JP2917682B2 - Video signal processing circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal processing circuit for a high-definition television receiver or a wide-screen television receiver. The present invention relates to a circuit capable of adjusting brightness.

[0002]

2. Description of the Related Art In recent years, high-definition television receivers and wide-screen television receivers have been put on the market.

[0003] In the following, a part related to the present invention in a conventional wide television receiver will be described. At present, a television signal which is generally broadcast has an aspect ratio of 3: 4, and a high definition signal has a wide screen having an aspect ratio of 9:16.
For this reason, a wide television receiver using a cathode ray tube having a wide aspect ratio of 9:16 has been commercialized. In this case, in order to correctly display a conventional television signal with a 9:16 cathode ray tube, it is necessary to perform scan conversion of the signal to make the screen of the television to have an aspect ratio of 3: 4. FIG.
1 shows a configuration and a waveform of a signal processing circuit of a conventional wide television receiver. 3A, A is an input luminance signal, B is an input color difference signal, C is a converted luminance signal, D
Is a converted color difference signal, E is an output luminance signal, 11 scan conversion circuit, 12 is a horizontal contour enhancement circuit, and 13 is an RGB processor. The operation will be described with reference to the waveform diagram of FIG. 3B. The input luminance signal A is converted into an appropriate signal by the scan conversion circuit 11 (when converted from 3: 4 to 9:16,
(4/3 times) to obtain the converted luminance signal C. Input color difference signal B
Similarly to the luminance signal, the scan conversion circuit 11 converts the signal into an appropriate signal to obtain a converted color difference signal. It is easy to see that these converted signals have portions without signals. The converted luminance signal C non-video signal portion is set to an appropriate signal level (generally low luminance) to prevent partial deterioration of the cathode ray tube.

Next, the contour of the converted luminance signal C is emphasized by a horizontal contour emphasizing circuit 12 to obtain an output luminance signal E.
At this time, unsightly and undesirable false contours are emphasized at the horizontal start and end portions of the luminance signal. The output luminance signal E and the converted chrominance signal D are driven by a RGB processor 13 in which the contrast of the luminance signal, the degree of saturation and brightness of the color, and the like are appropriately set, and the CRT is driven. On a cathode ray tube, a false horizontal contour emphasizing signal or streaking due to the influence of a large amplitude signal occurs at a boundary portion between a video signal portion and a non-signal portion, resulting in an unsightly image. Also, on the CRT, the ABL circuit of the television receiver operates according to the content of the video signal, and the brightness level and the contrast level of the RGB processor 13 are controlled to change the brightness level of the non-video signal portion, causing the viewer to feel uncomfortable. To make the image unfavorable.

[0005]

SUMMARY OF THE INVENTION A level in which an unsightly signal such as a false horizontal contour emphasizing signal or streaking generated at a horizontal start portion and an end portion of a video signal is removed, and a luminance level of a non-video signal portion is always set. To obtain a preferable image.

[0006]

In order to achieve this object, a video signal processing circuit according to the present invention is provided with means for switching between a video signal of a scan conversion output and a DC voltage, and for appropriately setting a horizontal start portion and an end portion of a video signal. A video signal processing circuit having a configuration for switching with a control pulse corresponding to a non-video signal period included in the video signal processing, and further having a circuit configuration for arbitrarily setting a voltage value of the DC voltage. circuit.

[0007]

With this configuration, in the horizontal start portion and the end portion of the video signal, the DC voltage set in the same manner as in the non-video signal period can be switched to the video signal, so that an unsightly false contour can be removed. It is. further,
Since the luminance level during the non-video signal period does not change according to the content of the video signal, it is possible to eliminate a sense of incongruity, and the luminance level can be appropriately set by the viewer.

[0008]

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, the same reference numerals are used for the same parts and signal names as in FIG.

In FIG. 1, reference numeral 11 denotes a scan conversion circuit;
Is a horizontal contour emphasis circuit, 13 is an RGB processor, 14
Is a control pulse generation circuit, 15 is a switching circuit, 16 is a DC voltage generation circuit, and 17 is a voltage control circuit. The luminance conversion signal of the scan conversion circuit 11 is input to the RGB processor 13 via the horizontal contour enhancement circuit 12 and the color difference conversion signal is directly input to the RGB processor 13. The output signal H of the RGB processor is input to one of the switching circuits 15. The DC voltage generation circuit 16 is controlled by a voltage control circuit 17 to generate an appropriate DC voltage, and is input to the other of the switching circuit 15. Further, a pulse F indicating a non-video signal period is supplied from the scan conversion circuit 11 to the control pulse generation circuit 14, and the control pulse output G is supplied to a control input of the switching circuit 15.

The operation of the video signal processing circuit configured as described above will be described with reference to the waveforms of FIG.

First, the input luminance signal A shown in FIG. 2A is supplied to the scan conversion circuit 11 and is appropriately converted to obtain a luminance conversion signal C shown in FIG. The outline of the luminance conversion signal C is emphasized by the horizontal outline emphasis circuit 12 to obtain an output luminance signal E shown in FIG. The input chrominance signal B is also appropriately converted by the scan conversion circuit 11 and supplied to the RGB processor 13 at the subsequent stage together with the output luminance signal E. The RGB processor 13 sets brightness, contrast, and the like. The ABL circuit of the television receiver operates according to the content of the video signal, and controls the brightness adjustment and the contrast adjustment of the RGB processor 13 to obtain the RGB processor output signal H of FIG. The output signal H and the control output voltage J of the DC voltage generating circuit 16 appropriately controlled by the voltage control circuit 17 are switched by the switching circuit 15, and FIG.
Is obtained.

Next, a control pulse of the switching circuit 15 will be described. First, a pulse F indicating the non-video signal period shown in FIG.
4 to obtain a control pulse G shown in FIG. 2F corresponding to a non-video signal period appropriately including a horizontal start portion and an end portion of the video signal. The control pulse G causes the switching circuit 15
Is controlling. With this configuration, as shown in FIG. 2 (G), the false contour is removed from the video output signal, and the non-video signal portion is processed to a fixed luminance level. Further, it is apparent that the luminance level at which the non-video signal portion is fixed can be appropriately controlled by the voltage control circuit 17.

[0013]

As described above, the present invention provides a control pulse corresponding to a non-video signal period appropriately including a horizontal start portion and an end portion of a video signal, and a DC pulse which can be arbitrarily controlled with the RGB processor output signal by using this pulse. By providing the means for switching the voltage, an unsightly false contour enhancement signal generated at the start and end of the horizontal video signal can be removed, and the non-video signal can be adjusted to an appropriate luminance level. A video signal processing circuit can be realized.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a video signal processing circuit according to an embodiment of the present invention.

FIG. 2 is a waveform diagram of a video signal processing circuit according to one embodiment of the present invention.

3A is a configuration diagram of a conventional video signal processing circuit, and FIG. 3B is a waveform diagram of the conventional video signal processing circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Scan conversion circuit 12 Horizontal contour enhancement circuit 13 RGB processor 14 Control pulse generation circuit 15 Switching circuit 16 DC voltage generation circuit 17 Voltage control circuit

Claims (2)

(57) [Claims] 1. A means for displaying a video signal in a range narrower than a display range of a CRT, a means for generating a DC voltage, a means for switching between the video signal and the DC voltage,
Means for generating a control pulse corresponding to a non-video signal period appropriately including a horizontal start portion and an end portion of the video signal,
Video signal processing circuit and means for controlling the <br/> obtain means switches said video signal and said DC voltage by the control pulse. 2. The video signal processing circuit according to claim 1 , further comprising means for arbitrarily setting a voltage value of said DC voltage.