标题: 超越 100Mpixels 之即时JPEG XR影像编码器设计
Over 100Mpixels Real Time JPEG-XR Encoder Design
作者: 丁建杉
Ding, Chien-Shan
张添烜
Chang, Tian-Sheuan
电机学院电子与光电学程
关键字: 影像压缩;JPEG;XR;HDPHOTO
公开日期: 2011
摘要: 在现在资讯快速发展的时代,许多手持式装置与照相机都需要使用到高解析度与高精细度的影像处理,于是对于影像储存的压缩率也显得越来越重要。由Microsoft所开发的最新影像压缩技术JPEG XR不论在影像压缩率或是影像的支援度也比传统的JPEG与JPEG2000都拥有更好的演算法。
在JPEG XR的实践电路中,有三个最主要的路径会影响到编码器的性能。一是适应性的量化器运算(Adaptive Normalization),二是须不断更新新的系数扫描顺序(Adaptive Scan),第三个则是判断最佳的Huffman Tabel并得到最佳的压缩率。因此,如何设计最佳化的管线设计让编码运算进行顺畅或是使用并行方式让编码器增加输出量则成为此篇论文最大的挑战。此篇论文中,我们研究了适应性量化器的特色并利用它对系数数目具有有效减少其数量的能力。进而改善了每个管线中的控制器使其能够有效的减少多余的扫描、快速推进每一阶的处理器,更有效的减少晶片的耗电与增加编码器的每个单位时间的输出量。
经过最佳化的硬体设计后,我们量测了晶片的效能。经量测,四张具有相同大小但拥有不同画面细节的测试图片在经过编码器的处理之后,皆得到近乎相同的运算成果。其运算能力的输出量达到了超过1 Pixel/Cycle。根据Synposys Design Compiler 0.18 um CMOS合成的结果与设定100MHz的条件之下,晶片的Gate Count为235,377而需使用的SRAMs大小则为992 X 3 channels。编码器的即时运算能力达到了100Mpixels。
In modern industry, although high resolution and wide dynamic range images had be used with in several applications like digital camera sensors, web display devices, so the compression of visual information becomes more and more important. JPEG XR [1] is an new image coding standard, based on high definition (HD) Photo developed by Microsoft [3]. It supports high compression performance higher than JPEG and JPEG2000.
Entropy coding was the throughput bottleneck in previous architectures. There are three feedback loops in entropy coding stage; (1) Control of ModelBits, (2) Updating of the scanning order, and (3) Decision of the Huffman table to be used. Therefore, how to design a pipelined module in a straightforward implementation or processing Macroblocks in parallel structure becomes main design challenge. We generalized the characteristic of Normalization (Update ModelBits) and took advent -age of reduction of Levels. Our propose pipeline controller can optimal the encoding forward steps to decrease un-necessary data processing. We could safely pipeline all the encoding processes including the entropy coding and achieves higher throughput than those of related works.
After our optimization, estimation of the encoding speed in our implementation is measured. The four images with same size but different manner are tested and represent quite similar results. The calculated throughput in terms of pixel/cycle shows that our implementation can achieve more than 1 pixel/cycle. The architecture is synthesized by Synposys Design Compiler with 0.18 um CMOS standard cell library. The result shows that the gate count of the designed JPEG XR encoder with 100MHz as target frequency is 235,377, number of used SRAMs is required by 992 × 3 channels. An over 100Mpixels real time JPEG XR encoder is designed.
URI: http://140.113.39.130/cdrfb3/record/nctu/#GT079667507
http://hdl.handle.net/11536/43785
显示于类别:Thesis


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