertical blanking interval (VBI) that do not have data and/or reference signals.
  • the unreliable vertical signal can be a time varying (for example, pedestal) voltage, of about blanking level to about peak white video level, during at least a portion of each modified horizontal line.
  • the cable black box (such as shown in Figure 1) outputs an unstable video signal, resulting in a concealed picture.
  • the present invention again provides an added signal which jams or disrupts the operation of the black box.
  • new color burst can be put into those lines normally lacking color burst in the VBI.
  • Color burst itself may also be modified, in frequency for example, such that only an authorized decoder can transform a modified burst into the correct one.
  • Alternate variations to that of modifying the burst can be an added signal in the form of a change in burst location, that is, in line and/or pixel locations.
  • the burst signal itself may be modified so that the cable black box receives the wrong color burst signal (i.e. burst frequency) while the authorized decoder senses the correct color burst. By making the cable black box sense the wrong burst, the timing circuitry within the cable black box will deliver erroneous counts thereby causing an unstable video signal output.
  • Figure 1 illustrates a typical illegal cable television decoder with adjustment for video gain and/or threshold levels.
  • Figure 2 illustrates another illegal cable decoder that relies on the use of color burst.
  • Figure 2A illustrates a standard color burst for a television signal.
  • Figure 2B illustrates a modification of color burst in accordance with the present invention by placing a wrong color burst signal where normal color burst is and then relocating normal color burst elsewhere.
  • Figure 2C illustrates a variation in the present invention of placing a wrong color burst signal in the sync area vicinity to upset the cable black box relying on burst. Normal burst is relocated elsewhere as depicted.
  • Figure 3 A illustrates a conventional television signal in the region of the vertical blanking interval (VBI) and its vicinity.
  • Figure 3B illustrates a modified television signal for defeating a cable black box such as that illustrated in Figure 1.
  • the vertical (broad) sync pulses are removed and/or modified.
  • lines designated by "A” have a jamming signal inserted and/or added.
  • the jamming signals cause the cable black box to mis-trigger and produce an unstable output.
  • Figure 3C illustrates a modified television signal for defeating a black box such as that of Figure 2, wherein color burst is inserted and/or added to those lines in the VBI vicinity that lacks color burst.
  • the inserted and/or added burst is designated by "B”. Note these added and/or inserted color bursts can be applied to the technique of Figure 3B as well.
  • Figure 4 and Figure 5 are block diagrams illustrating circuitry in accordance with the invention for defeating cable black boxes typified in Figure 1.
  • Figure 6 is a block diagram illustrating circuitry in accordance with the invention for defeating a cable black box typified in Figure 2.
  • Figure 7 A illustrates a modified color burst signal of the invention where the color burst frequency is not necessarily the correct frequency. The frequencies of color burst (envelopes) FI and/or F3 are different from the nominal burst frequency, and may be changed from line to line or field to field.
  • Figure 7B illustrates a modified optional color burst signal of the invention F5 for reference, and includes on that line color burst reference frequencies, F2 and F4.
  • Figure 7C and Figure 7D are block pictorial diagrams of the invention, illustrating how mixing for the sum frequency of FI and F2, or F3 and F4 produces the correct color frequency for the encoder and/or authorized decoder.
  • Figure 7E is a block pictorial diagram of the invention, illustrating how the correct combination of frequencies F2 or F4 is used to generate the correct color subcarrier frequency for the authorized decoder, using the DATA for the decoder.
  • Figure 8 A illustrates a conventionally scrambled signal with position modulated syncs.
  • Figure 8B illustrates a slightly improved scrambled signal which adds an edge-fill and/or added signal with edge modulation.
  • SI denotes a standard slice level for a sync separator, while S2 denotes the slice level for an illegal cable black box which still can provide a viewable picture.
  • Figures 9A-B illustrate a modification in the technique of Figure 8 where the edge fill signal now includes a form of amplitude modulation, with Figure 9C depicting an associated circuit.
  • Figures 10A-10K are waveforms illustrating various timing signals related to the edge fill modulation circuitry of Figure 11.
  • Figure 11 is a block diagram of the invention illustrating an implementation of the apparatus for providing the improved scrambling signals to defeat illegal cable decoders and/or TV sets.
  • Figures 12A-12D are waveforms illustrating portions of the video signal waveform that are modified so that an illegal cable decoder can be "fooled” into sensing the wrong vertical rate signal.
