JPH01208986A - Video signal processing circuit - Google Patents

Abstract

PURPOSE:To prevent a cross color and a fading by outputting a subtracted signal when a C signal tandem filter output is at a small level. CONSTITUTION:When the level of a C signal tandem filter output signal is large, the signal h1 of an unchanged wave form is made, when it is at a small level, a signal (f) is made into the signal h2 of a zero level and added to a signal (g) by an adder 9. In the case of a large level, the signal i1 of which signal (f) is added to the leading edge 1/2 wave length and the trailing edge 1/2 wave length of the signal (g) is made, in case of a small level, the signal i2 of a wave form same as the signal (g) is made and removed from a terminal 10. Thus, in the case of an oblique signal, no cross color nor fading is generated, even when the C signal, which is outputted since the YC separation performance of the C signal tandem filter is imperfect, comes into.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a video signal processing circuit, for example, in a VTR, etc.
In a YC separation circuit that separates and extracts a Y (luminance) signal and a C (carrier color) signal from a composite video signal, the C signal comb filter output is passed through a wideband filter or a narrowband filter depending on its level. Regarding output circuits.

[Conventional technology]

FIG. 6 shows a block diagram of an example of a conventional circuit.

In the same figure, a general C signal comb filter (as shown in FIG. 7, a wideband filter 25 and
Current line n, 1 line before (n-1), 1 line after (n
It is composed of a comb filter circuit 26 that separates the C signal using three signals of +1). ) output signal is
The signal is supplied to a narrow band filter 2 having a narrow band a and a wide band filter 3 having a wide band port b, where it is passed through each band and extracted. The output of the wide band filter 3 is subtracted by the output of the narrow band filter 2 in a subtracter 4, and is made into a signal having a band C. On the other hand, the signal input to the terminal 1 is envelope-detected by the rectifier 5, and compared with a predetermined equivalent level by the threshold level ratio AC circuit 6. If the C signal comb filter output level is below the threshold level, ro, In the above case, the signal [1] is taken out, and in the case of the signal rlJ, it is limited to a predetermined level by the level limiter 7 and output.

The output signal "1" or "0" of the limiter 7 is supplied to the multiplier 8 and output to the output of the subtracter 4.

As a result, the C signal comb filter output level is taken out from the second band, which is the same as the signal to the band where the output level is human level.
When the C signal comb filter output level is at a small level, a zero level signal H is extracted.

The output of the multiplier 8 is added to the output of the narrow band filter 2 in an adder 9, and when the level is large, a signal to the same band as the band entrance of the wide band filter 3 is taken out from the terminal 10, while when the level is small, the signal is output from the terminal 10. A signal in the same band G as band A of the narrow band filter 2 is taken out from the terminal 10.

Usually, the band of the comb filter used for YC separation is:
In general, for large-level C signals such as color bars, it is desirable to use a broadband filter from the viewpoint of resolution, while for small-level C signals such as wind heads, cross-coloring (colors are added to areas that should not be colored) is desirable. A narrow band is desirable in terms of For this purpose, a circuit as shown in FIG. 6 is required which switches the band and outputs the signal according to the level of the comb filter output of the input C signal.

[Problem to be solved by the invention]

In general, the separation performance of the YC separation circuit is not perfect, so if a diagonally shaded signal as shown in Figure 8 (A) on the screen enters the circuit shown in Figure 7, the Y signal is originally extracted. A low level C signal is taken out where it is needed. Therefore, in FIG. 6, when the above-mentioned low-level C signal and a C signal having a band around 3.58 MHz is input to terminal 1, the output of limiter 7 is [0, 1, so the addition? The output of the narrowband filter 2 is taken out from the X-device 9, which results in cross color and blurring.

[Means to solve the problem]

In FIG. 1, delay circuits 20 and 21, MAX (high potential detection circuit) 11 to 13, and MIN (low potential detection circuit) 14
~16, the adder 17 is combined with the carrier color signal comb filter] - 1/2 wavelength for extracting signals of 172 wavelengths at the leading edge and 172 wavelengths at the trailing edge of the carrier color signal separated from the video signal The output means, the subtracter 22, extracts the 1/2 color signal from the carrier color signal taken out from the carrier color signal comb filter.
Subtraction means for subtracting the output of the two-wavelength signal output circuit, rectifier S
5, l value relevel circuit 6 level limiter 7, multiplier 8
, the adder 9 detects the level of the carrier color signal taken out from the carrier color signal comb filter, and the adder 9 detects the level of the carrier color signal taken out from the carrier color signal comb filter,
In each embodiment of the first stage of selection, the output of the 1/2 wave output means is added to the output of the subtraction means, while when the level thereof is small, the output of the subtraction means is output as is. be.

