Abstract: A method and apparatus for synchronizing a randomized video signal to a phase-locked sampling system. The phase-locked system is part of a scrambling apparatus capable of scrambling and subsequent descrambling of video signals recorded on videotape recorders which undesirably introduce time-base errors into the luminance/chrominance phase relationship. These time-base errors are removed without use of a time-base corrector by programmable delay line memory circuitry which introduces a programmable amount of delay into the video path. The delay line includes a programmable length FIFO memory module.

Abstract: A method and apparatus for disabling the effect of copy-protect signals placed in a recording video signals which is based on differences in the characteristics of television and VCR circuitry. Copy-protect signals include pseudo-sync pulses and/or added AGC pulses in the blanking interval of a video signal. The specific method described includes altering the level of the video signal during the vertical blanking interval, e.g., level-shifting, so as to render the copy-protect signals ineffective to prevent unauthorized copying by a VCR. A circuit for achieving the method includes a sync separator for detecting the vertical blanking interval, pulse generating circuits for producing pulses of predetermined widths during this interval, and a summing circuit for summing the predetermined pulses with copy-protect signals thereby to shift their level.

Abstract: Audio signals are scrambled by single side band modulating with a modulation signal carrier having a frequency lying within the audio frequency band so that the signals are frequency translated upward. The scrambled audio signals are descrambled after broadcasting or recording/reproducing using a substantially identical modulation carrier signal to restore the original audio signals. Security is enhanced by varying the frequency of the modulation carrier signal in a pseudo random manner in response to start (ACLK) and rate (A0, A1) control signals. The control signals accompany the scrambled audio signals and are used during the descrambling process to aid in the generation of the descrambling carrier modulation signal.

Abstract: A method and apparatus for disabling the effect of copy-protect signals added to a video signal using differences in the characteristics of television and VCR circuitry. Copy-protect signals as described include pseudo-sync pulses and/or added AGC pulses in the vertical blanking intervals of a video signal. The specific method described includes increasing the effective frequency of the copy-protect signals during the vertical blanking intervals so as to achieve attenuation and/or low-pass filtering in the VCR circuitry to thereby render the signals ineffective in preventing copying. A circuit for achieving this method comprises pulse narrowing and/or pulse multiplication circuitry which effectively increases the high-frequency content of the pseudo-sync and/or AGC pulses.

Abstract: A video signal is modified so that a television receiver still produces a normal color picture from the modified signal, whereas a videotape recording of this signal produces generally unacceptable pictures. This invention relies on the fact that videotape recorders feature some form of automatic level control circuit. These automatic level control circuits measure the sync pulse level in the video signal and develop a gain correction signal for keeping the video level applied to an FM modulator in the videotape recording system at a fixed predetermined value. In accordance with the present invention either a positive or a negative pulse is added to the video signal immediately following the trailing edge of sync. The effect of these added pulses is to cause the automatic level control circuit in the recorder to assess the video level at either many times its actual value or as a fraction of its actual value.

Abstract: A system and method for generating a variable frequency sine wave carrier signal operates in response to a start signal and a rate signal. The system includes a first counter which drives a second counter via an EPROM; the second counter is clocked by the output of an oscillator. The output of the second counter is converted by filtering to the desired sine wave signal.

Abstract: Audio signals are scrambled by inverting the original; frequency spectrum so that frequency portions originally lying at the lower end of the audio frequency band are shifted to the upper end while those portions originally lying near the upper end of the band are shifted to the lower end. A pilot tone of known frequency is recorded along with the frequency shifted audio signals, along with accompanying video signal portions. Upon reproduction, any variations in phase and frequency introduction by the recording or reproduction process are tracked by the pilot tone, which is used to generate the demodulation signal for restoring the original frequency content of the audio signals.

Abstract: A technique for encrypting and decrypting information signals normally arranged as a succession of lines of active information, with each line having a line timing reference, such as color video information signals. The active video portion is time shifted with respect to the horizontal sync portion of the corresponding line using a predetermined slowly varying time shifting function. The time shifting information is conveyed to the decryption site by encoding the instantaneous vlue of the time shifting wave form for the beginning of each field in the vertical blanking portion of that field. To provide a reasonable maximum time shifting range, portions of the trailing edge of the active video in the preceding line and portions of the leading edge of the active video in the current line are discarded. During decryption, the original line timing and color burst signals are discarded and new signals are generated which are time displaced from the actie video portion by the original amount before encryption.

