JPS6259493A - Digital television circuit - Google Patents

Abstract

PURPOSE:To eliminate the dislocation of an internal signal and an external signal on a screen and to easily see a superimposing screen by using one of line memories of a comb-line filter part as a delay element for adjusting a time. CONSTITUTION:In the digital comb-line filter 22 of a digital TV circuit, (n) line delay elements 221, 222 respectively having the delay quantity of approximateley one line are provided, and the correlation of input and output digital signals of the elements 221, 222 is operated by the first and the second arithmetic units 223, 224. In this operation, the chromaticity signal information and the luminance signal information are obtained. To the respective elements 221, 222 and the arithmetic units 223, 224, a change over signal SWS is added, when the signal SWS is a prescribed A mode, the input and output signals of the elements 221, 222 are used in the arithmetic units 223, 224 to perform a filtering. Further, when the signal SWS is a different prescribed A mode, the quantity of a delay of the element 221 of the elements 221, 222 is shortened by a prescribed quantity from one horizontal cycle and the correlation operation is carried out by the arithmetic units 223, 224.

Description

[Detailed description of the invention] [Technical field of invention] The present invention provides external primary color signals (hereinafter referred to as external R and G).

This invention relates to a digital television 77 circuit having a function of superimposing a signal (referred to as a B signal) on a screen.

[Technical background of the invention]

A digital television circuit is a circuit that processes a television signal, which was conventionally handled in an analog signal state, into a digital signal state. The advantages of digitized signal processing are
These include stable and accurate signal processing, various signal operations using memory, and ease of connection with other digital devices.

By the way, in the television signal processing circuit, the main functions that affect the image quality of the television 1 include a luminance/chromaticity separation (hereinafter referred to as Y/C separation) function and an edge correction function. Comb filters have recently been widely used to improve these Y/C separation and contour correction characteristics.

In analog circuits, the one-line delay line used in the comb filter is composed of an ultrasonic delay line or a C0D (charge-coupled device). However, in order to sufficiently ensure these performances, various correction circuits and adjustment volume controls are required.

On the other hand, digital comb filters can use shift registers or RA hi (random access memory) as delay lines, and there is no variation or fluctuation in characteristics, making it possible to realize high-performance comb filters. can.

FIG. 3 is a basic block diagram of a digital television circuit. An analog video signal (AVD) is converted into a digital video signal (DVD) by analog/digital conversion 11.
) and supplied to the Y/C separation circuit 12 including a digital comb filter. The digital chromaticity signal (DCH) separated by the Y/C separation circuit 12 is supplied to the chromaticity processing circuit 13, where it undergoes processing such as automatic color control, color killer, color saturation/hue adjustment, etc. I) and Q signal (Q). ■Signal (I), Q signal (Q
) is supplied to the matrix circuit 14 together with the luminance signal (Y) and subjected to matrix calculation. by this,
From the matrix circuit 14, R, G.

B-J No. 15 is obtained.

For the above system, external R, G, B (it no. 16
When a supply circuit such as a teletext decoder 17 is added, the external R, G, B reconnaissance 16 signal section R, G, B signals 15 are supplied to a combining circuit 18/C. Then, the selected or synthesized output in this synthesis circuit 18 is R for display,
It is used as G and B signals 19. ), either R or G depending on the switching signal (SWS).

The B signal is selected or superimposed and output.

[Problems with background technology]

In the digital television signal processing circuit, data processing is performed in units of sampling cycles (T8) during analog-to-digital conversion. The sampling period is usually selected as 'TBO (Tso; color subcarrier period), and is approximately 7Qn8 in NTSC signal processing.

The time required for signal processing varies depending on the system configuration and filter characteristics, but is generally about 20Ts to 40T8, which corresponds to 1.4 to 2.8μs in real time, which is the time required to demodulate the internal R, G, and B signals. This is the time it takes to do so. This value is considerably larger than that of an analog television circuit.

As mentioned above, the teletext decoder J7 is added to the signal processing circuit that takes a relatively long time to demodulate the internal R, G, B signals. When superimposing, there is a problem that the screen may shift left and right.

This is because the external R, G, and Bi signals are not designed in consideration of a large delay time as in the signal processing circuit of a digital television circuit.

[Purpose of the invention]

This invention was made in order to deal with the above-mentioned situation, and the time difference on the screen between the internal R, G, B signals and the external R, G, B signals that occurs due to the digital signal processing time. An object of the present invention is to provide a digital television circuit that can be corrected by relatively simple means.

