Applicability of wavelet transform in Multi-Resolution Motion estimation technique

Abstract

The lossy compression scheme is often used to compress data such as digital image and video. Such a video compression scheme based on the wavelet transform is presented in this paper. The multi-resolution/multi-frequency nature of the discrete wavelet transform is an ideal tool for representing images and video signals. Wavelet transform decomposes a video frame into a set of sub-frames with different resolutions corresponding to different frequency bands. These multi-resolution frames also provide a representation of the global motion structure of the video signal at different scales. The motion activities for a particular sub-frame at different resolutions are different but highly correlated since they actually specify the same motion structure at different scales. In the multi-resolution motion compensation approach, motion vectors in higher resolution are predicted by the motion vectors in the lower resolution and are refined at each step. In this paper, we propose a variable block-size MRMC (Multi-Resolution Motion Compensation) scheme. The approximate sub-image which carries the maximum information of the image sequence is compensated using the smallest block size and the other approximate sub-images are compensated using relatively bigger block sizes. The motion vectors of the approximate sub-images in lower resolution are used for motion compensation of their corresponding sub-images. This scheme considerably reduces the computing load, storage and transmission bandwidth. During transmission of an image sequence, only the residual image after motion compensation and the motion vector of the first level decomposition need to be transmitted to the decoder in order to reconstruct the original image. The simulation results show that the proposed approach has a satisfactory performance in terms of peak-to-peak signal-to-noise ratio (PSNR).