KR20000044692A - Caption display device using graphic controller - Google Patents

Abstract

PURPOSE: A caption display device using a graphic controller is provided to reduce a manufacturing cost by using pixel data of a graphic controller without IC for OSD(On Screen Display) for realizing OSD. CONSTITUTION: A caption display device using a graphic controller comprises a microprocessor(11), a graphic controller(12), an RAM-DAC(15), and a video switch(17). The microprocessor executes programs realized OSD. The graphic controller outputs pixel data according to a control of the microprocessor. The RAM-DAC converts the pixel data to analog RGB signals. The video switch mixes a part of the analog RGB signals and the pixel data and outputs the mixed part on a display portion.

Description

Subtitle Display Device Using Graphic Controller

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an OSD (On Screen Display) for displaying captions on a television screen, and more particularly, to a caption display apparatus using a graphic controller.

Displaying subtitles on a television is called OSD in English. Conventionally, an OSD dedicated IC is used to display subtitles. In the case of television, OSD data is generated by using an OSD-only IC, and the OSD is implemented on a television screen by mixing the data with the television video signal. An OSD implementation circuit using a conventional OSD dedicated IC is shown in FIG. The system shown in Fig. 1 shows a circuit using TFTLCD as a display means and implementing a OSD as a system capable of graphic processing as well as a television screen.

Referring to FIG. 1, there is a video signal unit 1, and a composite video signal output from the video signal unit 1 is input to a chroma mixing IC (CHROMA & MIXING IC; 5) of an LCD module. have. The chroma mixing IC 5 receives the RGB signal and the video switch signal VSW from the OSD IC 3, and the control signal CONTROL of the microcomputer 9 is input to the OSD IC 3. It is becoming. The RGB signal outputted from the chroma mixing IC 5 is inputted to the TFTLCD 7, and the synchronization signal H / V SYNC outputted from the TFTLCD 7 is inputted to the OSD IC 3.

The OSD IC 3 generates OSD data under the control of the microcomputer 9 and in accordance with the horizontal / vertical synchronization signal H / VSYNC output from the TFTLCD 7 and converts the OSD data into the TFTLCD 7. Outputs an RGB signal and a video switch signal (VSW) for display on the screen. The RGB signal and the video switch signal VSW output from the OSD IC 3 are input to the chroma mixing IC 5 of the next stage. In the chroma mixing IC 5, the composite image signal (video signal + blanking signal + synchronization signal + color burst signal) output from the video signal unit 1 and the RGB signal output from the OSD IC 3 are video. One RGB signal is output by mixing according to the switch signal VSW. The RGB signal output from the chroma mixing IC 5 is input to the TFTLCD 7 and the video and subtitles are displayed on the TFT LCD 7 screen according to the RGB signal.

The implementation of an OSD using a conventional OSD-only IC is performed in a manner similar to that of FIG. In addition, the OSD IC is mainly used for televisions, but not only televisions but also general graphic processing systems use OSD-specific ICs in addition to graphic controllers to realize OSD. In the case of a graphic processing system, it may be somewhat complicated, but even though subtitles can be expressed as a part of the graphic by using a graphic controller, an OSD-specific IC is used in addition to the graphic controller. This happens. This can be said to be contrary to the recent trend of light and thin electronic products.

Accordingly, it is an object of the present invention to realize an OSD using a graphics controller instead of an OSD dedicated IC in a graphics processing system.

1 is a conventional OSD implementation circuit.

2 is an OSD implementation circuit in accordance with an embodiment of the present invention.

Figure 3 is a waveform diagram of each part of the present embodiment.

4 is an implementation principle of various colors according to RGB signal combination.

* Description of the symbols for the main parts of the drawings *

11: CPU 13: Graphic Controller

15: ram deck 17: video switch

19: TFTLCD 21: TV Tuner

In order to achieve the above object, a caption display apparatus using a graphic controller according to the present invention includes a microprocessor for executing an OSD implementation program, a graphic controller for outputting pixel data under control of the microprocessor, and converting the pixel data into an analog RGB signal. RAMDAC for converting the signal, and a video switch for mixing the analog RGB and a portion of the pixel data to output to the display device.

Hereinafter, the present invention will be described in detail with reference to the exemplary embodiment of FIG. 2. 2 is configured to generate OSD data as a pixel data signal using a graphic controller, add this pixel data signal to an analog RGB signal, and output the same together to a TFT LCD to realize the OSD. In addition, the present invention is applied to a system for outputting through a TFT LCD at the same time not only graphics processing but also TV reception.

