JP3011413B2 - Outline enhancement amount adjustment circuit and television receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Purpose of the Invention] (Industrial application field) The present invention displays a sub playback screen in a main playback screen and a frame screen at a boundary between the main playback screen and the sub playback screen. The present invention relates to an image display system for displaying
The present invention relates to a contour enhancement amount adjustment circuit and a television receiver that adjust the contour enhancement amount for a sub-play screen and a frame screen, respectively.

(Prior Art) As is well known, for example, a conventional edge enhancement circuit used in an image display system such as a color television receiver includes:
It is configured as shown in FIG. That is, 11
Is an input terminal to which a digitized luminance signal obtained by separating a video signal into Y / C (luminance signal / color signal) is supplied.
The luminance signal supplied to the input terminal 11 is subjected to a contour component extraction by an HPF (high-pass filter) 12, gain-adjusted by a gain adjustment circuit 13, and then supplied to one input terminal of an addition circuit 14.

The other input terminal of the adder circuit 14 has an input terminal
A signal obtained by delay-adjusting the luminance signal supplied to 11 by a predetermined amount by a delay circuit 15 is supplied, and the delayed signal and the output of the gain adjustment circuit 13 are added, and the luminance signal with the edge emphasized is added thereto. It is generated and taken out from the output terminal 16.

Here, in a recent image display system, a sub-reproduction screen based on the second video signal is displayed in a reproduction screen using the first video signal, and a boundary between the main reproduction screen and the sub-reproduction screen is displayed. PIP (Picture-in-Picture) that displays a frame screen using a third video signal
Type things have appeared. In this type of image display system, the first to third video signals are switched during the respective display periods of the main reproduction screen, the sub reproduction screen, and the frame screen to be used for image display.

By the way, when the video signal transmitted in such a PIP type is edge-enhanced by the conventional edge enhancement circuit shown in FIG. 8, the first to third video signals are selectively supplied to the input terminal 11. Therefore, not only the main reproduction screen but also the sub reproduction screen and the frame screen are subjected to the same contour emphasis as the main reproduction screen.

In this case, first, if the same contour enhancement as that of the main playback screen is performed on the sub-playback screen, excessive contour enhancement occurs, and only the sub-playback screen looks sharp, and the image quality balance between the main playback screen and the sub-playback screen is obtained. Is very bad. Further, in the case of the frame screen, the rising and falling of the third video signal are digitally set very sharply, so that there is a problem that ringing occurs.

For example, when the ratio of the horizontal scanning period between the main reproduction screen and the sub reproduction screen is 1/2, the frequency f of the first and second video signals is
The relationship of the gain g with respect to is as shown in FIG.
In FIG. 9, a straight line LP indicates the frequency spectrum of the first video signal, and a straight line LA indicates the frequency spectrum of the second video signal. In the figure, fs is a sampling frequency.

As can be seen from FIG. 9, the second reproduction screen is generated.
The video signal has a frequency component twice that of the first video signal for generating the main reproduction screen, and the sub-reproduction screen has a longer frequency band. It becomes.

(Problems to be Solved by the Invention) As described above, when the conventional contour emphasis circuit is used for PIP, the sub-playback screen becomes excessively sharpened, and the image quality balance between the main playback screen and the sub-playback screen is extremely low. And the ringing occurs on the frame screen.

Therefore, the present invention has been made in view of the above circumstances, and when performing image display by PIP, the image quality balance between the main playback screen and the sub-playback screen becomes equal, and ringing does not occur on the frame screen. It is an object of the present invention to provide a very good contour enhancement amount adjustment circuit and a television receiver which can be used.

[Constitution of the Invention] (Means for Solving the Problems) The contour enhancement amount adjusting circuit according to the present invention provides a first video signal and a second video displayed smaller on the reproduction screen than the first video signal. A signal is input, and there is provided a contour emphasis means for weakening the contour emphasis of the reproduction screen by the second video signal in accordance with the area of the reproduction screen rather than the reproduction screen by the first video signal.

