一种新的MPEG音频解码方案及算法优化

设计了一种新的MPEG音频解码框架.输入音频数据不需经过串行化,通过桶型移位器组织数据读取,提高了解码效率.解码器针对硬件处理特性设计了专用比特流输入单元和解组处理单元.对运算瓶颈子带滤波器设计了优化算法,使运算量降低为标准算法的1/4左右,存储空间降低为原来的1/2.该方案可用于DVB和DAB信源解码芯片中.     

利用缓存加快量化数据取得的编码和解码方法

提出一种在音频算法中利用音频帧间与帧内的相关性,用缓存来加快量化数据取得的编码和解码方法.这种方法可以减少量化数据时重复的运算量.从而有效地提升编码与解码的计算速度,保证在原有量化条件下,在原有音频质量不变的基础上,减少比特数的使用量并降低解码端的运算量从而节省解码时间.     

MPEG-2 AAC解码器的优化算法

作为新一代的音频编码国际标准,先进音频编码(AAC)提供了良好的压缩性能,具有广阔的发展和应用前景。但是由于AAC标准给出的算法比较复杂,按照标准算法进行测试时发现其并不能满足实时解码的要求,因此,必须对标准算法进行优化以达到实时解码的要求。在叙述了MPEG-2 AAC解码器的模块组成和原理的基础上,针对各个模块的特点采用优化算法,对MPEG-2 AAC解码器的部分模块进行了优化设计,较大程度地提高了解码速度。     

单频网同步音频IRD系统关键性分析

本文针对用于组建基于卫星传输信号源的传统音频广播单频网的同步卫星IRD系统的技术特性要求，通过对卫星IRD系统中与音频输出延时和抖动等技术指标密切相关的信道解码、解复用及音频解码等环节工作时序的深入分析，提出相应以降低音频输出延时、减小抖动为目的的电路结构和算法的选择和优化意见。勾改进同步卫星IRD系统的相关技术指标提供了基础数据，为分析单频网覆盖工程建设中的相关问题和提高单频网覆盖质量提供了理论依据和解决方案。     

用于版权管理的数字音频水印算法

该文提出了一种用于多媒体资料版权管理的自同步音频盲水印算法。由于版权应用需要通过解码结果得到素材的使用情况,对解码结果时间精度有一定要求,同时对鲁棒性和不可感知性要求也较高。针对之前算法存在鲁棒性不够,时间精度低的问题。该文提出的算法利用扩频的方法和音频信号的短时相关的特性提高嵌入水印的鲁棒性的同时,通过心理声学模型的应用改善算法的不可感知性。算法通过合理设计了水印信息帧结构和同步策略提高了解码结果的时间精度。实验结果表明,该文的方法在具有很高不可感知性的情况下,能够有效地抵抗各种常见的音频编辑操作。     

基于ARM嵌入式的无损音频解码器研究

FLAC编码可实现对音频数据的无损压缩。针对目前尚未出现硬件解码芯片的情况,介绍了基于ARM嵌入式的解码方案。系统可实现通过USB接口读取FLAC数据,解码后的PCM数据流通过IIS总线输出,整个方案可应用于高端音频流播放设备。     

基于SOC芯片ATJ2135的MP3播放器设计

介绍了一款多媒体应用SOC（片上系统）芯片ATJ2135,并给出了基于ATJ2135的MP3播放器的设计。采用ATJ2135的嵌入式处理器,结合μC／OS-Ⅱ实时操作系统移植实现了嵌入式操作系统,完成应用程序和用户数据的处理。采用ATJ2135的嵌入式DSP,结合音频解码算法实现软件模式的MP3文件解码。给出了软硬件设计、MP3解码流程、实时操作系统设计、软硬件调试等嵌入式系统的设计与实现。     

DAB+音频解码器中TNS模块优化设计及硬件实现

时域噪声整形技术被广泛地应用于各种感知音频编解码方案中,能有效地消除由量化噪声所产生的预回声现象。由于数字音频广播音频解码器(HE-AAC v2)算法复杂、运算量大,目前多采用DSP或嵌入式软件方式实现,本设计基于数字音频广播音频解码纯硬件系统,通过对时域噪声整形(TNS)解码算法的优化,以极低的硬件代价完成了时域噪声整形全硬件解码模块设计,具有高硬件资源利用率、低复杂度、高解码效率等特点。     

