Abstract
Fast normalized covariance based similarity measure for fractal video compression with quadtree partitioning is proposed in this paper. To increase the speed of fractal encoding, a simplified expression of covariance between range and overlapped domain blocks within a search window is implemented in frequency domain. All the covariance coefficients are normalized by using standard deviation of overlapped domain blocks and these are efficiently calculated in one computation by using two different approaches, namely, FFT based and sum table based. Results of these two approaches are compared and they are almost equal to each other in all aspects, except the memory requirement. Based on proposed simplified similarity measure, gray level transformation parameters are computationally modified and isometry transformations are performed using rotation/reflection properties of IFFT. Quadtree decompositions are used for the partitions of larger size of range block, that is, 16 × 16, which is based on target level of motion compensated prediction error. Experimental result shows that proposed method can increase the encoding speed and compression ratio by 66.49% and 9.58%, respectively, as compared to NHEXS method with increase in PSNR by 0.41 dB. Compared to H.264, proposed method can save 20% of compression time with marginal variation in PSNR and compression ratio.
Highlights
The emerging multimedia applications such as video conferencing, video over mobile phones, video email, and wireless communications require an effective video coding standard to achieve a low bit rate with good quality
High encoding time is main drawback of fractal based method; due to this it is not useful for real time applications. The motivation of this method is that it gives high compression ratio with good quality output which is useful for storage and transmission of bulky videos
We proposed a FFT based Zero Mean Normalized Cross Correlation (ZNCC) method with new matching criteria which reduced the block searching time
Summary
The emerging multimedia applications such as video conferencing, video over mobile phones, video email, and wireless communications require an effective video coding standard to achieve a low bit rate with good quality. Fractal based video compression [1] is an alternative to accomplish high compression ratio with good quality reconstructed output video than the existing video standards (MPEG, H.263, H.264). Jacquin [2] proposed an innovative technique which is based on the fractal theory of iterated function system for image compression. It reduces an affine redundancy of an image by using its self-similarity properties. High encoding time is main drawback of fractal based method; due to this it is not useful for real time applications The motivation of this method is that it gives high compression ratio with good quality output which is useful for storage and transmission of bulky videos. To increase the encoding speed with keeping motivational parameters, a fast fractal video coder system is proposed
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