JP2740209B2 - Y / C separation circuit - Google Patents

Description

The present invention relates to a color TV (television) receiver, a VTR (video tape recorder), and other such color video equipment which performs digital processing, particularly It relates to the Y / C separation circuit.

(B) Conventional technology A so-called digital TV receiver employs a motion-adaptive Y / C separation circuit, which is a well-known Y (luminance) signal and a C (color) signal of a color video signal. Are separated by a comb filter using frame correlation in the still image part,
The moving image portion is separated by a comb filter using line correlation.

By the way, Y / C separation using the above-mentioned frame correlation cannot be applied to non-standard signals that do not have a frequency interleaving relationship between frames, such as VTR playback signals,
It has been proposed to always perform Y / C separation based on line correlation without performing motion-adaptive Y / C separation. This is introduced as, for example, "Method for Enhancing Non-Standard Signal Quality in IDTV" in the Transactions of the Institute of Television Engineers of Japan 13-13.

(C) Problems to be Solved by the Invention Incidentally, in order to perform the Y / C separation based on the line correlation as described above, basically, a clock signal phase-locked to a color burst signal (hereinafter referred to as a burst-locked clock). It is necessary to operate the A / D conversion circuit and the line memory in the comb filter.

On the other hand, to perform a so-called scanning line interpolation process, a clock signal phase-locked to a horizontal synchronization signal (hereinafter, a line-locked clock) is required. For this reason, in the conventional digital TV receiver and the like, the above-mentioned two types of clock signals are used properly.

However, using two types of clock signals in this way not only complicates the circuit configuration, but also causes the clock signals to interfere with each other and cause a malfunction, so that only the line-locked clock must be used. Can be considered.

Incidentally, in the VTR reproduction signal, strictly to the color subcarrier frequency fsc and the horizontal scanning frequency f _H has been in the offset relationship, the average is established close relationship thereto. That is, Becomes

Therefore, with respect to such a non-standard signal, a Y / C separation circuit can be realized even if a comb filter using a line correlation that operates with a line-locked clock is used. However, with a color video signal from a personal computer, In many cases, non-standard signals for which such an offset relationship does not hold at all are set to Y / C by the comb filter operated by the line-locked clock.
There was a problem that it could not be separated.

Therefore, an object of the present invention is to provide a Y / C separation circuit that solves such a problem.

(D) Means for Solving the Problems The present invention is to perform A / D conversion of a color video signal and separate a luminance signal and a color signal from a digital color video signal after the A / D conversion by a comb filter. A frame comb filter for separating a digital color signal based on a correlation between frames of the digital color video signal; a line comb filter for separating a digital color signal based on a correlation between lines of the digital color video signal; A motion detection output for detecting the motion of the color video signal; a non-standard signal detection output that is output when the digital color video signal is a non-standard signal; and a digital color signal output from the frame comb filter and the line comb filter. A first output means for selectively outputting the motion detection output and the non-standard signal detection output. Extracting means for extracting a digital luminance signal based on the digital video signal and the digital color signal from the first output means; a band-pass filter for extracting a color signal component from the digital luminance signal; Color burst signal detection means for detecting a color burst signal component from the output of the filter; and when the color burst signal detected by the color burst signal detection means is at or above a predetermined level, the digital color signal from the band-pass filter is A second output means for outputting a digital color signal from the first output means in place of the digital color signal; and when the color burst signal detected by the color burst signal detection means is equal to or higher than a predetermined level, a digital luminance signal from the extraction means is output. Alternatively, the digital luminance signal and the digital chrominance signal from the band pass filter are reduced. And a third output means for outputting the calculated output signal as a digital luminance signal.

(E) Operation According to the above configuration, color signals that cannot be separated by the comb filter are separated and calculated by the band-pass filter.

(F) Embodiment One embodiment of the present invention shown in the drawings will be described below. In the figure, (1) is an input terminal to which an analog color video signal is input, and (2) is an A / D conversion circuit for digitally converting the color video signal using a line lock clock (CK) as a sampling pulse. , (3) is a first comb filter utilizing the line correlation to which the output signal is inputted. This filter (3) is a one-frame memory (4) which performs reading and writing by the clock (CK), and This is a known configuration including a coefficient multiplier (5) (6), an adder (7), and the like.

On the other hand, (8) is a second comb filter utilizing frame correlation to which the output signal of the A / D conversion circuit (2) is inputted, and is a one-line memory in which reading and writing are performed by the clock (CK). It has a configuration including (9) and (10), counting multipliers (11), (12) and (13), and an adder (14), and this filter is no different from the conventional one.

Next, reference numeral (15) denotes a first switching circuit which is switched by a non-standard detection output or a motion detection output inputted through an OR gate (16).
Side, and switches to the m side when there is a motion with the standard signal and when there is a non-standard signal. Also,
(17) outputs the output signal of the first switching circuit (15) to the A / D
This is a subtracter for subtracting from the output signal of the conversion circuit (2).
The above-described circuit configuration constitutes a so-called motion-adaptive comb filter (18).

