JPH06153227A - Color signal correction circuit - Google Patents

Abstract

PURPOSE:To recover a deteriorated color signal into the same state before the deterioration. CONSTITUTION:A color signal correction circuit 1 includes a high speed Fourier transformation device 3 applying high speed Fourier transformation to a 1st signal 3a corresponding to a burst signal Caa of an input color signal Ca and a 2nd signal 3b corresponding to all input color signals Ca including the burst signal Caa respectively, a computing element 8 using the 1st and 2nd signals 3a, 3b, a 3rd signal 7a obtained by applying high speed Fourier transformation to an ideal burst signal 5a and making arithmetic operation to compensate a transmission loss of the input color signal Ca and a high speed inverse Fourier transformation device 9 applying high speed inverse Fourier transformation to an output of the computing element 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color signal correction circuit for correcting a color signal deteriorated in a transmission system.

[0002]

2. Description of the Related Art A color signal correction circuit used in a reproducing system of a VTR corrects a color signal in a reproducing color signal system by using transmission system distortion information obtained from a reproducing luminance signal system.

[0003]

However, since the conventional color signal correction circuit corrects the color signal by using the transmission distortion information of the reproduction luminance signal system, the color signal has a certain degree of amplitude distortion. Corrected but not in terms of phase distortion. The conventional color signal correction circuit is not based on the idea of restoring the deteriorated reproduced color signal to the state before the deterioration.

[0004]

SUMMARY OF THE INVENTION Therefore, the present invention is to solve the above-mentioned problems, and corresponds to all the input color signals including the first signal corresponding to the burst signal of the input color signal and the input color signal including the burst signal. A fast Fourier transformer for outputting a fast Fourier transform and a second signal for
An arithmetic unit for performing an arithmetic operation for compensating for a transmission loss in the input color signal using the first and second signals and a third signal obtained by performing a fast Fourier transform on the ideal burst signal, and the arithmetic unit And a fast inverse Fourier transformer for performing a fast inverse Fourier transform of the output of the input color signal, the calculation of the computing unit being (second signal × third signal) / first signal The present invention provides a color signal correction circuit characterized by correcting deterioration.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIGS. 1 to 3 are block diagrams showing first to third embodiments of a color signal correction circuit according to the present invention, respectively.

The color signal correction circuit according to the present invention is used, for example, in a VTR reproduction system, and has a transmission characteristic of a VTR recording / reproduction system (transmission system) (that is, a deteriorated color signal burst signal / ideal burst). Signal), and using this transmission characteristic, the deteriorated color signal is restored to the state before the deterioration.

In the color signal correction circuit 1 of the first embodiment shown in FIG. 1, Ca is an input color signal deteriorated by the influence of the transmission system. Then, this input color signal Ca
Is an output color signal Cb corrected through the color signal correction circuit 1. The color signal correction circuit 1 for correcting the color signal as described above includes the A / D converter 2, the fast Fourier transformer 3, the crystal oscillator 4, the burst gate 5, the A / D converter 6, the fast Fourier transformer 7, and the correction. Circuit 8, fast inverse Fourier transformer 9, D / A converter 10, detector K, timer T
It consists of

The input color signal Ca is input to the A / D converter 2 and A / D converted. The digital signal 2a output from the A / D converter 2 is converted by the fast Fourier transformer 3 from information on the time axis to information on the frequency axis. The fast Fourier transformer 3 outputs a first signal 3a corresponding to the burst signal Caa of the input color signal Ca and a second signal 3b corresponding to all of the input color signal Ca.

Further, the ideal burst signal 5a which is generated by intermittently outputting the oscillation output 4a output from the crystal oscillator 4 by the burst gate 5 at a certain time interval is A /
After being converted into the digital signal 6a through the D converter 6, it is Fourier-transformed by the fast Fourier transformer 7 to obtain a third signal.
Is output as the signal 7a. This ideal burst signal 5
The output timing of a is the burst signal C of the color signal Ca.
It is synchronized with the output timing of aa, and these synchronizations may be performed as follows, for example. Composite video signal Ba
(Before the input color signal Ca and the luminance signal are separated), the horizontal synchronizing sync pulse Ba in the
The time from the falling portion of a to the rising portion of the burst signal Caa is defined by time t1. Therefore, the detector K detects the falling time of the horizontal synchronizing pulse Baa of the composite video signal Ba and outputs the detection pulse P1, and the time T1 starts from the application start time of this detection pulse P1 by the timer T.
And outputs the detection pulse P2. In this way, the ideal burst signal 5a which is output for a predetermined time in synchronization with the output timing of the burst signal Caa of the input color signal Ca is obtained from the burst gate 5 which is opened for a predetermined time in synchronization with the output of the detection pulse P2.

Reference numeral 8 denotes the above-mentioned first to third signals 3a, 3
b, 7a is a correction circuit (calculator) that obtains the transmission characteristic of the transmission system and restores the deteriorated input color signal Ca from this transmission characteristic. The first calculator 81 and the second calculator 8
2 and.

The input color signal C is input to the first arithmetic unit 81.
a first signal 3a corresponding to the burst signal Caa of a,
The third signal 7a corresponding to the ideal burst signal 5a is input, and the calculation of (first signal 3a / third signal 7a) is performed here. Assuming that the ideal burst signal 5a is the same as the burst signal of the color signal Ca before deterioration, the transmission characteristic of the transmission system
That is, the deterioration characteristic of the input color signal Ca can be obtained as a value on the frequency axis. The calculation result of the first calculator 81 representing the transmission characteristic is output as the fourth signal 81a.

