JPS61290892A - Television signal y/c separating circuit - Google Patents

Abstract

PURPOSE:To execute the separation of a luminance signal and the color difference signal of both systems of NTSC/PAL and to decrease a fact that the color difference signal leaks into the luminance signal, by changing the number of addresses and switching a signal level which is inputted to a chroma band pass filter by a switch. CONSTITUTION:C signal is outputted by two times of the C signal level of an original signal in case of NTSC and as the same level as the C signal of the original signal, in case of a PAL system therefore, by switching a switch 8, the C signal of the same level as the original signal is obtained. At the time, 0H-2H signals are inputted to a line correlation detecting circuit 10 and a line correlation is detected. A line correlation signal obtained in this circuit controls a switch 12, and in case when the line correlation is weak, a 1H signal is inputted as it is to a C signal band pass filter 11, and in case when the line correlation is strong, a C signal 9 obtained by a bomb-line filter is inputted to the C signal band pass filter 11. The output of a color difference signal band pass filter 11 is a C signal separated from a composite video signal, and also by eliminating this signal from the 1H signal, a separated Y signal can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a circuit that digitally separates a luminance signal and a color difference signal from composite video signals of the NTSC system and PAL system of a television.

(Prior art) As a conventional circuit of this type, "Television Society Journal, Vol.
l, 33. No. 4. April 1979, published by the Television Society of Japan, Takahiko Fukinuki, "Synthesis and Field of Color Television Signals", pp. 271-276. This is a method of digitally separating a color difference signal (hereinafter referred to as a Y signal) and a color difference signal (hereinafter referred to as a C signal).

FIG. 2 is a block diagram of an example of a conventional digital Y/C separation circuit. In the NTSC system, as shown in Figure 3, the subcarriers separated by one scanning line have a phase difference of 180 degrees, so for signals with line correlation, the signals separated by two scanning lines are added together to determine the center of gravity. A C signal was obtained by performing subtraction with a signal separated by a total of one scanning line, and a Y signal was obtained by subtracting this C signal from the original signal.

(Problem to be solved by the invention) However, in the circuit with the above configuration, in the PAL system,
As shown in Figure 3(b), since there is a phase difference of about 900 between the scanning lines, Y/C
Even in the NTSC system, there is a drawback in that the C signal leaks into the Y signal in signals where separation is not performed and there is no line correlation.

By sharing the common parts of the Y/C separation circuits of the above-mentioned PAL system and NTSC system, the present invention can eliminate line correlation without having separate Y/C separation circuits. It is an object of the present invention to provide a circuit that realizes 'Y/C separation without a C signal leaking into a Y signal even in a TV signal that is not present.

(Means for Solving the Problems) One feature of the present invention for achieving the above object is to use a filter that includes two delay circuits that delay a television signal by one scanning line, and a filter that includes two delay circuits that delay a television signal by one scanning line. In the Y/C separation circuit that connects the color difference signal band-pass filter that provides the color signal and the Y/C separation circuit that provides the luminance signal during calculation of the color signal and the original signal, the T
a V system discrimination circuit (2) and receiving an input television signal;
A comb-shaped filter (4,
5, 6, 16, 7), and means (8, 16a) for inputting the output of the comb filter to the color difference signal bandpass filter while varying the level according to the input TV system according to the determined system. It is in the TV signal Y/C separation circuit.

Another feature of the present invention is that when the line correlation is weak, the color difference signal is transmitted to the bandpass filter (TV signal delayed by one scanning line of the IH multiplied signal from the output of the comb filter). It is in the switching Y/C separation circuit.

Preferably, the television signal is converted into a digital signal and processed.

(Function) Contains a delay circuit for 2 scanning lines (4, 5
, 6, 7, 16) (For the D output, in the case of the NTSC system, a signal with twice the amplitude of the original signal is obtained due to the phase relationship of the subcarriers, and in the case of the PAL system, the same amplitude as the original signal is obtained. Therefore, in the case of the NTSC system, by setting the amplitude to 10, and in the case of the PAL system, by inputting the same amplitude to the color difference signal bandpass filter, the color (chroma) signal is output. The luminance (Y) signal is obtained by subtracting the chrominance signal from the television signal (IH multiplied signal) delayed by one scanning line.

Note that when the line correlation is weak, the IH multiplied signal is directly input to the color difference signal bandpass filter, and the color signal C is obtained as the output.

(Embodiment) FIG. 1 is a block diagram showing an embodiment of the present invention. The composite video signal inputted from the input terminal 1 is sent to a system discrimination circuit (cLK GEN) 2 which determines whether the input signal is an NTSC system or a FAT system, and reproduces the burst signal from the system carrier. By doing this, we obtain a clock that is four times that of the system support carrier, and the A/D converter 3
By supplying this clock to the input composite video signal, the input composite video signal is converted into a digital signal. The digitized composite video signal (hereinafter referred to as OH signal)
It is input to AM4 using an address that matches the TV system. Output from delay RAM4 (hereinafter referred to as IH double signal)
is input to the RAM 5 for one scanning line delay. The output signal of the RAM 5 will be referred to as a 2H signal hereinafter.

