Processing arrangement and correcting device for color television signals

Claim 2

A processing arrangement for processing, prior to transmission or recording, a video frequency composite colour television signal including: horizontal sync. pulses, a chrominance information comprising a modulated chrominance sub-carrier outside the blanking intervals, and burst signals each of which is formed by a train of oscillations at the sub-carrier frequency and is transmitted in a horizontal blanking interval, and a picture signal, said arrangement comprising first and second processing circuits having respective inputs for receiving said composite signal, and respective outputs, said first circuit comprising first selecting means for selecting said sync. pulses, and a first correcting circuit for receiving said sync. pulses and imparting thereto a predetermined amplitude, said second circuit comprising second selecting means, having an output, for selecting an upper portion, including said chrominance information, of the frequency spectrum of said composite signal, at least when said chrominance information is formed by said burst signals, and a second correcting circuit for receiving the output signal from said second selecting means and giving it a predetermined amplitude, said arrangement further comprising a mixer circuit having two inputs respectively coupled to said outputs of said first and second processing circuits, and an output for delivering a processed video frequency composite signal.

Claim 3

A processing arrangement as claimed in claim 1, wherein said first selecting means comprises a low pass filter, having an output, for selecting the lower portion, complementary to said upper portion, of said frequency spectrum, and an amplitude splitter having first and second outputs, and an input coupled to said filter output, for separating the horizontal sync. pulses from the other components of the output signal from said filter and directing said pulses to said splitter first output and said others components to said splitter second output; and wherein said first correcting circuit comprises: an amplifier having an output, a gain control input and a signal input connected to said splitter first output; generating means, having an output, for supplying pulses coinciding with said sync. pulses; a source having an output for supplying a bias voltage having the nominal amplitude of said sync. pulses; an adder circuit having two inputs, respectively connected to said splitter second output and to said amplifier output, and an output forming the output of said first processing circuit; sampling means having a control input connected to said output of said generating means, a signal input connected to said adder output, and an output; and a comparator having a first input coupled to said sampling means output, a second input connected to said output of said source, and an output coupled to said gain control input.

Claim 4

A processing arrangement as claimed in claim 1, for processing a composite colour signal including an amplitude-modulated chrominance sub-carrier, wherein said second selecting means comprise: a filter, having an output, for selecting said upper portion of said frequency spectrum, first and second outputs; first generating means supplying a gating signal coinciding with said burst signals; and switching means, controlled by said gating signal, for directing the output signal from said filter either to said first or to said second output of said second selecting means according to whether said output signal includes or not oscillations of one of said burst signals; and wherein said second correcting circuit comprises: a first amplifier having a signal input connected to said first output, a gain control input, and an output; a second amplifier having a signal input connected to said second output, and an output; second generating means, having an output, for supplying a short pulse derived from said gating signal; a source having an output for suppling a bias voltage having the nominal amplitude of said oscillations; an adder having two inputs respectively coupled to said outputs of said first and second amplifiers, and an output forming said output of said second processing circuit; a detector having an input coupled to said output of said adder and an output; sampling means having a control input connected to said output of said second generating means, a signal input connected to said detector output, and an output; and a comparator having a first input coupled to said sampling means output, a second input connected to said output of said source, and an output coupled to said gain control input.

Claim 5

A processing arrangement as claimed in claim 1, for processing a composite signal including a chrominance sub-carrier frequency modulated by the chrominance information and amplitude modulated by means of a sub-carrier frequency pre-emphasis filter, wherein said second selecting means comprise a filter, having an output, for selecting said upper portion of said frequency spectrum, and wherein said second correcting circuit comprises: an amplifier having a signal input connected to said filter output, a gain control input and an output forming said second processing circuit output; a de-emphasis filter having an input connected to said amplifier output; a detector circuit having an output, for detecting the output signal from said de-emphasis filter; means for generating sampling pulses in the course of the back porche of each horizontal blanking interval; a source having an output for supplying a bias voltage having the nominal amplitude of said sync. pulses; a sampling means, having a trigger input coupled to said generating means output, a signal input coupled to said detector output and an output; a comparator having a first input connected to said sampling means output, a second input connected to said output of said source and an output coupled to said gain control input.

Claim 6

A processing arrangement as claimed in claim 1, further comprising a test pulse circuit for introducing into a predetermined available line of each one of the vertical blanking intervals of the processed composite video fequency signal, a test pulse when this signal has been processed.

Claim 7

A device adapted for automatically correcting the amplitude of a composite video frequency signal, including horizontal sync. pulses, which has been processed by means of a processing arrangement as claimed in claim 1, said device comprising: an amplifier having a signal input for receiving said composite signal, a gain control input and an output; generating means, having an output, for supplying pulses coinciding with said sync. pulses; a source having an output for supplying a bias voltage having the nominal amplitude of said sync. pulses; sampling means, for sampling said horizontal sync. pulses, having a trigger input coupled to said output of said generating means, a signal input connected to said amplifier output, and an output; and a comparator having a first input coupled to said sampling means output, a second input coupled to said output of said source, and an output coupled to said control input; said amplifier output forming the output of said automatically correcting device.