Method and apparatus for enhancing video displays

• US 4,720,745 A
• Filed: 06/22/1983
• Issued: 01/19/1988
• Est. Priority Date: 06/22/1983
• Status: Expired due to Fees

• Current Assignee: Z Microsystems Visualization Technologies, LLC
• Original Assignee: Digivision, Inc.
• Inventors: DeForest, Sherman, Seegmiller, S. Dale
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): Faris, E. Anne
• Application Number:
  US06/506,826
• Time in Patent Office: 1,672 Days
• Field of Search: 358/140, 358/287, 358/166, 358/280, 358/283, 358/260, 358/160, 358/163, 358/137, 358/167, 358/37
• US Class Current: 348/448
• CPC Class Codes: H04N 9/646 for image enhancement, e.g. vertical detail restoration, cross-colour elimination, contour correction, chrominance trapping filters

Abstract

An NTSC composite color video signal is dematrixed and its RGB components are digitized so that each image or input frame is represented by a 512×512 pixel array. One high resolution output field is generated for each input frame by deriving a plurality of subpixel values for each input pixel. The subpixel values for a given pixel are derived by examining the nearest neighboring pixels and by utilizing enhancement algorithms represented by data in lookup tables. Signal to noise ratio improvement is achieved by comparing each given pixel value to the values of its neighboring pixels and then deciding whether or not to keep the given pixel value or to replace it with the median of it and its nearest neighbors. The subpixel values are fed through a digital to analog converter where the appropriate synchronization is added so that the analog outputs of the three branches of the device conform to the RS 343A format.

Claims

1. A method of enhancing the quality of a video signal, comprising the steps of:

generating in real time from an input video signal having a first presentation bandwidth and including a succession of interlaced video fields a set of pixel values representing an image, each of said pixel values comprising a multi-bit digital value representing video signal intensity;

deriving in real time a single set of subpixel values for each said pixel value according to a predetermined function, said function deriving each subpixel value solely from the values of a central pixel and a set of pixels surrounding said central pixel and contained in a video field which is interlaced with the video field containing the central pixel, and said function providing said subpixel values as multi-bit digital values; and

converting in real time only the subpixel values obtained in said deriving step into an output signal corresponding to a video signal having a second presentation bandwidth higher than said first presentation bandwidth.

2. A method according to claim 1 wherein each pixel value generated for an image represents a portion of an area of said image.

3. A method according to claim 2 wherein each subpixel value derived for a given pixel value represents a portion of said area represented by said given pixel value.

4. A method according to claim 3 wherein the subpixel values for any given pixel value are generated as a function of the values of pixels representing areas adjacent to the area represented by the given pixel value.

5. A method according to claim 1 wherein the pixel values are generated by digitizing the video signal.

6. A method according to claim 5 wherein the subpixel values derived for any pixel value are derived through digital processing.

7. A method according to claim 6 further including the step of converting said output signal into an output analog signal having said second presentation bandwidth,

8. A method according to claim 1 wherein the pixel values of an entire image are stored before the subpixel values corresponding to that image are derived.

9. A method according to claim 1 wherein said input video signal provides successive odd and even interlaced input fields to generate successive input frames, and the subpixel values for an output field included in said output video signal are derived from the pixel values of a respective input frame,

10. A method according to claim 9 wherein the pixel values for each input field are momentarily stored and the subpixel values for its corresponding output field are generated as the pixel values for the succeeding input field are being generated and stored.

11. A method according to claim 1 wherein the video signal is a composite color video signal.

12. An apparatus for enhancing the quality of a video signal, comprising:

means for generating in real time from an input video signal having a first presentation bandwith and including a succession of interlaced video fields a set of pixel values representing an image, each of said values representing video signal intensity;

means for deriving in real time a single set of subpixel values for each said pixel value according to a predetermined function, said function deriving each subpixel value solely from the values of a central pixel and a set of pixels surrounding said central pixel and contained in a video field which is interlaced with the video field containing the central pixel, and said function providing said subpixel values as multi-bit digital values; and

means for converting in real time only said subpixel values for said image into an output signal corresponding to a video signal having a second presentation bandwidth higher than said first presentation bandwidth.

13. An apparatus according to claim 12 wherein said input video signal is of the raster-type and said generating means defines each pixel value for said image so that it represents a portion of an area of said image.

14. An apparatus according to claim 13 wherein said deriving means defines each subpixel value so that it represents a portion of the area represented by the pixel value from which it is derived.

15. An apparatus according to claim 14 wherein said deriving means derives the subpixel values for any given pixel value as a function of the values of pixels representing areas adjacent to the area represented by said given pixel value.

16. An apparatus according to claim 12 wherein said generating means includes means for digitizing the video signal.

17. An apparatus according to claim 16 wherein said deriving means includes at least one lookup table having stored therein subpixel values addressed according to pixel values.

18. An apparatus according to claim 17 wherein said converting means includes at least one digital to analog converter for converting said subpixel values to analog form.

19. An apparatus according to claim 12 wherein said generating means includes means for storing pixel values corresponding to an entire image before the subpixel values corresponding to that image are derived.

20. An apparatus according to claim 16 wherein said deriving means includes:

means for accelerating the rate of the pixel values generated by said means for generating; and

means for momentarily defining a pixel matrix centered about each pixel in each set of pixel values.

21. An apparatus according to claim 12 wherein said input video signal provides successive odd and even interlaced input fields to generate successive input frames, and the deriving includes means for deriving subpixel values for an output field contained in said output video signal from the pixel values of a respective input frame.

22. An apparatus according to claim 21 wherein said generating means includes means for momentarily storing pixel values corresponding to each input field and said deriving means includes means for deriving the subpixel values for the corresponding output field as pixel values corresponding to the succeeding input field are being generated and stored.

23. A method of enhancing the quality of a video signal comprising the steps of;

generating, in real time from an input video signal having successive odd and even interlaced input fields to produce successive input frames, a set of pixel values representing an image;

storing a set of pixel values representing an input field;

deriving in real time a plurality of multi-bit subpixel values for each pixel value of an input frame generated from two successive interlaced input fields of said input video signal, one of said input fields including a stored input field; and

converting in real time said derived subpixel values into an output signal having the format and synchronization required to produce a single output field on a video display.

24. A method according to claim 23 wherein the pixel values for each input field are momentarily stored and the subpixel values for its corresponding output field derived as the pixel values for the succeeding input field are being generated and stored.

25. An apparatus for enhancing the quality of a video signal, comprising:

means for generating, in real time from an input video signal having successive odd and even interlaced input fields to produce successive input frames, a set of pixel values representing an image;

means for storing a set of pixel values representing an input field;

means for deriving in real time a plurality of multi-bit detail subpixel values for each pixel value of an input frame generated from two successive interlaced input fields of said input video signal, one of said input fields including a stored input field; and

means for converting in real time said derived subpixel values into an output signal having the format and synchronization required to produce a single output field on a video display.

26. An apparatus according to claim 25 wherein the generating means includes means for momentarily storing the pixel values for each input field and the deriving means includes means for deriving the subpixel values for the corresponding output field as the pixel values for the succeeding input field are being generated and stored.

27. A method of enhancing the quality of a video signal, comprising the steps of:

generating a sequence of pixels having a first rate from an input video signal which includes a succession of interlaced video fields, each of said pixels being expressed in the form of a multi-bit digital pixel value representing video signal intensity;

deriving a single set of subpixels for each of a predetermined group of pixels in said pixel sequence according to a predetermined function, said function deriving each subpixel value solely from the values of a central pixel and a set of pixels surrounding said central pixel and contained in a video field which is interlaced with the video field containing the central pixel, each of said subpixels being expressed in the form of a multi-bit digital subpixel value;

formatting the subpixels derived from said pixel sequence as an output subpixel sequence having an output rate higher than said first rate; and

providing said output subpixel sequence for display in analog video format.

28. A method according to claim 27 wherein said input video signal has a first video bandwidth and further including the step of converting said output pixel sequence into an output video signal having a second video bandwidth higher than said first video bandwidth.

29. A method according to claim 27 wherein said input and output video signals both provide successive odd and even interlaced video fields to generate successive video frames, and subpixels corresponding to a field in said output video signal are derived from pixels corresponding to two successive fields of said input video signal.

30. A method according to claim 29 wherein pixels for a video field of said input video signal are temporarily stored and subpixel values for a corresponding video field of said output video signal are derived as the pixels for the succeeding video field in said input video signal are being generated.

31. An apparatus for enhancing the quality of a video signal, comprising:

means for generating a sequence of pixels having a first rate from an input video signal and including a succession of interlaced video fields, each of said subpixels being expressed in the form of a multi-bit digital subpixel value;

means for deriving a single set of subpixels for each of a predetermined group of pixels in said pixel sequence according to a predetermined function, said function deriving each subpixel value solely from the values of a central pixel and a set of pixels surrounding said central pixel and contained in a video field which is interlaced with the video field containing the central pixel, each of said subpixels being expressed in the form of a multi-bit digital subpixel value;

means for formatting the subpixels derived from said pixel sequence into an output subpixel sequence having an output rate higher than said first rate; and

means for providing said output subpixel sequence for display in analog video format.

32. An apparatus according to claim 31 wherein the input video signal includes a sequence of first video fields occurring at a first field rate, one of which includes a horizontal sequence of pixels, and said means for deriving include means for deriving subpixel values for a pixel in said sequence of pixels based upon pixels in a video field which precedes or succeeds said one video field.

33. An apparatus according to claim 32 wherein said subpixel values are based upon pixels adjacent said one pixel in said sequence of pixels and pixels in another sequence of pixels adjacent said one sequence of pixels, said other sequence of pixels being contained in a field which precedes or succeeds said one field.