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VLSI Design
Volume 2012 (2012), Article ID 748019, 20 pages
Research Article

Low-Complexity Hierarchical Mode Decision Algorithms Targeting VLSI Architecture Design for the H.264/AVC Video Encoder

1Microelectronics Group (GME), Federal University of Rio Grande do Sul (UFRGS), Av. Bento Gonçalves, 9500, P.O. Box 15064, 91501-970 Porto Alegre, RS, Brazil
2Group of Architectures and Integrated Circuits (GACI), Federal University of Pelotas (UFPel), Campus Universitário s/n, P.O. Box 354, 96010-900 Pelotas, RS, Brazil

Received 18 December 2011; Accepted 1 March 2012

Academic Editor: Maurizio Martina

Copyright © 2012 Guilherme Corrêa 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.


In H.264/AVC, the encoding process can occur according to one of the 13 intraframe coding modes or according to one of the 8 available interframes block sizes, besides the SKIP mode. In the Joint Model reference software, the choice of the best mode is performed through exhaustive executions of the entire encoding process, which significantly increases the encoder's computational complexity and sometimes even forbids its use in real-time applications. Considering this context, this work proposes a set of heuristic algorithms targeting hardware architectures that lead to earlier selection of one encoding mode. The amount of repetitions of the encoding process is reduced by 47 times, at the cost of a relatively small cost in compression performance. When compared to other works, the fast hierarchical mode decision results are expressively more satisfactory in terms of computational complexity reduction, quality, and bit rate. The low-complexity mode decision architecture proposed is thus a very good option for real-time coding of high-resolution videos. The solution is especially interesting for embedded and mobile applications with support to multimedia systems, since it yields good compression rates and image quality with a very high reduction in the encoder complexity.