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With the growing popularity of personal digital assistant devices and smart phones, consumers have become increasingly enthusiastic to watching videos from these mobile devices. However, when browsing videos in mobiles, users often feel that the display resolution greatly affects their perceptual experience with the limited screen size. In this paper, an attention based spatial video adaptation scheme is proposed to overcome the display constraints by producing and displaying the region of interest. According to the size of the target display, we automatically detect and crop the informative region in each frame to generate a smooth sequence. To avoid costly full encoding operations, we develop a set of transcoding techniques based on the H.264 standard. Experimental results show that this approach not only improves the perceptual quality but also saves the bandwidth and computation, especially for the videos which have not been well edited.

Scalable video coding (SVC) can provide different bitrate, resolution, or quality formats of the same video through the one-time encoding process. However, SVC also increases encoding complexity significantly, making real-time implementations difficult especially when applied to high definition videos. In this work, we proposed to utilize a fast mode decision algorithm to speed up the SVC encoder. A simple model of the relationship of the video complexity is proposed, the rate-distortion (RD) cost and the statistical mode distribution of the enhancement layer (EL). The proposed mode decision algorithm evaluates the complexity of the video content, then sets the rate distortion RD cost thresholds for inter coding modes. The method also optimizes the process INTRA_BL for I slices. We demonstrate the method using four different resolutions (1080p, 720p, VGA and QVGA), four temporal layers, and two quality layers. We find that the proposed algorithm can reduce the computational complexity significantly while maintaining or even improving encoder efficiency.

In this paper, an improved interframe coding scheme consisting of both the adaptive directional motion search and improved mode selection is proposed to reduce the computational complexity of video coding. The motion direction is divided into four regions, and different multi-hexagon templates are designed for each region to enhance directional search, which can improve the search accuracy. Subsequently, the improved mode decision that integrates the detection of all zero blocks is proposed for further computation reduction. Experimental results demonstrate that the proposed scheme can reduce encoding time by an average of 60% while maintaining almost the same coding efficiency as existing fast interframe coding schemes.