A second signal 82a representing a transmission characteristic and a second signal 3b corresponding to all the input color signals Ca are input to the second calculator 82. In the second calculator 82, a calculation of (second signal 3b / fourth signal 81a) is performed. This calculation involves multiplying the fast Fourier transformed input color signal Ca by the reciprocal of the fourth signal 81a representing the transmission characteristic, whereby the fast Fourier transformed input color signal Ca is not degraded on the frequency axis. Can be restored to its original state. The calculation result of the second calculator 82 is output as the fifth signal 82a.

A fifth signal 82 output from the second computing unit
a is the output of the entire correction circuit 8. Where: fourth signal 81a = (first signal 3a / third signal 7
a) fifth signal 82a = (second signal 3b / fourth signal 8)
1a), the fifth signal 82a = (second signal 3b × third signal 7)
a) / first signal 3a.

Then, the fifth output which is the output of the entire correction circuit 8
Signal 82a is converted from information on the frequency axis to information on the time axis by the fast inverse Fourier transformer 9. The digital signal 9a output from the fast inverse Fourier transformer 9 is converted into an analog signal by the D / A converter 10, and the output color signal C is output.
b.

Since the color signal correction circuit 1 is configured as described above, the deteriorated color signal can be restored to the state before the deterioration, and the color signal is corrected from both the amplitude distortion point and the phase distortion point. There is an advantage that

In the color signal correction circuit 100 of the second embodiment shown in FIG. 2 which will be described below, in the color signal correction circuit 1 described above, the crystal oscillator 4, the burst gate 5 and the A / D are used.
The converter 6 and the fast Fourier transformer 7 are put together in one ROM 70, and at the time when the detection pulse P2 is output, the ROM 7
The third signal 7a described above is read from 0. The same components as those in the first embodiment are designated by the same reference numerals.

In the color signal correction circuit 1000 of the third embodiment shown in FIG. 3, the digital signal 2a obtained by A / D converting the input color signal Ca is converted into the color difference signal BY and the color difference signal RY. The correction is performed after decomposing into two digital signals corresponding to and. Color signal correction circuit 100
0 is different from the color signal correction circuit 100 of the second embodiment in that the digital signal 2a is the first digital signal 11a and the second digital signal 11b corresponding to the color difference signal BY and the color difference signal RY. The color demodulator 11 for decomposing into two is provided in the subsequent stage of the A / D converter 2, two fast Fourier transformers 31 and 32, and two first arithmetic units 811 and 8
12 and two second calculators 821 and 822, and a correction circuit 80 and two fast inverse Fourier transformers 91 and 92.
And the color modulator 1 in front of the D / A converter 10.
2 is provided. The same components as those in the second embodiment are designated by the same reference numerals.

In this color signal correction circuit 1000, the digital signal 2a obtained by A / D converting the input color signal Ca corresponds to the color difference signal BY and the color difference signal RY.
Since the correction is carried out after being decomposed into the two digital signals 11a and 11b, the clock frequency of the digital circuit is higher than that in the case where the digital signal 2a is directly Fourier-corrected as in the first and second embodiments. Can be reduced. The reason for this is that, when decomposed as described above, the input color signals having a center frequency of 3.58 MHz are changed into signals having the highest frequency of 500 KHz. Since the clock frequency of the digital circuit can be reduced in this way, the circuit can be constructed using an inexpensive digital circuit. Further, since the correction is performed after the data is decomposed into the two digital signals 11a and 11b, it is possible to apply a technique of performing processing while thinning out the data of these digital signals 11a and 11b. By thinning out data in this way, the processing speed of the entire circuit can be increased. Note that FIG.
In the above, the two digital signals 11a and 11b were processed by different paths.
11b is not output at the same time, so if the concept of time division (time sharing) is applied, the fast Fourier transformers 31 and 32 and the first arithmetic units 811 and 81
It is also conceivable that the number of each of the second and second arithmetic units 821 and 822 and the fast inverse Fourier transformers 91 and 92 is one.

[0020]

As can be seen from the above description, in the color signal correction circuit according to the present invention, the deteriorated color signal can be restored to the state before the deterioration, and the color signal has a point of amplitude distortion and a phase distortion. The effect is that it is corrected from both points.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of a color signal correction circuit according to the present invention.

FIG. 2 is a block diagram showing a second embodiment of the same color signal correction circuit.

FIG. 3 is a block diagram showing a third embodiment of the same color signal correction circuit.

[Explanation of symbols]

 1 Color Signal Correction Circuit 2 A / D Converter 3 Fast Fourier Transformer 8 Operation Unit (Correction Circuit) 9 Fast Inverse Fourier Transformer 10 D / A Converter Ca Input Color Signal Caa Burst Signal 5a Ideal Burst Signal 3a First Signal 3b second signal 7a third signal

Claims (1)

[Claims] 1. A fast Fourier transformer for outputting a fast Fourier transform output of a first signal corresponding to a burst signal of an input color signal and a second signal corresponding to all of the input color signals including the burst signal, respectively. An arithmetic unit for performing an arithmetic operation for compensating for a transmission loss in the input color signal using the first and second signals and a third signal obtained by performing a fast Fourier transform on the ideal burst signal; Fast inverse Fourier transformer for performing a fast inverse Fourier transform on the output of the input device, the operation of the operation device is (second signal × third signal) / first signal A color signal correction circuit, which corrects transmission deterioration.