Referring to Fig. 2, there is a CPU 11, and a graphic controller 13 is connected to a bus of the CPU 11. The 8-bit pixel data V0 to V7 of the graphics controller 13 are input to a RAMDAC 15 of the next stage, and the RAMDK 15 is transferred from the CPU 11 between the CPU 11 and the RAMDK 15. ) Is connected to the signal line (PALETTE DATA R / W) for reading / writing. The analog RGB output (ANALOG RGB) and the data active signal DA of the ram deck 15 are next input to a video switch 17. The lower four bit signals V0 to V3 of the 8 bit pixel data V0 to V7 outputted by the graphic controller 13 are also input to the video switch 17. Among the lower four bits V0 through V3 of the pixel data V0 through V7, the lower three bits V0 through V2 and the fourth bit signal V3 are separated from each other and input to the video switch 17. The RGB and VSW signals output from the video switch 17 are input to the TFTLCD 19, and the synchronization signal SYNC and the video signal from the TV tuner 21 are transferred to the TFT LCD 19. It is being input. The horizontal vertical synchronizing signal H / VSYNC output from the TFTLCD 19 is input to the graphic controller 13 earlier.

The CPU 11 manages the entire system executing or necessary for the OSD implementation program. The graphic controller 13 outputs 8-bit pixel data V0 to V7 for the graphic image.

Pixels (dots) are the smallest points (dots) that make up the screen on the display. For example, a screen of 640 x 400 dots can be screened with 400 in the lateral direction (256,000 pixels in total). Will be constructed. In the color display, three dots of red (R), green (G), and blue (B), which are three primary colors of the phosphor, are set as one pixel. The pixel data is data defining the color, attributes, and the like of pixels constituting the screen, and the graphic controller 13 outputs such pixel data. The output of such pixel data is made in synchronism with the horizontal / vertical synchronization signal H / VSYNC from the TFTLCD 19 in the graphic controller 13.

The synchronization signal CSYNC generated by the TV tuner 21 is input to the TFTLCD 19, and a horizontal / vertical synchronization signal H / VSYNC is generated inside the TFTLCD 19. The horizontal / vertical synchronization signal H / VSYNC is input to the graphic controller 13, and the graphic controller 13 produces an image synchronized with the signal H / VSYNC.

Since the pixel data V0 to V7 are digital signals, the pixel data V0 to V7 cannot be directly input to a TFTLCD 19 or a monitor that handles analog signals. Therefore, it is necessary to convert the digital pixel data V0 to V7 into an analog signal using the ram deck 15.

The ram deck 15 is a kind of palette that stores information about 256 colors, and stores information related to a combination of RGB signals for representing this color on the screen. The 256 colors can be converted by the CPU 11 and the CPU 11 can write or read the colors to the ram deck 15 by the PALETTE DATA R / W. When the 8-bit pixel data V0 to V7 is input from the graphic controller 13 to the ram deck 15, the ram deck 15 outputs an analog RGB signal for expressing a color designated by the pixel data V0 to V7. . Since the pixel data V0 to V7 are digital signals, they cannot be directly input to the TFTLCD 19, but must be converted into analog signals and input. In other words, a process of converting the analog RGB signal is required, and this is done by the ram deck 15. The ram deck 15 also outputs the data active signal DA in addition to the analog RGB signal ANALOG RGB.

The analog RGB signal ANALOG RGB and the data active signal DA are next input to the video switch 17.

The video switch 17 is a kind of analog switch and an IC. In case of digital switch, if high is inputted, only high is outputted regardless of voltage. That is, if the reference voltage for determining the high and low is 2.5 [V], if the input is 5 [V], the output of the digital switch may be 3 [V]. As an example of a digital switch, a switching transistor can be recalled. However, unlike the digital switch, the analog switch outputs the input signal without change in voltage or waveform. The video switch 17 is also an IC type solid state switch used for turning on / off a video signal.

As described above, the video switch 17 has four bits of pixel data V0 to VO output from the graphic controller 13 in addition to the analog RGB signal ANALOG RGB and the data active signal DA output from the ram deck 15. V3) is input. The 4-bit pixel data V0 to V3 are divided into three-bit RGB signals V0 to V2 and a 1-bit control signal V3. Then, the video switch 17 mixes the analog RGB signal ANALOG RGB and the lower 3 bit signals V0 to V2 among the pixel data and outputs them to the TFTLCD 19. Then, the video of the TV and the OSD subtitles are output together on the TFTLCD 19 screen. This is how the OSD is implemented. To help understand this part, a timing chart of each signal is shown in FIG. 3.