基于缓冲区控制策略的TS流软件复用的研究

介绍了单节目TS流的复用，分析了MPEG-2标准中T-STD的视频VBV缓冲模型和音频缓冲模型对复用交织算法的要求。据此，提出一种通过软件模拟视、音频T-STD缓冲区状态来控制码流的交织调度算法。实验结果表明，生成的TS流符合T-STD缓冲模型要求，可以有效避免解码缓冲区的上下溢。     

音频工作站MPEG-I Layer-II码流快速解码混音

为了能实时完成数字音频工作站中多路MPEG-ILayer-II音频压缩码流的快速解码混音,在分析MPEG-I解码器中的多相滤波器组这个核心算法的基础上,提出了多路MPEG-ILayer-II码流的快速解码混音算法。此算法在进行混音计算时,只需做一次在解码中较为费时的子带综合滤波计算,大大提高了多路混音的速度。实验表明,用该算法进行8路MPEG-ILayer-II解码混音时,在PI-II600MHz的PC机达到了0.25倍实时的解码速度,完全满足了专业数字音频工作站的要求。     

Information geometry of turbo and low-density parity-check codes

Since the proposal of turbo codes in 1993, many studies have appeared on this simple and new type of codes which give a powerful and practical performance of error correction. Although experimental results strongly support the efficacy of turbo codes, further theoretical analysis is necessary, which is not straightforward. It is pointed out that the iterative decoding algorithm of turbo codes shares essentially similar ideas with low-density parity-check (LDPC) codes, with Pearl's belief propagation algorithm applied to a cyclic belief diagram, and with the Bethe approximation in statistical physics. Therefore, the analysis of the turbo decoding algorithm will reveal the mystery of those similar iterative methods. In this paper, we recapture and extend the geometrical framework initiated by Richardson to the information geometrical framework of dual affine connections, focusing on both of the turbo and LDPC decoding algorithms. The framework helps our intuitive understanding of the algorithms and opens a new prospect of further analysis. We reveal some properties of these codes in the proposed framework, including the stability and error analysis. Based on the error analysis, we finally propose a correction term for improving the approximation.     

基于多元LDPC码译码算法研究的Qt设计与实现

为了实现Qt对多元LDPC码译码算法理论测试的界面操控,在多元LDPC码译码算法研究的基础上设计了Qt程序,用Matlab实现基本仿真,将其编译成可供Qt调用的动态链接库文件(dll)并进行调用,最终实现了该Qt界面对译码理论测试的直观操控,并进一步分析了译码数据。     

一个基于随机神经网络的信息传输系统模型及其实现

提出了一个基于随机三层前向网络的信息传输系统（ITS）模型。在此系统框架下，把编码、信道与译码统一考虑，设计系统完成信息的智能传输。与传统的编译码相比，该模型具有很大的通用情形与自适应性。通过把BP算法引入随机神经元的学习，从而推出信息传输系统的学习算法（ITBP）。对于二进对称信道传输仿真结果表明了此模型的有效性及特点。     

基于自适应下采样和超分重建的图像压缩框架

针对联合图像专家组(JPEG)标准设计了一种基于自适应下采样和超分辨力重建的图像压缩编码框架。在编码器端,为待编码的原始图像设计了多种不同的下采样模式和量化模式,通过率失真优化算法从多种模式中选择最优的下采样模式(DSM)和量化模式(QM),最后待编码图像将在选择的模式下进行下采样和JPEG编码;在解码器端,采用基于卷积神经网络的超分辨力重建算法对解码后的下采样图像进行重建。此外,所提出的框架扩展到JPEG2000压缩标准下同样有效可行。仿真实验结果表明,相比于主流的编解码标准和先进的编解码方法,提出的框架能有效地提升编码图像的率失真性能,并能获得更好的视觉效果。     

Low-density parity check codes for partial response channels

The goals of this article are twofold: (1) to provide a brief tutorial of the application of low-density parity check (LDPC) codes for partial response (PR) channels under the framework of turbo equalization and (2) to highlight the use of structured LDPC codes in PR systems. We begin by introducing LDPC codes, their graph representations and associated sum-product decoding algorithm, followed by describing the general framework of iterative equalization and decoding approach to combat ISI. We then present explicit constructions of structured LDPC codes, which facilitate efficient implementation of encoding and decoding and show simulation results.     

