Parallel Scalability of Video Decoders
Parallel Scalability of Video Decoders
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DOI：
10.1007/s11265-008-0256-9
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发表时间：
2009-11
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通讯作者：
C. Meenderinck;A. Azevedo;B. Juurlink;Mauricio Alvarez;Alex Ramírez
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作者：
C. Meenderinck;A. Azevedo;B. Juurlink;Mauricio Alvarez;Alex Ramírez
一个重要的问题是，新兴和未来的应用程序是否表现出足够的并行性，特别是线程级并行性，以利用未来芯片多处理器（cmp）所期望包含的大量核心。作为一个案例，我们研究了视频解码器的并行性，这是一个重要的应用领域，现在和未来。具体来说，我们分析了H.264解码过程的并行可扩展性。首先，我们讨论了H.264的数据结构和依赖关系，并展示了它允许利用的并行类型。我们还表明，以前提出的并行化策略，如片级、帧级和帧内宏块（MB）级并行，都没有足够的可扩展性。基于帧间依赖关系具有有限空间范围的观察，我们提出了一种新的并行化策略，称为动态3D-Wave。它允许若干mb的连续帧并行解码。利用这种新策略，我们分析了H.264中可用的mb级并行性的限制。使用真实的电影序列，我们发现最大的MB并行度范围从4000到7000。我们还进行了一个案例研究，以评估高度并行化的H.264应用程序的实用价值和可能性。结果表明，H.264具有足够的并行性，可以有效地利用未来多核cmp的能力。
An important question is whether emerging and future applications exhibit sufficient parallelism, in particular thread-level parallelism, to exploit the large numbers of cores future chip multiprocessors (CMPs) are expected to contain. As a case study we investigate the parallelism available in video decoders, an important application domain now and in the future. Specifically, we analyze the parallel scalability of the H.264 decoding process. First we discuss the data structures and dependencies of H.264 and show what types of parallelism it allows to be exploited. We also show that previously proposed parallelization strategies such as slice-level, frame-level, and intra-frame macroblock (MB) level parallelism, are not sufficiently scalable. Based on the observation that inter-frame dependencies have a limited spatial range we propose a new parallelization strategy, called Dynamic 3D-Wave. It allows certain MBs of consecutive frames to be decoded in parallel. Using this new strategy we analyze the limits to the available MB-level parallelism in H.264. Using real movie sequences we find a maximum MB parallelism ranging from 4000 to 7000. We also perform a case study to assess the practical value and possibilities of a highly parallelized H.264 application. The results show that H.264 exhibits sufficient parallelism to efficiently exploit the capabilities of future manycore CMPs.