  • Figure 13 is a block diagram illustrating an implementation of the invention for generating, for example, the waveforms shown in Figures 12A-C.
  • Figure 1 illustrates an illegal cable black box that works by adjusting the video level and/or bias voltage into the high gain amplifier 12 of previous mention.
  • V Reset vertical rate
  • V Reset synchronizes the sync generator circuit 18 in a vertical fashion.
  • Optional horizontal timing into the sync generator circuit is established by extracting horizontal rate signals via the filter/slicer circuit 20.
  • Circuit 20 may be similar to circuit 16 and may also have filters and phase lock loop oscillators and/or slicing circuits.
  • the sync generator circuit 18 then reinserts a stable sync into the video signal via the switching circuit 22, whose output then is a video signal with replaced stable syncs and a viewable picture.
  • the decoder of Figure 1 will decode without too much problem. If the scrambled signal is missing vertical sync signal, then the circuit of Figure 1 will "slice" or detect at a level around or above blanking level. Since there is usually at least one line in the VBI vicinity near blanking level, a somewhat stable vertical rate signal will be available through the comparator 16 and a somewhat stable picture will be displayed. Under these conditions, the operator may have to periodically readjust the video gain and/or bias (slicing threshold of comparator 16) for a stable picture when the average picture level of the program video varies.
  • Figure 3B shows a solution to neutralizing the cable black box by removing (at least some of) the broad vertical sync pulses and/or eliminating some of the pre and post horizontal equalizing pulses and adding a jamming signal in lines, as designated by the notation "A", wherein "A” designates the lines available for inserting the jamming signal in the VBI and its vicinity in accordance with the invention.
  • Figure 3 A illustrates a conventional television signal in the VBI and vicinity. It is acknowledged that in scrambling systems, there are always some television lines reserved for DATA and reference signals in the VBI area.
  • the jamming signal will be inserted, for example, in the VBI where there are no DATA and/or reference signals for the authorized decoder, and in the lines before and after the VBI. Because of overscan conditions in television sets, some of the jamming signals can be placed about 5 lines before and/or after the VBI. In some cases, the DATA and reference signal can tolerate a level shifted signal added to cause problems for the cable black box.
  • the jamming signal can be a fixed or varying signal. For a fixed signal, for example, a 30% white signal may suffice. For a varying signal, the last few lines of the active field can be averaged and the average voltage can be used as the jamming signal.
  • Yet another method of the invention is to interpolate the average luminance voltage from the bottom of the field to the top of the field. This interpolated (average) voltage then is used to "fill" in the lines in the VBI. See the waveforms 46, 48 (or 53, 55) of the circuit of Figure 4. Filling in the non data and/or reference lines with a jamming signal in accordance with the invention, causes a black box operator to have to constantly readjust the cable black box for momentary stability. Part of the reason there is momentary stability is that the black box now is using the video signal as a source for a vertical rate reset signal. When the average picture levels change during the video program, the black box will have a different threshold level for a vertical reset signal which requires the continuous operator readjustment.
  • the preferred jamming signal (for, e.g. Figure 1) is to insert and/or add a voltage that varies, or is in the range, from about blanking level to about peak white level.
  • the jamming signal may be amplitude, and/or position and/or pulse width modulated.
  • the rate of modulation can be, for example, at about 11 Hz (periodic or random), although many other frequencies or waveforms will also cause black box instabilities.
  • each filled line may also have independent (for example, jamming) source generators.
  • the varying signal is asynchronous with the video field rate, and thus causes the black box's comparator to generate unstable vertical signals.
  • Figure 4 thus illustrates a block diagram of a circuit for neutralizing a cable black box of the type illustrated in Figure 1.
  • Video is fed to a low pass filter 50 to average the luminance (luma) video voltage.
  • Sample and hold circuits 52, 54 then store the average bottom picture and top picture luminance values, respectively, as depicted by waveforms 53, 55 (or 46,48).
  • a switch 56 supplies thus a signal that contains the bottom TV field luminance values before the VBI and the top TV field luminance values during the VBI.
  • An interpolation filter 58 such as a low pass filter, filters the output of switch 56 and supplies it to a summing circuit 60.
  • the other input to summing circuit 60 is a signal source, such as a varying voltage, VNl, varying over a voltage range within the overall range of from about blanking to about peak white level.
  • VNl varying voltage
  • the output of summing circuit 60 then supplies an interpolated voltage ranging from the bottom picture luminance values to the top picture luminance values, plus any "dithering" supplied from VNl.
