JP2001024905A - Video signal input system for display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce flickering of an image. SOLUTION: A reference level detecting part 40 generates a reference level by smoothing a signal corresponding to the back porch of an R (G or B) signal outputted from an RGB signal input part 22. This reference level is held for a prescribed period by a reference level holding part 42. The RGB signal outputted from the RGB signal input part 22 and the reference level outputted from the reference level holding part 42 are inputted to a changeover switch 30 and by switching a connecting state of the changeover switch 30 on the basis of a timing signal outputted from an exchange timing signal generating part 28, a signal level corresponding to the pedestal level of the RGB signal is exchanged with the reference level.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal input system for a display device which performs display based on a video signal composed of RGB signals.

[0002]

2. Description of the Related Art Liquid crystal display devices have advantages such as space saving and low power consumption, and are therefore used for various applications including portable electronic devices. For example, a liquid crystal display device is often used as an in-vehicle display device for displaying an image output from a navigation device, a television receiver, or the like.

As described above, when a liquid crystal display device is used in a vehicle, a single liquid crystal display device is shared by a plurality of in-vehicle devices such as a navigation device to perform display because of installation space or cost. That is common. Also, for in-vehicle devices such as navigation devices,
In many cases, a video signal in the form of an RGB signal is output in order to display a clearer image. For this reason, an in-vehicle liquid crystal display device generally receives a video signal in the form of an RGB signal. Met. Therefore, the in-vehicle television receiver outputs a video signal generated by converting an NTSC signal into an RGB signal, and inputs the video signal to a liquid crystal display device for display.

[0004]

Generally, in a display device, the display device itself determines a reference color to be used as a reference when reproducing colors. In a liquid crystal display device, this reference color is often set to black. That is, the liquid crystal display device extracts the pedestal level included in the back porch of the input RGB signal, and reproduces another color using the reference color corresponding to the signal level as black. However, NTS
Since the RGB signal generated based on the C signal includes noise peculiar to the back porch, there is a problem that the pedestal level fluctuates due to the influence of the noise. The specific noise included in the back porch of the RGB signal is caused by the color burst signal superimposed on the back porch in the NTSC signal. Since this color burst signal is unnecessary in the RGB signal, it is removed when converting the NTSC signal into the RGB signal. However, it is difficult to completely remove the color burst signal, and the back porch of the RGB signal is difficult. Noise due to the residual color burst signal is included.

For this reason, when the pedestal level included in the back porch of the RGB signal is extracted to determine the reference color as in the above-described liquid crystal display device, the reference color is changed for each scanning line by the fluctuation of the pedestal level. When reproducing the same color on different scanning lines, the reproduction color slightly changes depending on the scanning line. This slight change in the reproduced color appears as flickering of the image, which causes a decrease in image quality.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a video signal input method for a display device capable of reducing flickering of a video.

[0007]

In order to solve the above-mentioned problems, the present invention relates to a video signal input method for a display device, which uses RG.
When a display is performed based on the video signal composed of the B signal, a signal level replacement unit for replacing a signal level corresponding to a pedestal level of an RGB signal input to the display device with a predetermined reference level is provided. For this reason,
When the reference color is set based on the pedestal level in the display device, it is possible to prevent the reference color from fluctuating due to the influence of noise or the like, and to reduce flickering of an image.

When the video signal (video signal composed of RGB signals) is generated based on the NTSC signal, the above-mentioned signal level replacement means includes a reference level generation means, a replacement timing instruction means, and a switching means. It is desirable to have The reference level generating means generates a reference level based on at least one of the front porch and the back porch signal levels included before and after the horizontal synchronizing signal of the video signal. Replace the pedestal level contained in the pouch with the generated reference level. In this case, since the reference level generation means generates the reference level based on the signal level of at least one of the front porch and the back porch included in the video signal, the reference level corresponding to the input video signal Can be generated, and even when the signal levels of the front porch and the back porch change due to a channel change or the like, the reference level can be changed following the change. Also, N
Although the RGB signal generated based on the TSC signal includes noise peculiar to the back porch, the pedestal level included in the back porch is replaced with the reference level by the switching means at the timing designated by the replacement timing designating means. This can prevent the reference color from being changed due to noise included in the back porch.

Preferably, the reference level is generated by smoothing the signal level of a predetermined section included in the back porch of the RGB signal and including a portion corresponding to the color burst signal of the NTSC signal. As described above, since the noise corresponding to the color burst signal of the NTSC signal causes flickering of the image, R
By smoothing a portion corresponding to the color burst signal in the GB signal to generate a reference level without level fluctuation, it is possible to set an accurate reference color reflecting an actual signal level.