[Summary of the invention]

This invention, for example, as shown in FIG.
(inserting an image based on a signal) mode, the delay amount of the line delay element 22 used in the comb filter 22 is switched, and as a result, the external R, G, B signals and the internal R,
G.

B () The horizontal position of the image is synchronized, and the screen shift can be corrected.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, in which an analog video signal (AVD) is converted into a digital video signal by an analog-to-digital converter 21 and then supplied to a digital comb filter 22. In FIG.

The digital comb filter 22 has line delay elements 221 and 222 connected in series. Here, the line delay element 22 has a maximum delay amount of one horizontal period (TH),
In response to the switching signal (SWS), the delay fit(Ta
) (when the switching signal is 1") and the delay amount (TH-T
X) (when the switching signal is O") can be switched to From the output of element 222, three digital video signals a, b, and c are obtained, each having a different delay amount by approximately one horizontal period (TH).

The digital video signals a, b, c are processed by the first arithmetic unit 2.
23 and a second arithmetic unit 224. The first arithmetic unit 223 is for obtaining a chromaticity signal, and the second arithmetic unit 224 is for obtaining a luminance signal. Here, the first and second arithmetic units 223 and 224 calculate each arithmetic expression when the switching signal (SWJ) is 1n (non-superimpose mode) and when it is ON (superimpose mode). Can be switched.

A: In non-superimpose mode (signal 5WS=″
'1'') The first arithmetic unit 223 and the second arithmetic unit 224 perform the calculation bc 7+7+1.

B: In superimpose mode (signal 5WS=”
Q'') The first arithmetic unit 223 performs c-11 arithmetic operation, and the second arithmetic unit 224 performs c-11 arithmetic operation.

The output signal obtained by the first arithmetic unit 224 is supplied to a band pass filter 23 whose pass band is around the color subcarrier frequency (fsa) and a low pass filter 24. As a result, the bandpass filter 23 outputs the chromaticity signal (CH).
is obtained, which is supplied to the color processing circuit 25. Further, a vertical contour signal (yv) is obtained from the low-pass filter 24, and this signal is supplied to an adder 27, and
The signal is supplied to an adder 29 via a gate circuit 28.

On the other hand, since the output signal obtained by the second arithmetic unit 224 is a luminance signal lacking vertical high-frequency components, the previous vertical contour signal (yv) is added to this signal in the adder 27. This becomes a regular luminance signal (Yl).

Furthermore, by passing the output signal of the second arithmetic unit 224 through the bandpass filter 26, a horizontal contour correction signal (YH
) is obtained. This horizontal contour correction signal (YH) is combined with the vertical contour correction signal (yv) in the adder 29 to become a luminance contour correction signal (YHV), which is supplied to the adder 3o. In this adder 30Vc, the brightness contour correction signal (YHV) and the previous regular brightness signal (Yl) are combined to form a contour-corrected brightness signal (¥2), which is supplied to the matrix circuit 31. .

The matrix circuit 31 is supplied with an optical signal (I) and a Q signal (Q) obtained by the color processing circuit 25.

This signal (I') <Q') is (RY), (
B-Y) color difference signals may be used. In the color processing circuit 25, automatic color gain adjustment, color killer, color saturation/hue adjustment, etc. are performed, and the above-mentioned engineering signal (I) and Q signal (Q) are derived by matrix calculation.

Internal R and G obtained by the matrix circuit 31.

The B signal 32 is input to the external R9G, B signal in the synthesis circuit 33.
Switched or combined with the signal. In other words, the synthesis circuit 33 responds to the switching signal (SWS), and when the Q signal is 1'', it derives, for example, internal R2G and B signals, and when it is '0'', it derives the internal R1G and B signal and the external R signal. , G, and B signals are superimposed and derived. In addition, the switching signal (SW
S) is also supplied to the gate circuit 28, r, "l"
When this happens, the gate circuit 28 is turned on.

0", the gate circuit 28 is turned off. Note that the external R,
The G and B signals 34 are, for example, signals from a teletext decoder 35.

The present invention is configured as described above, and the switching signal (SWS)
is 0", which is the cis-bar impose mode. In this mode, the delay of the line delay element 221 changes from TH to (TH-TX). FIG. , is a diagram showing the delay relationship of each signal 32 and 34.

In Fig. 2, T INT is the delay time of the internal R, G, and B signals without correction, and T EXT is the external R, B signal delay time.
This is the delay time of G and B signals. Note that TINT is shown with the fixed TH delay caused by the line memory omitted. Here, the delay time 'rx is TXNT and T EXT
If no correction is made, both screens will be shifted left and right by the amount of TX during superimposition. In order to correct this, line delay element 2
21, the digital video signal (
AVD) (therefore internal R,G.

