Computer graphics processing and selective visual display system – Computer graphics processing – Attributes
Reexamination Certificate
1998-07-21
2001-11-20
Jankus, Almis R. (Department: 2672)
Computer graphics processing and selective visual display system
Computer graphics processing
Attributes
Reexamination Certificate
active
06320594
ABSTRACT:
FIELD OF THE INVENTION
The present invention is related to video compression and in particular to a circuit and method for compressing 10-bit video streams for display through an 8-bit VGA video port of a computer.
BACKGROUND OF THE INVENTION
A standardized YUV video system represents video information using a luminance component (Y) and a two-dimensional chromaticity component (UV). Such representations are sometimes called chromaticity spaces. The YUV system was designed to allow measurement of color differences, and exhibits a correlation between, “distance” computed from coordinate differences and subjective color differences reported by observers.
In some computer systems, digital video signals are provided as streams of ten-bit YUV values: a ten-bit value for Y. the luminance component; a ten-bit value for the U portion of the two-dimensional chromaticity component, and a ten-bit value for the V portion of the two-dimensional chromaticity component.
In many computer video-graphics adaptors, eight-bit values are used for representing colors. Such systems often use three color values for a total of 24 bits representing the color of each pixel.
For speed, cost, and convenience it would be desirable to present digital video in eight-bit quantities, but at the same time preserve subjective qualities of the video signal. Therefore, there is a need for a circuit and method for compressing 10-bit video streams for display through an 8-bit VGA video port of a computer.
SUMMARY OF THE INVENTION
The present invention provides a nonlinear digital video compression circuit and method. The circuit includes a source of digital video data signal, wherein the digital video data has M-bits of information for each of a Y, U, and V value per pixel. Y represents a luminance component, and U and V each represent portions of a two-dimensional chromaticity component. The circuit also includes a compression lookup table having an M-bit input coupled to the source of digital video data, and an N-bit compressed digital video data output, where N is less than M. The compression lookup table includes a non-linear compression transformation for at least one of Y, U and V.
In one embodiment, the compression lookup table of the non-linear digital video compression circuit includes a non-linear compression transformation that provides a different conversion for Y than for U or that provides a different conversion for Y than for V. In one such embodiment, the digital video compression circuit further includes a state circuit coupled to the compression lookup table that controls which one of the conversions for Y and U and V is performed. In one such embodiment, M is ten and N is eight (thus providing a 10-bit to 8-bit compression), and the state circuit has an output coupled to the compression lookup table that specifies which one of the conversions is performed.
In another embodiment, the compression transformation of the non-linear digital video compression circuit further includes a conversion for blanking portions of the digital video data signal. In one such embodiment, the digital video compression circuit further includes a state circuit coupled to the compression lookup table that controls which one of the conversions for Y and U and V and blanking is performed. In one such embodiment, M is ten and N is eight.
Another aspect of the present invention provides a digital video compression circuit and method. This compression circuit includes a source of digital video data signal, the digital video data having M-bits of information for each of a Y, U, and V value per pixel, where Y represents a luminance component, and U and V each represent portions of a two-dimensional chromaticity component. A compression lookup table having an M-bit address input is coupled to the source of digital video data. This compression lookup table has an N-bit compressed digital video data output, where N is less than M. The compression lookup table includes a compression transformation that provides three different conversions for Y and U and V.
In one embodiment, the digital video compression circuit has a compression transformation that further includes a fourth conversion for blanking portions of the digital video data signal. In one such embodiment, the digital video compression circuits further includes a state circuit coupled to the compression lookup table that controls which one of the conversions for Y and U and V and blanking is performed.
In another embodiment, the digital video compression circuit further includes a state circuit coupled to the compression lookup table that controls which one of the three different conversions for Y and U and V is performed. In one such embodiment, M is ten, N is eight, and the state circuit has an output coupled to the compression lookup table that specifies which one of the three conversions is performed.
Yet another aspect of the present invention provides a method for compressing digital video. This method includes the steps of:
providing a digital video data signal, the digital video data having M-bits of information for each of a Y, U, and V value per pixel, where Y represents a luminance component, and U and V each represent portions of a two-dimensional chromaticity component;
performing an M-bit to N-bit compression transformation that is non-linear for at least one of Y, U and V; and
outputting N-bit compressed digital video data output having N-bits of information for each of a compressed Y, U, and V value per pixel, where N is less than M.
In one embodiment, the method includes a compression transformation that provides a different conversion for Y than for U or that provides a different conversion for Y than for V.
In another embodiment, the method includes a compression transformation that further includes a conversion for blanking portions of the digital video data signal.
In yet another embodiments, the method further includes the step of determining a state of at least Y, U, or V, wherein the state controls which one of the conversions for Y and U and V and blanking is performed, or the step of determining a state of at least Y, U, or Y. wherein the state controls which one of the conversions for Y and U and V is performed.
In some embodiments of the methods described above, M is ten and N is eight.
REFERENCES:
patent: 5012163 (1991-04-01), Alcorn et al.
patent: 5227863 (1993-07-01), Bilbrey
patent: 5519439 (1996-05-01), Keith
patent: 6021216 (2000-02-01), Sathe et al.
Cunningham G. F.
Gateway Inc.
Jankus Almis R.
Schwegman - Lundberg Woessner - Kluth
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