The above-mentioned reference level is generated based on the video signal corresponding to one or a plurality of scanning lines and held for a predetermined period, and is at least higher than the scanning line of the video signal for which the reference level is generated. It is desirable to replace the pedestal level contained in the back porch of the video signal input with a delay of one scanning line or more. By performing the above-described reference level replacement process on a video signal input with a delay of one scan line or more after the generation of the reference level, it is possible to secure a certain amount of time from the generation of the reference level to the replacement. Therefore, the processing speed can be reduced. For this reason, the range of selection of components to be used is widened, and the cost can be reduced. Also, 1
By targeting the video signal input with a delay of the scanning line or more to the reference level replacement processing, the signal level of the pedestal level used to generate the reference signal can be replaced by the reference signal, It is possible to set an accurate reference color reflecting the actual signal level.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image display system according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a configuration of a video display system according to one embodiment. Video display system 10 shown in FIG.
0 includes a TV (television) tuner 1, a video signal input unit 2, a navigation device 3, a navigation video signal input unit 4, a video changeover switch 5, and an LCD (liquid crystal display device) 6.

The TV tuner 1 generates an NTSC signal based on a television wave received by the receiving antenna 7, and converts the NTSC signal into a video signal composed of an RGB signal and a synchronization signal. The synchronization signal includes a horizontal synchronization signal and a vertical synchronization signal.

The video signal input unit 2 generates a predetermined reference level based on the RGB signal and the synchronization signal output from the TV tuner 1, and converts the signal level corresponding to the pedestal level included in the back porch of the RGB signal into this signal. Replace with reference level. RG after this replacement process
The B signal and the synchronizing signal become a video signal output from the video signal input unit 2. Details of the configuration of the video signal input unit 2 will be described later.

The navigation device 3 detects the position of the vehicle and displays a map around the position of the vehicle, and performs route search and route guidance to the destination selected by the user. The video signal output from the navigation device 3 is
It has the form of an RGB signal. The navigation video signal input unit 4 performs necessary processing such as signal amplification on a video signal output from the navigation device 3.

The video changeover switch 5 is connected to the video signal input unit 2
And the video signal output from the navigation video signal input unit 4 are input, and by switching the connection state according to an operation or the like given by the user, any of these video signals is Select and output. The LCD 6 performs display based on a video signal output from the video changeover switch 5.

The above-mentioned video signal input unit 2 includes a horizontal synchronizing signal detection unit 20, an RGB signal input unit 22, a reference level generation unit 24, a reset signal generation unit 26, a replacement timing signal generation unit 28, and a changeover switch 30. It is configured.

The horizontal synchronizing signal detecting section 20 receives the synchronizing signal output from the TV tuner 1 and detects a horizontal synchronizing signal from the synchronizing signals. RGB signal input unit 2
Reference numeral 2 receives an RGB signal output from the TV tuner 1 and performs necessary processing such as signal amplification on the RGB signal.

The reference level generation section 24 generates a predetermined reference level based on the RGB signals output from the RGB signal input section 22 and holds this reference level for a predetermined period. Reference level holding unit 4
2 is included.

The reference level detecting section 40 extracts a signal corresponding to the back porch of the RGB signal output from the RGB signal input section 22, removes a high frequency component from the extracted signal and smoothes it, thereby converting a DC component. To detect. The detected DC component becomes the reference level detected by the reference level detection unit 40.

The reference level holding section 42 holds the reference level output from the reference level detecting section 40 for a predetermined period.
The timing of holding the reference level is set based on the reset signal output from the reset signal generator 26.

The reset signal generator 26 detects the rise of the horizontal synchronizing signal output from the synchronizing signal detector 20 and after a predetermined time has passed, the reference level holding unit 42
The reset signal is output toward. The above-mentioned predetermined time is set to a time t corresponding to the back porch of the RGB signal.

The replacement timing signal generation unit 28
A timing signal for replacing a signal level corresponding to the pedestal level included in the back porch of the GB signal with the reference level generated by the reference level generation unit 24 is generated and output to the changeover switch 30.

The changeover switch 30 is a switch that switches the connection state based on a timing signal output from the replacement timing signal generator 28. The switch 30 outputs the reference level output from the reference level generation unit 24 while the timing signal is output, and outputs the RGB signal output from the RGB signal input unit 22 while the timing signal is not output. Is output.