341 No. 32), TINT and T ICX'r
The difference between the two signals becomes TH, thereby eliminating the left and right deviation between the two signals on the screen.

As a result, the internal, external R, G, and B signals 32.degree. 34 are shifted vertically by one line, but there is no problem in practical use. In this way, since the line delay element 221 is used simply to delay the signal, the actual filtering operation is performed at the input and output parts of the line delay element 222 in this correction mode (superimpose mode). Signals S and C are the objects of calculation. The first and second calculations are performed.

In the superimpose mode, the gate circuit 28 is turned off to prevent the output of the low-pass filter 24 from being input to the adder 29. This is because the calculation of the chromaticity signal is <-2--2> This is because the signal (YV) cannot be a normal vertical contour signal unless it contains only one contour with respect to changes in the vertical direction. However, in non-superimpose mode, vertical correlation is taken using three lines and centering on the middle line, so normal vertical contour components are included, but in superimpose mode, This is because chromaticity separation is performed using the upper and lower two lines, so that accurate vertical contour components cannot be obtained with respect to changes in the vertical direction.

In the above explanation, a comb filter using two line delay elements is shown, but the principle of the present invention is not limited to this, and the principles of the present invention can also be applied to a comb filter using n line delay elements. be. Further, although a teletext decoder is shown as the external R, G, B signal generating means, external R, G, B signals from other digital video equipment may be used.

〔Effect of the invention〕

As explained above, according to the present invention, external R, G, and B signals are superimposed on internal R, G, and B signals obtained by requiring a relatively long delay time, such as in digital video signal processing. When pausing, one of the line memories of the comb filter section is used as a delay element for time adjustment, thereby eliminating the deviation between the internal signal and the external signal on the screen. In this case, compared to the case where there are two line memories, the filter performance will be lower because it will be a comb-shaped filter that uses one line memory, but in the superimposed screen, the viewer can see the external R, G, B (Since we are focusing on the information from No. 8, it is not a big problem.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, Fig. 2 is a delay time explanatory diagram for explaining the operation of the circuit in Fig. 1, and Fig. 3 is a generally considered digital television. It is a diagram showing a circuit. 22...Digital comb filter, 221, 222...
・Line delay element, 223, 224... Arithmetic unit, 23
．． 26... Band pass filter, 24... Low pass filter, 25... Color processing circuit, 31... Matrix circuit, 33... Synthesizing circuit.

Claims (3)

[Claims] (1) A first and a second line delay element each having a delay amount of approximately one line and a correlation operation of the input and output digital video signals of each line delay element to obtain chromaticity signal information and luminance signal information. The comb-type filter has a switching signal input section, and when the switching signal is in a predetermined mode (hereinafter referred to as A mode), all the inputs and inputs of the n line delay elements are The output signal is used by the first and second calculation means for filtering, and the switching signal is in a mode different from the A mode (
(hereinafter referred to as @A@ mode), the delay amount of a specific delay element among the n line delay elements is made shorter than one horizontal period (T_H) by a predetermined amount (T_X), and The correlation calculation between the input and output signals of this delay element is performed in the first
, the first and second arithmetic means are not performed by the second arithmetic means.
a comb filter configured to switch the calculation elements of the calculation means so that the delay element provides a delay of (T_H-T_X) between its input and output signals; and an output signal of the comb filter is supplied; demodulating means for demodulating into first primary color signals (red, blue, green signals), the switching signal, the first primary color signal and the second primary color signal are supplied, and when the switching signal is in the A mode; derives either the first primary color signal or the second primary color signal, and superimposes the second primary color signal on the first primary color signal when the switching signal is in the @A@ mode. 1. A digital television circuit comprising: a composition means for deriving a digital television circuit. (2) The number n of the line delay elements is 2, and these 2
2. The digital television circuit according to claim 1, wherein the line delay elements are connected in cascade, and the particular one delay element is a first-stage one. (3) The number n of the line delay elements is 2, and these 2
line delay elements are cascade-connected, the specific one delay element is the one at the first stage, and the first and second arithmetic means each operate at -(a/4) when in the A mode.
) + (b/2) - (c/4), (a/4) + (b/2)
+(c/4) calculation, respectively (b/2 in A mode)
) - (c/2), (b/2) + (c/2) (where a is the input signal of the first stage delay element, b and c are the input and output signals of the next stage delay element) A digital television circuit according to claim 1, characterized in that: