KR100326289B1 - Video signal output apparatus synchronized with the external system output - Google Patents

Abstract

A digital TV relates to a video signal output device synchronized with an external system output to prevent a screen from flowing by synchronizing a video output based on an external video synchronization signal when the screen is not synchronized. In the digital broadcasting reception system, a phase locked loop (PLL) circuit for generating a clock required for a system based on an external video synchronization signal, an internal clock generator for generating an internal system clock for operation inside the system, and And a control unit controlling to select and use any one of clocks generated by the PLL circuit and the internal clock generator. Therefore, when the screen is out of sync, the video flow can be solved by selecting the sync of the video output based on the external sync signal according to the input of a control switch or a microcomputer external control signal.

Description

Video signal output apparatus synchronized with the external system output}

The present invention relates to a digital broadcast receiving system such as a digital TV (DTV) or a European digital TV (DTTV). More specifically, when the screen is out of sync, the video output is synchronized based on an external sync signal. The present invention relates to a video signal output device synchronized with an external system output to prevent a screen from flowing.

In accordance with the recent digital trend, high definition (HD) digital broadcasting will soon begin. Therefore, a TV system capable of receiving and watching digital broadcasting that satisfies the strict requirements of high quality and high sound quality in terms of service has been required. In this regard, MPEG (Moving Picture Experts Group) 2 is a very suitable technical standard. . Most digital broadcasting systems adopt MPEG2 video as the video encoding method and MPEG2 system as the multiplexing method.

1 is a configuration diagram showing an example of a general digital broadcasting receiving system. The system shown in FIG. 1 includes a TS (Transport Stream) unit 12 for separating video, audio, and data streams from a broadcast signal input in the form of a transport stream (TS), and a video for decoding the separated video data. A decoder 13, a format converter 14 for converting the decoded video data into a preset display format, and an analog video of a color signal (R, G, B) format by inserting additional information to be displayed on the screen into the format converted video data. OSGM (On Screen Graphic Mixer) 15 for outputting the signal is provided. The video decoder 13, the format converter 14, and an oscillator (OSC) for providing a clock necessary for the OSGM 15 are provided.

In FIG. 1, the TS unit 12 receives a PES stream by a fixed clock CLK1 and an enable signal EN that are applied from the outside, and separates a video, audio, and data stream. The video stream is input to the video decoder 13, the audio stream is input to an audio decoder not shown, and the data stream is input to a controller not shown. The video decoder 13 receives video data in synchronization with the clock CLK2 applied from the TS unit 12. The OSC 11 converts a predetermined frequency, that is, a clock (CLK3) frequency of 74.25 MHz for 1080 interlace and 72.175 MHz for 720 progressive to the video decoder 13, the format converter 14, and the OSGM 15. Supply. The video decoder 13 decodes MPEG-2 standard video data from the TS unit 12 using a clock frequency of 74.25 MHz applied from the OSC 11. The format converter 14 converts the video data decoded by the video decoder 13 into a preset display standard by using an input clock frequency of 74.25 MHz. The format-converted video data is inserted as additional information to be displayed on the screen through the OSGM 15 and output as an analog color signal of red (R), green (G), and blue (B).

However, such a digital broadcasting reception system has a problem that the screen is not synchronized when the video output is output as its own synchronization signal when monitoring or editing the video signal in a broadcast studio environment, causing the screen to flow during shooting.

Accordingly, an object of the present invention is to select the synchronization of the video output based on the external synchronization signal according to the input of the control signal through the operation button or the microcomputer instead of the internal clock generated in the system when the screen is not synchronized. The present invention provides a video signal output device synchronized with an external system output.

1 is a block diagram showing a general digital broadcasting receiving system,

Figure 2 is a block diagram showing a digital broadcast receiving system to which the present invention is applied.

