New Complexity Scalable MPEG Encoding Techniques for Mobile Applications
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New Complexity Scalable MPEG Encoding Techniques for Mobile Applications Stephan Mietens Philips Research Laboratories, Prof. Holstlaan 4, NL-5656 AA Eindhoven, The Netherlands Email: [email protected]
Peter H. N. de With LogicaCMG Eindhoven, Eindhoven University of Technology, P.O. Box 7089, Luchthavenweg 57, NL-5600 MB Eindhoven, The Netherlands Email: [email protected]
Christian Hentschel Cottbus University of Technology, Universit¨atsplatz 3-4, D-03044 Cottbus, Germany Email: [email protected] Received 10 December 2002; Revised 7 July 2003 Complexity scalability offers the advantage of one-time design of video applications for a large product family, including mobile devices, without the need of redesigning the applications on the algorithmic level to meet the requirements of the different products. In this paper, we present complexity scalable MPEG encoding having core modules with modifications for scalability. The interdependencies of the scalable modules and the system performance are evaluated. Experimental results show scalability giving a smooth change in complexity and corresponding video quality. Scalability is basically achieved by varying the number of computed DCT coefficients and the number of evaluated motion vectors, but other modules are designed such they scale with the previous parameters. In the experiments using the “Stefan” sequence, the elapsed execution time of the scalable encoder, reflecting the computational complexity, can be gradually reduced to roughly 50% of its original execution time. The video quality scales between 20 dB and 48 dB PSNR with unity quantizer setting, and between 21.5 dB and 38.5 dB PSNR for different sequences targeting 1500 kbps. The implemented encoder and the scalability techniques can be successfully applied in mobile systems based on MPEG video compression. Keywords and phrases: MPEG encoding, scalable algorithms, resource scalability.
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INTRODUCTION
Nowadays, digital video applications based on MPEG video compression (e.g., Internet-based video conferencing) are popular and can be found in a plurality of consumer products. While in the past, mainly TV and PC systems were used, having sufficient computing resources available to execute the video applications, video is increasingly integrated into devices such as portable TV and mobile consumer terminals (see Figure 1). Video applications that run on these products are heavily constrained in many aspects due to their limited resources as compared to high-end computer systems or highend consumer devices. For example, real-time execution has to be assured while having limited computing power and memory for intermediate results. Different video resolutions have to be handled due to the variable displaying of video
frame sizes. The available memory access or transmission bandwidth is limited as the operating time is shorter for computation-intensive applications. Finally the product success on the market highly depends on the product cost. Due to these restrictions, video applications ar
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