JPH02245798A - Image digitizing device - Google Patents

Abstract

PURPOSE:To prevent a displayed image from being distorted by setting a sampling frequency so that the ratio of a sampling interval in the horizontal direction of a horizontal scanning line in the image of a television receiver to an interval in a vertical direction between the horizontal scanning lines may be the aspect ratio of the picture element of a display device. CONSTITUTION:As for a TV video, consecutive values are obtained in the horizontal direction of a horizontal scanning line. Then, in order to make the TV video into a digital image, it is necessary to sample the video at specified sampling intervals so as to obtain the interval of the picture element in the horizontal direction of the digital image. A synchronizing signal extraction part 13 extracts a horizontal synchronizing signal Hs and a vertical synchronizing signal Vs from an NTSC signal and transmits them to a sampling clock generation part 14. On the basis of the transmitted signals, the sampling clock generation part 14 generates a sampling clock SC at the sampling frequency (fs) and supplies it to an A/D converter 12 as a clock for giving data conversion timing. Thus, the displayed image is prevented from being distorted even when the TV video is displayed on the display device for a computer.

Description

[Detailed Description of the Invention] [Summary] In order to display images from a television receiver on a display device for a computer system, an analog video signal from the television receiver is converted to a digital image signal for the computer display device. Regarding image digitizing equipment.

The purpose of this invention is to prevent the displayed image from becoming distorted even when TV images are displayed on a computer display device.

For computers, the sampling frequency for converting an analog video signal into a digital image signal is the ratio of the horizontal sampling interval of horizontal scanning lines of a television receiver image to the vertical interval between horizontal scanning lines. The frequency is configured to be set to the aspect ratio of the pixels of the display device.

[Industrial application field]

The present invention is for displaying images of a television receiver on a display device for a computer system.

The present invention relates to an image digitizing device that converts an analog video signal from a television receiver into a digital image signal for a computer display device.

The display word f for a computer system is VTR.

When displaying images displayed on a laser disc or a regular TV receiver, differences in the display method and size of the two display devices pose a major problem, but television images displayed on a computer display device are not distorted. That is required.

[Conventional technology]

Figure 8 shows a comparison of the relationship between the display screens of a TV receiver and a display device for a personal computer.The screen of a normal TV receiver (cathode ray tube) has a horizontal and vertical aspect ratio (aspect ratio) In the NTSC system, the size ratio is 4:3. In addition, the screen of a computer display device is different from the dimensional ratio of a TV receiver, for example, in the case of a personal computer, the ratio is expressed by the difference in the number of horizontal and vertical display pixels. In the case of , horizontal: 640 dots, 1ii
f: The ratio is 400 dots.

[Problem to be solved by the invention]

If you try to display the screen of a TV receiver as is on the screen of a personal computer display device, the aspect ratio of the screen is different between the two devices, so for example, the screen of the TV receiver will be displayed as a perfect circle. When the picture is displayed on the screen of a computer display device, it is not displayed as the same perfect circle picture,
The two images become distorted, either as a vertically long ellipse or as a horizontally long ellipse.

Therefore, it is an object of the present invention to prevent a 9-display image from being distorted even when TV images are displayed on a computer display device.

[Means to solve the problem]

FIG. 1 is a diagram explaining the principle of the present invention.

In the image digitizing device according to the present invention, the sampling frequency rs for converting an analog video signal into a digital image signal is between the horizontal sampling interval DI of the horizontal scanning line of the image of the television receiver and the horizontal scanning line. The frequency is set such that the ratio between the vertical distance Dv and the vertical distance Dv corresponds to the aspect ratio of the pixels of the computer display device.

[Effect]

When the sampling frequency fs is set as described above.

Since the relationship between the horizontal and vertical ratios of the picture displayed in the television image is maintained as it is and displayed as the display image on the computer display device, the screen is not distorted by digitization.

〔Example〕

The present invention will be described in detail below with reference to one drawing.

FIG. 2 shows a personal computer system in which an image digitizing apparatus as an embodiment of the present invention is used. In Figure 2, 1 is the NTS for TV receivers.
an A/D converter that converts a C-format analog video signal (NTSC signal) into a digital image signal for a computer, 2
3 is a processor; 4 is a digitizing unit that stores digital image signals in a frame memory etc. and executes various processes;
A frame memory 85 that stores the digital image signal processed by the digitizing section 2 for image display is a display control section that reads out the digital image signal from the frame memory 4 and controls the display device 6 to display it. The display device 6 is a display device that displays images using a dot display method of 640 dots horizontally and 400 dots vertically.

FIG. 3 shows a detailed configuration example of the A/D converter 1. As shown in FIG. This A/D converter 1 includes a two-color separation circuit l1, an A/D converter 12. Synchronization signal extraction section 13. It is configured to include a sampling clock (sampling clock) generation section 14 and the like. Here, the one color separation circuit 11 separates the NTSC signals into red (R) and green (G) signals.
) and blue (B) color signals and send them to the A/D converter 12.

Further, the synchronization signal extraction section 13 extracts a horizontal synchronization signal Hs and a vertical synchronization signal v3 from the NTSC signal and sends them to the sampling clock generation section 14. The sampling clock generation unit 14 generates a sampling clock SC at a sampling frequency rs, which will be described later, based on the horizontal synchronization signal Hs and the vertical synchronization signal V3.
The signal is supplied to the /D converter 12 as a clock that provides data conversion timing.

FIG. 4 shows a detailed configuration example of the sampling clock generation section 14. As shown in FIG. 4, the sampling clock generation section 14 includes a video display period signal generation circuit 141. AND circuit circuit 14 complete 2 includes a digital phase synchronization circuit 144 and the like.

The video display period signal generation circuit 141 generates a vertical synchronization signal v3.
and horizontal synchronization signal Hs are input, and based on these signals, the television image area E (
That is, a horizontal period signal Hs' and a vertical period signal Vs' indicating the period of the video display area (excluding the horizontal and vertical retrace periods) are generated and outputted to the AND circuit 142. Along with this, the horizontal scanning line 485 of the TV video area E
A 400L signal indicating the period of 400 horizontal scanning lines in the book is output to the AND circuit 142. This 400L signal is
This shows a vertical area (corresponding to 400 horizontal scanning lines) to be digitized in the TV video area E, and the position of this vertical area is instructed by the digitizing section 2.

To explain this TV video area E in more detail, T
The V video display method is as shown in FIG. That is, the TV video area E has a vertical length Lv and a horizontal length Lo. The total number R of horizontal scanning lines is 525, the number R1 of horizontal scanning lines in the display period corresponding to the length Lv is 485, and the number R2 of horizontal scanning lines in the vertical blanking period is 40. Further, the total horizontal scanning period T is IH, the horizontal scanning period T1 corresponding to the horizontal length LH of the TV video area E is 0.85H, and the horizontal blanking period T2 is 0.85H. It is 1 6 H. Here, IH
is the time required to perform one horizontal scan (i.e. horizontal period), and in the NTSC system, one frame is 1/3
Since it takes 0 seconds, IH = 1/3 0÷525 seconds.

The AND circuit 142 converts the area signal AREA, which is output only in the 400 horizontal scanning line area in the TV video area E, into a digital phase by performing an AND logic of the horizontal period signal Hs, the vertical period signal 3°, and the 40OL signal. Output to the synchronization circuit 144.

The digital phase synchronization circuit 144 is a flip-flop 14
It is a circuit of a known configuration consisting of 6,147 circuits, and the area signal A
When REA is received, the oscillation output from 1 oscillation circuit 143 is
Divide the frequency and output as a sampled SC. That is, from the digital phase synchronization circuit 144, the area signal AR
Only during the period when EA is being input, the sampling clock SC with the sampling frequency rs is output.

Here, the oscillation frequency of the oscillation circuit 143 is the sampling clock S
The reason why it is four times as large as C is to enable the sampling clock SC to be output without phase delay with respect to the area signal AREA. Therefore, the oscillation frequency of the oscillation circuit 143 is not limited to 4SC, and if the three-phase delay is not a problem, the circuit may be configured to output 23C or SC itself.

The sampling frequency fs of the sampling clock SC output from the sampling clock generation section 14 is determined by the following procedure.

First, as a prerequisite, as mentioned above.

Total number of horizontal scanning lines of TV video R = 525 Number of horizontal scanning lines during display period R. = 484 lines Number of horizontal scanning lines in vertical blanking period - 40 lines Total horizontal scanning period T = IH Horizontal scanning period T1 of TV video area = 0.86H Horizontal blanking period T2 = 0.16H The aspect ratio is 4:3. The aspect ratio of pixels on the display screen of the computer display device 6 is 1:1. Furthermore, since the vertical display area of the computer display device 6 has a length of 400 dots, it is not possible to display the entire TV video area E, so the horizontal scanning lines R,
- Only 400 of the 4.85 lines are used for display for digital images.

When digitizing images from a TV receiver.

The vertical distance Dv between horizontal scanning lines of a TV video is:

This is the vertical pixel interval between pixels of the digital image after digitization. On the other hand, in TV video, the horizontal direction of the horizontal scanning line is a continuous value, so in order to make it a digital image, it is necessary to sample it at a predetermined sampling interval to obtain the horizontal pixel interval of the digital image. However, this sampling is performed so that the ratio of the interval between horizontal scanning lines of the TV video to the sampling interval is 1:1 in the aspect ratio of the pixels of the digital image. This is necessary in order not to distort the

First, find the interval Dv between horizontal scanning lines in the vertical direction of a TV image.

Dv=Lv÷(485-1)=Ly/484. Here, Lv is the length of the TV video area E in the vertical direction.

One pixel on the computer display device 6 has an aspect ratio of 1:1.
Therefore, the horizontal sampling interval DH needs to match the horizontal inter-scanning line interval D. The sampling time interval Ts for this purpose is determined as follows.

First, the number N of sampling points on the horizontal scanning line is:

N=Ln/D)I=LH/Dv The time required for one horizontal scan of the TV video area E is T,
=0.84H, so the time Ts of one sampling interval
teeth.

Ts”T10N=T, ÷ (LH/Dv) where LH=4
Because it's LV/3.

2.52 30492X103 The sampling frequency f3 is the reciprocal of this time interval T3, so fs = 12-IMHz.

According to the above-mentioned hardware configuration and sampling frequency fs, the sampling clock generation unit 14 can generate signals only in the 400 horizontal scanning line area in the TV video area E, as shown in FIG. The sampling clock having the above-mentioned sampling frequency f3 is output to the A/D converter 12 to convert the analog video signal into a digital image signal. In this case, TV
Since the ratio of the horizontal edges of the displayed image of the video matches the ratio of the horizontal edges of the displayed image of the digital image, for example, a perfect circle will not be distorted into an ellipse after digitization.

In carrying out the present invention, various modifications are possible. For example, in the above-mentioned embodiment, a case has been described in which a TV video ftj is displayed on a display device of a personal computer, but the present invention is not limited to this. It may also be displayed on a digital display device. Therefore, it goes without saying that the horizontal:vertical dot number of the computer display device is not limited to the 640:400 ratio of the embodiment.

Furthermore, the present invention is applicable not only to TV signals of the NTSC system but also to video signals of other television systems.

〔Effect of the invention〕

According to the present invention, distortion of one displayed image can be prevented even when TV images are displayed on a computer display device.

[Brief explanation of drawings]

FIG. 1 is a diagram explaining the principle of the present invention. FIG. 2 is a block diagram showing a personal computer system in which an image digitizer device as an embodiment of the present invention is used. FIG. 3 is a diagram showing a configuration example of an A/D conversion section in the embodiment. FIG. 4 is a diagram showing an example of the configuration of a sampling clock generation section in an A/D conversion section. FIG. 5 is a diagram showing a configuration example of a digital phase synchronization circuit in a sampling clock generation section. FIG. 6 is a diagram showing the relationship between the TV video area and each signal. FIG. 7 is a diagram illustrating a TV video display system; FIG. 8 is a diagram showing the relationship between the display screen of the TV receiver and the display screen of the personal computer display device. In fig. 1-A/D conversion section 2--Digitizing section 3-Processor 4--Frame memory 5--Display control section 6--Display device for personal computer 11--Color separation circuit 12--A/D conversion Device 13 - Synchronization signal extraction section - Sampling, lock generation section 1 - Video display period signal generation circuit 2 - A N D circuit 3 - Oscillation circuit 4 - Digital phase synchronization circuit Immersion of the present invention i Sun/Moon Map Figure 1 TV Gorge Elephant 1 Holo] Figure 2 V 1!! 1 side and Besokosha aJ side r drawing Figure 8

Claims (1)

[Scope of Claims] 1. An image that converts an analog video signal of a television receiver into a digital image signal of a computer display device and captures the image in order to display the image of the television receiver on a display device for a computer system. A digitizing device, wherein the sampling frequency (f_S) for converting the analog video signal to the digital image signal is equal to the horizontal sampling interval (D_H) of the horizontal scanning line of the image of the television receiver.
and the vertical spacing between horizontal scan lines (D_V) is set at a frequency such that the ratio of the vertical spacing (D_V) between the horizontal scan lines is the aspect ratio of the pixels of the computer display device. 2. The analog video signal is an NTSC video signal, the aspect ratio of the screen of the television receiver is 4:3, the aspect ratio of the pixels of the computer display device is 1:1, and the sampling frequency is f_S. is the frequency found by f_S=[4(M-1)]/(3×0.84H) when the number of horizontal scanning lines in the television image area is M and the horizontal period is 1H. An image digitizing device according to claim 1.