Abstract: The invention relates to color television receivers.Bursts which are transmitted during the line and field retrace-periods and whose frequencies change from one line to the other between 4.25 MHz (blue, luminance) and 4.40625 MHz (red-luminance) are used to obtain a color identification for each line.To that end a frequency-shift discriminator in which the chrominance subcarrier is switched between two paths, one path being direct and the other comprising a phase shifting circuit, the two parts (9, 10) being thereafter switched to the two inputs of a multiplier (4) whose output signal thus comprises a frequency-dependent DC component. According to the invention, the phase shifting circuit included in one of the paths is constituted by the so-called "cloche" filter (2) which is usually used in all SECAM television sets and which thus fulfills in the circuit according to the invention a special function in addition to its customary functions (FIG. 1).

Abstract: Gain control of signals processed in a digital TV receiver is split between serially connected coarse and fine gain blocks. The coarse gain block consists of bit shifters to shift the sample bits to greater or lesser significant bit positions which provides a 6 dB gain change for each bit position change. Fine gain control is performed in the digital-to-analog converters which ultimately produce the analog signals for driving the display tube. The digital-to-analog converters are selectively reset each sample period with reset pulses that are developed by a fine gain control. The output signal from the digital to analog converter is an amplitude and pulse width modulated signal. The average amplitude of the signal over a sample period is determined by the pulse width and is thus a function of the fine gain control.

Abstract: In a video signal processor for a progressive scanning system, an interlaced composite video signal, repeating at an f.sub.H line rate of approximately 16 KHz, is coupled to a comb filter. Separated luminance and chrominance signals are developed at respective output terminals of the comb filter. The chrominance signal is demodulated to develop color mixture signals. The luminance and color mixture signals are applied to a color matrix for generating a first set of R, G, B color signals, with each signal repeating at the f.sub.H line rate. A time compression circuit is coupled to the output of the color matrix for time compressing the R, G, B color signals to generate a comparable set of three time compressed and processed color signals, with each time compressed signal repeating at a double line rate of 2f.sub.H. The video signal processor is also capable of converting f.sub.H line rate, interlaced R, G, B signals, obtained from an external video source, into double line rate, non-interlaced signals.

Abstract: A television system having a fully compatible high-definition signal with extended aspect ratio information receivable at conventional resolution by conventional TV receivers without auxiliary apparatus with one TV channel carrying the conventional TV signal while high-frequency luminance and chrominance information plus extended aspect ratio information are provided in a second TV channel. The extended aspect ratio information including luminance and chrominance information is transmitted during the horizontal retrace interval of the second TV channel. The extended aspect ratio chrominance information comprises I.sub.e and Q.sub.e segments which are transmitted during alternate horizontal retrace intervals. Since the segments are alternately transmitted, a storage mechanism is provided so that a segment received during a previous horizontal retrace interval can be reused during the present horizontal retrace interval for displaying the complete chrominance edge information.

Abstract: In an NTSC system color television camera with a shading correction circuit, the correction circuit comprises differential amplifier means for comparing a level difference between Y and R signals and between Y and B signals to produce analog difference signals, analog-to-digital converter means for converting levels resulting from sampling the analog signals by clock pulses into digital signals, a random access memory for storing and reading the digital signals, and shading amplifier means responsive to the read-out signals to perform such an amplification that the chrominance signal level is made equal to the luminance signal level.

Abstract: A color sign inserting circuit for a video signal reproducing system is disclosed, which comprises a the color burst detecting circuit for extracting color burst from a video signal detected from a recording system, a flywheel oscillator locked to the average values of the frequency and phase of a color burst signal extracted from the color burst detecting circuit for detecting time axis variation components, a phase shifter for controlling the phase of the clock output of the flywheel oscillator, and a sign inserting circuit for superimposing the output of the phase shifter and a sign signal on the video signal. Display of an inserted sign in color in the reproduction of video thus can be realized by merely adding an inexpensive color signal shifter to the conventional functions necessary for the video signal processing.

Abstract: A conventional phase locking loop for locking a local oscillator in phase and frequency to a color burst signal in a television system requires a highly stable (i.e. crystal controlled) oscillator whose free running frequency must be individually adjusted to be as close as possible to the desired frequency. The present invention enables such adjustment to take place automatically in operation rather than as a separate manufacturing step. The output from the oscillator is compared in phase with the color burst signal to which it is to be locked. The output from the phase comparator is applied to one input of a differential amplifier whose output constitutes an error signal for application to a frequency controlling input of the oscillator. The error signal is also applied to a threshold control circuit which causes an up/down counter to count up or down when the error signal lies outside a predetermined range.

Abstract: Phase reversal of solely the chrominance component of only alternate frames of an NTSC format signal prior to pre-emphasis and again subsequent to de-emphasis permits simpler and less costly filter structure to be employed without any loss of filtering capability.

Abstract: A noise reducing circuit, including a circuit to reduce noises contained in a low frequency band with a clamping circuit, having a first circuit with an attenuating characteristic near a first frequency which is the upper frequency limit of a noise that can be reduced by the clamping circuit and a second circuit with a characteristic of the first circuit. The first circuit is provided in front of the clamping circuit and the second circuit following the clamping circuit.