Further, a television receiver according to the present invention is provided with a display means for receiving a video signal output from the contour emphasis means and displaying the input video signal.

Further, the contour emphasis amount adjusting circuit according to the present invention has the first
An image for displaying a sub-reproduction screen based on the second video signal in a main reproduction screen based on the video signal and displaying a frame screen based on the third video signal at a boundary between the main reproduction screen and the sub-reproduction screen It is intended for display systems.

Then, during the display period of the main reproduction screen by the first video signal, gain adjustment is performed on the outline component of the first video signal to perform outline emphasis, and during the display period of the good reproduction screen by the second video signal. Is (1/3) ｛(4 / n) of the gain given to the first video signal with respect to the contour component of the second video signal.
-1｝ (where n is the ratio of the effective scanning period of the main playback screen to the sub-playback screen, and 1 ≦ n ≦ 4) or less, and the gain adjustment is performed during the display period of the frame screen by the third video signal. Is designed to perform a gain adjustment of 1/9 or less of the gain applied to the first video signal to the contour component of the third video signal.

(Operation) According to the configuration described above, first, the contour enhancement of the reproduction screen by the second video signal is made weaker in accordance with the area of the reproduction screen than by the reproduction screen by the first video signal. When screen display is performed by PIP, the balance of image quality between the main playback screen and the sub playback screen can be made equal.

Further, a display period of the main playback screen by the first video signal,
The first and second frames are displayed in the first and second frames, respectively, according to the display period of the sub-reproduction screen by the second video signal and the display period of the frame screen by the third video signal.
Further, since the gain for contour enhancement given to the contour component of the third video signal is changed, when the image display by PIP is performed, the image quality balance between the main reproduction screen and the sub reproduction screen is made equal. Ringing can also be prevented from occurring on the frame screen.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In FIG. 1, reference numeral 17 denotes an input terminal to which a digitized luminance signal obtained by Y / C separation of a video signal is supplied. The luminance signal supplied to this input terminal 17 is HP
After the contour components are extracted by F18, the gain adjustment circuit 1
Supplied to 9.

Here, the gain adjustment circuit 19 is provided with a plurality of (four in the illustrated case) multiplication circuits 20 to 23 for multiplying the output of the HPF 18 by different coefficients to give a gain, and a later-described supply to the selection control terminal S. And a multiplexer 24 for selecting the outputs of the multiplication circuits 20 to 23 based on the gain adjustment control signal.

As will be described in detail later, the multiplexer 24 supplies a frame signal supplied to the input terminal 25 and having an H (high) level during the display period of the frame screen and an H level supplied to the input terminal 26 during the horizontal blanking period. And a signal obtained by performing a logical operation on the blanking signal by the NOR circuit 27.

When the output of the NOR circuit 27 is at the L (low) level, that is, when at least one of the frame signal and the blanking signal is at the H level, the multiplexer 24 outputs the signal output from each of the multiplication circuits 20 to 23. Set the gain to “0”
That is, the contour enhancement amount is set to “0” and output.

The signal selected by the multiplexer 24 in this manner is supplied to one input terminal of the adding circuit 28. A signal obtained by delay-adjusting the luminance signal supplied to the input terminal 17 by a predetermined amount by the delay circuit 29 is supplied to the other input terminal of the addition circuit 28, and the delayed signal and the output of the gain adjustment circuit 19 are supplied to the other input terminal. The luminance signal with the added edge is added and the output signal is generated.
It comes out of 30.

Here, the gain adjustment control signal supplied to the multiplexer 24 of the gain adjustment circuit 19 is output from the multiplexer 31. The multiplexer 31 selects the outputs of a plurality (three in the illustrated case) of multiplying circuits 33 to 35 for multiplying the gain adjustment signal supplied from the microcomputer (not shown) to the input terminal 32 by different coefficients. is there.