[Effect]

1/2 wavelength of the leading edge of the carrier color signal extracted from the carrier color signal comb filter and after! '1/2 wavelength of A (bug)
This signal f is O level at fSC, 2 r
If it is sc or zero, it is level 0, which is confidence 8. This transmission f
The carrier color signal is extracted from the carrier color signal extracted from the comb filter, and the signal q from which the leading edge 1/2 wavelength and trailing edge 1/2 wavelength are removed is 1! ′? Ru. This signal q is a broadband signal minus 9f, so it is 3.58M.
Shows narrow band characteristics centered around Hz. When the level of the carrier color signal is low, the a5ci signal f is added to the signal q, and when the level is low, the signal Ra is output as is.

Especially in the case of the diagonal lined signal (the C signal level is low), is it reliable? 3
a1. becomes zero, and as a result, there is no cross color and no blurring occurs.

[Actual example]

FIG. 1 shows a block diagram of an embodiment of the circuit of the present invention, in which the same components as those in FIG. 6 are given the same numbers.

C signal coming into terminal 1 comb filter output (for example, a band-shaped C signal on the screen, the waveform is a continuous sine wave) a
(Fig. 3 (A)) is for adjusting the Q extension characteristics, and converts Δ to the delay circuit 20 (1/2fs, assuming the color subcarrier frequency is fsc) via the delay circuit 19 (delay time Δ1+).
c (sec) with a delay time Δt) and 1/
The two-wavelength processed signal b (FIG. 3(B)) is supplied to a high potential detection circuit (hereinafter referred to as MAX) 11 and a low potential detection circuit (hereinafter referred to as MIN) 15.

Shin5'+bGiMAX 11, 12, MIN15.1
On the other hand, the signal Pjc is further delayed by 1/2 wavelength by being supplied to the ΔL delay circuit 21 (FIG. 3(C)), and is supplied to MAX12 and MIN16. MAXl
The output of l and the output of MAX12 are supplied to MIN14, and the output of MIN15 and the output of MIN16 are supplied to MAX13.
is supplied to

t-L, TE, MAXll, 12.13 is shown in Figure 2 (A>
MIN14゜15.16 has the configuration shown in Figure 2 (B), and outputs the higher potential of the two input signals. Outputs the lower potential.

As a result of comparing the two human power signals at J3 at MIN14, a signal d (Fig. 3 (D)) is output, and on the other hand, as a result of comparing the two human power signals at MAX13, a signal C (Fig. 3 (D)) is output.
E)) is output. 1. Signal d corresponds to the signal of the leading edge 1/2 wave of the signal line, and signal C corresponds to the signal of the trailing edge 1/2 wave of the signal line. C) is added to the signal 8f (Fig. 3 (F)), and the reduction value 18 which can be varied from 1/2 to 1 (in this case, the constant K・1
) is supplied to the subtracter 22 and is reduced from the output signal of the delay circuit 20 to become a signal g (FIG. 3(G)). The signal q is the leading edge 1/2 wave and the trailing edge 1/2 of the signal line.
This is the signal with the wavelength (indicated by the dashed line) removed. Also, consider that the signal f is essentially the addition of the signals a, b, and c (which are shifted by 1/2 fsc) 1r'? , for this the signal f
is level 012fSC for l'sc or level O for zero
This shows a frequency characteristic in which both sides of 3.58 M l-I Z are at a high level.

As a result, the signal q is a broadband signal, so the signal f is reduced to 0.
Therefore, signal q exhibits a narrow band characteristic centered at 3.588117 (same as band t in FIG. 6).

