JPH0822082B2 - Digital Y / C separation device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital Y / C separation device installed in a color television receiver.

2. Description of the Related Art In a standard color television signal such as the NTSC system, a luminance signal and a carrier color signal are frequency-interleaved and transmitted, so that it is generally difficult for the receiver side to completely separate the two.

Separation of such luminance signal and carrier color signal (Y / C separation)
As for the method, a method using a frequency separation filter that extracts a color signal with a band-pass filter whose center frequency is the color subcarrier frequency and a luminance signal with a low-pass filter that passes only frequency components lower than this, There is a comb filter method that uses the leaving relationship and the correlation between adjacent lines.

In addition, various Y / C separation methods as described above have been realized by making full use of digital signal processing technology, which is remarkable in the recent technological sophistication and circuit cost reduction.

Problems to be Solved by the Invention In the above-mentioned conventional Y / C separation method using the frequency separation filter, when a high frequency component appears in the luminance signal, it leaks to the color signal side and the image quality deteriorates.

Further, in the Y / C separation method using the comb filter, the interleaving relationship is broken during variable speed reproduction from a video tape recorder, so that there is a problem that image quality deteriorates significantly.

Means for Solving the Problems A digital Y / C separator according to the present invention is a Y / C separator using a comb filter, a Y / C separator using a frequency separation filter, and the outputs of both Y / C separators. A digital Y / C separation unit composed of a synthesizing circuit, an interleaving determination unit that determines the degree of interleaving in the Y / C separation target video signal, and phase synchronization with the horizontal synchronization signal extracted from the video signal. A clock supply unit that generates a clock signal and supplies it to the digital Y / C separation unit and the interleaving determination unit is provided.

The interleaving determination unit is a phase locked loop for reproducing a color subcarrier phase-synchronized with a color burst signal in a video signal, an A / D converter for converting the reproduced color subcarrier into a digital signal, and A one-line delay device that delays the digital color subcarrier by one line, an adder that adds the digital color subcarriers before and after the one-line delay device, and the output of this adder is added over one cycle of the color subcarrier. And an averaging circuit.

Further, in the digital Y / C separation device of the present invention, the combination circuit of the digital Y / C separation unit decreases the combination ratio with respect to the output of the Y / C separator by the comb filter as the output of the interleaving determination unit increases. Is configured.

Function In the digital Y / C separation device of the present invention, the deviation from the interleaving that occurs during variable speed reproduction from the video tape recorder is judged by the interleaving judging section, and the comb type is determined according to the size of the deviation. The synthesis ratio of the output of the Y / C separator by the filter is reduced.

As a result, it is possible to effectively prevent deterioration of image quality during variable speed reproduction.

 Hereinafter, further details of the present invention will be described together with examples.

Embodiment FIG. 1 is a block diagram showing the configuration of a digital Y / C separation device according to an embodiment of the present invention.

In FIG. 1, IN is an input terminal of an analog video signal for Y / C separation, 11 is an A / D converter, 12 is a digital Y / C separation unit, 13 is a timing generation unit, 14 is a clock generation unit, 15 Is an interleaving determination unit.

The digital Y / C separation unit 12 is a Y
/ C separator 12a and Y / C separator with frequency separation filter
12b and luminance signals Y1 and Y output from both Y / C separators
2 and the carrier color signals C1 and C2 are respectively weighted and combined to output a luminance signal Y and a carrier color signal C.
It consists of and.

The interleaving determination unit 15 includes a color subcarrier reproduction circuit 15a that reproduces a color subcarrier from a color burst signal in the video signal supplied to the input terminal IN, and an A that converts the reproduced color subcarrier into a digital signal. / D converter 15b,
It is composed of an interleaving decision circuit 15c which decides the degree of interleaving from the digital color subcarrier.