Systematic analysis of the decoding delay in multiview video

We present a framework for the analysis of the decoding delay in multiview video coding (MVC). We show that in real-time applications, an accurate estimation of the decoding delay is essential to achieve a minimum communication latency. As opposed to single-view codecs, the complexity of the multiview prediction structure and the parallel decoding of several views requires a systematic analysis of this decoding delay, which we solve using graph theory and a model of the decoder hardware architecture. Our framework assumes a decoder implementation in general purpose multi-core processors with multi-threading capabilities. For this hardware model, we show that frame processing times depend on the computational load of the decoder and we provide an iterative algorithm to compute jointly frame processing times and decoding delay. Finally, we show that decoding delay analysis can be applied to design decoders with the objective of minimizing the communication latency of the MVC system.     

Convergence analysis of turbo decoding of product codes

Geometric interpretation of turbo decoding has founded an analytical basis, and provided tools for the analysis of this algorithm. We focus on turbo decoding of product codes, and based on the geometric framework, we extend the analytical results and show how analysis tools can be practically adapted for this case. Specifically, we investigate the algorithm's stability and its convergence rate. We present new results concerning the structure and properties of stability matrices of the algorithm, and develop upper bounds on the algorithm's convergence rate. We prove that for any 2×2 (information bits) product codes, there is a unique and stable fixed point. For the general case, we present sufficient conditions for stability. The interpretation of these conditions provides an insight to the behavior of the decoding algorithm. Simulation results, which support and extend the theoretical analysis, are presented for Hamming [(7,4,3)]² and Golay [(24,12,8)]² product codes     

A unified framework for tree search decoding: rediscovering the sequential decoder

We consider receiver design for coded transmission over linear Gaussian channels. We restrict ourselves to the class of lattice codes and formulate the joint detection and decoding problem as a closest lattice point search (CLPS). Here, a tree search framework for solving the CLPS is adopted. In our framework, the CLPS algorithm is decomposed into the preprocessing and tree search stages. The role of the preprocessing stage is to expose the tree structure in a form matched to the search stage. We argue that the forward and feedback (matrix) filters of the minimum mean-square error decision feedback equalizer (MMSE-DFE) are instrumental for solving the joint detection and decoding problem in a single search stage. It is further shown that MMSE-DFE filtering allows for solving underdetermined linear systems and using lattice reduction methods to diminish complexity, at the expense of a marginal performance loss. For the search stage, we present a generic method, based on the branch and bound (BB) algorithm, and show that it encompasses all existing sphere decoders as special cases. The proposed generic algorithm further allows for an interesting classification of tree search decoders, sheds more light on the structural properties of all known sphere decoders, and inspires the design of more efficient decoders. In particular, an efficient decoding algorithm that resembles the well-known Fano sequential decoder is identified. The excellent performance-complexity tradeoff achieved by the proposed MMSE-DFE Fano decoder is established via simulation results and analytical arguments in several multiple-input multiple-output (MIMO) and intersymbol interference (ISI) scenarios.     

Iterative multiuser joint decoding: unified framework andasymptotic analysis

We present a framework for iterative multiuser joint decoding of code-division multiple-access (CDMA) signals, based on the factor-graph representation and on the sum-product algorithm. In this framework, known parallel and serial, hard and soft interference cancellation algorithms are derived in a unified way. The asymptotic performance of these algorithms in the limit of large code block length can be rigorously analyzed by using density evolution. We show that, for random spreading in the large-system limit, density evolution is considerably simplified. Moreover, by making a Gaussian approximation of the decoder soft output, we show that the behavior of iterative multiuser joint decoding is approximately characterized by the stable fixed points of a simple one-dimensional nonlinear dynamical system