Abstract: A video signal processing apparatus used for a video tape recorder performs chrominance signal processing which is digitalized. The chrominance signal is up-converted and phase-shifted in a recording block, and, in a reproducing block, phase-shifted in the opposite direction, filtered by a comb filter, compensated for jitter, and up-converted to the original chrominance signal. Both the recording block and the reproducing block are digitalized or only the reproducing block is digitalized. The digital chrominance signal processing circuit includes an A/D converter, a digital phase shifter, a digital comb filter, a digital jitter compensator, and a D/A converter.

Abstract: A magnetic recording and playback apparatus for teletext signals which accurately records and reproduces the teletext signal superposed within the vertical blanking period of television signal, includes at least one wide band filter, at least one narrow band filter, a filter selection switch which switches at least one filter for a luminance signal processing system to the wide band filter and at least one filter for a chrominance signal processing system to the narrow band filter, and a control circuit which generates a control signal for controlling the filter selection switch. The control circuit generates the control signal only during a specified period where the teletext signal is superposed. In case a comb filter is used, a switch is provided for selectively passing an output of the comb filter and an input video signal to the succeeding stages and a control circuit for producing a control signal to allow the input video signal to pass during a specified period where the teletext signal is superposed.

Abstract: A video signal recording/reproducing apparatus for recording and reproducing a video signal onto and from a recording medium with a magnetic head. In this apparatus, the recording chrominance signal processing block is provided with a circuit for producing a continuous oscillation signal having the same frequency, gain and phase with those of a normal color burst signal, a switch for normally passing the chrominance signal and, at a period including the normal color burst signal and longer than the duration of the normal color burst signal, passing the continuous oscillation signal, so that a chrominance signal is obtained at the output of the switch with a duration expanded color burst signal. This chrominance signal is mixed with the frequency converted chrominance signal, and the thus mixed signal is recorded on the recording medium. The duration expanded color burst signal is contracted to the normal duration of color burst signal by a muting circuit in the reproduced chrominance signal processing block.

Abstract: A dropout compensating apparatus used in a video signal recording/reproducing apparatus employs a digital delay circuit such as a digital memory. An input video signal is converted to a digital signal by an A/D converter. The digital signal is applied via a first switch to the digital delay circuit where it is delayed by a specified period. The delayed digital signal is converted to a delayed video signal by a D/A converter. The delayed video signal is applied to a second switch. A dropout detector produces a dropout detected signal when a dropout occurs in the input video signal. The first switch normally passes the digital signal from the A/D converter and is responsive to the dropout detected signal for passing the delayed digital signal from the digital delay circuit back to the digital delay circuit. The second switch normally passes the input video signal as it is and is also responsive to the dropout detected signal for passing the delayed video signal from the D/A converter.

Abstract: A digital noise reducing apparatus improves the signal to noise ratio (S/N) of a luminance signal of a video signal reproduced from a recording medium. This apparatus includes: an analog to digital (A/D) converting circuit for converting the luminance signal into a digital luminance signal; a digital delay circuit for delaying the digital luminance signal by one horizontal scanning period (1H); a first calculating circuit for calculating the difference between the digital luminance signal and the delayed digital luminance signal; a limiting circuit for limiting the amplitude of an output signal of the first calculating circuit, and a second calculating circuit for subtracting a signal output which is from the limiting circuit from the digital luminance signal. The apparatus operates to reduce noise at the line offset frequency of the luminance signal.

Abstract: A video disc reproducing apparatus is provided with a pickup by which the information recorded on a video disc is detected as a variation in electrostatic capacity. The signal output from the pickup is processed so as to generate a control signal proportional to the logarithm of the pickup signal. This control signal is then utilized to control the pressure of the pickup on the video disc. Element functions of the apparatus may be combined such that an automatic gain control device may also serve to generate the logarithmic control signal.

Abstract: A magnetic recording/reproducing apparatus has a rotor drum with a group of rotary magnetic heads mounted thereon, a reproducing amplifier, a recording/reproducing mode switching circuit, a head selection circuit, a control circuit and a DC voltage source. The control signal circuit and the DC voltage source receive a control signal transmitted from a stator drum through a rotary transformer and produce signals for controlling the mode switching circuit and the head selecting circuit and a DC voltage for energizing all the circuits on the rotor drum, respectively.

Abstract: A downconverter having a voltage controlled local oscillator supplied with a control DC voltage, obtained from a frequency discriminator and responding to variations of the difference between a reference produced by a stable oscillator and an output signal frequency of the downconverter is employed for facilitating output channel alterations without changing local oscillator stability characteristics. When used as a television channel converter, it changes a channel in the UHF or SHF band to VHF channels.