JPH02131694A - Yc separator circuit - Google Patents

Abstract

PURPOSE:To utilize the YC separation system of moving adaptive type even with a nonstandard signal by generating a correction coefficient correcting a data of a luminance signal or a color signal in the nonstandard signal and multiplying the coefficient with the data of the luminance signal and color signal. CONSTITUTION:A composite signal is delayed by two line memories 1, 1 for 1H and 2H and the original signal and the 2H delay signal are multiplied with a coefficient of -1/4 at coefficient devices 2, 3 and the 1H delay signal is multiplied with 1/2 at a coefficient device 4 and they are added respectively at an adder 5. Then the output of the adder is inputted to a multiplier 7 and the correction coefficient generated from a correction coefficient generator 8 is multiplied Then the result is outputted as a color signal CL. On the other band, a color signal is subtracted from the output of a line memory 1 at a subtractor 6 and a luminance signal YL is outputted. Thus, the movement adaptive type YC separator system is used for the nonstandard signal, then the picture quality at the input of the nonstandard signal is considerably improved.

Description

[Detailed description of the invention] (a) Industrial! FIELD OF THE INVENTION This invention relates to a luminance and chrominance signal separation circuit for separating luminance and chrominance signals from a composite color television signal.

(Example) Conventional technology As a method of separating luminance signals and color signals from a composite color television signal, after A/D converting the input signal, motion-adaptive YC separation uses line correlation and frame correlation depending on the motion. By using circuits, the image quality can be improved in digital TVs such as IDTVs.
78).

On the other hand, like a VTR playback signal, the luminance signal fluctuates on the time axis with respect to the color signal, and the phase relationship between the horizontal synchronization signal and the color subcarrier signal, which serves as a reference during playback ( r sc =
455/2x f H However, fsc is the color subcarrier, f
If YC separation using the above-mentioned frame correlation is performed on a non-standard signal in which the horizontal frequency (H is a horizontal frequency) is not strictly observed, a large deterioration in image quality has been caused.

Furthermore, in IDTV and the like, motion adaptive scanning line interpolation is performed in addition to motion adaptive YC separation. These processes are preferably performed for standard signals by using a burst lock clock locked to the burst signal as the system clock. However, in the case of non-standard signals, scanning line interpolation requires accurate alignment of pixel positions between fields and lines, and for this purpose a clock locked to the horizontal frequency (H-lock clock) is used. There must be.

On the other hand, YC separation is inconvenient if an H clock is used because dot interference occurs as will be described later, and a burst clock clock must be used.

The reason for the inconvenience caused by performing YC separation using the H clock when receiving a non-standard signal will be explained below.

Now, a video signal without a luminance component as shown in FIG.
The color subcarrier (sine wave of frequency fsc) is converted to H of frequency Is.
Consider the case of sampling with a candle clock. Here, if fs=4fsc, if the video signal is a standard signal, fs=4fsc will be accurate, but if it is a non-standard signal, the relationship will not be maintained accurately and fs=4fsc.

Then, the result of sampling -F is given by the following formula.

Now, the signal obtained by sampling is subjected to YC separation using a two-dimensional YC separation circuit shown in FIG. In the figure, (1) is a line memory that delays the signal by 1 hour, and has a delay time of 910 chronok. The color signal (CI.) after separation is expressed by the following formula.

CL=g(a)sin(an) Historically, the luminance signal (YL) is YL=fn-CL=sin(-on)-g(a)sin
(-on)=I1-g(a)lsi口(-an)・
・・・・・・・・・・・・・・・・・・・・・・・・・・・
・(2) becomes.

Since the video signal shown in FIG. 8 does not include a luminance component, the value of equation (2) must be O.

However, when the standard signal is used, YL=O, but when the signal is not standard, YL≠0, and dot interference occurs in the luminance signal from the color signal, resulting in a large deterioration in image quality.

