CA1278120C - Real time digital video positioner system - Google Patents

Abstract

REAL TIME DIGITAL VIDEO POSITIONER SYSTEM

Abstract of the Disclosure A real time video positioning system for a raster scan video image on the display screen of a video monitor.
A user's line of sight data input means enters a horizontal delay count and a vertical delay count required for shifting the video image. These delay counts are used for delaying the horizontal and vertical sync signals provided externally to the video monitor for shifting the video image by an amount corresponding to changes in the viewer's line of sight with respect to a real world reference. Blanking means are responsive to the delayed sync signals for producing delayed sync blanking signals to properly blank the video and enable the display to shift the position of the image and maintain a constant black reference level during beam retract time.
In this fashion, video scene motion is provided in response to the user's defined line of sight by the subsequent movement of the video image displayed upon the monitor.

Description

` Ri~AL TII`5E l~IGITAL VIDEO POSITIO~IEE~ SYSTEM

Field of the Invention The present invention relates to video image display systems, and more particularly to systems for positioning a raster scan video image on a display screen to provide real time apparent motion of a video scene.
In some applications requiring positioning of a raster scan video image, it is necessary to provide video scene n,otion in response ~o control inputs. Tnis would be applicable to any visual simulation system wherein ~he viewer's line of SigLIt changes in relation to changes in control inputs. Here, the total video scene is re~ositioned in response to these inputs. A portion of the screen (visible window) is to be viewed, so tihat when the total scene is re-positioned, apparent motion of the scene through the visible window resulted. It is thus necessary to reposition tne video each frame time. The repositioner must be stable, accurate, and flexible to enable correlation of the display witn respect to a particular simulation problem.
Known systeMs for repositioning tne raster scan video image employed analog techniques and requires modification of ~he horizontal and/or vertical position circuitry o~ the monitor to perform this task. Other digital methods employed to accomplish this task utilize D/A converters, image storage memory, complex timing circuitry, and A/D converters. These systems furtller require specially designed and complex display moni~ors having specially designed horizontal and vertical .

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Sum~ary of the Invention It is an object of the present invention to provide a system for positioning a raster scan video image anywhere on a display screen. It is another object to provide a sys~em for positioning a raster scan video image anywhere on a screen using a standard display monitor having separate sync input ter~inals. It is another objct to position the video image appearing on a display monitor with respect to changes in a line of sight by r.leans external to the display monitor, in order to simulate physical movement of tile line of sight relative to a real world ~rame of reference. It is another object to provi~e video positioning of a raster scan video image using a minimum of hardware. It is a further object to provide a system capable of positioning of the displayed video image appearing on a display monitor for each video frame, so as to generate real time apparent motion of the video scene.
These and otller objects are achieved by t~le present invention which provides a video positioning system for a raster scan video image being generated on a display monitor for generating real time apparent motion of a video scene.
The video positioning system includes a horizontal delay circuit for receiving the video source horizontal sync signal and generating a delayed horizontal sync pulse, for horizontal sync positioning of the video image in accordance with the horizontal`position data from a computer or control interface, for shifting the picture. Similarly, a vertical delay circuit ~.... .... ~... i~

3_ 35-GS-2696 receives tle video source vertical sync signal and generates a delayed vertical sync pulse, for vertical positioning of tne video image in accordance with the vertical position data from the computer or control interface, for vertically shifting the picture. Sync generation logic circuits receive the delayed horizontal and vertical sync pulses and generate standard width horizontal and vertical sync and blanking pulses required by the display monitor and R/G/B blan~ing circuitry therefor.
By delaying the blanking signals such that the image is lined up with t'ne line of sight, the framing of the wider display is shifted, per each frame. The blanking circuitry, therefore, blanks the video during the delayed sync blanking perio~ to enable the display to maintain a constant black reference level during beam retrace time.
In this fashion, the video positioning system o~ ~he present invention enables the positioning of a raster scan video image, being generated in the red/green/blue/sync mode, anywhere on tne display screen. The system permits a monitor independent process in that any standard display monitor designed for R/G/B
sync video signals with independent horizontal and vertical sync input terminals may be employed.
The video positioning system of the present invention positions the di~played image each video frame by means external to the display monitor and thereby simulates real 2~ time apparent motion of the video scene and raster scan image.

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_4_ 35-GS-2696 Brief Description of the Drawin~s Figure 1 is a circuit block diagram of the video display system including the di~ital vid~o positioner system, illustrative of the present invention:
Figure 2 shows the viewin~ area containing an image and located behind a mask;
Figure 3.1 is a signal diagram of the video source horizontal sync pulse, Figure 3.2 is a signal diagram of a source video si~nal;
Figure 3.3 shows the viewin~ area and mask occurring with ~he standard sync signal;
Figure 4.1 is a signal diagram of the horizontal sync signal, lS Figure 4,2 is a si~,nal dia~ram of the delayed - horizontal sync pulse;
Figure 4.3 is a si~nal diagram o~ the source video si~nal;
~igure 4.4 shows the viewin~ area and mask occurrin~ with ~he delayed sync pulse; and Figure 4.5 shows the monitor viewing area with the video image lined up with the line of sight.

