JP2001169205A - Television receiver - Google Patents

Abstract

(57) [Summary] [Problem] When a video based on digital broadcasting and a video based on analog broadcasting are displayed on the same screen, there is a difference in brightness between the two, which makes a viewer watching the screen feel uncomfortable. There was a problem that it could make you feel. SOLUTION: An output of a digital broadcast decoding circuit 1 for demodulating a digital broadcast signal and an output of an A / D converter 3 for converting an output of an analog broadcast decode circuit 2 into a digital signal are input to a digital image processing circuit 4. The D / A converter 5 converts the digital signal output from the digital image processing circuit into an analog signal,
To enter. When a video based on a digital broadcast signal and a video based on an analog broadcast signal are compressed and displayed on the same screen, a voltage supply circuit for supplying a voltage to a gain adjustment input terminal 5a of the D / A converter 5 8 to change the D / A for the analog broadcast signal portion on the screen.
The gain of the converter 5 was increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television receiver, and more particularly, to a television receiver capable of displaying an image based on digital broadcasting and an image based on analog broadcasting on the same screen.

[0002]

2. Description of the Related Art FIG. 3 shows an example of a television receiver capable of displaying a plurality of videos on one television screen. In this receiver, analog broadcast decoding circuits 101 and 102
Are converted to digital signals by A / D converters 103 and 104, respectively, and input to a digital image processing circuit 105. The digital output from the circuit 105 is converted into an analog signal by a D / A converter 106 and then displayed on a screen of a CRT 108 via an analog image processing circuit 107. Note that A
The signal level supplied to the / D converters 103 and 104 is
In order to secure a margin so that the waveform is not distorted even if the amplitude changes due to a ghost or other factors, the maximum level (so-called dynamic range) that can be input to the A / D converter is suppressed to, for example, about 80%. General.
In the case of this example, the analog broadcast signal decoding circuits 101, 1
02, the level of the analog broadcast signal is suppressed to, for example, 80% as described above, but both are suppressed to the same level. Even if both images are displayed on the screen at the same time, the brightness levels of both images are the same and there is no uncomfortable feeling. However, if one of the analog broadcast decoding circuits 101 and 102 is replaced with a digital broadcast decoding circuit and an analog broadcast video and a digital broadcast video are projected on the same screen, a problem occurs. That is, in the case of digital broadcasting, the signal level is often supplied at 100% of the full dynamic range. Therefore, when the signal obtained by decoding the analog broadcasting signal and that of the digital broadcasting signal are simultaneously displayed on the screen, the digital broadcasting signal is obtained. This makes the screen part brighter, and the brightness and level of the screen differ due to the analog signal, resulting in a sense of discomfort on the screen.

[0003]

As described above, when a video based on a digital broadcast and a video based on an analog broadcast are displayed on the same screen, there is a difference in brightness between the two, and this is a result of viewing the screen. There is a problem that the viewer may feel uncomfortable.

[0004] The present invention has been made in response to the above-mentioned problem, and even when a video based on digital broadcasting and a video based on analog broadcasting are displayed on the same screen, there is no difference in brightness level between screens. It is an object of the present invention to provide a television receiver that does not make a viewer watching the TV feel uncomfortable.

[0005]

According to a first aspect of the present invention, there is provided a television receiver comprising: a digital broadcast decoding circuit for demodulating a digital broadcast signal; an analog broadcast decode circuit for demodulating an analog broadcast signal; An A / D converter for converting an output of a decoding circuit into a digital signal; an output of a digital broadcasting decoding circuit;
A digital image processing circuit that performs image processing on the output of the converter;
A D / A converter having an input terminal for gain adjustment and converting an output digital signal of the digital image processing circuit into an analog signal; and supplying a voltage to the input terminal for gain adjustment of the D / A converter. A voltage supply circuit for displaying an image based on a digital broadcast signal and an image based on an analog broadcast signal on the same screen, by changing an output voltage of the voltage supply circuit to obtain a D / A for the analog broadcast signal. This is to increase the gain of the converter. According to a second aspect of the present invention, in the television receiver according to the first aspect, the voltage supply circuit has a resistor, and changes an output voltage by changing a current flowing through the resistor. It is like that.