The above-described LCD 6 corresponds to a display device, and the reference level generator 24, the replacement timing signal generator 28, and the changeover switch 30 correspond to signal level replacement means.
In addition, the reference level generation unit 24 includes a reference level generation unit,
The replacement timing signal generator 28 corresponds to replacement timing instruction means, and the changeover switch 30 corresponds to switching means.

The video display system 100 of this embodiment has such a configuration. Next, when the video signal input unit 2 replaces the signal level corresponding to the pedestal level of the RGB signal with a predetermined reference level. Will be described. Here, only the R signal among the RGB signals will be described, but the same processing is performed for the G signal and the B signal.

FIG. 2 is a signal waveform diagram for explaining the operation of the video signal input unit 2. FIG. 2A shows an example of the waveform of the R signal output from the RGB signal input unit 22. FIG. 2B shows the waveform of the horizontal synchronization signal output from the horizontal synchronization signal detection unit 20. Is shown. FIG.
2C shows the waveform of the timing signal output from the replacement timing signal generator 28, and FIG. 2D shows the waveform of the reset signal output from the reset signal generator 26. FIG. 2E shows the waveform of the reference level held in the reference level holding unit 42.
(F) shows the waveform of the R signal in which the signal level corresponding to the pedestal level included in the back porch has been replaced by the reference level.

When an RGB signal and a synchronization signal are input from the TV tuner 1 to the video signal input unit 2, the horizontal synchronization signal detection unit 20 extracts and outputs the horizontal synchronization signal shown in FIG. The replacement timing signal generating section 28 generates a timing signal which becomes high level only during a time t after the horizontal synchronizing signal rises and becomes low level during the other periods (FIG. 2 (c)). In response to the high level period of the timing signal, the signal level corresponding to the pedestal level of the back porch of the R signal shown in FIG. 2 (e)) (FIG. 2 (f)).

When a time t has elapsed since the rise of the horizontal synchronizing signal, a reset signal is output from the reset signal generator 26 (FIG. 2 (d)), so that the replacement process corresponding to the pedestal level is performed. The reference level generated by smoothing the portion corresponding to the back porch of the R signal is taken in and held by the reference level holding unit 42 in synchronization with the reset signal (FIG. 2 (e)) and delayed by one scanning line. The reference level used for the replacement process corresponding to the input R signal is prepared.

As described above, in the video display system 100 of the present embodiment, the RG generated based on the NTSC signal is used.
When a display is performed by the LCD 6 using the video signal composed of the B signal and the synchronization signal, the video signal input unit 2 converts the signal level corresponding to the pedestal level included in the back porch of the RGB signal into the reference level generation unit 24. An RGB signal replaced with the generated reference level is generated, and display is performed based on the RGB signal. Therefore, when extracting the pedestal level from the back porch and setting the reference color in the LCD 6, it is possible to prevent the reference color from fluctuating due to the fluctuation of the pedestal level due to the noise included in the back porch. In addition, it is possible to reduce the flicker of the image.

Further, the video signal input unit 2 of the present embodiment
A reference level is generated by smoothing the signal level corresponding to the pedestal level included in the back porch for each scanning line of the RGB signal, and the generated reference level is set to the pedestal level of the RGB signal of the next input scanning line. Since the signal level is replaced with the corresponding signal level, it is possible to set an accurate reference color reflecting the actual signal level of the RGB signal.
Accordingly, even when the pedestal level of the RGB signal changes, for example, when the receiving channel is changed in the TV tuner 1, the reference level can be generated so as to follow this change, and an accurate reference level based on this reference level can be generated. Color reproduction becomes possible.

Further, the video signal input unit 2 of the present embodiment
The video signal composed of the RGB signal and the synchronization signal is T
When the video signal is input from the V tuner 1, the video signal is subjected to predetermined processing, and then the video signal composed of the RGB signal and the synchronization signal is output to the LCD 6 via the video switch 5 again. Therefore, even in the existing video display system, there is an advantage that satisfactory display can be performed only by adding the video signal input unit 2 of the present embodiment between the TV tuner and the LCD.

