Robert Boschgmbh

Bts Broadcast Television Systems Gmbh

Hans-Peter Richter

Reiner Noske

Jurgen Heitmann

Gerhard Wischermann

Gerhard Illetschko

Winfried Deckelmann

Stefan Ott

Color television signals obtained by scanning a still picture are converted into digital video signals and stored in video frame memory for delaying the signals. Undelayed and delayed digital video signals are added together to produce a luminance signal in which the color carrier is suppressed. A circuit for detecting a change of picture provides a start signal after which the first frame of a still picture is stored and is then recycled until there is another picture change. To reduce the effect of recycling, the continuously supplied picture signal is modified by a factor of 1-k, and the recycled picture is modified by the factor k, wherein k varies between 0 and 1 (or 100%) and is a gradually rising function whose rise time extends over a multiplicity, for example 2-4, video frame periods.

Still picture decoder for color television signals having a phase

A test pattern generator for digital television signals produces a zone plate pattern on an orthogonal pixel raster generated by pixel and line counters. The counter outputs are supplied to respective ROMs each storing a parabolic function. Their outputs are added to define zone plate circles on the basis of the circle equation x.sup.2 =y.sup.2 =r.sup.2. Circular patterns of evenly spaced color bars are produced by interposing a square root extracting ROM ahead of another ROM which converts the phase values into amplitude values. The optional interposition of a square root function after the addition and before the conversion into amplitude values provides a different circular test pattern. It can be readily modified in various ways under control of a microprocessor or EPROM.

Test pattern signal generator for producing zone plate and other test

A generator of circular zone plate signals for testing digital television signals, particularly those in circuits conforming with CCIR-Rec. 601, contains counters operating at horizontal and vertical sampling scan frequencies for producing an orthogonal pattern. The phase values generated by ROMs in response to the horizontal and vertical counters are combined additively and then converted into amplitude values by another set of ROMs separately for the luminance and chrominance signals. The counters also drive still another set of PROMs that provide, through a logic circuit, modulation of the luminance signal to show horizontal and vertical frequency markers that can be turned on and off by switches. The horizontal marker PROM also produces chrominance blanking signals for eliminating frequency components above half the sampling frequency.

Zone plate signal generator

Both the analog and the video component of a television signal are converted to digital form, the audio component being converted at a much lower sample rate with a word length which is an integral multiple of the video word length. The digital audio component is then compressed by use of a temporary memory and read-out therefrom at a rate that is half of the sample rate of the digtal video component, after which the word length is halved and the word rate doubled in a shift register circuit. In that form the audio component is inserted in horizontal blanking intervals of the video component in a compatible form by a multiplexer, the output of which is read into a single picture field or full picture memory under control of an address generator clocked in synchronism with the incoming video component. The buffer memory is read-out at a rate controlled by a reference signal such as is used for synchronism in a television studio. On the output side the digital video and audio components of the television signal are separated by a demultiplexer, the audio word length is doubled and the word rate halved and the still compressed audio signal is expanded, to make available a substantially continuous digital component. The audio component can then be converted to analog form and will be correctly timed for accompanying the digital video component converted to analog form at the output of the demultiplexer. Separate audio signal delay circuits are thus avoided by the use of relatively simple multiplexing circuits and audio processing circuits.

Method and apparatus for maintaining audio/ video synchronism in a

The synchronously demodulated chrominance signals (C.sub.1d, C.sub.2d) each alternately represent, line by line, the sum and difference of the color difference signals U and V. They are supplied to a multiplexer (21) switched by a meander wave having a 2H oscillation period and supplied therefrom to an accumulator for evaluation of the synchronizing color carrier bursts. During the burst, a succession of sampling frequency pulses sample the burst portion of one chrominance signal (C.sub.2d) with the results being added in an accumulator and then loaded in a first register (25) to provide a control signal for the color carrier oscillator and from the burst portion of the other chrominance signal (C.sub.1d) a potential is similarly produced by the accumulator, loaded in a second register (26) and evaluated in a PROM to determine whether the switching of the reversal circuit or one of the color difference signals (V) is timed for the correct horizontal line or for the wrong one. In the latter case, the meander wave is held for a half period of its oscillation which in effect inverts it, thereby correcting its timing.

Apparatus for decoding a PAL standard color television signal

A single television signal delay chain is interconnected with linear combination matrices for frame comb filtering and line comb filtering. Related circuits provide correction signals for controllably eliminating the frame or the line comb filtering. Detectors are provided for movement and for edges in the picture content and these detectors supply signals to a picture blending circuit for selecting the most appropriate kind of comb filtering for the current picture content. The circuits operate on a digital basis with a sampling frequency which is an integral multiple of the line scanning frequency.

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Gross-Bieberau, Germany

Hans-Peter Richter