Rapid fractional pixel hierarchical searching method
A technology of fractional pixels, search method, applied in the field of video processing
Inactive Publication Date: 2011-09-14
NORTHWESTERN POLYTECHNICAL UNIV
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[0004] In order to overcome the disadvantages that the process of parsing quadratic surface equations in the prior art involves more division operations and is relatively complicated, the present invention proposes a method based on the fact that the error distribution surface in the decimal pixel search window is a relatively regular unimodal distribution. A fast fractional pixel hierarchical search algorithm FHFPS (Fast Hierarchical Fractional Pel Search algorithm), based on the separable unimodal characteristic of the error surface, divides the two-dimensional operation in the PPFPS algorithm into two one-dimensional operations, respectively in the horizontal pixel direction and vertical The parabola model is used to simulate the profile of the error surface in the pixel direction, and the position of the half-pixel optimal matching point is determined by solving the parabolic equation, and the optimal matching point of the half-pixel is determined according to the size relationship between the search window center point, the horizontal direction and the vertical direction half-pixel optimal matching point. Determine the search range of 1 / 4 pixel, predict the best matching point of 1 / 4 pixel, effectively reduce the complexity of fractional pixel motion estimation, and ensure the necessary coding efficiency
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[0039] Method example:
[0040] The FHFPS algorithm is tested in the H.264 test program JM11.0, and compared with the fractional pixel hierarchical search algorithm HFPS and the fast fractional pixel search algorithm PFPPS to compare the performance of the algorithm. Select four QCIF format images Container, Silent, Carphone, foreman, and a CIF format image mobile sequence as the test sequence, encode 100 frames for testing. Among them, only the first frame is coded as an I frame, and the rest of the frames are coded as a P frame. The quantization parameter QP is taken as a fixed value of 28. In order not to affect the search accuracy of fractional pixels, a full search algorithm is used to obtain the best matching position for integer pixel prediction, 5 frames are used as reference frames, and exhaustive search mode is used for intra-frame prediction. The code rate, PSNR and ME encoding time obtained by the three algorithms are counted.
[0041] The present invention comp...
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The invention discloses a rapid fractional pixel hierarchical searching method, which comprises the following steps: simulating the hatching line of an error SAD surface with a parabola respectively from a horizontal pixel direction and a vertical pixel direction; calculating integer pixel searching best matching points in the same horizontal line and the SAD values of two adjacent integer pixel points at two sides in the horizontal direction; selecting a next-step searching reference point in accordance with the position of the vertex coordinate of the horizontal parabola; calculating integer pixel searching best matching points on the same vertical line and the SAD values of two adjacent integer pixel points at two sides in vertical direction; selecting a next-step searching reference point in accordance with the position of the vertex coordinate of the vertical parabola; and finally searching the best one fourth pixel matching point. The PSNR loss of a brightness signal in the invention is less, thus the influence on the quality of video reconstruction can be basically ignored; better code-rate distortion property is kept; and the coding speed is improved.
Description
technical field [0001] The invention belongs to the technical field of video processing, in particular to a decimal pixel search method. Background technique [0002] The motion estimation module of the new-generation video compression standard H.264 is composed of integer pixels and fractional pixels. Motion estimation with fractional pixel precision can more effectively reduce prediction residuals and improve image quality. Since the motion vector displacement is not necessarily exactly at integer pixel positions, but may be at fractional pixels, a motion vector search of 1 / 4 pixel is used. Before the launch of the H.264 standard, the research on the fast block matching algorithm mainly focused on the integer pixel search algorithm, because the decimal pixel search in the previous standard (H.263, MPEG-2) used 1 / 2 pixel precision, and its calculation The amount only accounts for a small part of the whole motion estimation unit. With the introduction of many efficient and...
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IPC IPC(8): H04N7/26H04N7/50H04N19/533
Inventor周巍周欣段哲民
OwnerNORTHWESTERN POLYTECHNICAL UNIV