US 4,233,622 A · SECAM-PAL Converter

Abstract

A SECAM-encoded chrominance signal is converted to a chrominance signal of a quasi-PAL form for further processing in PAL decoder apparatus. Converter includes an FM detector serving to demodulate respective SECAM subcarriers sequentially, and a modulator wherein the color-difference signals recovered by the FM detector amplitude modulate in appropriate sequence quadrature-related phases of PAL subcarrier frequency oscillations derived from the PAL decoder. The color-difference signals supplied to the modulator are augmented by line rate pedestals effecting the insertion of bursts in the quasi-PAL signal developed by the modulator. The phasing of the inserted bursts alternates between a first phase corresponding to the oscillation phase subject to modulation by R-Y color-difference signals, and a second phase differing from the first phase by 180.degree.. Insertion of bursts of the first phase immediately precedes the development of R-Y modulated subcarrier waves by the modulator, while insertion of bursts of the second phase immediately precedes the development of B-Y modulated subcarrier waves by the modulator.

Claims6

Dependent claims

Apparatus for converting chrominance information encoded in SECAM fashion to a chrominance signal suitable for application to a PAL decoder, said chrominance information appearing during image portions of successive line intervals, said image portions of said line intervals following blanking portions thereof;

said apparatus comprising:
frequency discriminator means, responsive to said chrominance information encoded in SECAM fashion, for sequentially developing, during image portions of successive line intervals, respective first and second color-difference signals;
a source of oscillations of a frequency corresponding to the standard PAL color subcarrier frequency;
and
means, responsive to the output of said frequency discriminator means and the output of said source of oscillations, for developing an output chrominance signal comprising (a), during alternate line intervals, oscillations of said PAL color subcarrier frequency, having a first phase and modulated in amplitude in accordance with said first color-difference signal, and immediately preceded by substantially constant amplitude bursts of oscillations of said PAL color subcarrier frequency and of said first phase, and (b), during intervening line intervals, oscillations of said PAL color subcarrier frequency, having a second phase differing from said first phase by 90.degree. and modulated in accordance with said second color-difference signal, and immediately preceded by substantially constant amplitude bursts of oscillations of said PAL color subcarrier frequency and of a third phase differing from said first phase by 180.degree..

2 more elements

said apparatus comprising:
frequency discriminator means, responsive to said chrominance information encoded in SECAM fashion, for sequentially developing, during image portions of successive line intervals, respective first and second color-difference signals;
a source of oscillations of a frequency corresponding to the standard PAL color subcarrier frequency;
and
means, responsive to the output of said frequency discriminator means and the output of said source of oscillations, for developing an output chrominance signal comprising (a), during alternate line intervals, oscillations of said PAL color subcarrier frequency, having a first phase and modulated in amplitude in accordance with said first color-difference signal, and immediately preceded by substantially constant amplitude bursts of oscillations of said PAL color subcarrier frequency and of said first phase, and (b), during intervening line intervals, oscillations of said PAL color subcarrier frequency, having a second phase differing from said first phase by 90.degree. and modulated in amplitude in accordance with said second color-difference signal, and immediately preceded by substantially constant amplitude bursts of oscillations of said PAL color subcarrier frequency and of a third phase differing from said first phase by 180.degree.;
wherein said output chrominance signal developing means includes:
means, having a subcarrier input terminal and a modulating signal input terminal, for amplitude modulating oscillations delivered to said subcarrier input terminal in accordance with signals delivered to said modulating signal input terminal;
means for augmenting the color-difference signal output of said frequency discriminator means with burst gating pulses respectively occupying a given segment of each blanking portion of said successive line intervals;
means for applying the augmented color-difference signal output to said modulating signal input terminal;
and
means, responsive to oscillations from said source, for delivering to said subcarrier input terminal:
(1) oscillations of said PAL color subcarrier frequency and of said first phase, during the image portion of those line intervals when said first color difference signal is developed by said frequency discriminator means;
(2) oscillations of said PAL color subcarrier frequency and of said second phase, during the image portion of those line intervals when said second color difference signal is developed by said frequency discriminator means;
(3) oscillations of said PAL color subcarrier frequency and of said third phase, during each of said blanking portion segments which immediately precede development of said second color difference signal by said frequency discriminator means;
and
(4) oscillations of said PAL color subcarrier frequency and of said first phase, during each of said blanking portion segments which immediately precede development of said first color difference signal by said frequency discriminator means.

13 more elements

A color television receiver subject to alternative operation in a SECAM-encoded signal reception mode and a PAL-encoded signal reception mode;

said receiver including apparatus for converting chrominance information encoded in SECAM fashion to a chrominance signal suitable for application to a PAL decoder, said chrominance information appearing during image portions of successive line intervals, said image portions of said line intervals following blanking portions thereof;
wherein said converting apparatus comprises:
frequency discriminator means, responsive to said chrominance information encoded in SECAM fashion, for sequentially developing, during image portions of successive line intervals, respective first and second color-difference signals;
a source of oscillations of a frequency corresponding to the standard PAL color subcarrier frequency;
and
means, responsive to the output of said frequency discriminator means and the output of said source of oscillations, for developing an output chrominance signal comprising (a), during alternate line intervals, oscillations of said PAL color subcarrier frequency, having a first phase and modulated in amplitude in accordance with said first color-difference signal, and immediately preceded by substantially constant amplitude bursts of oscillations of said PAL color subcarrier frequency and of said first phase, and (b), during intervening line intervals, oscillations of said PAL color subcarrier frequency, having a second phase differing from said first phase by 90.degree. and modulated in amplitude in accordance with said second color-difference signal, and immediately preceded by substantially constant amplitude bursts of oscillations of said PAL color subcarrier frequency and of a third phase differing from said first phase by 180.degree.;
said receiver also including:
a 1-H delay line having an input and an output;
a first synchronous detector responsive to the additive combination of signals derived from the input and output of said delay line;
a second synchronous detector responsive to the subtractive combination of signals derived from the input and output of said delay line;
means coupled to said source of oscillations for applying oscillations of said second phase to said second synchronous detector;
means responsive to oscillations from said source for supplying oscillations of said first phase to said first synchronous detector during alternate line intervals and for supplying oscillations of said third phase to said first synchronous detector during the intervening line intervals;
burst separator means for passing signals only during said blanking portion segments of said successive line intervals;
a phase detector responsive to the output of said first separating means for developing a phase control signal for said source of oscillations;
means for coupling said phase control signal to said source of oscillations;
a first signal path, independent of said frequency discriminating means and said output chrominance signal developing means, and selectively enabled during receiver operation in said PAL-encoded signal reception mode, for supplying received signals to the inputs of said delay line and said burst separator means;
a second signal path, enabled only during receiver operation in said SECAM-encoded signal reception mode, for supplying said output chrominance signal to the inputs of said delay line and said burst separator means;
and
means for disabling said phase control signal coupling means during receiver operation in said SECAM-encoded signal reception mode, and for enabling said phase control signal coupling means during receiver operation in said PAL-encoded signal reception mode.

16 more elements

Dependencies are inferred from the claim text.

SECAM-PAL Converter

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SECAM-PAL Converter

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Abstract

Claims6