Image analysis – Image enhancement or restoration – Image filter
Patent
1996-05-06
1999-10-26
Tran, Phuoc
Image analysis
Image enhancement or restoration
Image filter
382236, 382254, 382261, 382262, 382275, 348607, G06K 936, G06K 940, H04N 521
Patent
active
059741929
ABSTRACT:
Blocks in frames of a video are matched to similar blocks across frames using qualitative characteristics of the pixels in the block. Pixels in a frame are categorized into two or more categories. In one embodiment, three pixel categories are: 1) quasi-constant (QC) pixels having intensity values that vary slowly (e.g., pictorial portions), 2) textured pixels characterized by many small edges and thin-line signals (e.g., texture portions), and 3) dominant-edge (DE) pixels characterized by few sharp and dominant edges (e.g., edge portions). Blocks in different frames are matched by minimizing a cost function that measures the mismatch between a block in a first frame and a plurality of candidate blocks in a second frame. In one embodiment, a cost function comprises a contrast component and a brightness component. The brightness component is determined as a function of the pixel categories. Block matching in sequential frames of a video enables a calculation of displacement or motion estimation in the video. Motion estimation is used, for example, in video compression to encode a reference frame and subsequent displacements of blocks in the frame. The present block-matching invention is also useful in pre-processing video images to minimize noise. Blocks (or even pixels) in a reference frame are matched to corresponding blocks (or pixels) in prior frame and subsequent frames. Various visual components (e.g., contrast, brightness, color) of the matched blocks are used to generate a modified visual component for the block in the reference frame. Noise and other defects are thereby significantly reduced.
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Carey Judson D.
Mariam Daniel G.
MediaOne Group Inc.
Tran Phuoc
U S West, Inc.
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