In this case, the coefficient of each of the multiplication circuits 33 to 35 is "1" corresponding to the gain given to the video signal forming the main playback screen.
In this case, the coefficient K for the sub reproduction screen is K = (1/3) {(4 / n) -1}. Here, n is the ratio of the effective scanning period between the main reproduction screen and the sub reproduction screen. That is, when the area ratio between the main playback screen and the sub playback screen is 1/4, 1/9, respectively, n is
The coefficients of the multiplication circuits 33 to 35 are 1,1 / 3 and 1/9.

The multiplexer 31 is supplied to the input terminal 36 and indicates a signal representing the area ratio between the main reproduction screen and the sub reproduction screen, and is supplied to the input terminal 37 and goes high during the display period of the sub reproduction screen. Based on the area signal, each multiplication circuit 33
~ 35 outputs have been selected. That is, the multiplexer
31 selects an output of the multiplication circuits 34 and 35 when a signal indicating that the area ratio between the main reproduction screen and the sub reproduction screen is 1/4, 1/9 is supplied to the input terminal 36, L to input terminal 37
When the level area signal is supplied, the output of the multiplication circuit 33 is selected.

Here, the frame signal and the area signal will be described. Now, as shown in FIG. 2, if a main playback screen 38, a sub playback screen 39, and a frame screen 40 are set, the frame screen 40
Is displayed twice in one horizontal scanning period as indicated by a dotted line 41 in the same figure, or is displayed once in one horizontal scanning period as indicated by a dotted line. For this reason, the frame signal is generated at the timing shown in FIG. 3 (a) in the case of the dotted line 41 in FIG. 2, and is generated in the case of the dotted line 42 in FIG.
It is generated at the timing shown in FIG.

The area signal corresponds to one horizontal scanning period of the sub-reproduction screen 39, as shown by a dotted line 43 in FIG. 2, and is generated at the timing shown in FIG. 3 (c).

Next, the above-described coefficient K, that is, the ratio of the gain given to the video signal constituting the main playback screen to the gain given to the video signal constituting the sub-playback screen will be described. That is, when the area ratio between the main reproduction screen and the sub reproduction screen is 1/16, the relationship of the gain g with respect to the frequency f of each video signal of the main and sub reproduction screens is as shown in FIG. In FIG. 4, a straight line LP indicates the frequency spectrum of the video signal on the main playback screen, and a straight line LA indicates the frequency spectrum of the video signal on the sub-playback screen. In the figure, fs is a sampling frequency.

As shown in FIG. 5, (1/2) (cosf
In the case where the filter having the function of -1) is applied with the contour emphasis at the frequency of fs / 2 with the gain GA as a peak, the straight line LP becomes like the one-dot chain line LPG in FIG. If the quantity is “0”, the curve LPG and the straight line La have substantially the same frequency components.

Therefore, in such a case, K = 0, and the sub-reproduction screen of 1/4 and 1/9 of the sub-reproduction screen in area ratio with respect to the main reproduction screen are also plotted on the straight line LP with the filter having the characteristics shown in FIG. When contour enhancement is performed, a straight line LB (a straight line representing the frequency spectrum of the 1/9 sub-reproduction screen) and a line LC shown in FIG.
Consider a contour enhancement amount to be added to (a straight line representing the frequency spectrum of the 1/4 sub-reproduction screen).

Assuming that the gains g of the straight lines LA, LB, and LC at the frequency fs / 2 in FIG. 6 are GA, GB, and GC, respectively, in the 1/16 sub-reproduction screen, the n (the main reproduction screen and the sub-reproduction screen Of the effective running period) is 4, and the gain GA becomes GA = (3/4) GP with respect to the gain GP when the frequency of the straight line LP is "0".

Similarly, GB = (2/3) GP GC = (1/2) GP, and the contour enhancement amount given to the straight line LB is GA = GB when considering the gain of the frequency fs / 2, and (3/4) GP -(2/3) GP = (1/12) GP and (1/12) GP = (1/9) GA, so that the gain ratio is K = 1/9.

