Optimization Of H.264 Baseline Decoder On ARM9TDMI Processor
Sheshadri, Sandya B.
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With the newly introduced features and advancements to the pre-existing features, the emerging H.264 video coding standard achieves significant improvements in coding performance over all existing standards, in a wide variety of applications. The coding-efficiency advantages of H.264, however, come at the expense of higher computational complexity. H.264 decoders can exhibit more than double the complexity of H.263 decoders. Furthermore, previous studies have shown that fractional-pixel motion-compensation interpolation and the loop filtering consume a significant amount of computational power in emerging H.264 decoders. Since these operations are part of the baseline profile of H.264, there is a need to evaluate new ways for minimizing complexity for H.264 decoders on low-complexity devices. In particular, new wireless devices have both complexity and bit rate constraints, yet the range of these constraints differ from traditional systems (e.g., powerful PCs that are networked over the best-effort Internet). Under common operational scenarios, a low complexity wireless handheld may have significantly greater complexity/power constraints than bit rate limitation (e.g., over a wireless access LAN). This thesis analyzes the bottlenecks of H.264 decoders on ARM9TDMI processor, targeted for mobile devices, using performance-profiling tools. Optimizations are performed to achieve real time decoding. The code is built with Real View Compiler for ARM and ported on Symbian using Metroworks© Codewarrior© for Symbian V3.0 to achieve real time H.264 decoding on Nokia 6630 cellphone. The compiler flags were optimized for speed.