Abstract: A signal processing apparatus includes a scaling device for increasing the magnitude of a signal from a source to better use the dynamic range of processing apparatus, and to reduce the effects of noise and error sources. This is particularly useful in a television receiver where the maximum magnitude of the (B-Y) chrominance signal component of a composite video signal is smaller than that of the (R-Y) chrominance signal component. To provide improved resolution of the (B-Y) signal components, a gain scaling arrangement increases the magnitude of the (B-Y) signal component to more closely approximate that of the (R-Y) signal component. In a TV receiver having digital signal processing apparatus, a digital multiplier scales the digitized (B-Y) signal component thereby to reduce the errors inherent in processing digital data having a limited number of bits, especially where such processing includes rounding or truncating operations which can introduce additional errors or decrease resolution.

Abstract: Frame comb filters effectively separate the chrominance and luminance components of composite video signal but produce undesirable image distortion when interframe motion occurs. Luminance cross components introduced into the comb filtered chrominance signal component during interframe motion intervals contribute to the image distortion. The luminance cross components are eliminated from the comb filtered chrominance signal by successively filtering the chrominance signal with a chrominance bandpass filter and an interline chrominance comb filter.

Abstract: A color television receiver includes AKB control circuits, operative during periodically recurring kinescope bias control intervals, for automatically adjusting the cathode biases of the receiver's color kinescope.

Abstract: The present invention provides a matching circuit for connecting a chrominance decoding integrated circuit normally connected by terminals to a conventional analog delay line so as to make it compatible with a digital delay line. This matching circuit comprises a switch connecting alternately each of the outputs of the integrated circuit to an analog-digital convertor connected to a digital delay line, to a digital-analog convertor, then to a switch routing the signal alternately to each of the two summators whose other inputs receive directly the output of the integrated circuit. The summators supply then respectively the chrominance signals R-Y and B-Y.

Abstract: A frame-to-frame comb filter system which reduces motion induced artifacts in the comb filtered luminance signal includes line comb filter circuitry for extracting luminance cross components from the comb filtered chrominance signal and reinserting them into the comb filtered luminance signal and a line comb filter in the luminance path following reinsertion of the luminance cross components to reject motion induced chrominance cross components occurring in the comb filtered luminance signal. The latter line comb filter is switched into the system during periods of interframe image motion.

Abstract: A two-color reading system includes binary encoders for signals of wide and narrow wavelength ranges. The reference level of the narrow wavelength encoder is set proportionately to the level of the wide wavelength signal by means of a voltage divider, so that the second color of the two color system may be more accurately separated.

Abstract: Motion induced image distortion resulting from processing video signals in a frame-to-frame comb filter is substantially reduced by extracting motion induced luminance cross components in frame combed chrominance signal and reinserting them in the frame combed luminance signal. The chrominance signal is applied to a low pass filter to extract luminance components for reinsertion in the combed luminance signal. Higher frequency luminance cross components required to completely compensate the combed luninance signal are rejected by the low pass filter, however, to account for the missing high frequency luminance cross components, the combed luminance signal is selectively low pass filtered during interframe motion intervals before reinsertion of the cross components.

Abstract: An auto-flesh circuit for a TV receiver is described which operates an I and Q color mixture signals to produce flesh corrected color mixture signals I' and Q'. The received I and Q signals are demodulated in respective circuitry to generate the magnitude and angle of their vector sum. The angle values are applied as address codes to a ROM programmed to produce the sines and cosines of the applied address codes. For address code angles corresponding to chrominance signals representing flesh tones, the values of the programmed sines and cosines correspond to values of flesh corrected chrominance angles. The sine and cosine values output by the ROM are then multiplied by the magnitude of the vector sum (chrominance magnitude) to produce corrected Q' and I' color mixture signals respectively.

Abstract: In a digital television receiver, a signal processing stage generates color mixture digital signals representing color picture information as components in a first color mixture coordinate system such as the I-Q system. The I and Q digital signals are applied to a read only memory look-up table in which memory locations are stored the logarithmic values of the signals in order to convert the signals into digital words represented in logarithmic form. A microprocessor or other digital circuit generates or retrieves digital coefficients in logarithmic form that enable the I and Q digital signals to be transformed into second color mixture digital signals representing the color picture information as components in a second color mixture coordinate system such as the R-Y, B-Y, color difference coordinate system. The I and Q digital signals in logarithmic form are applied to a first input of an adder.

Abstract: A subcarrier regenerator circuit for use in color television receiver demodulators. The regenerator includes a voltage-controlled oscillator and a fixed frequency oscillator set to the nominal subcarrier frequency. During the vertical retrace period, a phase detector forces the output of the voltage-controlled oscillator to match that of the fixed-frequency oscillator. The output of the detector is also stored. During the active vertical scan, the phase detector compares the voltage-controlled oscillator output with the color burst synchronization signal and produces an output which is added with the stored output. The added signal is used to adjust the output of the voltage-controlled oscillator to match the color burst signal in phase and frequency, so that the output can be used by the synchronous color signal demodulators.

Abstract: Digital representations of analog signals are limited in resolution accuracy by the number of bits in the digital output signal of an analog-to-digital converter which limits the number of analog output levels produceable by a digital-to-analog converter. The apparent resolution accuracy can be improved, however, by the addition of two "dithering" signals, one at a lower frequency and one at a higher frequency, to increase the number of transitions of the least significant bit (LSB) of the digital signals. In a television receiver employing digital signal processing apparatus, dither signals having magnitudes equivalent to 1/2 and 1/4 LSB and at frequencies related to the TV line frequency and the color subcarrier frequency are preferred.