Robert Boschgmbh

Michael Hausdorfer

Heinz Hess

Jurgen Heitmann

Klaus Lehmann

A decision signal for switching or fading between foreground and background television signals in accordance with the chroma-key method is subjected to vertical scan delay filtering for line signal averaging in television signals to avoid disturbance of the decision signal by results of the field interlace feature of a standard television signal. The delay for such filtering is provided by a random access digital memory and provides a delay of one period of the vertical scan frequency. Filtering is obtained by averaging delayed and undelayed output of the chromakey color selection signal or by recursively filtering that signal utilizing the same period and type of delay.

Method and circuit apparatus for combining two television signals

The luminance signal is connected to a transmission channel which includes a subtraction circuit (3) and a branch circuit, to apply a subtraction signal to the subtraction circuit. The branch circuit includes a band-pass filter connected to receive the luminance signal and a controlled amplifier (5) serially connected with a band-pass filter. The branch circuit is additionally connected to a circuit to derive the control signal for the controlled amplifier, the control signal being obtained from a control signal generating circuit which generates the control signal as a function of the portion of the luminance signal which is within the band-pass width of the chrominance subcarrier. The signal can be obtained, for example, by forming a level signal representative of the luminance components based on the color difference signals; and/or by synchronous demodulation of the luminance signal with respect to the chrominance subcarrier; and/or by a comb filter.

Color mixing or interference reduction circuit in color TV decoding

To improve TV image reproduction, and to suppress interference in the luminance channel of a color TV decoder, a controlled portion of the amplitude of a part of a TV signal, which part is within the frequency range of the chroma subcarrier, is subtracted from the TV signal. The portion of the luminance signal which is within the frequency range of the chroma subcarrier is rectified to derive a control signal and the amplitude of the controlled portion which is subtracted is controlled as a function of the controlled signal. Non-linearities of reproduction by the TV tube and of human perception can be compensated within the circuit which includes, for example, a matrix, and a non-linear signal transfer channel, or derived from the TV tube itself.

Method and system for interference suppression in a color television

The invention concerns a method and apparatus for mixing a foreground signal and a background signal under the control of a switching signal which is derived as a function of the color of the foreground signal. In response to the switching signal selected parts of the foreground signal are desaturated while maintaining their luminance component substantially unchanged; non-corresponding parts of the background signal are suppressed. Both signals so treated are additively superimposed. This leads to a better representation of fine details in the contours of a foreground object of interest.

Method for mixing two color television signals

For reduction of the relative noise amplitude a modulator or chopper stage is provided in front of the input of a video preamplifier and at the preamplifier output balanced demodulators are provided with a subtraction circuit combining their outputs. Preferably the carrier wave used for chopping or modulation is applied to the demodulators for synchronous demodulation, with a phase shifter if necessary in the carrier supplied to the demodulators for compensation of the signal propogation time through the preamplifier.

Low-noise video preamplifier

The present invention relates to a chrominance sub-carrier modifier for PAL-color television signals, particularly for signals from a video storage medium operating in a still picture mode.

Chrominance sub-carrier modifier for PAL-color television signals

To transmit color video information from one point to another within a color television studio complex, particularly for distribution of source signals which are intended to be processed in a digital mode at another location in the studio, the information is transmitted in form of a color television signal comprising a luminance component having a given frequency range and a carrier frequency chrominance component having a frequency range outside that of the luminance component, the chrominance component simultaneously obtaining the full color information for the luminance component. The selected mode permits the ready separation of the luminance and chrominance components without perceptible quality losses, and recording and cutting processing.

Method for producing color television signals

Each one of plural SECAM color-T.V. signals to be mixed is processed as follows: the signal is split into a luminance component and a video-frequency color component; the color component is amplitude-modulated onto a carrier, and the thusly modulated carrier is superimposed onto the respective luminance component to yield a frequency-multiplex signal which is then applied to one respective input channel of a mixer. The output signal of the mixer is split into a mixed luminance component and an amplitude-modulated mixed color component. The latter must be amplitude-demodulated, and then is frequency-modulated and superimposed onto the mixed luminance component to yield the desired mixed SECAM color-T.V. signal. Suppressed carrier amplitude-modulation is used, and each original video-frequency color component has superimposed, during the horizontal blanking intervals, reference oscillations from the carrier used for amplitude-modulation. The carrier signal needed by the amplitude-demodulator is derived from or furnished in dependence upon the amplitude of the reference oscillations in the horizontal blanking intervals of the amplitude-demodulated mixed color component, the reference oscillations having a phase which differs by 90.degree. from the phase which the carrier signal used for amplitude-modulation has outside the horizontal blanking intervals.

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Muhltal, Germany

Michael Hausdorfer