Reference numeral (19) denotes a color band-pass filter to which the output signal from the subtracter (17) is input. The color band-pass filter separates and extracts the C signal component in the output signal of the subtractor by one-dimensional filter processing. (20) and the second and third switching circuits (21) and (22). The burst gate circuit (20) extracts a color burst signal in the C signal component by a burst gate pulse (GP).

Next, (23) is a burst level detection circuit for detecting the level of the color burst signal from the gate circuit (20), and switches the second and third switching circuits (21) and (22) according to the detection output. That is, when the level of the burst signal is equal to or less than the reference value (Vref), both the second and third switching circuits (21) and (22) are switched to the a side, and the reference value (Vre) is set.
If it exceeds f), it switches to b side. In addition, (24) (2
5) a delay circuit having the same delay time as the bandpass filter (19); (26) a subtracter for subtracting the output signal of the bandpass filter (19) from the output signal of one of the delay circuits (25). It is.

Therefore, in this embodiment, if the color video signal input to the input terminal (1) is a standard signal and has no motion, the first switching circuit (15) outputs the first comb filter. The C signal accurately separated by (3) is derived, whereby almost only the Y signal is output from the subtractor (17). Therefore, the level of the burst signal detected by the detection circuit (23) is very small and becomes equal to or lower than Vref, and the second and third switching circuits (21) and (22) are switched to the a side.
Therefore, in this case, the C signal and the Y signal separated by the first comb filter (3) are output to the output terminals (27) and (28).
Respectively.

In the case where the color video signal to the input terminal (1) is a standard signal and moves, or in the case of a non-standard signal having a relation relatively close to the offset as in the above-described VTR reproduction signal, the first switching circuit ( Since the C signal separated by the second comb filter (8) is derived from 15), the subtracter (1)
From 7), the Y signal from which the C signal component is substantially removed is output. Therefore, also in this case, since the level of the burst signal detected by the detection circuit (23) is small, the second and third switching circuits (21) and (22) are switched to the a side, and the second comb filter (8 ) Are output to the output terminals (27) and (28), respectively.

On the other hand, in the case of a non-standard signal whose offset relation is completely broken, such as a signal from a personal computer or the like, since the C signal is not separated by the second comb filter (8),
In the output signal of the subtractor (17), the Y signal and the C signal almost remain as they are. For this reason, the level of the burst signal detected by the detection circuit (23) considerably exceeds Vref, whereby the second and third switching circuits (21) and (22) are switched to the b side. Therefore, in this case, the color bandpass filter (1
The C signal extracted from the output signal of the subtracter (17) by 9) is led out to the output terminal (27), and the C signal is subtracted from the output signal of the subtractor by the subtracter (26). The signal is led to the output terminal (28).

In the above embodiment, the A / D conversion circuit (2) and the motion-adaptive comb filter unit (18) have been described as operating with a line-locked clock. However, they may be operated with a burst-locked clock. However, the Y / C separation circuit of the present invention can also be applied to a case where separation of the C signal by the comb filter unit (18) becomes impossible due to, for example, a disturbance in synchronization of the burst clock.

Therefore, the present invention is not limited to the case where a line-locked clock is used.

(G) Effects of the Invention According to the Y / C separation circuit of the present invention, regardless of the clock to be used, a high fidelity comb-filter is used for a standard signal and a non-standard signal having a relationship close to offset, regardless of the clock used. Y /
The advantage is that C separation can be performed, and Y / C separation can be performed for non-standard signals whose offset relationship is completely broken, and that the switching can be performed automatically. .

[Brief description of the drawings]

The drawing is a circuit block diagram showing one embodiment of the Y / C separation circuit according to the present invention. (3) (8): first and second comb filters, (18): motion-applied comb filter section, (Y): luminance signal, (C): color signal

Claims (2)

(57) [Claims] 1. A circuit for A / D converting a color video signal and separating a luminance signal and a color signal from the digital color video signal after the A / D conversion by a comb filter. A frame comb filter for separating a digital color signal based on a correlation between frames of the digital color video signal; a line comb filter for separating a digital color signal based on a correlation between lines of the digital color video signal; and a motion for detecting a motion of the digital color video signal A detection output; a non-standard signal detection output that is output when the digital color video signal is a non-standard signal; a digital color signal output from the frame comb filter and the line comb filter; First output means for selectively outputting based on a standard signal detection output; Extraction means for extracting a digital luminance signal based on the digital color signal from the output means of the first band, a band-pass filter for extracting a color signal component from the digital luminance signal, and a color burst signal from an output of the band-pass filter. A color burst signal detecting means for detecting a component; and when the color burst signal detected by the color burst signal detecting means is equal to or higher than a predetermined level, a digital color signal from the band pass filter is output from the first output means. Second output means for outputting in place of a digital color signal; and when the color burst signal in the color burst signal detection means is at or above a predetermined level, the digital brightness signal is output in place of the digital brightness signal from the extraction means. The output signal obtained by subtracting the digital color signal from the band pass filter is And a third output means for outputting a signal Y / C separation circuit. 2. The apparatus according to claim 1, wherein said A / D conversion circuit and said comb filter are operated by a clock signal phase-locked to a horizontal synchronizing signal of said color video signal.
Y / C separation circuit.