Computer graphics processing and selective visual display system – Computer graphics processing – Graph generating
Reexamination Certificate
1998-11-06
2001-05-29
Nguyen, Phu K. (Department: 2772)
Computer graphics processing and selective visual display system
Computer graphics processing
Graph generating
Reexamination Certificate
active
06239811
ABSTRACT:
FIELD OF INVENTION
The present invention is related to measuring the relative visibility of time-varying data in transform space, and, more particularly, to displaying the effects of variations in the level of a parameter in transform space from which a video signal is generated.
BACKGROUND ART
FIG. 1
is a pictographic representation of motion video in the form of a sequence of still frames. Moving images are typically composed of still images, such as these frames
1
. For animation, sequences of these frames are presented at a typical speed of 15-100 frames per second, creating an illusion of continuous motion. When these moving images are captured as digital data in order to apply complex compression techniques, the frames are normally represented as a two-dimensional array of “pixels”
5
. For the purposes of many compression techniques, pixels are organized into sequences. For example, pixels on the same row within a single frame
1
are organized into a horizontal sequence of pixels
7
, pixels on the same column within a single frame are organized into a vertical sequence of pixels
6
, and pixels within consecutive frames are organized into a time-varying sequence of pixels
FIG. 2
is a graphical view of a conventional sequence
9
of pixels, which may occur in space, as a horizontal or vertical pixel sequence, or in time, as a time-varying pixel sequence.
FIG. 3
is a graphical view of a transformed equivalent representation
10
, with some desirable property, in transform space, resulting from an application of a transform as the first step in a conventional “lossy” compression technique to the pixel sequence
9
of FIG.
2
. This representation
10
is subsequently quantized according to some criterion, reducing its resolution, and the resulting quantized representation is encoded into its compressed form. On decompression, the quantized representation is recovered, and an inverse transformation is applied to the representation to recover its representation in time and space, instead of in transform space.
FIGS. 4A
,
4
B, and
4
C show, respectively, the inverse transform of first, second, and third components of the equivalent representation
10
of FIG.
3
. These components are pixel sequences occurring in the horizontal, vertical, and temporal dimensions.
The transformed equivalent representation
10
is a signal having continuously varying levels. The process of quantization changes each representation
10
to a signal having a number of discrete levels. For effective video compression, i.e. to maximize the compression ratio, the number of different levels should be minimized. However, if the number of levels is reduced too much, a video sequence resulting from compression and subsequent decompression of video data is noticeably changed from its original form. Thus, what is needed is a way to evaluate the effects of quantization and subsequent dequantization of signals in transform space to determine the minimum number of levels which can be used in quantization without effecting the way video sequences are perceived.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention, there is provided apparatus for displaying effects of variations in the level of an input signal on video generated from said input signal. The apparatus includes an input circuit for providing the input signal, a first and second scaling circuits, first and second video generators, and first and second display screens. The first scaling circuit provides a first intermediate signal by scaling the input signal in accordance with a first constant value, while the second scaling circuit provides a second intermediate signal by scaling the input signal in accordance with a second constant value. The first display screen is driven by the first stream of video data to form a first visible image, while the second display screen is driven by the second stream of video data to form a second visible image. The two display screens are preferably placed adjacent to one another, so that an individual using the apparatus can easily view both display screens to determine whether a visible difference exists between the images formed thereon.
The apparatus of the present invention preferably emulates a portion of video system including compression of video data, with the transformation of the video data into a matrix of data in transform space, quantization of the data in transform space, and subsequent decompression of the data with dequantization and processing through a inverse transform to return a video signal, which drives a video display. Thus, in the apparatus of the present invention, the input signal is preferably a signal representing a single element of a data matrix in transform space, which is set to a value of one, while all other elements of the matrix data are set to a value of zero. After the input signal is quantized to first and second levels, the resulting signals are separately processed through an inverse transform for conversion into video data.
In one version of the present invention, the inverse transform is three-dimensional, so that a matrix of data in transform space is changed into data representing a number of video frames in horizontal, vertical, and temporal dimensions. Two versions of a block of frames, differing only in the scaling factor applied to the input signal, are repeatably viewed in the two screens. When the user of the system determines whether there is a visible difference between the block of frames, he presses a button to indicate his choice, which is stored as one of the blocks is changed to provide a new comparison. Alternately, the inverse transform is two-dimensional, so that a matrix of data in transform space is changed into data representing a single video frame in horizontal and vertical dimensions.
REFERENCES:
patent: 5202960 (1993-04-01), Seiler
patent: 5381522 (1995-01-01), Seto et al.
Friedland Norman
Nguyen Phu K.
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