Changing the number of addresses given to RAM4 and RAM5 is done by NT.
This is because the number of samples per line is different between the SC method and the PAL method. As shown in Figure 3, in the NTSC system,
The subcarrier phases of two lines apart are in the same phase! D
Since there is a 180° phase difference in the PAL system, the adder 6 performs i) addition of the OH signal and the 2H signal, which are separated by two lines, so that the center of gravity of the pNTscNTSC system is
A composite video signal with twice the amplitude that is the same as the H times signal can be obtained, and in the PAL system, a Y signal with twice the amplitude whose center of gravity is the same as the IH times signal can be obtained. These signals are sent to the subtracter 7 after the amplitude is multiplied by the multiplier 16.
A C signal is obtained by performing calculations on the IH signal.

In the case of NTSC, the C signal obtained here is the C signal of the original signal.
It is output as twice the signal level, which is the same level as the C signal of the original XPALPAL signal. Therefore, by switching the switch 8 according to the NTSC/PAL system discrimination signal obtained by the system discrimination circuit 2, a C signal having the same level as the original signal is obtained.

At the same time, the line correlation is detected by inputting the OH, IH, and 2H signals to the line correlation detection circuit IO. The line correlation signal obtained here controls the switch 12,
If the line correlation is weak, input the IH multiplied signal as it is to the C signal band-pass filter 11; if the line correlation is strong, input the C signal 9 obtained by using a comb filter) to the C signal band-pass filter 11. . Here, C signal 9 is
The reason why this signal is input to the signal band pass filter 11 is that the comb filter acts on this signal up to the low frequency range of the Y signal.By passing this signal through the color difference signal band pass filter 11, only the chroma signal component is combed. This is for filtering.

The output of the color difference signal bandpass filter 11 is a C signal separated from the composite video signal, and a separated Y signal can be obtained by passing this signal through an IH multiplied signal.

(Effects of the Invention) As explained in detail above, according to the present invention, the NTSC system T
When separating a V composite video signal and a PAL TV composite video signal into a luminance signal and a color difference signal using a digital method,
Luminance signal/chrominance signal separation for both NTSC/PAL systems can be performed by simply changing the number of addresses and switching the chroma bandpass filter input signal and the input signal to/from the switch. Therefore, the circuit size can be significantly reduced compared to the conventional method, and the system that detects line correlation and switches between comb filter Y/C separation and bandpass filter Y/C separation allows TV composites with weak line correlation. Even in video signals, it can be expected to reduce the leakage of color difference signals into luminance signals.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a separation circuit according to the present invention, FIG. 2 is a block diagram of the separation circuit, and FIG. 3 is a diagram showing the relationship between subcarrier phase and scanning line in NTSC and PAL. 1: TV composite video signal input terminal, 2: Clock generation and TV system discrimination circuit, 3: Analog/digital conversion circuit, 4.5:1 scanning line delay circuit, 8.12: Changeover switch, 10: Line correlation detection circuit , 11; color difference signal bandpass filter; 14; delay circuit; 7.15: attenuator; 16: multiplier.

Claims (2)

[Claims] (1) A filter that includes two delay circuits that delay a television signal by one scanning line, a color difference signal bandpass filter that is connected to its output and provides a color signal, and a calculation of the color signal and original signal. In the Y/C separation circuit that provides the luminance signal, (a) A TV that determines whether the TV system is NTSC or PAL;
(b) A filter (4, 5, 6, 16, 7) that includes two 1-scan line delay circuits that receive the input television signal.
and (c) means (8, 16a) for inputting the output of the comb filter to the color difference signal bandpass filter by varying the level according to the input TV method according to the determined method.
A television signal Y/C separation circuit comprising: (2) A filter that includes two delay circuits that delay the television signal by one scanning line, a color difference signal bandpass filter that is connected to its output and provides a color signal, and a calculation of the color signal and the original signal. In the Y/C separation circuit that provides the luminance signal, (a) a TV system determination circuit that determines the television signal system (
2) and (b) a filter (4, 5, 6, 16, 7) containing two one-scan line delay circuits for receiving an input television signal.
(c) amplitude adjusting means (8, 16a) for varying the level of the output of the comb filter according to the input TV system according to the determined system; and (d) detecting the correlation of three adjacent scanning line information. a correlation detection circuit (10); and (e) switching means for inputting the output of the amplitude adjustment means or a signal obtained by delaying the input television signal by one scanning line to the color difference signal bandpass filter according to the magnitude of the detected correlation. (12) A digital Y/C characterized by having
Separation circuit.