  • the dotted lines on the waveforms 46, 48 show examples of the interpolated response of filter 58.
  • VN2 may be similar to VNl, it may be independent. This is done through a suirirning circuit 62. Of course if a constant voltage (i.e., 30% white level) is chosen, then a voltage V14 is connected to an input of the summing circuit 62 via a selector circuit 64 with the additional optional dithering noise voltage VN2 supplied to circuit 62. If just a varying voltage is desired, then VN2 can be set to vary and the other input of the summing circuit 62 can be set to zero for example.
  • a selector circuit 66 is coupled the outputs of the summing circuits 60, 62 and thence to one input of a switch 68.
  • the video is fed to a tuning circuit 70 to generate signals coincident with the VBI, top and/or bottom portion of the TV field, and DATA and/or reference signal line location.
  • Timing circuit 70 also generates a signal VSYNCR that controls the removal (or reduction) of the vertical sync (i.e., broad vertical signal pulses).
  • a switch circuit 72 is activated by the signal VSYNCR and outputs a signal substantially free of vertical sync signals. Because the broad vertical sync pulses are removed, it may be necessary to supply a new vertical sync identification signal, VSYNC LD for authorized decoding.
  • VSYNC ID can be a signal anywhere in the video signal and does not have to be of field rate.
  • the signal VSYNC ID is inserted via a switch circuit 74 whose output then is a video signal without standard vertical sync signal with an identification signal for the authorized decoder (identified as VSYNC ID).
  • the timing circuit 70 inserts the jamming signal by controlling the switch 68 of previous mention.
  • An AND circuit 76 and an inverter 78 control the insertion of the signal from the selection circuit 66 or the switch 74 during the active lines in the VBI area (and/or lines near it) not necessarily including lines with DATA or reference signals in the VBI.
  • the output of an amplifier 80 then has jamming signals inserted and vertical syncs removed or reduced, to cause instabilities for a cable black box of the type for example in Figure 1.
  • Figure 5 illustrates an alternative embodiment of a circuit that inserts wider than normal horizontal sync pulses (one or more per TV field) to the video signal at a preferably non synchronous rate (for example 27 HZ).
  • This wide horizontal sync pulse is used to further cause instabilities in the cable black box.
  • the cable box may sense these as vertical sync pulses. Since these pulses occur preferably asynchronously to the field and/or frame rate, the cable black box develops an erroneous vertical reset upon detecting them.
  • a circuit 82 inserts the wider than normal sync pulses along with a color burst.
  • a horizontal rate signal, WHBI which is about 13 microseconds for example and may be supplied from Figure 4, is fed to one input of an AND gate 84.
  • WHBI also is supplied to an inverter gate 86, whose output is used to clock in an asynchronous signal, VGEN.
  • the signal VGEN can be any waveform such as for example, a 27 HZ signal.
  • VGEN is fed to the "D" input of a flip flop 88, whose output is fed to an optional one line one shot, or half shot, timing circuit 90.
  • the output of timing circuit 90 (if used) is fed to the other input of the AND gate 84, whose output becomes logic high for a duration of about 13 microseconds (for example) at a 27 Hz rate and during a widened horizontal blanking interval.
  • the switch 82 then inserts the wide or modified sync with color burst accordingly into the mcoming video signal, which then is outputted via an amplifier 92.
  • the color burst can be modified such as in Figure 2B, Figure 2C and/or Figure 3C to cause the cable black box to generate an unstable output.
  • Figure 2A illustrates a standard color burst signal in an HBI. Modifications as illustrated in Figure 2B or Figure 2C that have the wrong color burst frequency will cause the cable black box to count incorrectly in its sync regeneration circuit.
  • the VBI is filled with color burst, leaving no lines in the television signal without burst, the cable black box then has no way of referencing a vertical signal.
  • burst filled in the VBI as shown in Figure 3C may have normal color burst and/or the type of burst modifications as shown in Figure 2B and Figure 2C. Also burst may be reduced or modified at various locations in the VBI vicinity so as to cause the cable black box to have an unstable vertical signal.
  • Figure 6 illustrates a way to modify a video signal such that the burst has incorrect frequencies.
  • video is fed to a sync separator/timing circuit 94.
  • a burst phase lock loop oscillator 96 is locked to the input's video signal.
  • a generator 98 with the incorrect frequency is fed to a modified burst inserter circuit 100.