On the other hand, the signal a entering the terminal 1 is transmitted through the narrow band filter 23 (
The signal is supplied to the rectifier 5, the threshold level comparison circuit 6, and the level limiter 7 via the C signal (having a delay time of Δt1), and as in the conventional circuit, it is "1" when the level of the C signal comb filter output signal a is high; The small 051 to 10'' signal is taken out and supplied to the input device 8. At the human level, the signal f is multiplied by "1" in the multiplier 8 and the waveform (n h +
(Fig. 3 ((1)), and when the signal is at a small level, the signal Mfiz is multiplied by 10 at the east main device 8 and the signal Mfiz is at zero level.
((H) in FIG. 3), and is added to the signal QQ in the adder 9. At the high level, signal 11 (third
(1)), and when the level is small, a is made into a signal +2 (FIG. 3 (I)) with the same waveform as signal q, and is taken out from the end f10.

In this case, the signal taken out from the terminal 10 becomes the signal 12 in a random image condition without vertical correlation such as a normal outdoor scene (the C signal level is lower than that in color par). Since the signal 12 is the same as the narrowband signal Q, there are few cross colors, and since the signal 12 is a signal from which the leading edge 1/2 wavelength and the 1!2 edge 17/2 wavelength have been removed, the screen outline portion The number of cross colors can be reduced. on the other hand,
Like color par! In the image condition with IFiU correlation (C signal level is human), the signal taken out from terminal 10 is signal i.
+, and is extracted as a wideband signal.

Next, we will explain the case where a diagonally shaded signal (the C signal level is small) as shown in Fig. 8 (Δ) on the screen enters the circuit added to Fig. 7. The circuit 26 is provided with two delay circuits as shown in Table 3, and at the timing shown in FIG. 8(B), the signal of the previous line (n-1) shown in FIG. 8(C) and the signal of the current line are output. The signal after n and one line (nmo 1) is output as 17, and the signal on line n is taken out as the output when it is at a low level.

If this signal is a' (Fig. 3 (A)), the output of the delay circuit 20.21 is the people signal b' (Fig. 3 ([3)
), the signal c' (Fig. 3 (C)) becomes MIN14.
The output of MAX13 becomes the signal d' (Fig. 3 (D)), the output of MAX13 becomes the m signal Q' (Fig. 3 (E)), and the adder 1
The output of 7 becomes the signal f' (FIG. 3('')). The signal f' is essentially the same as the signal b'. 0 unit 22, and is subtracted from the signal b' to produce a zero level signal Q' (third
Figure (G)).

On the other hand, since the C signal level of the diagonally shaded signal is small, the output of the limiter 7 is 1'O', and the output of the Q multiplier 8 is a zero level signal h2' ((+-1) in Figure 3). , C>
The signal Qi21 (
As shown in Figure 3 (1)'), in the case of the diagonally shaded signal, the C signal Q a / (originally Y
Even if a signal (must be output) is input, it will be at zero level in the circuit of the present invention, so unlike the conventional circuit, the loss color (the color will appear in the part where the color should not be applied) is not applied. Therefore, no blurring occurs.

Note that, experimentally, the constant of the attenuator 18 is k = 1/2 ~
1 was good.

FIG. 4 is a block diagram in which the video signal processing circuit according to the present invention is actually applied to a YC separation circuit of the NTSC system. In the figure, 30 is a conventionally well-known C signal comb filter;
Same as shown in the figure. 1314.1 The video signal processing circuit according to the present invention as described in Fig. 1'C, 32 is a composite video signal input terminal, 33 is a wideband filter having a Collin filter configuration with a delay time Δ and 0, and 34 is a 1-day delay. 35 is a loop circuit having a delay time (Δto-1Δ1+), 36 is a β reducer, and 37 is a Y signal 8 output terminal. .

Here, in the C signal comb filter 30, the input signal is A (after 1 line), and the output of the 1-day delay circuit 4° is 8 (
current line), the output of the 11-1 delay circuit 41 as C(1
Output the potential of the person of the signal A and [3 at MΔX/12, and output the signal 5q at MAX43.
Output the potential of person B and C, and make MIN44
Outputs the smaller of the output of MAX42 and the output of MΔX43 (+7X(,), and X(,)=M IN
(B, MAX (A, C)) J knee is written. Similarly, signal A is generated at MIN45.

