Television – Format conversion – Field rate type flicker compensating
Reexamination Certificate
1998-08-03
2001-10-02
Eisenzopf, Reinhard J. (Department: 2614)
Television
Format conversion
Field rate type flicker compensating
C348S448000, C348S449000, C348S458000, C348S910000
Reexamination Certificate
active
06297847
ABSTRACT:
FIELD OF THE INVENTION
This invention pertains generally to the field of computer graphics and more particularly to removal of visually discernible artifacts in a digitally sampled non-interlaced video signal.
BACKGROUND OF THE INVENTION
Video data originally developed for television screens must be reformatted before it can be displayed on most computer displays. Television screens typically require data in 2:1 interlaced format, which means a full frame of data is comprised of two spatially and temporally offset fields, typically referred to as odd and even fields. Computer displays typically require non-interlaced data (also referred to as “progressively scanned” data). Displaying video data produced for standard televisions on personal computers therefore typically requires that the video data be converted from an interlaced format to a non-interlaced format.
In Personal Computers (PCs), the two most common conversion techniques are spatial line doubling by interpolation and field recombining. Spatial line doubling by interpolation which is embodied in a technique referred to as “Bob” supported by the Microsoft Corporation, involves taking one field at a time and spatially interpolating to obtain the missing lines, usually by averaging the line above and below each missing one. Field recombining which is embodied in a technique referred to as “Weave” supported by the Microsoft Corporation involves interleaving both fields back together to get a spatially complete frame. The former approach (“Bob”) is better suited for video with high motion content but produces a clearly visible loss of resolution for relatively static scenes. The latter technique (“Weave”) is better suited for relatively static scenes but produces highly objectionable artifacts called feathering or ghosting when significant motion is present.
In current and past commercially available PC systems it has generally not been possible to determine whether a live video source has motion in it or not, hence “Bob” is typically used because it produces less objectionable artifacts. Moreover, the “Bob” technique allows for a relatively low cost hardware implementation using only one line delay memory. Unfortunately, artifacts produced by the “Bob” technique still exist, the most objectionable being jagged or staircase like effects on diagonal lines and edges in an image.
SUMMARY OF THE INVENTION
In a principal aspect, the present invention provides processing to remove visually objectionable artifacts from a non-interlaced video signal. In accordance with the principles of the present invention, a graphics processor comprises a scan conversion module that is responsive to an interlaced video signal for generating a non-interlaced signal as a function of interpolation of scan lines of the interlaced signal. An adaptive non-linear filter is responsive to the non-interlaced signal for adaptively removing jagged-edge artifacts in images represented by the non-interlaced signal.
Advantageously, jagged lines or edges introduced into a video signal by conversion from interlaced to non-interlaced format are masked (smoothed) without noticeable degradation of the quality of the rest of the picture. Moreover, field memories, which increase hardware requirements and costs, are not required.
These and other features and advantages of the present invention may be better understood by considering the following detailed description of a preferred embodiment of the invention. In the course of this description, reference will frequently be made to the attached drawings.
REFERENCES:
patent: 4982280 (1991-01-01), Lyon et al.
patent: 5610661 (1997-03-01), Bhatt
patent: 5995154 (1999-11-01), Heimburger
patent: 6034733 (2000-03-01), Balram et al.
patent: 6040869 (2000-03-01), Dischert
“Bob Method,” Jul. 20, 1998, Page 1 of 1.
“Displaying Interleaved Video with VPE: Bob and Weave,” Jul. 20, 1998, Page 1 of 1.
“Weave Method,” Jul. 20, 1998, Page 1 of 1.
Carr & Ferrell LLP
Eisenzopf Reinhard J.
S3 Graphics Co., Ltd.
Yenke Brian P.
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