<Description of the symbols for the main parts of the drawings>

12: TS unit 13: video decoder

14: format converter 15: OSGM

16: PLL 17: Internal Clock Generator

18: clock switch 19: clock selector

20: control unit

A video signal output device synchronized with an external system output of the present invention for achieving the above object is a phase locked loop (PLL) circuit for generating a clock required for a system based on an external video synchronization signal in a digital broadcast reception system. And an internal clock generator for generating an internal system clock for operation inside the system, and a controller for selecting and using any one of clocks generated by the PLL circuit and the internal clock generator.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 shows a video signal output device synchronized to an external system output according to a preferred embodiment of the present invention. The system shown in FIG. 2 includes the configuration of the general digital broadcasting reception system of FIG. 1, and is a phase-locked loop that generates a clock of the system based on an external video synchronization signal instead of an OSC (11 in FIG. 1) fixed at a single frequency. A phase locked loop (PLL) circuit, an internal clock generator 17 for generating an internal system clock of a digital TV, a clock selector 19 for inputting a synchronous selection signal from an external button or a microcomputer, and a clock selection; And a clock switch 18 that is switched by the control signal of the unit 19 and selects an external system clock. The PLL circuit 16 is composed of a phase detector, a low pass filter (LPF), a voltage controlled oscillator (VCO), and the like. Since this is a general configuration, detailed illustration of the drawings is omitted.

The operation of the video signal output device synchronized with the external system output having the above configuration will be described in detail as follows.

First, in a digital TV, an RF signal is received and demodulated by an RF tuner, and then decoded by a channel decoder to generate a transport stream. The TS unit 12 receives a digital broadcast transport stream (TS IN) input from an RF reception signal block (not shown) and a channel block (not shown), and separates video, audio, and data streams, Output to each decoder. The video stream is input to a video decoder 13, and the video decoder 13 decodes the input video data based on the clock CLK2 from the TS unit 12. The format converter 14 converts the decoded video data received from the video decoder 13 into a preset display format according to the frame rate information. The format-converted video data is inserted as additional information to be displayed on the screen through OSGM (On Screen Graphic Manager) 15 and outputted as an analog color signal of red (R), green (G), and blue (B). Meanwhile, the PLL circuit 16 receives an external synchronization signal from an external synchronization generator (not shown) which is installed outside the system and outputs a horizontal synchronization signal by a user's key input setting. The PLL circuit 16 receives an external video synchronization reference signal such as a horizontal synchronization signal or a black burst signal by an external synchronization generator, and generates a system clock based on the input external input synchronization signal. The internal clock generator 17 generates a system clock inside the digital TV. That is, a clock CLK3 frequency of 74.25 MHz for the 1080 interlace and 72.175 MHz for the 720 progressive is supplied to the video decoder 13, the format converter 14, and the OSGM 15, respectively. The controller 20 selects and controls the clock of the external system according to a user's selection signal. The clock selector 19 may directly select an external sync input by directly operating a system external switch, or may indirectly select an external sync input through a microcomputer. The clock switch 18 has a contact connected to each of the output terminals of the PLL circuit 16 and the internal clock generator 17, and switches one of the two contacts in accordance with a control signal applied from the clock selector 19. Select the clock. That is, the clock switch 18 selects the clock generated by the internal clock generator 17 in the normal case according to the control signal of the clock selector 19, and generates the PLL circuit 16 when the screen is not synchronized. Select the clock to be used. Therefore, when the external synchronization input is selected by the clock switch 18, the system clock signal generated by the PLL circuit 16 based on the external synchronization signal is the video decoder 13, the format converter 14, and the OSGM 15. To ensure accurate motivation.

As described above, the video signal output device synchronized with the external system output according to the present invention, in the digital TV, when the screen is out of sync, the external synchronization signal according to the input of the control signal through the operation button or the microcomputer By selecting the synchronization of the video output as a reference, the effect that the screen flow disappears.

Claims (3)

In the digital broadcasting reception system, A phase locked loop (PLL) circuit for generating a clock required for the system based on an external video synchronization signal; An internal clock generator for generating an internal system clock for operation inside the system; And And a control unit for controlling to select and use any one of clocks generated by the PLL circuit and the internal clock generator. The apparatus of claim 1, wherein the external video synchronization signal is a horizontal synchronization signal or a black burst signal. The method of claim 1 or 2, wherein the control unit A clock selector for outputting a selection signal for selecting a clock to be synchronized according to a user operation; And And a clock switch for disconnecting a contact from the internal clock generator according to a selection signal of the clock selector and switching the contact to the phase locked loop circuit to select an external system clock. Signal output device.