Conventionally, as shown in RL987 National Conference of the Television Society JP 309-310, when the input signal is a standard signal or a non-standard signal is detected and the input signal is a standard signal, the burst clock is activated. In the case of non-standard signals, the system is operated with an H-lock clock, so an analog comb filter had to be used for Y/C separation.

Therefore, motion-adaptive YC separation cannot be performed on non-standard signals, and satisfactory image quality cannot be obtained.

(c) Problems to be Solved by the Invention +- The invention has been made in view of the above points, and is based on J. This invention provides a YC separation circuit that can utilize the YC separation method of tL motion-adaptive attack.

(2) Means for solving the problem + the invention is a YC separation circuit that separates a composite video signal from a luminance signal using line correlation or frame correlation after A/D converting the composite video signal. When the standard signal is a standard signal, a correction coefficient generating means for generating a complementary coefficient for correcting the luminance signal and/or color signal data; Jli! A YC separation circuit, comprising: a multiplier for calculating the correction coefficient, and outputs the data after being multiplied by the correction coefficient as a luminance signal and a color signal.

(e) Effect When receiving a non-standard signal, the present invention multiplies YC-separated luminance signal and/or color signal data by a correction coefficient, and then
Since it is output as a YC separated output, no color signal is leaked into the luminance signal.

(f) Example First, the principle of the present invention will be explained.

The reason why YL=O does not hold in the non-standard time in equation (2) described in 1ri is because g(α)≠1 in equation (l)', and the right side does not become sin('on). Therefore, g
(α) is calculated and multiplied by its reciprocal 1/g(a) as a correction coefficient on the right side of equation (1). And this addition L5 output is multiplication! (7) and is multiplied by the correction coefficient generated by the correction coefficient generation section (8). That is,
The output of the adder (5) is g(a) sin (-an), and when this is multiplied by the correction coefficient 1/g (*), the equation (2) becomes \LJn-CL=sin(- on)-sin(-on)
=U.

Next, FIG. 1 shows a YC separation circuit according to an embodiment of the present invention. That is, in the same figure, the composite signal is sent to IH and 2H by two line memories (1) and (1), respectively.
The original signal and the 2H delayed signal are each passed through a coefficient multiplier (2
)(3), the IH delay signal is multiplied by a coefficient of -174, and the IH delay signal becomes 1/2 in the coefficient multiplier (4), which becomes the color signal (CL).
is output as

On the other hand, in the reduction $5 (6), the line memory (1)
The color signal is subtracted from the output and a luminance signal (YL) is output.

Therefore, the luminance signal separated by the YC separation circuit of this embodiment from the signal fn obtained by sampling the color subcarrier with the H clock is S'L=fn-CL=sin(-an)-sin(-a
n)-0, and good YC separation can be performed even for non-standard signals.

Next, a specific example of the correction coefficient generating section (8) is shown in FIG.

(8l) is a burst lock PLL circuit that generates a sine wave locked to burst, and (82) is a horizontal synchronous signal generator.
H that generates a pulse of 9 1 0 fH
The output lock PLL circuit (83) is the burst lock P[
．． 1. The circuit (8l) output is connected to the H-lock PLL circuit (
82) An A/D converter that samples the output and performs A/D conversion.

Figure 3 shows the sampling process.

That is, the black circles indicate sampling points, and the phase detection means (84) detects the phase θ(n) corresponding to the sampled data and outputs it. This phase detection means (84) can be realized by a table look amplifier method using a ROM or the like.

The output of this phase detection means (84) is then supplied to the frequency ratio extraction means (85). This frequency ratio detection means (8
5) is to detect a = 4fsc/fs in the above equation (1), detect the phase of point P and point q in Fig. 3, and calculate C-{θ(n)J(n-1)l It can be obtained by calculating. FIG. 4 shows a specific example of this frequency ratio detection means (85). (851) is a delay means for one dot, and after the input and output of this delay means (851) is subtracted by a subtracter (852), L P F (
853), the noise is removed and the frequency ratio is detected.