3 shows an analog RGB signal (ANALOG RGB) and a horizontal synchronization signal (HSYNC), a data active signal (DA) input from the ram deck 15 to the video switch 17, and a video switch 17 from the graphic controller 13. The waveforms of the V0 to V3 signals and the VSW signals output by the video switch 17 are shown. Although the RGB signal output from the video switch 17 is not shown in FIG. 3, the RGB signal output from the video switch 17 is a waveform in which V0 to V3 are mixed with the analog RGB signal of FIG. 3. For reference, Vpp of general TV video signal is about 0.7 [V] and Vpp of V0 ~ V2 is 5 [V].

The Vpp value of the TV video signal is about 0.7 [V], and the level of each RGB signal for OSD that is ON SCREEN on this screen can be OSD if the level is more than 0.7 [V]. However, since the level of the analog RGB signal (ANALOG RGB) from the ram deck 15 is 0.7 [V], the output signal of the ram deck 15 cannot be used as a signal source for the OSD. Therefore, in the present embodiment, the OSD is implemented by using the pixel data V0 to V3 of 5 [V] of the graphic controller 13. For the OSD, there are a few more signals to consider: horizontal sync signal (HSYNC), data active signal (DA), and VSW signal.

During the synchronization period, i.e., during the period when the horizontal synchronization signal HSYNC is low, the OSD should not be influenced and the VSW signal should be low during the OSD. In other words, the OSD should be enabled only during the period during which the VSW signal is high and the data active signal DA is high. Therefore, in this embodiment, the timing of each signal is taken into consideration as shown in FIG.

In the present embodiment, the VSW signal is generated by inverting the V3 signal of the pixel data, the R signal of the third bit V2 of the pixel data, the G signal of the second bit of V1, and the first bit of V0. It is configured to represent the B signal. The lower 3 bits V0 to V2 of the pixel data are used to express only 8 colors of characters displayed in the OSD. The principle of expressing color using these three bits (V0 to V2) is shown in FIG.

RGB is the three primary colors of light. When these three primary colors are combined, all natural colors can be expressed. When the third bit V2 of the pixel data is high and the second bit V1 is high, the R signal and the G signal are mixed to become yellow (YELLOW). If all of the first, second, and third bits V0 to V2 are high, the color becomes white. As such, eight colors can be expressed by controlling the high / low of the lower 3 bits V0 to V2 of the pixel data.

As described above, the present embodiment is configured to implement the OSD by mixing three primary colors of RGB, so that only three bits (V0 to V2) of pixel data are used for the OSD. However, if the OSD is to be implemented in CMYK (Cyan, Magenta, Yellow, blacK) primary colors without following the present embodiment, it is also possible to configure 4 bits of pixel data to be used as the color signal during OSD. In other words, it is also possible to separate 5 bits from the pixel data output from the graphic controller 13 so that 1 bit is used to generate a VSW signal and the remaining 4 bits are used as color signals.

As described above, the caption display device using the graphic controller according to the present invention is configured to implement the OSD using pixel data of the graphic controller without using an OSD-only IC. In this way, the OSD can be implemented by using the pixel data of the graphics controller without using the OSD IC in the part where the OSD is required in the general graphic screen, thereby reducing the cost of the product due to the purchase of the OSD IC. In addition, the configuration of the circuit is simpler than in the prior art, thus making it possible to reduce the weight and thickness of the product. The present invention can be applied to various graphic screen processing systems such as televisions, monitors, car navigation systems, and car audio / video systems.

Claims (3)

A microprocessor running the OSD implementation, A graphics controller for outputting pixel data under the control of the microprocessor; A RAMDAC for converting the pixel data into an analog RGB signal; And a video switch for mixing the analog RGB signal and a part of the pixel data and outputting the mixed video signal to a display device. The caption display apparatus of claim 1, wherein the display apparatus is a TFTLCD. 3. The caption display using a graphic controller of claim 2, wherein a part of the pixel data mixed with the analog RGB signal is a color signal bit for expressing the color of the caption in the OSD and a control bit for controlling the OSD viewpoint. Device.