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_5_ 35-GS-2696 Description of_the Preferred ~mbodiments Figure l is a functional block diagram of ~he video display system including the digital video positioner of the presen~ invention. A video iG.a~e is provided from a video source 10 as a Red/Green/Blue (~/G/~) video signal on line 12 to a video display monitor 14 via a blanking logic circuit 16. ~he source video horizontal sync and vertical syn~ on lines 20 and 22 from video source 10 are applied to a horizontal delay circuit 24 znd a vertical delay circuit 26, respectively.
If composite video is available, rather than separate R/G/B/Sync and video, then a video decoder, not shown, shall be used to convert the composite video into the required R/G/B/Sync and video signals. Both tne horizontal and vertical delay circuits 24 and 26 receive clock pulses from a pixel clock 28 via line 30 or from another suitable internal clock generator, not shown.
A computer or control interface 32 provldes the communication and interface either directly with the user's scene viewing controls 34, or with a computer 35 performing the scene positionin~ computations frorn such controls.
The interface 32 receives the timing and control data provided on line 36 from con~rol circuit 37, loads a horizontal (h) delay count into ~i (horizontal) delay co~mt buffer 38 and a vertical (v) delay count into V (vertical) delay count buffer 40 with the required nurnber of pulse counts calculated for providing the corl~anded snift of the video image. The H and V
delay counts are loaded via lines 42 and 44, respectively, into the horiz~ontal delay circuitry 24 and vertical delay circuitry 26 upnn receiving a load signal command on line 46 from computer35.

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The horizontal delay circuit 24 generates a delayed horizontal sync pulse ~or horizontal posi.ioning of ~he video i~age. Circuit 24 has a digi~al counter, count decode logic, and delay lines. The counter is loaded upon command by the load signal on line 46. The counter then counts until overflow or underflow is reached, at wilich time the counter initiates a series of subcycle (subpixel) pulses generated by a set of delay lines and a selection logic in delay circuit 24. The subcycle logic is controlled by the least significant bits (LSB'S) of the delay count on line 42 and ~I delay count buf~er 38. The subcycle pulses were generated to achieve a video position resolution greater than that of the clock. The total horizontal delay is the sum of the horizontal counter delay and the subpixel clock delay.
The vertical delay circuit 26 provides a similar function as the norizontal delay circuit 24 except that there is generated a delay vertical sync pulse rather than a delayed horizontal sync pulse.
The llorizontal and v~rtical delay circuits 24 and 26 provides the delayed pulses to horizontal and vertical pulse gen-erators 48 and 50, respectively, which generate pulses of fixed duration and polarity for utilization by the logic circuits in a sync generator 52. The sync generator 52 receives the delaye~
horizontal and vertical sync pulses and generates standard width, delayed, 'norizontal and vertical sync and blanking signals. More particularly, the sync generator 52 provides the delayed sync pulses on line 54 to the video display 14 and on line 56 provides blanking pulses to the blanking logic circuit 16 corresponding to _7_ ' 35-GS- 269 6 the delayed blanking period. This enables the display to maintain a constant black reference level during bea~ retrace time. If desired, a video amplifier can be incorporated in this section, following the video blanking circuits 16, to provide impedance matching and gain control of the individual R/G/B signals.
According ~o the present inventio~, and as shown in Figure 2, the total image is repositioned each frame time, with only a portion of the total image, for example, 65 per cent, visible througn the window 62 cut in mask 64. Thus, only a portion of the monitor is visible due to the mask 64. As long as the video image is not shifted beyond the mask limits, ~he source video blanking interval will not be visible, and the image 60 will appear to move with respect to the line of sight 61. ~ere, the object is to shift the framing of tne visual display, per frame, by delaying the blanking signals such that the image is lined up with the line of sight. This is accomplished via manual positioning of the user's controls 34.
Figure 3.1 shows the unshifted video source horizontal sync pulse 76 present on line 20, Figure 3.2 shows the corres-ponding unshif~ed red source video signal for a typical raster line, which includes an active portion 78 and a blanking portion 80. The blanking portion 80 is shown to occur after the active line and corresponds to the beam retrace period. Figure 3.3 shows the corresponding image.
Figure 4.1 ShOWS the source horizontal sync signal 76, as shown in ~igure 3.1, while the delayed horizontal sync pulse 82 is shown in Figure 4.2. The red source video signal is shown in Figure 4.3 and includes the normal source video blanking portion 84, an active line 86 and a reblanking portion 88 which occurs during the delayed sync portion 82 when retracing actually occurs~
By delaying the sync signal 82, there is caused a spatial shift in the position of the video on the monitor, as well as a shift in the blanking period 84 as indicated in Figure 4.4. Thus the image 60 appears to move within the window 62 proportional to the amount that the sync signal is delayed.
Figure 4.5 shows the video image 60 lined up with the line of sight 61. Again, it is noted that the mask 64 causes only a portion of the monitor to be visible since such mask 64 covers the peripheral portions of the monitor screen.
Thus, there has been provided, in a system having a video monitor for displaying an image, a system external to the video monitor, for reposltloning such video image corresponding to changes in the viewers defined line of sight with respect ~o a real-world reference, by shifting the sync signal to thereby shift the video image.
While the invention has been described above with respect to its preferred embodiments, it should be understood that other forms and embodiments may be made without departing from the spirit and scope of the invention.

