US 4,283,738 A · NTSC to PAL transcoder

Abstract

R-Y and B-Y color difference components of an NTSC format input signal are demodulated to base-band and a burst flag is added to the R-Y signal. Both the B-Y signal which includes the original base-band burst component and the R-Y signal with the added burst flag are then remodulated on respective quadrature related PAL subcarriers. Alternate line phase reversal is achieved in one embodiment by switching the phase of the R-Y demodulator and inverting the burst flag every other line. In another embodiment the added flag is of constant polarity and the R-Y remodulator reference phase is switched. The remodulator outputs are combined with a luminance component of the NTSC input signal whereby a non-standard video output signal is produced having an NTSC luminance component and a PAL chrominance component to enable monitoring of the NTSC input signal on a PAL color television monitor operating at 525/60 line/field rate.

Claims10

Dependent claims

A transcoder comprising first and second synchronous demodulators, input means for supplying a quadrature amplitude modulated input signal to each of said synchronous demodulators, first oscillator means for supplying first and second quadrature related reference signals to said first and second demodulators, respectively, for causing said demodulators to produce respective first and second baseband output signals, second oscillator means for producing third and fourth quadrature related reference signals, a first modulator responsive to said third reference signal and said first baseband signal for producing a first modulated output signal, a second modulator responsive to said fourth reference signal and said second baseband signal for producing a second modulated output signal and output means for combining said modulated output signals to provide a composite output signal, characterized by:

pulse generator means for producing periodic spaced apart pulses;
combiner means for combining said periodic spaced apart pulses with said second baseband signal for causing said second modulated output signal produced by said second modulator to include a modulated periodic pulse component;
and
means for periodically reversing the phase of a selected one of said second and fourth reference signals.

1 more element

A transcoder for use with a source of NTSC standard luminance and chrominance input video signals for producing an non-standard video output signal having a PAL format chrominance component and an NTSC format luminance component so as to enable monitoring of said input video signals on a PAL type color television monitor, said transcoder comprising:

first demodulator-remodulator means for demodulating said chrominance input signal along a first demodulation axis to provide a first baseband signal having a B-Y color difference component and a burst component and for remodulating said first baseband signal on a first PAL subcarrier;
second demodulator-remodulator means for demodulating said chrominance input signal along a second demodulation axis in quadrature with said first demodulation axis for providing a second baseband signal having an R-Y color difference component devoid of burst component and for remodulating said second baseband signal on a second PAL subcarrier in quadrature with said first PAL subcarrier;
burst flag generator means responsive to said luminance input signal for producing a baseband burst flag signal;
combiner means for combining said baseband burst flag signal with said second baseband signal;
circuit means synchronized with a recurrent horizontal synchronizing component of said luminance signal and coupled to said second demodulator-remodulator means for effectively reversing the phase of the remodulated output signal thereof upon the occurrence of each horizontal synchronizing component;
and
output means for combining said luminance input signal with the output signals produced by said first and second demodulator-remodulator means to produce said non-standard output signal.

4 more elements

Dependencies are inferred from the claim text.

NTSC to PAL transcoder

Life of this patent

NTSC to PAL transcoder

Life of this patent

Abstract

Claims10