According to a third aspect of the invention, there is provided the television receiver according to the first aspect, wherein the voltage supply circuit has a plurality of reference power supplies, and the output voltage is changed by switching these reference power supplies. It is like that.

According to a fourth aspect of the invention, there is provided a television receiver,
A digital broadcast decoding circuit for demodulating a digital broadcast signal, an analog broadcast decode circuit for demodulating an analog broadcast signal, an A / D converter for converting an output of the analog broadcast decode circuit into a digital signal, and an output of the digital broadcast decode circuit A digital image processing circuit for performing image processing on the output of the A / D converter, a D / A converter having an input terminal for gain adjustment, and converting an output digital signal of the digital image processing circuit into an analog signal; A voltage supply circuit for supplying a voltage to the gain adjustment input terminal of the D / A converter; and an analog broadcast for displaying a video based on a digital broadcast signal and a video based on an analog broadcast signal on the same screen. Alternatively, the output voltage of the voltage supply circuit is changed based on the signal output indicating the display position of the digital broadcast screen, and the analog broadcast is output. It is obtained so as to increase the gain of the D / A converter for No..

[0008]

Embodiments of the present invention will be described below in detail. FIG. 1 is a circuit block diagram showing an embodiment of the present invention.

1 is a digital broadcast signal decoding circuit, 2 is an analog broadcast signal decode circuit, and 3 is an A / D converter connected to the circuit 2. 4 is a decoding circuit 1
And a digital image processing circuit connected to the A / D converter 3. The output terminal of the circuit 4 is connected to a D / A converter 5, which has a gain adjustment reference voltage input terminal 5a generally provided in the D / A converter. An analog image signal processing circuit 6 is connected to an output terminal of the D / A converter 5 and finally connected to a CRT 7. Further, resistors 8 and 9 are connected to the terminal 5a of the converter 5 described above.
The emitter of the transistor 10 is connected to the connection point between the resistors 8 and 9. Transistor 1
The collector of 0 is connected to a power terminal (not shown) together with the other end of the resistor 8, and the other end of the resistor 9 is grounded. The base of the transistor 10 is a digital image signal processing circuit 4
Is connected to the output terminal 4a. Here, the resistors 8 and 9 and the transistor 10 constitute a reference voltage supply circuit to the D / A converter 5.

In the above configuration, the output signal of the digital broadcast signal decoding circuit 1 is in a digital signal format, and the maximum amplitude of this signal is 100%.
On the other hand, the output signal level of the analog broadcast signal decoding circuit 2 has a maximum amplitude of 80 which is the maximum input level of the A / D converter 3.
% Has been adjusted. This is to provide a margin so that waveform distortion does not occur at the input section of the A / D converter 3 even if the maximum amplitude changes due to ghost or other reasons. In the digital image signal processing circuit 4, the output signal of the digital broadcast signal decoding circuit 1 and the A / D
From the converter 3, a digital broadcast image signal and an analog broadcast image signal (decoded analog broadcast signal) are respectively provided.
, And compresses and synthesizes both signals so that an image based on these signals can be displayed on one screen, and finally outputs an analog image signal from the D / A converter 5. I do. The digital image signal processing circuit 4 simultaneously outputs a signal indicating an image display area based on the analog broadcast signal (analog broadcast screen portion: H, other: L) and supplies it to the base of the transistor 10. In a screen portion other than the analog broadcast screen portion, a voltage obtained by dividing the power supply voltage by the resistors 8 and 9 is supplied to the reference voltage input portion 5a of the D / A converter 5; Is supplied from the voltage supplied to the base, the reference voltage increases, and the amplitude of the signal output from the D / A converter 5 increases. Therefore, the video based on digital broadcasting and the video based on analog broadcasting, which are simultaneously compressed and displayed on the screen of the CRT monitor 7 via the analog image signal processing circuit 6, have substantially the same brightness on the screen. The viewer does not feel uncomfortable.