Further, the output of the frequency ratio detection means (85) is supplied to the correction coefficient calculation means (86), and the correction coefficient γ is calculated using the following calculation formula.

Here, since it is amil, it becomes γmi1. Incidentally, this T-stage is realized by a table-look-associative method using a ROM or the like.

Next, another embodiment of the correction coefficient generating section is shown in FIG.

In the figure, the burst signal is extracted from the composite video signal by the first burst gate circuit (90) and the first burst signal is extracted from the composite video signal.
The peak detection circuit (91) detects the wave, and further the I L P
It is converted into a direct current by F (92) and supplied to a division circuit (93).

On the other hand, the burst signal of the color signal (CL) after YC separation is extracted by the second burst gate circuit (94), and the burst signal is extracted by the second peak detection circuit (95) and the second 1. P
It passes through F (95) and becomes another input to the division circuit (93). Then, the output of this division circuit (93) is the correction coefficient γ=
It becomes 1/g (a).

That is, the correction coefficient can be obtained by calculating the amplitude ratio K/Kg(a)=1/g(a) of both burst signals in the composite video signal.

Although the above explanations are all about two-dimensional YC separation, they can also be applied to three-dimensional YC separation using frame correlation.

That is, the equation corresponding to the above equation (101)' is as follows.

l CF-11-cos(910X525X-a)lsi
n(?n)−−・−・=(3)CF=gF(*)si
npial)・・・・・・・・・・・・・・・・・・
(3) Therefore, the correction coefficient γ=gF (a) can be obtained in the same way as in the two-dimensional case.

FIG. 6 shows an example in which the present invention is applied to a motion adaptive YC separation circuit, in which, in addition to the same two-dimensional YC separation circuit as in FIG. )
(13), an adder (14), a multiplier (15), and a subtracter (16), which derive a luminance signal (YF) and a chrominance signal (CF). Then, a mixing circuit (17) is provided along with each two-dimensionally processed signal.
A luminance signal (Y) and a color signal (C) are derived by varying the mixing ratio by the motion detection output of a motion detection section (18) using a well-known interframe difference signal.

In addition to the correction coefficient (γL) for the two-dimensional YC separation circuit, the correction coefficient generation unit (8)' also generates a correction coefficient (γF) and (
γM) is generated.

As shown in FIG. 7, the correction coefficient generating section (8)' has three correction coefficient calculating sections (86), (87), and (88), but the other parts may be of l system.

(g) Effects of the Invention As described above, according to the present invention, since a motion adaptive YC separation method can be used for non-standard signals, the image quality when the non-standard signals are input is greatly improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a YC separation circuit according to an embodiment of the present invention, FIG. 2 is a block diagram of the correction coefficient generation section of FIG. 1, FIG. 3 is a diagram showing the sampling operation, and FIG. 4 is a diagram showing the frequency ratio. A block diagram of the detection means, FIG. 5 is a block diagram showing another embodiment of the correction coefficient generation section, FIG. 6 is a block diagram of a YC separation circuit in another embodiment of the present invention, and FIG. FIG. 2 is a block diagram of a correction coefficient generating section of FIG. FIG. 8 is a diagram showing color subcarriers, and FIG. 9 is a block diagram of a conventional YC separation circuit. (1)... Line memory, (10)... Frame memory, (7) (15)... Multiplier, (8) (8)'.
・・Correction coefficient generation unit, (17) ・・Mixing circuit, (18
)...Motion detection section.

Claims (1)

[Claims] (1) After A/D converting the composite video signal, it is separated from the luminance signal using line correlation or frame correlation.
In the C separation circuit, when the composite video signal is a non-standard signal, a correction coefficient generating means for generating a correction coefficient for correcting data of the luminance signal and/or chrominance signal; and a multiplication means for multiplying the data of
A YC separation circuit characterized in that the data after being multiplied by the correction coefficient is output as a luminance signal and a color signal.