The present invention is not limited to the above embodiment, and various modifications can be made within the scope of the present invention. For example, in the above-described embodiment, when the reference level generation unit 24 generates the reference level,
A signal corresponding to the back porch of the RGB signal is extracted, a high-frequency component is removed from the extracted signal and smoothing is performed to detect a DC component, and this is used as a reference level. A signal corresponding to the front porch may be extracted and generated. When the reference level is generated based on the signal corresponding to the front porch in this manner, the timing used to replace the reference level with the signal level corresponding to the pedestal level of the back porch was used when generating the reference level. The replacement may be performed on the back porch that is input immediately after the front porch, or the replacement may be performed on the back porch included in the scanning line that is input one or more scan lines later.

In the above-described embodiment, the horizontal synchronizing signal included in the synchronizing signal is detected, and the reference level and the signal level corresponding to the pedestal level of the back porch are determined for each scanning line based on the cycle of the horizontal synchronizing signal. However, the replacement operation may be performed at a cycle set based on the vertical synchronization signal detected by the vertical synchronization signal included in the synchronization signal.

In the above-described embodiment, each time one scanning line is input, the reference level is generated based on the scanning line. However, the reference level is generated based on a plurality of scanning lines. You may make it. Specifically, a plurality of reference levels are generated corresponding to a plurality of sequentially input scanning lines, each of them is held for a predetermined period, and an averaging process or the like is performed based on the plurality of reference levels. Thus, a reference level to be replaced with a signal level may be generated. In this case, since the reference level is generated based on the plurality of scanning lines, the fluctuation of the reference level can be further reduced, and the flicker of the image on the LCD 6 can be further reduced.

In the above-described embodiment, the case where the LCD is used as the display device has been described. However, the display device is not limited to the LCD, and a video signal in the form of an RGB signal is input. The present invention can also be applied to other display devices that determine the reference color by detecting the pedestal level from the display device.

In the above-described embodiment, the case where the present invention is applied to the case where the display is performed by the LCD 6 based on the video signal in the form of the RGB signal input from the TV tuner 1 in the vehicle interior has been described. The present invention is not limited to this. Even if the display device is used in a place other than the interior of the vehicle, the display device performs display based on a video signal in the form of an RGB signal. Can be applied.

[0038]

As described above, according to the present invention, the signal level corresponding to the pedestal level of the input RGB signal is replaced with a predetermined reference level, and the reference color is changed in the display device based on the pedestal level. At the time of setting, it is possible to prevent the reference color from fluctuating due to the influence of noise or the like, and it is possible to reduce the flickering of an image.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a video display system according to an embodiment.

FIG. 2 is a signal waveform diagram for explaining an operation of a video signal input unit.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 TV (television) tuner 2 video signal input unit 3 navigation device 4 navigation video signal input unit 5 video changeover switch 6 LCD (liquid crystal display device) 7 reception antenna 20 horizontal synchronization signal detection unit 22 RGB signal input unit 24 reference level generation Unit 26 reset signal generating unit 28 replacement timing signal generating unit 30 changeover switch 40 reference level detecting unit 42 reference level holding unit 100 video display system

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Satoshi Hara 1-8-1, Nishigotanda, Shinagawa-ku, Tokyo Alpine, Inc. F-term (reference) 5C021 PA28 PA34 PA58 PA62 PA64 SA05 SA11 XA61 5C066 AA03 BA02 CA05 EA08 EA26 GA01 GA11 GA18 GA33 GB09 GB12 KC02 KD06 KG01 KG08

Claims (4)

[Claims] 1. A display device for performing display based on a video signal composed of RGB signals, and a signal level replacement for replacing a signal level corresponding to a pedestal level of an RGB signal input to the display device with a predetermined reference level A video signal input method for a display device, comprising: 2. The video signal according to claim 1, wherein the video signal is generated based on an NTSC signal, and the signal level replacement unit includes at least a front porch and a back porch included before and after a horizontal synchronization signal of the video signal. Reference level generating means for generating the reference level based on one signal level; replacement timing instructing means for instructing a timing of replacing the pedestal level included in the back porch with the reference level; Switching means for replacing the pedestal level with the reference level at a designated timing. 3. The signal processing apparatus according to claim 2, wherein the reference level generating means smoothes a signal level in a predetermined section included in a back porch of the RGB signal and including a portion corresponding to a color burst signal of the NTSC signal. A video signal input method for a display device, wherein the reference level is generated by: 4. The replacement timing according to claim 2, wherein the reference level generation unit generates and holds the reference level based on the video signal corresponding to one or a plurality of scanning lines. The instruction unit instructs the timing of the video signal input at least one scan line later than the scan line of the video signal for which the reference level is to be generated. A video signal input method for a display device, wherein the pedestal level is replaced using the reference level held by a reference level generation unit.