基于ARM-Linux的H.264编解码器研究

发布时间：2018-10-20 07:40

【摘要】：在信息化高速发展的当今社会,视音频等作为信息的载体,在社会生活的各个领域中起着越来越重要的作用。然而,由于数字视音频信息具有大量冗余信息,并且占用的存储空间极大,限制了多媒体技术的发展。在这种情况下,由国际电信联合会视频编码专家组和国际化标准组织运动图像专家组联合制定的H.264视频压缩标准,以其高性能的压缩效率和优秀的图像质量,成为目前最主流的视频处理协议。H.264通过运动估计/运动补偿(MP/MC)消除视频时间冗余,对差值图像进行离散余弦变换(DCT)消除空间冗余,对量化后的系数进行可变长编码(VLC)消除统计冗余,获得了极高的压缩效率。由于其计算复杂度,目前主流的实现方式主要是基于SoC+ASIC的专用集成电路和DSP软件实现。由于H.264在提升编解码性能的同时所付出的代价是成倍增加算法复杂度,并且实际应用中人们对视频解码的实时性要求比较高。已有的算法多是基于PC通用处理器实现的。虽然近年来ARM处理器以及嵌入式技术发展迅猛,但毕竟处理能力有限,并且存储能力有限,因此必须进行移植和优化,才能满足实际应用需要。本文首先对H.264标准及其新特性进行了详细的介绍,分析了解码耗时较多的函数及模块。然后以友善之臂的mini2440开发板为硬件平台,对Linux系统、bootloader、内核的移植以及根文件系统的制作进行了详细的说明。将基于H.264标准的X264、ffmpeg等参考软件进行交叉编译后移植到ARM平台,并针对ARM平台特点进行了编译优化和代码优化。其中编译优化是选择合适的交叉编译环境以及配置最佳的编译参数,从而生成效果更好的目标软件；代码级优化则是包括了去除冗余代码、重写循环结构以及汇编优化等等。最后完成解码播放,并给出了实验测试结果以及评价。实验结果表明,对于qcif分辨率的视频流,可以达到实时解码和播放。
[Abstract]:As the carrier of information, video and audio plays an increasingly important role in various fields of social life. However, digital video and audio information has a lot of redundant information and takes up a lot of storage space, which limits the development of multimedia technology. In this case, the H.264 video compression standard, developed jointly by the International Telecommunication Union Video coding expert Group and the International Standards Organization moving Image expert Group, is designed for its high compression efficiency and excellent image quality, H.264 uses motion estimation / motion compensation (MP/MC) to eliminate video time redundancy, and uses discrete cosine transform (DCT) to eliminate spatial redundancy. The variable length coding (VLC) is used to eliminate the statistical redundancy of the quantized coefficients, and the compression efficiency is very high. Due to its computational complexity, the main implementation methods are mainly based on SoC ASIC and DSP software implementation. The cost of H.264 in improving the performance of codec is multiplying the complexity of the algorithm, and the real time requirement of video decoding is very high in practical applications. Most of the existing algorithms are based on PC general purpose processor. Although the ARM processor and embedded technology have developed rapidly in recent years, the processing capacity is limited and the storage capacity is limited, so it is necessary to transplant and optimize to meet the practical application needs. In this paper, the H.264 standard and its new features are introduced in detail, and the decoding functions and modules are analyzed. Then using the mini2440 development board of friendly arm as the hardware platform, the Linux system, the transplantation of the bootloader, kernel and the manufacture of the root file system are described in detail. The X264ffmpeg reference software based on H.264 standard is cross-compiled and transplanted to the ARM platform, and the compiler and code optimization are carried out according to the characteristics of the ARM platform. Compiler optimization is to select the appropriate cross-compilation environment and configure the best compilation parameters, so as to generate better target software. Code level optimization includes removing redundant code, rewriting loop structure, assembly optimization and so on. Finally, the decoding and playing are finished, and the experimental test results and evaluation are given. Experimental results show that real-time decoding and playback can be achieved for qcif resolution video streams.
【学位授予单位】：长江大学
【学位级别】：硕士
【学位授予年份】：2012
【分类号】：TP368.1;TN919.81

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