  • Circuit 100 also receives timing and color burst signals as well. The output of circuit 100 then generates a video signal that causes cable black boxes dependent on burst to misbehave while allowing an authorized decoder to work properly.
  • Figure 7A illustrates a burst modification provided, for example, throughout the active field including the VBI. This modification applies the burst at a frequency such that the cable black box will lock to an erroneous frequency and thus cause an unstable output.
  • the correct color frequency at least one line per field for example, is set aside for reference signals as shown in Figure 7B.
  • a correct color frequency is provided by multiplying the modified bursts of Figure 7A by a continuous wave version of frequency F2 or F4.
  • the continuous wave version of F2 and/or F4 is accomplished by known phase lock loop oscillator techniques.
  • the scrambler's DATA as a control signal, the correct frequency is chosen for authorized decoding.
  • Figure 7E illustrates at the output of a band pass filter 102 (BPF) the correct color subcarrier frequency and/or phase, provided by a multiplier 104 and selected frequencies F 1 or F3 with F2 or F4.
  • BPF band pass filter 102
  • Figures 7C and 7D are simple examples of multiplying selected bursts by selected continuous wave frequencies. It should be noted that two different pairs of frequencies (for modified burst and reference frequency) can be used for extra security, as shown in Figure 7E. Referring back to Figure 1, one can see that the cable black box achieves its
  • jamming signal by providing slicing for the sync separator at levels generally above blanking level. See RADJ and RBIAS of Figure 1.
  • the inserted and/or added jamming signals in the VBI vicinity ( Figure 3B for example) cause erroneous vertical reset signals for the cable black box.
  • the jamming signals are the signals that are sliced or sensed since me jamming signals vary from about blanking level to about peak white level.
  • Figure 8 A illustrates a previously scrambled video signal with sync modulation.
  • an end of line edge 106 delivers a stable edge for the cable black box when it is adjusted for sensing above blanking level, even though an erroneous clamp pulse (ECP) signal has its leading edge 108 modulated.
  • ECP erroneous clamp pulse
  • a blanking sensing level S2 still will not supply a defeating position modulated signal to the cable black box because of the fact that the leading edge of the signal 107 and the trailing edge of an erroneous clamp pulse (ECP) 109 still are stable and detectable by the black box even though the edges 106 and 108 are modulated.
  • ECP erroneous clamp pulse
  • Figure 9 A illustrates a modification of Figure 8B which overcomes the problems of Figure 8B in that an edge fill signal 110 and/or an ECP signal 116 now include a form of amplitude modulation. That is, in Figure 9A, although a leading edge 112 of the signal 110 and a trailing edge 120 of signal 116 are fixed, the trailing edge 114 is position modulated and the edge fill signal 110 and the ECP signal 116 are amplitude modulated so that the stable edge 112 increases and decreases with time, i.e., periodically drops below the black box slice level S2, thereby causing an unstable edge and enhanced concealment.
  • the modulation of the edge fill and ECP signals can be tied together or can each be modulated at a respective rate.
  • FIG. 9B A further, even more effective embodiment is shown in Figure 9B where both edges of the edge fill signal 110 are position modulated along with the amplitude modulation. It has been found with some illegal cable decoders, that more effectiveness is achieved by modulating the edge fill signal 110. Further, turning on and off (or modulating) the edge fill signal and/or the ECP signal (as for example designated by numerals 110, 112, 114 and 116, 118, 120 in Figures 9A and 9B), causes the illegal decoder to generate an even more unviewable picture. Modulating the edge fill signal can be in the form of pulse width, pulse amplitude, pulse coding and/or frequency transformations and/or frequency modulation techniques.
  • edge 114 in Figure 9A can be a sync locking signal.
  • an annoying rate i.e., 500 milliseconds on and 200 milliseconds off
  • the illegal cable decoder and/or TV set causes a more unviewable picture.
  • FIGS 9A and 9B also show modulated erroneous clamp pulse signals (ECP) 116.
  • ECP erroneous clamp pulse signals
  • the illegal cable decoder and/or TV set may display a more annoying picture by periodic picture shifts and/or darkening.
  • Figures 9A and 9B also show a preferable finite rise time for the ECP signal leading edge 118 and a fixed trailing edge 120.
  • This finite rise time is used sometimes to allow the decoder's chroma circuits to lock on to the position modulated burst (riding on top of the ECP's amplitude modulated leading edge) without phase lock loop errors. It has been found when the rise time of edge 118 is at least 100 nanoseconds, for example, the decoder will output a stable and substantially error free subcarrier burst signal.
