Hybrid Video Coding Based on Bidimensional Matching Pursuit
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Hybrid Video Coding Based on Bidimensional Matching Pursuit Lorenzo Granai Signal Processing Institute, Swiss Federal Institute of Technology (EPFL), 1015 Lausanne, Switzerland Email: [email protected]
Emilio Maggio Department of Electronic Engineering, Queen Mary University of London, London E1 4NS, UK Email: [email protected]
Lorenzo Peotta Signal Processing Institute, Swiss Federal Institute of Technology (EPFL), 1015 Lausanne, Switzerland Email: [email protected]
Pierre Vandergheynst Signal Processing Institute, Swiss Federal Institute of Technology (EPFL), 1015 Lausanne, Switzerland Email: [email protected] Received 23 February 2004; Revised 1 July 2004; Recommended for Publication by Mark Liao Hybrid video coding combines together two stages: first, motion estimation and compensation predict each frame from the neighboring frames, then the prediction error is coded, reducing the correlation in the spatial domain. In this work, we focus on the latter stage, presenting a scheme that profits from some of the features introduced by the standard H.264/AVC for motion estimation and replaces the transform in the spatial domain. The prediction error is so coded using the matching pursuit algorithm which decomposes the signal over an appositely designed bidimensional, anisotropic, redundant dictionary. Comparisons are made among the proposed technique, H.264, and a DCT-based coding scheme. Moreover, we introduce fast techniques for atom selection, which exploit the spatial localization of the atoms. An adaptive coding scheme aimed at optimizing the resource allocation is also presented, together with a rate-distortion study for the matching pursuit algorithm. Results show that the proposed scheme outperforms the standard DCT, especially at very low bit rates. Keywords and phrases: image processing, greedy algorithms, matching pursuit, redundant dictionaries, video coding, H.264/AVC.
1. INTRODUCTION The most successful class of video compression algorithms is based on hybrid methods consisting in the combination of prediction loops in the temporal dimension (motion estimation/motion compensation) with a suitable uncorrelation technique in the spatial domain (transform coder). The state of the art for hybrid video coding is specified by the recent standard H.264, also named advanced video coding (AVC) (ITU-T Rec. H.264, or ISO MPEG-4, part 10). In this work, we aim at exploiting the advantages of coding the displaced frame diļ¬erence (DFD), output of the motion compensation (MC) algorithm, using a redundant dictionary. This kind of dictionaries leaves more freedom to the basis functions design and therefore they can be created with the goal of catching the structures of DFDs.
In order to remain as close as possible to the state of the art, we adopt a motion estimation algorithm that is compatible with H.264 (see Section 2). The output of this block is then coded using a pursuit algorithm and an appositely designed bidimensional, anisotropic dictionary. Thanks to this technique, we achi
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