If the same applies to the 1/4 sub-reproduction screen, K = 1/3, and eventually the relational expression between n and K is as shown in FIG. From this, when a relational expression between n and K is obtained, K = (1/3) {(4 / n) -1} as described above. However, 1 ≦ n ≦ 4. Furthermore, the contour enhancement amount on the frame screen may be set to a value of n = 3, K = 1/9 or less.

Therefore, according to the configuration as in the above-described embodiment, according to the display period of the main reproduction screen, the display period of the sub reproduction screen, and the display period of the frame screen, the outline emphasis given to the outline component of each video signal is performed. Since the gain is switched, when the image is displayed by PIP, the image quality balance between the main playback screen and the sub playback screen can be made equal, and ringing does not occur on the frame screen. it can.

It should be noted that the present invention is not limited to the above-described embodiment, and can be implemented with various modifications without departing from the scope of the invention.

[Effects of the Invention] As described in detail above, according to the present invention, when an image is displayed by PIP, the image quality balance between the main playback screen and the sub playback screen becomes equal, and ringing does not occur on the frame screen. Thus, it is possible to provide a very good contour emphasis amount adjustment circuit and a television receiver that can be made.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an outline emphasis amount adjusting circuit and a television receiver according to the present invention.
FIG. 3 and FIG. 3 are diagrams for explaining a frame signal and an area signal used in the embodiment, respectively. FIGS. 4 to 7 are characteristic diagrams for explaining the operation of the embodiment, respectively.
FIG. 1 is a block diagram showing a conventional contour emphasizing circuit, and FIG. 9 is a characteristic diagram for explaining problems of the conventional circuit. 11 Input terminal, 12 HPF, 13 Gain adjustment circuit, 1
4 ... Addition circuit, 15 ... Delay circuit, 16 ... Output terminal, 17
…… Input terminal, 18… HPF, 19 …… Gain adjustment circuit, 20
~ 23 ... Multiplier, 24 ... Multiplexer, 25,26 ...
Input terminals, 27: NOR circuit, 28: Addition circuit, 29: Delay circuit, 30: Output terminal, 31: Multiplexer, 32:
Input terminals, 33 to 35 Multiplying circuits, 36, 37 Input terminals, 38 Main reproduction screen, 39 Sub-reproduction screen, 40 Frame screen, 41 to 43 Dotted line.

──────────────────────────────────────────────────続 き Continuing the front page (72) Isao Miyazaki, Inventor, 8-8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture Toshiba Audio-Video Engineering Co., Ltd. (56) References JP-A-63-189086 (JP, A) JP-A-61-224785 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04N 5/14-5/217

Claims (3)

(57) [Claims] 1. A first video signal and a second video signal which is displayed on a playback screen smaller than the first video signal are input, and the second video signal is displayed on the playback screen based on the first video signal. A contour emphasis amount adjusting circuit, comprising contour emphasis means for weakening the contour emphasis of a reproduction screen by a video signal in accordance with the area of the reproduction screen. 2. The television receiver according to claim 1, further comprising display means for receiving a video signal output from said edge enhancement means and displaying the input video signal. 3. A sub-reproduction screen based on a second video signal is displayed in a main reproduction screen based on a first video signal, and a third video signal is provided at a boundary between the main reproduction screen and the sub-reproduction screen. In the image display system for displaying a frame screen according to the first aspect, a gain adjustment is performed on a contour component of the first video signal to enhance the contour during a display period of a main reproduction screen based on the first video signal. The second emphasis means and the second video signal during the display period of the sub-reproduction screen.
(1/3) {(4 / n) -1} (where n is the effective scanning between the main playback screen and the sub playback screen) for the contour component of the video signal Period ratio,
1 ≦ n ≦ 4) a second contour emphasizing means for performing gain adjustment of the following, and a display period of a frame screen by the third video signal,
And a third contour emphasis means for performing a gain adjustment of 1/9 or less of a gain given to the first video signal to a contour component of the third video signal. Emphasis amount adjustment circuit.