  • Figures 10A through 10K illustrate waveforms that generate the signals as shown in Figures 9A and 9B.
  • Figure 10B shows a starting timing signal, HBI, that is preferably larger than the normal horizontal blanking period (i.e., about 11.3 microseconds).
  • Figure 10C is timed off the leading edge of Figure 10B. It is varied by a modulating signal such that the trailing edge of Figure 10C is for example from about 100 nanoseconds to about 5.6 microseconds.
  • Figure 10C triggers a timing circuit one shot to generate the signal as seen in Figure 10E.
  • Figure 10E is then the not yet modulated version of pulse 110 and edges 112, 114 of Figure 9B.
  • the yet to be modulated version of pulse 110 and edges 112, 114 of Figure 9A are generated by the waveform as seen in Figure 10D which is generated by a varying one shot off the leading edge of signal HBI, Figure 10B.
  • the variation of pulse widths of Figure 10D is from about 500 nanoseconds to about 6 microseconds (for example).
  • Gap g", ( Figures 9 A, 9B) is designated in Figure 10F and is normally a fixed (sometimes varied) pulse which is triggered off the trailing edge of Figure 10D or 10E. This gap, g", is generally very small (i.e., less than 300 nanoseconds).
  • An actual sync modulation signal 122, Figure 10G, for concealment in unauthorized viewing is generated by a timing circuit from the trailing edge of Figures 10F or 10E or 10D.
  • the pulse width of 122 in Figure 10G is typically fixed (although can be also varied) at about 3 to 4 microseconds (for example). In some TV sets displaying a signal that has a horizontal sync width less than about 3 microseconds, the sync modulation is not effective for concealment.
  • Figure 10H illustrates another gap signal, gl, used by the decoder to establish a video reference level such as blanking level.
  • the signal gl is triggered off the trailing edge of signal 122 and has a duration of about 500 nanoseconds to 2 microseconds. A duration of about 1.2 microseconds is typical for signal gl, although other durations can be used for gl.
  • a burst gate signal shown in Figure 101 is used to reinsert color burst as shown in Figures 9A and 9B. It is triggered off the trailing edge of signal 122, the modulated sync signal.
  • the waveform of Figure 10J is timed off the trailing edge of gap pulse gl and becomes the basis for the ECP signal 116.
  • Figure 10K represents the unprocessed version of the ECP signal 116 as shown in Figures 9A and 9B.
  • Figure 10K shows an ECP signal within the HBI, which is preferable, while Figure 10J shows an ECP signal which may at times be outside the HBI.
  • Figure 11 illustrates an implementation of the apparatus for generating the improved scrambling signals for illegal cable decoders and/or TV sets.
  • Figure 11 is an example of an apparatus that produces signals similar to those shown in Figures 9 A and 9B.
  • the horizontal blanking signal HBI as described previously and shown in Figure 10b is used as a "master" timing signal.
  • a one shot timing circuit OS 124 triggers off the leading edge of the HBI to generate a signal as shown in Figure 9 A.
  • the OS 124 output pulse width is varied by a control voltage, Vcontl which determines the scrambling pattern as displayed on the TV through the illegal cable decoder and/or just through the TV set.
  • a frequency in the range of 450 HZ to 700 HZ provides the maximum concealment.
  • the preferred frequency of Vcontl is about 603 Hz with a variation of about 5.5 microsecond.
  • the variation of OS 124 can be larger (varied from about 500 nano-seconds to 7 microseconds) given a longer duration of HBI, for example, which may cause a slight loss in active video in the horizontal direction for the authorized decoded output.
  • the output of OS 124 is fed to a modulator 126 which is controlled by a signal Vmodl.
  • the output of modulator 126 is then preferably an amplitude modulated edge fill signal that is fed to an input of a summing amplifier circuit 128.
  • the gap signal g" of previous mention is generated by a OS 130 which is triggered by the trailing edge output of OS 124.
  • a new (modulated) sync signal (122 of Figure 10G), is generated by a OS 132 which is fed to an input of the summing amplifier circuit 128 and is triggered by the trailing edge of gap pulse g".
  • the trailing edge of signal 122 triggers a OS 134 to generate the gap signal gl of previous mention.
  • Signal 122 also triggers a OS 136 for a burst gate signal which in turn controls a burst gate switch 138.
