【作者】 金欣；

【导师】 朱光喜；

【作者基本信息】 华中科技大学 ， 信息与通信工程， 2005， 博士

【摘要】 伴随着无线移动通信技术的快速发展,应用在无线移动环境下的多媒体通信业务已经成为第三代以及第四代移动通信发展的核心。与此同时,目前无线多媒体终端处理器相对台式机或专业设备在处理能力上的不足,以及处理器功耗约束性问题已成为限制移动多媒体业务发展的主要障碍。本文在国家863 项目“数字音视频编码、传输、测试与应用示范”(No. 2002AA119010)和武汉市青年科技晨光计划项目“无线多媒体通信的联合功率率失真模型研究”(No.20045006071-18)的共同资助下,研究无线多媒体通信在处理器功耗约束条件下的信源信道联合编码技术和复杂度控制模型,目的是通过面向功率控制的信源信道联合编码系统的建立、相关技术及其复杂度模型的提出和联合功率控制策略的设计,达到在移动终端处理器功率约束或变化条件下,定量调节信源、信道编解码的复杂度,使视频数据在终端处理器功率约束下经无线信道传输后的质量尽可能达到最优。论文首先设计了功率可控的信源信道联合编码系统并建立了编解码系统的时间复杂度原型。与现有的仅考虑信源编码功耗开销的终端编码系统相比,本系统综合考虑了在终端算法复杂度和处理器功耗间存在抑制与平衡关系的信源编码、信道编码和差错控制三方面,由信源编解码子系统、联合信道保护子系统和复杂度控制子系统三部分组成,并论证了各编码子系统基本技术方案的先进性。随后,由功率和算法复杂度的对应关系,明确了实现功率控制的手段是控制算法的复杂度,定义算法的时间复杂度作为衡量各系统复杂度的物理参量以屏蔽实现方法的多样性。通过对各子系统相关技术算法时间复杂度相对系统时间复杂度的统计,初步建立了信源信道联合编码系统中信源编解码、信道编解码和差错控制的参数化复杂度控制原型,明确了影响算法复杂度的主要技术环节和控制参量,并简要分析了信源信道联合功率控制的实现策略和算法复杂度优化设计的方法。在信源编码子系统的研究中,提出了高性能、复杂度可控的空域伸缩性视频编码系统(Complexity and Spatiality Scalable Video Coding,CSSVC),与现有的空域伸缩性编码实现方式相比,本系统将低频域压缩性能优越的H.264 编码技术和高频域的带内预测技术相结合,具有优越的编码性能和与H.264 完全兼容的伸缩性码流。同时,针对高频子带系数的近随机分布特征,论证了原型系统主要编码技术的选择及有效性,设计的基于ODWT 的参考子带重建和运动补偿方法以及提出的高频子带残差系数的优化重排序方法、高频子带5 模式优化帧内预测和自适应的运动估计与补偿等技术改进,使本CSSVC 系统取得了超过H.264 Main Profile 全分辨率时0.04dB 的系统性能,更多还原

【Abstract】 With the rapid development in wireless communication, multimedia applications in wireless environment draw great attention in the third and forth generation mobile communication. While, the processing capabilities insufficiency of mobile device compared to PC and the microprocessor’s power-constraint problem caused by battery become the major restrictions on the development of multimedia applications. Sponsored by “Joint Source and Channel Adaptive Coding Technology Based on Wireless Channel”, subproject of National 863 project “Digital Audio, Video Encoding, Transporting, Testing and Applying Model”(No. 2002AA119010), and “Research on Joint Power-Rate-Distortion Model for Wireless Multimedia Communication”( No.20045006071-18), Chenguang Project of Youth S&T, this dissertation is focusing on the establishment of complexity-controllable joint source channel coding (JSCC) system with related techniques optimization and complexity model definition under the constraint of the microprocessor’s power. Together with the power control policy, the work aims to adjust the source/channel encoding/decoding complexity adaptively to achieve the best-effort visual quality when the power level is fluctuant or limited. Firstly, a power controllable JSCC system is designed with the complexity prototype definition for each subsystem. Compared to the existing encoding system only considering the energy consumed by source coding, the proposed system takes the source coding, channel coding and error control into consideration to make a good balance between algorithm complexity and energy consumption of microprocessor. The JSCC system consists of three subsystems as: source encoding/decoding subsystem, joint channel protection subsystem and complexity control subsystem. The basic schemes of every subsystem are proved to be advanced. Based on the corresponding relationship between power and algorithm complexity, we clarified that the major way to control power consumption is controlling algorithm complexity. The time complexity of an algorithm is defined for complexity measurement to shield the model from realization variety. Through the statistical data retrieval for the ratio of technique time complexity to system time complexity, the complexity prototypes of source encoding/decoding, channel encoding/decoding and error control are established with major complexity-controlling parameter specifying. Furthermore, the strategy of JSCC power control and the method of complexity optimization are also discussed briefly. Secondly, a complexity and spatiality scalable video coding (CSSVC) system is proposed for the source encoding/decoding subsystem. Compared to the existing spatially scalable video coding system, the proposed system integrates the good compression performance of H.264 in low frequency domain with the attractive advantages of in-band prediction in wavelet domain to provide the good coding efficiency while maintaining the H.264 fully compatible scalable bitstream. Because of the obvious Gaussian distribution properties concluded by series of analysis for high frequency subband, the efficiency of the coding techniques selected for CSSVC prototype is discussed carefully. Several technical improvements in reference reconstruction and motion compensation, reordering scan, intra prediction, and motion estimation for high frequency decompositions endure our system with average 0.04dB gain in PSNR and better visual quality compared with the H.264 main profile in the full resolution. For each technical improvement, the complexity variation is analyzed and complexity scalable schemes are investigated for different processing capabilities. Through the theoretical analysis, statistical data retrieval and performance test, all of the technical improvements are proved to be efficient. Thirdly, a complexity-controllable hybrid error control system is constructed for joint channel protection subsystem. Compared to the existing approaches, the proposed system is designed for the unstable feedback channel. In order to integrate the advantages of hybrid ARQ (HARQ) I and HARQ II, a novel HARQ scheme called hybrid independent retransmission and self-decodable ARQ is proposed with parameters optimization in data retransmission time, data retransmission delay, response retransmission time, and response retransmission delay for ARQ protocols in transmitter and receiver. Using the more appropriate parameters for the wireless communication, the optimized HARQ system shows lower end-to-end delay and more stable performance by comparing to the general scheme. Moreover, the complexity control strategy is also specified for the joint channel protection subsystem. Finally, the time complexity models are investigated and established for the source encoding/decoding, channel encoding/decoding and joint channel protection system. Major technical components, such as motion estimation (ME), motion compensation (MC), intra prediction, transform and context-adaptive binary arithmetic coding (CABAC), are analyzed to figure out the proportion they occupied in the system complexity respectively.Based on the theoretical analysis and statistical data retrieval, the time complexity of proposed technique improvements, as reordering scan, intra prediction and motion estimation, is described measurably. The complexity control capabilities of INTRA mode, INTER mode, coding subbands, ratio of non-zero blocks and quantization parameter are further discussed and the relative encoding/decoding complexity variation is measured for different coding schemes. The experimental results have proved accuracy of the models. For the time complexity model of rate compatible punctured turbo code (RCPT), complexity influenced by interleave, recursive systematic code (RSC) encoding/decoding and de-interleave are analyzed detailedly. Model amendment is made for joint channel protection system and the JSCC power controlling strategy is designed taking complexity relationship among subsystems, microprocessor capability, fast complexity control and bitstream match into consideration. It provides a complete solution for the joint power control.更多还原