Efficient MPEG-2 to H.264/AVC Transcoding of Intra-Coded Video
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Research Article Efficient MPEG-2 to H.264/AVC Transcoding of Intra-Coded Video Jun Xin,1 Anthony Vetro,2 Huifang Sun,2 and Yeping Su3 1 Xilient
Inc., 10181 Bubb Road, Cupertino, CA 95014, USA Electric Research Labs, 201 Broadway, Cambridge, MA 02139, USA 3 Sharp Labs of America, 5750 NW Pacific Rim Boulevard, Camas, WA 98607, USA 2 Mitsubishi
Received 3 October 2006; Revised 30 January 2007; Accepted 25 March 2007 Recommended by Yap-Peng Tan This paper presents an efficient transform-domain architecture and corresponding mode decision algorithms for transcoding intra-coded video from MPEG-2 to H.264/AVC. Low complexity is achieved in several ways. First, our architecture employs direct conversion of the transform coefficients, which eliminates the need for the inverse discrete cosine transform (DCT) and forward H.264/AVC transform. Then, within this transform-domain architecture, we perform macroblock-based mode decisions based on H.264/AVC transform coefficients, which is possible using a novel method of calculating distortion in the transform domain. The proposed method for distortion calculation could be used to make rate-distortion optimized mode decisions with lower complexity. Compared to the pixel-domain architecture with rate-distortion optimized mode decision, simulation results show that there is a negligible loss in quality incurred by the direct conversion of transform coefficients and the proposed transformdomain mode decision algorithms, while complexity is significantly reduced. To further reduce the complexity, we also propose two fast mode decision algorithms. The first algorithm ranks modes based on a simple cost function in the transform domain, then computes the rate-distortion optimal mode from a reduced set of ranked modes. The second algorithm exploits temporal correlations in the mode decision between temporally adjacent frames. Simulation results show that these algorithms provide additional computational savings over the proposed transform-domain architecture while maintaining virtually the same coding efficiency. Copyright © 2007 Jun Xin et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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INTRODUCTION
The latest video compression standard, known as H.264/AVC [1], is able to achieve significantly improved compression efficiency over prior standards such as MPEG-2. Due to its superior performance, it is being widely adopted for a broad range of applications, including broadcasting, consumer electronics storage, surveillance, video conference and mobile video. As H.264/AVC becomes more widely deployed, the number of devices that are capable of decoding H.264/AVC bitstreams will grow. In fact, multiformat standard decoder solutions, which have the capability to decode multiple video compression formats including MPEG2, H.264/AVC, and VC-1, are becoming available. This will give those in the content delivery chain greater flexibi
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