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Claims (7)

1. A real time video system for positioning a raster scan video image with respect to a line of sight on a video monitor in response to input commands, comprising:
a video monitor for displaying a source video signal;
a user's data input means for entering a horizontal and vertical delay count required for shifting said video image;
means for receiving video source horizontal and vertical sync signals;
timing means for providing a video source pixel rate clock and load data timing signals;
horizontal sync delay means and vertical sync delay means for respectively receiving said horizontal and vertical delay counts and delaying said respective horizontal and vertical sync signals by the amount of said horizontal and vertical delay counts, said delayed horizontal and vertical sync signals being applied to said video monitor;
blanking means responsive to said delayed horizontal and vertical sync signals for producing properly blanked video to enable the display to maintain a constant black reference level during beam retrace time; and means for masking the peripheral portion of the video monitor so that the shift in the blanking level is not visible on the monitor;
whereby video scene motion is provided in response to a user's data input means by the subsequent movement of the video image displayed upon said monitor.

2. System as recited in Claim 1, wherein said horizontal sync delay means includes a horizontal counter which is loaded by the most significant bits of said horizontal delay count, and said vertical sync delay means includes a vertical counter which is loaded by the most sig-nificant bits of said vertical delay count, and horizontal and vertical sub pixel clock delay means controlled by the least significant bits of said horizontal and vertical delay counts, whereby the total horizontal delay becomes the sum of the horizontal counter delay means and the horizontal sub pixel clock delay means and the total vertical delay becomes the sum of the vertical counter delay means and the vertical sub pixel clock delay means producing the desired delayed horizontal sync signals and delayed vertical sync signals for respective horizontal and vertical positioning of said video image.

3. System as recited in Claim 2, wherein said horizontal and vertical sync delay means are independent from and external to said video monitor whereby said delayed hori-zontal and vertical sync signals are applied externally to said video monitor to provide the sync for the source video signal.

4. System as recited in Claim 2, wherein said horizontal counter is a digital counter and said vertical counter is a digital counter, and said horizontal sync delay means further includes a horizontal pulse generator connected to receive the output of said horizontal counter for generating a horizontal sync pulse, and said vertical sync delay means further includes a vertical pulse generator connected to receive the output of said vertical counter for generating a vertical sync pulse.

5. System as recited in Claim 1, wherein said user's line of sight data input means includes a control interface for interacting with a user's system, and a buffer means for storing both said horizontal delay count and said vertical delay count.

6. A real time video positioning system for produc-ing a raster scan video image on a video monitor, comprising:
a video monitor for displaying a composite source video signal;
a user's line of sight data input means for entering the horizontal delay count and a vertical delay count required for shifting the video image;
means for receiving video source horizontal and vertical sync signals;
sync delay means for receiving said delay positional count data and delaying said respective sync signals by the amount of said delay positional count data, said delayed sync signals being applied to said video monitor; and blanking means responsive to said delayed sync signals for producing delayed sync blanking signals for producing properly blanked video to enable the display to maintain a constant black reference level during beam retrace time;
whereby video scene motion is provided in response to a user's defined line of sight by the subsequent movement of the video image displayed upon said monitor.

7. A real time video positioning system for a raster scan video image on the display screen of a video monitor, comprising:
a user's line of sight data input means for entering a horizontal delay count and a vertical delay count required for shifting said video image;
sync generator means for generating a horizontal sync position signal, a vertical sync position signal and video blanking signals for proper display of said video image signals;
horizontal sync delay means and vertical sync delay means for respectively delaying said horizontal sync position signal and said vertical sync position signal in accordance with respective horizontal and vertical delay counts for shifting the video image by the amount of said horizontal and vertical delays;
blanking logic means responsive to said horizontal and vertical delay means and said video blanking signals for producing properly blanked video to enable the display to maintain a constant black reference level during beam retrace time; and whereby video scene motion is provided in response to a user's defined line of sight by the subsequent movement of the video image displayed upon said monitor.