Abstract: A method and apparatus are described for preventing a dual deck video recorder from being used to record a copy-protected video signal. A switch is included on the recorder to indicate whether a video signal input to one of the deck locations for recording originates externally of the machine or internally at another deck location. Recording is prevented whenever the switch indicates that the video signal originates from the other deck location if the video signal at such location includes a selected copy-protect signal. If a video signal to be recorded comes from externally of the machine, copying of the same is prevented if (1) the video signal includes the copy-protect signal; or (2) the video signal to be copied is the same as the play back video signal and the latter has the selected copy-protect signal.

Abstract: Time sequential information signals, such as color video signals having a line timing reference and an active video portion, are encrypted by time shifting the active video signal portion towards and away from the line timing reference signal in psuedo-random fashion prior to broadcasting or recording on tape or disk and transmittal to the user. The signals are decrypted by an inverse time shifting technique. By limiting the amount of time shifting between lines, potential signal degradation for color video signals is minimized, and drop out compensation processing is minimally affected, so that the color resolution and picture quality are substantially unaffected.

Abstract: A video signal is modified so that a television receiver will still provide a normal color picture but which a video tape recorder will detect and prohibit its being recorded. A plurality of ordered pairs of pseudo-sync and positive pulses are added to the video signal vertical blanking interval following the normal sync pulse. A disabiling circuit associated with a recorder detects the modified signal. This detection may be by comparing the voltage differential between the pseudo-sync pulse tip and the positive pulse relative to the normal voltage differential between the sync pulse tip and the back porch of the blanking interval. Alternatively, the modified signal can be detected by identifying the pulse frequency of the signal in the blanking interval. A high frequency is indicative of the presence of the modified signal. Detection is also shown by peak-detecting the video signal and sampling this peak-detected signal during the vertical blanking period.

Abstract: A video signal is modified so that a television monitor/receiver still produces a normal picture from the modified signal, whereas a videotape recording of this signal produces generally unacceptable pictures. Videotape recorders have an automatic gain control circuit which 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 videotape recording 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 occuring sync pulse. These added pulses are clustered at the vertical blanking interval of each field to minimize the affect of the same on the viewability of the picture defined by the signal while still causing the automatic level control circuit in a recorder to assess the video level at many times its actual value.

Abstract: Added pseudo-sync pulses and AGC pulses are removed from a video signal to enable acceptable video recording thereof. The added signals previously interfered with acceptable video recording of the video signal because the automatic gain control of videotape recorders sensed false recording levels, while conventional televisions receivers were unaffected by those modifications to the video signal. Removal of the added pulses permits acceptable video recording of the previously modified video signal. A selectively-operable clipping circuit is used to remove selected negative-value components (i.e. pseudo-sync pulses) from the video signal, while added AGC pulses are effectively blanked from the video signal with an electrically-operable switch. Both the blanking and clipping functions are selectively achieved by sensing both the normal sync pulses of the video signal and the added pseudo-sync pulses.

Abstract: A video signal is modified so that a television receiver will still provide a normal color picture from the modified video signal while a videotape recording of the modified video signal produces generally unacceptable pictures. This invention relies on the fact that typical videocassette recorder automatic gain control systems cannot distinguish between the normal sync pulses (including equalizing or broad pulses) of a conventional video signal 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.

Abstract: A video signal of the type having phase modulation induced in the color burst component thereof to inhibit video tape recording, is modified to remove the phase modulation and permit acceptable video tape recording. The phase modulated color burst component of an incoming video signal drives a phase lock loop, which regenerates a color burst component free of the modulation for insertion into the video signal.

Abstract: A method and apparatus which modifies a color video signal in such a manner that a conventional television receiver produces a normal color picture from the modified signal, whereas a videotape recording made from the modified signal exhibits annoying color interference. This is achieved by phase modulating the color burst component of the video signal with a noise signal. A videotape recorder interprets the phase variation as a velocity error and alters the chrominance signal, giving rise to color noise in the videotape recording. The characteristics of the noise signal are chosen to preclude interfering with the receiver's subcarrier regenerator.