JPS62227296A - A/d conversion system - Google Patents

Abstract

PURPOSE:To improve resolution in the digitization of a video signal, by setting a voltage at a value corresponding to the maximum and the minimum values of the video signal in the periods of a burst signal and the video signal, and setting the voltage at the value corresponding to the maximum and the minimum values of a color video signal in the period of a synchronizing signal. CONSTITUTION:The video signal inputted from an input terminal l is A/D-converted at an A/D converter 2, then being inputted to a synchronizing signal detection circuit 3. At such a time, the voltage of VRT-VRB1 is impressed from a synchronizing signal period reference voltage generation circuit 5 as the reference voltages 100A and 100B of the A/D converter 2. The circuit 5 is separated from the converter 2 at the completing time of the synchronizing signal, and a burst signal/ video signal period reference voltage generation circuit 6 is connected to the converter 2, and the reference voltages 100A and 100B are switched to a VRT-VRB2. At the completing time of the video signal period, the reference voltages 100a and 100B are switched again to the VRT-VRB1. Hereinafter, the same operation is repeated. Thus, since thc reference voltage of the A/D converter 2 becomes a difference between the maximum value and the minimum value, the resolution of the A/D converter can be utilized over all area.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an A/D conversion system, and particularly to an A/D conversion system for color video.

[Conventional technology]

Conventionally, the difference between the highest and lowest values of the digitization reference voltage in a parallel color video A/L converter (to explain in terms of minute signals, the highest value of the video signal, VlLT, and the lowest value (+ctV)
For example, when an 8-bit A/D converter was used, A/D conversion was performed with a resolution of 256 levels.

[Problem that the invention seeks to solve]

level resolution, but the body signal period (
Even during the scanning period of the actual TV 1111i screen), A with a resolution of 256 levels, including the level equivalent to the synchronization signal.
/L) conversion, so the level resolution of only the video signal is 2.
The disadvantage is that the level resolution is reduced to approximately 85 inches (56 levels).

[Means to solve all problems]

The A/IJ conversion method of the present invention is based on the color bidet first . - during the period of the signal) and the video signal, the voltage shall be set according to the highest and lowest values of the video signal, and during the period of the synchronization signal, the voltage shall be set according to the highest and lowest value of the color video signal. It is configured with the following features.

〔Example〕

Figure 1 shows the application of the present invention to an A/L) converter - Implementation 91
FIG. 2 is a block diagram showing the configuration of the video signal.

First, looking at Figure 2, the input video signal is synchronization signal 2.
0, a burst signal (subcarrier reference signal) 21, and a video signal 22, and one frame of video signal continues after the front porch period 23 of the preceding video signal has elapsed. In general, the difference between the lowest value of the synchronizing signal 20 and the lowest values of the burst signal 21 and the video signal 22, that is, V
RBI VRBI is VxtT VRBI02/14
It becomes. Therefore, conventional VRT VRBI k is digitized with a resolution of a predetermined number of levels (for example, 256 levels when digitizing with 8 bits), but during the synchronization signal period, VLTr - VRBI
>VR'l' during the burst signal and video signal period with a predetermined resolution of a predetermined number of levels.By digitizing VRBI with a predetermined resolution.

Next, an embodiment to which the invention is applied will be described with reference to FIG. The video signal input from the video signal input terminal L is A/D converted by the A/D converter 2, and the converted 8-bit digital signal, for example, is output from the video signal output terminal L.
A and is also input to the synchronization signal detection circuit 3. At this time, the reference voltage of the width converter 2 is 100A/1oo
B (bath voltage is applied. The synchronization signal detected by the synchronization signal detection circuit 3 is input to the timing generation circuit 4.

The timing generation circuit 4 applies an analog switch disconnection signal to the analog switches 7A and 7C at the end of the synchronization signal (the beginning of the burst signal/video signal generation period) to disconnect them, and generates a reference voltage 1 for one synchronization signal period. 5 as A/
L) Disconnect from converter 2. Further, an analog switch disconnection signal t is applied to the inverter 8, and its output t is used as an analog switch connection signal, and this is applied to the analog switches 7B and 7D to connect them to the burst signal/video signal period reference voltage generation circuit 6 f A / Connect to D converter 2 and set reference voltage 100A-100B to va'r-VRBI
(for burst signal/video signal period).

At the end of the video signal period (i.e., front porch period 23 in FIG. 2), the output of the timing generation circuit 4 becomes an analog switch connection signal, and the reference voltage 100A-100B'kVRr VRBI (for the synchronization signal period) is generated again by the reverse operation to the above. ).

After that, this operation is repeated, and the reference voltage (
V + ζT - VRHI), and the reference voltage (VRT - VRn*) during the burst signal/video signal period.
L) Perform the conversion.

As described above, even during the video signal period, the A/IJ converter 2 (D% quasi-voltage (VRT VRBI)
(&(Since it is the difference between the maximum value and the minimum value of Rt, the resolution of the A/D converter is utilized over the entire range.

〔Effect of the invention〕

As described above, the present invention provides video signal iA/
When performing A/D conversion with a D converter, a reference voltage of the difference between the maximum and minimum values of the video signal (N) is provided during the video signal period, and the resolution of the predetermined number of levels of the A/D converter is approximately the same. Since it can be used in a 100-inch video signal (actual television scanning) period, it has the effect of improving the television picture quality when playing back images on a television screen compared to the conventional method.

[Brief explanation of drawings]

Figure 1 is the original L! ? FIG. 2 is a block diagram showing the configuration of an embodiment applied to an A/D converter, and FIG. 2 is a chart showing an outline of a video signal. 1...Video signal input terminal, lA...
Video signal output terminal, 2...A/D converter
Evening, 3... Synchronous signal detection circuit, 4...
Timing generation circuit, 5... Reference voltage generation circuit for synchronization signal period, 6... Reference voltage generation circuit for burst signal/video signal period, 7A to 7D... Analog switch , 8... Inverter.

Claims (1)

[Claims] In the A/D conversion method for color video signals, the difference between the highest and lowest values of the digitized reference voltage is expressed as a burst signal (
During the period between the subcarrier reference signal) and the video signal, the voltage is set according to the highest and lowest values of the video signal, and during the period of the synchronization signal, the voltage is set according to the highest and lowest value of the color video signal. An A/D conversion method that includes converting to voltage.