  • the output of burst gate switch 138 is regenerated color burst for a signal such as shown in Figures 9 A and 9B and is fed to another input of the summing amplifier circuit 128.
  • a color subcarrier signal is regenerated by way of a chroma phase lock loop circuit or equivalent (not shown) and is fed to the input of the burst gate switch 138.
  • a OS 140 generates the ECP signal 116 ( Figures 9A, 9B, 10J) by triggering off the trailing edge of gap gl.
  • the output of OS 140 is fed to an AND gate 142.
  • the other input of AND gate 142 is the HBI signal and the output of ECPLLM is then a limited pulse width ECP signal which in turn is fed to another modulator circuit 144 with an optional filter for finite ECP rise and/or fall time.
  • Modulator 144 is controlled by a signal Vmod2 to preferably amplitude modulate the ECPLLM signal.
  • the output of modulator 144 is fed to yet another input of amplifier circuit 128.
  • the HBI signal controls a switch 146 to insert in the "expanded horizontal blanking interval" during at least a portion of the active field, the modulated edge fill, modulated sync, new burst, and modulated ECP signal as shown in Figure 9A.
  • the output of switch 146 is amplified by an amplifier circuit 148 whose output is fed to an RF modulator in the cable system (not shown) for example to transmit the improved scrambled signal for better concealment in TV sets and/or illegal cable decoders.
  • the OS 124 is replaced with a OS 150 and a control voltage Vcont along with a OS 152, as illustrated in the Figure 11 via phantom lines.
  • Figure 9C depicts an example of the type of high pass filter or differentiator circuit that may be used in illegal cable decoders to sense edges of the video signal. These edges can provide just enough horizontal and/or vertical rate signals for the illegal cable decoder to lock up to provide unauthorized viewing.
  • the illegal cable decoder however can be "fooled” into sensing the wrong vertical rate signal if the parts of the video signal are modified as shown in Figure 12.
  • a gap signal, g8 as shown in Figures 12A and 12B, a "fake” vertical signal is produced in conjunction with an amplitude modulated fake broad(vertical) pulse signal, 156.
  • signal 156 moves up and down (i.e., from -10 IRE to +100LRE in NTSC for example), a differentiated version of the waveforms of Figures 12A-C results in a waveform illustrated in Figure 12D.
  • the larger differentiated "vertical sync" signals 156' are amplitude modulated.
  • the illegal cable decoder will experience sporadic vertical locking.
  • the signals as designated in Figures 12A-C are preferably in the vertical blanking interval vicinity (and can move around or vary in number of lines) with preferably, the real vertical syncs removed and replaced as illustrated at the output of Figure 4.
  • signals of Figures 12A-C can be inserted in place of the control signal V14 in Figure 4. For simplicity only one video line is shown with the modification described above, whereas other lines can be modified.
  • Figure 12 is an example of g8 locations, whereby it should be noted that the number and locations of gaps g8 are not limited to those shown in Figures 12A-B.
  • the signals 156 of Figures 12A-C can also extend to -40 IRE as long as the authorized decoder will still decode correctly. Also the gap g8 may be varied in width, or may be eliminated in selected situations.
  • Figure 13 illustrates an implementation to generate, for example, the waveforms as shown in Figures 12A-C.
  • the circuit of Figure 13 can be used in any combination with the circuit of Figure 11 and/or Figure 4.
  • video is fed to a timing circuit 160, one output of which defines selected lines around the VBI.
  • Another output of circuit 160 defines the active horizontal line.
  • AND gates 162, 163 use these two signals to control or to insert the modified signal as described for example in Figures 12A-C.
  • the selected lines signal from circuit 160 is fed to a timing circuit OS 166, which is provided with a control signal Vcont2 which varies the pulse width of the OS 166.
  • OS circuit 166 applies pulse width modulation on the selected lines signal, the duration of which may be for example 635.5 microseconds or 10 lines of duration, or a range of varying line durations.
  • the output of OS circuit 166 may vary between 31 microseconds (a half line) to 635.5 microseconds (ten lines).
  • timing circuit 160 also outputs the gap signal g8.
  • An invertor circuit 168 inverts the logic level of g8 to blank the output of the AND gate 162 during the g8 signal.
  • the output of AND gate 162 then is a logic high version of the signal 156 in Figures 12A-B.
  • a modulator circuit 170 preferably amplitude modulates the output of AND gate 162 via control signal Vcont3.