Outputs the smaller potential of B, outputs the smaller potential of ZB and C at MIN/16, and outputs the smaller one of the outputs of MIN45 and MIN46 at MAX47. Output potential x (-), X (-) = MAX (B,
It is written as M I N (A, C)). (No. 3 × (=)
, ×(-) are added by the Q adder 48, and 1! of the video signal processing circuit 31 is added. ? In circuit 49, reduce Li bell to 1/2.
TCc =-1/2 (X(1)→X()).

In this case, the transfer function of the filter 30 is 1/2(B+M
ID (A, B, C)). Here, MID (
Δ, B, C) is a function that outputs the second highest r-value for the three signals A, B, and C. Therefore, for the four patterns shown in FIG. 5, the CcC signal 1!
? It will be done.

The CcC signal thus obtained is subjected to signal processing in the video signal processing circuit 31 described above, and is taken out from the terminal 10 as a C signal. -The composite video signal input to the terminal 32 is 1Hi! ! Extension circuit 34, (Δto→Δt+
) is supplied to a subtracter 36 via a fl extension circuit 35, where (18) is subtracted, and taken out from a terminal 37 as a Y signal.

In addition, in FIG. 1, a switch may be used instead of using the transit device 8. In this case, the output of the threshold level circuit 6 is used as a switching signal, and when it is "1", it is switched and connected to the output side of the addition Q; 17, and when it is "1'0", it is switched and connected so that zero is output. A switch configuration is used. In this case, the level limiter 7 is not necessary.

Also, although FIG. 4 is applied to the NTSC system, if a 2[1 delay circuit is used instead of the IH'i1 delay circuit 40.41, the 3° delay circuit can be applied to the PAL system.[Effect of the invention] According to the invention, +1 from the output of the C signal comb filter.
The signal from which the η company 1/2 wave and the after-stroke 1/2 wavelength were removed,
C signal < The signal subtracted from the C-shaped filter output is 17, C
Since the configuration is such that the subtracted signal is output when the signal No. 1 comb filter output is at a small level, especially in the case of the diagonally shaded signal (the C signal level is small), the subtracted Iζ signal becomes zero, Therefore, cross color will not occur, and
No blurring occurs either.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the circuit of the present invention, FIG. 2 is a circuit diagram of the MAX circuit and MIN circuit in FIG. 1, and FIG. 3 is a signal waveform diagram of the circuit shown in FIG. 1. Fig. 4 is a block diagram in which the circuit of the present invention is applied to a YC separation circuit, Fig. 5 is a diagram explaining the C signal obtained by the C signal comb filter shown in Fig. 4, and Fig. 6 is an example of a conventional circuit. Block diagram, 7th
The figure is a schematic block diagram of a C signal comb filter, and FIG. 8 is a diagram illustrating the 01 operation when the diagonally shaded signal is input. 1...C signal comb filter output signal input terminal, 5.
... Rectifier, 6... Open chain level circuit, 7... Level limiter, 8... Multiplier rJ unit, 9.17... Adder,
10...C signal output terminal, 11-13...High potential detection circuit (MAX), 14-16-Wffi detection circuit ffl (HIM), 18...Q reduction device, 20.2
1... Eight delay circuits, 22... Subtractor. Patent applicant: Tanuki, representative of Victor Japan Co., Ltd. Patent attorney: Tadahiko Ito
(1,. −−7′ Same patent attorney Kaneyuki Matsuura −
゛:1 ,,, -,-' Fig. 1 Fig. 2 Fig. 3
Cco = 1/21X is l -X+-+ 1Figure 7Figure 8

Claims (1)

[Claims] 1/2 wavelength for extracting signals of 1/2 wavelength of the leading edge and 1/2 wavelength of the trailing edge of the carrier color signal separated from the composite video signal by the carrier color signal comb filter. a signal output circuit; a subtraction circuit that subtracts the output of the 1/2 wavelength signal output circuit from the carrier color signal extracted from the carrier color signal comb filter; and a carrier color signal extracted from the carrier color signal comb filter. Detects the signal level, and when the level is high, the above 1/2
A video signal processing circuit comprising: a selection circuit that adds the output of the wavelength signal output circuit to the output of the subtraction circuit, while outputting the output of the subtraction circuit as is when the level thereof is small.