FIG. 2 shows another embodiment of the present invention. The difference from FIG. 1 is that the configuration of the reference voltage supply circuit to the D / A converter 5 is different. That is, the common terminal 21a of the switch 21 is connected to the reference voltage input terminal 5a of the D / A converter 5, and the reference power supply circuit 2 is connected to the switching terminal 21b of the switch 21.
The reference power supply circuit 23 is connected to the switching terminal 21c. In this case, the digital image signal processing circuit 4
Outputs a signal indicating the display area of the analog broadcast image (H during analog broadcast, L in other cases),
1 is switched. During the period of displaying an image other than an analog broadcast image (ie, displaying a digital image), the reference voltage of the reference power supply voltage circuit 22 is supplied to the terminal 5a of the D / A converter 5 via the switch 21. The switch 21 is switched during the display period of the analog broadcast image, and the reference voltage of the reference power supply voltage circuit 23 is supplied.
Therefore, since the reference voltage changes, the gain of the D / A converter 5 changes, and the amplitude of the output signal from the converter 5 increases. Therefore, the brightness of each screen portion where both digital and analog image signals are compressed and displayed as one screen becomes almost the same, and the viewer does not feel uncomfortable.

[0012]

As described above, according to the present invention, when an image based on digital broadcasting and an image based on analog broadcasting are compressed and displayed on the same screen, the brightness of both images displayed on the screen is reduced. This makes it possible for the viewers to feel the same.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram showing an embodiment of a television receiver of the present invention.

FIG. 2 is a circuit diagram showing another embodiment of the present invention.

FIG. 3 is a circuit configuration diagram showing a conventional television receiver.

[Explanation of symbols]

 1: Digital broadcast signal decode circuit 2: Analog broadcast signal decode circuit 3: A / D converter 4: Digital image processing circuit 5: D / A converter 9: Transistor 10, 11: Resistance

Claims (4)

[Claims] A digital broadcast decoding circuit for demodulating a digital broadcast signal; an analog broadcast decode circuit for demodulating an analog broadcast signal; an A / D converter for converting an output of the analog broadcast decode circuit into a digital signal; A digital image processing circuit for performing image processing on the output of the broadcast decoding circuit and the output of the A / D converter; An A converter, and a voltage supply circuit for supplying a voltage to the gain adjustment input terminal of the D / A converter, so that a video based on a digital broadcast signal and a video based on an analog broadcast signal are displayed on the same screen. When displaying, the output voltage of the voltage supply circuit is changed to increase the gain of the D / A converter for analog broadcast signals. And a television receiver. 2. The television receiver according to claim 1, wherein the voltage supply circuit has a resistor, and an output voltage is changed by changing a current flowing through the resistor. 3. The television receiver according to claim 1, wherein the voltage supply circuit has a plurality of reference power supplies, and the output voltage is changed by switching the plurality of reference power supplies. 4. A digital broadcast decoding circuit for demodulating a digital broadcast signal, an analog broadcast decode circuit for demodulating an analog broadcast signal, an A / D converter for converting an output of the analog broadcast decode circuit into a digital signal, A digital image processing circuit for performing image processing on the output of the broadcast decoding circuit and the output of the A / D converter; An A converter, a voltage supply circuit for supplying a voltage to the input terminal for gain adjustment of the D / A converter, and an image based on a digital broadcast signal and an image based on an analog broadcast signal are displayed on the same screen. In the case, based on the signal output indicating the display position of the analog broadcast or digital broadcast screen, by changing the output voltage of the voltage supply circuit, A television receiver wherein the gain of a D / A converter for an analog broadcast signal is increased.