The color subcarrier reproduction circuit 15a extracts the color burst signal from the video signal based on the burst gate supplied from the timing circuit 13, and reproduces the color subcarrier by forming a phase locked loop in phase with the color burst signal. A /
The D converter 15b converts the analog reproduction color subcarrier received from the color subcarrier reproduction circuit 15a into a digital color subcarrier while sampling with the clock signal of the frequency 910f _H received from the clock generation circuit 14.

As shown in FIG. 2, the interleaving determination circuit 15c includes a 1-line delay unit 21, an adder 22, an absolute value circuit 23, an averaging circuit 24, and an output unit 25.

In this interleaving determination circuit 15c, the digital color subcarrier on the input terminal I is supplied to one input terminal of the adder 22 and the input terminal of the one-line delay device 21. 1
The line delay unit 2 delays the digital color subcarrier by the time (1 / f _H ) of one line based on the clock signal of the frequency 910f _H supplied from the clock generation circuit 14, and the adder 22
To the other input terminal of.

If the interleaving relationship, that is, the relationship of 910f _H = 4f _SC is completely established in the Y / C separation target video signal, the phase of the color subcarrier is inverted for each line,
The output of the adder 22 becomes zero. Therefore, the output of the adder 22 is an amount indicating the magnitude of the deviation from the interleaving relationship of the video signals at the time of variable speed reproduction in the video tape recorder.

The output of the adder 22 is converted into a non-polar signal in the absolute value circuit 23, and then the averaging circuit 24 composed of the delay units 24a, 24b, 24c of one sampling period (910f _H ) ^-1 and the adder 24d. In (1), the color subcarriers are added over one cycle (4 sampling cycles), and are supplied to the synthesis section 12c of the digital Y / C separation section 12 via the output section 25 and the output terminal O.

The synthesizing unit 12c decreases the synthesizing ratio with respect to the output of the Y / C separator 12a by the comb filter as the output of the interleaving determining unit 15 increases.

Above, the averaging circuit 24 in the interleaving determination unit 24
As an example, the comb filter has a configuration in which the synthesis ratio to the output is continuously decreased as the output is increased. However, the success or failure of interleaving is determined by comparing the output of the averaging circuit 24 with a predetermined value, and when the interleaving is not successful, the synthesis ratio to the output of the comb filter is changed to zero, that is, by the comb filter. The output of the Y / C separator may be switched to the output of the Y / C separator by the frequency separation filter.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a digital Y / C separation device according to the present invention, and FIG. 2 is a block diagram illustrating the configuration of the interleaving determination unit 15 of FIG. IN …… Video signal input terminal, 11 …… A / D converter, 12 ……
Digital Y / C separation part, 12a ... by comb filter
Y / C separator, 12b …… Y / C separator with frequency separation filter, 12c …… Synthesis unit, 13 …… Timing generation circuit, 14
...... Clock generation circuit, 15 …… Interleaving judgment unit, 15a …… Color subcarrier reproduction unit, 15b …… A / D converter, 15c
...... Interleaving judgment circuit.

Claims (1)

[Claims] 1. A digital Y / C composed of a Y / C separator using a comb filter, a Y / C separator using a frequency separation filter, and a combining circuit for combining the outputs of both Y / C separators.
The C separation unit, the interleaving determination unit that determines the degree of interleaving in the Y / C separation target video signal, and the digital Y / C that generates a clock signal that is phase-synchronized with the horizontal synchronization signal extracted from the video signal. A separation unit and a clock supply unit for supplying the interleaving determination unit, wherein the interleaving determination unit reproduces a color subcarrier phase-synchronized with the color burst signal in the video signal; A / D converter for converting the color subcarrier to a digital signal, a one-line delay device for delaying the digital color subcarrier by one line, and an addition for adding the digital color subcarriers before and after the one-line delay device And an averaging circuit for adding the output of the adder over one cycle of the color subcarrier, and combining the digital Y / C separation unit. Circuitry, digital Y / C separator apparatus characterized by reducing the synthesis ratio of the output of the interleaving determination unit Y / C separator by said comb filter with increasing output.