  • the modulator circuit 170 can be other types of modulators such as pulse width, position, PCM, FM, and the like modulators.
  • surriming resistors RS 1 and RS2 the varying signal 156 controlled by the signal Vcont is summed with the g8 signal into an input of a switch 172.
  • the output of switch 172 is amplified by circuit 174 which generates a signal as shown in Figures 12A-C with optional pulse width modulation and/or truncation of g8 and/or signals 156 in particular selected lines.
  • edge fill with an ECP signal shows more (horizontal tearing) concealment than without an ECP signal. If the edge fill is turned completely off, there is no difference in concealment whether ECP is on or off. In addition, concealment is less.

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Two-Way Televisions, Distribution Of Moving Picture Or The Like (AREA)
  • Television Systems (AREA)

Abstract

Dans les décodeurs illégaux, on utilise des seuils réglables pour obtenir une image stable illégale. Du fait de l'ajout et/ou de l'introduction d'un brouillage, c'est-à-dire de signaux verticaux non fiables dans l'intervalle de suppression vertical et dans ses environs, le décodeur illégal ne peut pas se caler sur un signal vertical fiable. En raison des signaux de brouillage, le décodeur illégal produit une image ou un signal verticalement instable, ce qui a pour effet de maintenir le masquage. Les signaux de brouillage sont compatibles avec un décodeur de câble autorisé ; ils peuvent se présenter sous la forme d'une piste et maintenir le signal dans tout l'intervalle vertical et dans ses environs. Dans un mode de réalisation d'un signal vertical non fiable, on introduit un signal modulé compris entre le niveau de suppression et le niveau de blanc maximal dans l'intervalle de suppression vertical et/ou dans ses environs et/ou on ajoute ce signal modulé à cet intervalle et/ou à ses environs. Pour provoquer une instabilité horizontale dans le décodeur de câble illégal, on modifie l'intervalle de suppression horizontal de manière que, quel que soit le niveau de seuil (qu'il se situe au-dessous du niveau de suppression pour la détection de synchronisation ou au-dessus du niveau de suppression pour un signal horizontal généralement stable), une position et/ou un signal modulé est découpé ou détecté.
PCT/US1999/012387 1998-07-22 1999-07-20 Procede et appareil permettant d'emettre un signal qui rend inoperants les decodeurs de cable illegaux WO2000005894A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
BR9912312-6A BR9912312A (pt) 1998-07-22 1999-07-20 Método e aparelho para gerar um sinal que anula os decodificadores a cabo ilegais
AU52033/99A AU5203399A (en) 1998-07-22 1999-07-20 Method and apparatus for generating a signal that defeats illegal cable decoders

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US9370598P 1998-07-22 1998-07-22
US60/093,705 1998-07-22
US10004398P 1998-09-11 1998-09-11
US60/100,043 1998-09-11

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AU (1) AU5203399A (fr)
BR (1) BR9912312A (fr)
TW (1) TW425822B (fr)
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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6839433B1 (en) * 1998-07-22 2005-01-04 Macrovision Corporation Method and apparatus for generating a signal that defeats illegal cable decoders

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0543294A1 (fr) * 1991-11-19 1993-05-26 Macrovision Corporation Méthode et appareil pour cryptage et décryptage de signaux vidéo avec remplissage de bord
US5651065A (en) * 1995-03-09 1997-07-22 General Instrument Corporation Of Delaware Insertion of supplemental burst into video signals to thwart piracy and/or carry data
US5768376A (en) * 1995-10-25 1998-06-16 Samsung Electro-Mechanics Co., Ltd. Video signal scrambling apparatus

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0543294A1 (fr) * 1991-11-19 1993-05-26 Macrovision Corporation Méthode et appareil pour cryptage et décryptage de signaux vidéo avec remplissage de bord
US5651065A (en) * 1995-03-09 1997-07-22 General Instrument Corporation Of Delaware Insertion of supplemental burst into video signals to thwart piracy and/or carry data
US5768376A (en) * 1995-10-25 1998-06-16 Samsung Electro-Mechanics Co., Ltd. Video signal scrambling apparatus

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6839433B1 (en) * 1998-07-22 2005-01-04 Macrovision Corporation Method and apparatus for generating a signal that defeats illegal cable decoders

Also Published As

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BR9912312A (pt) 2001-05-08
TW425822B (en) 2001-03-11
AU5203399A (en) 2000-02-14

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