基于Android的H264视频无线传输系统

为了让无线视频传输系统得到广泛的应用,设计并实现了一种采用Android智能手机作为采集端,H．264作为视频压缩编码的无线传输系统;介绍了无线视频传输系统的组成,重点论述了各模块的设计。     

H.264高清视频编码器的设计与实现

针对高清视频庞大的数据量以及H.264编码器复杂的编码结构引起的低编码速率的问题,对影响算法编码速率的原因进行了深入分析,并设计了高效的多核并行方案,进而充分利用TMS320C6678的多核性能,并结合TMS320C6678的运算存储特性,对H.264编码器进行了多方面的优化,最终使H.264编码器对720P高清视频序列编码速率从1.2 fps增加到27.2 fps,更加贴近于实际应用。     

Optimized H.264 compression of sign language video

In TV broadcasting deaf people are not able to get information from the audio content. In public television, some programs may be accompanied by a sign language interpreter as a part of the broadcasted signal. As a supplementary service, it would enable more programs to be accessible with a sign language interpreter to assist in comprehension. To be able to transmit such data flow separately, we define the parameters of compression of sign language interpreter image to ensure intelligibility and quality while maintaining low bitrate. This paper deals with specific video compression of Czech sign language interpreter based on regions of interest implemented to the ×264 open source library. The results of this approach are verified in subjective tests with the deaf and hearing evaluators. The experiments examine the intelligibility of sign language expressions containing minimal pairs for different levels of image compression and also evaluate the subjective quality of the final image.     

MIMO系统中的H.264/SVC数据流抽取和重组算法

为了使H.264可分级视频编码(SVC)生成的数据流分割为多个子数据流,便于在多输入多输出(MIMO)无线网络的不同子信道上传输以提高视频传输速率,提出了一个SVC数据流抽取和重组算法.在发送端,该算法利用SVC数据流的分层结构,将其中的基本层和增强层抽取为多个子数据流,并保持基本层子数据流能够独立解码.在接收端,该算法将接收到的子数据流重组成可解码的SVC数据流.实验证明该算法能充分利用MIMO系统提供的高带宽,并具有较低的冗余度和较好的灵活性.     

Incremental rate control for H.264/AVC video compression

In this study, the authors propose a new rate-complexity-quantisation model and an incremental rate control algorithm for H.264/AVC video coding. One unique property of this algorithm is that, the picture complexity estimation and rate-quantisation modelling are jointly designed with an incremental rate control for P-frames. In addition, the proposed algorithm also introduces a number of efficient rate control techniques, including accurate rate control for intra-frames, enhanced proportional--integral--derivative (PID) buffer controller, and adaptive quantisation parameter determination for B-frames. The proposed algorithm has low computational complexity while providing robust rate control. Our extensive experimental results demonstrate that the proposed algorithm outperforms the current rate control algorithm adopted in the H.264/AVC reference software JM13.2 by achieving more accurate rate control, reducing frame skipping, depressing quality fluctuation and improving the overall coding quality by up to 2.83 dB.     

H.264编码和SHDSL传输技术在井下电视的应用

井下电视应用一直受到传输速率的影响,数字井下电视可以分析并解决井下复杂状况问题。采用H.264编码技术可以在相同带宽传输更高的图像质量,以及采用单对线高速数字用户线(SHDSL)技术可以解决井下传输距离与速率相矛盾的问题。该传输技术具备自适应能力来适应同轴铠甲电缆,对传输介质降低了要求且节省成本。通过以上两种技术可以解决井下图像传输距离短和分辨率低的问题,并提高井下数据传输速率。     

H.264 video transmissions over wireless networks: Challenges and solutions

Multimedia video streaming is becoming increasingly popular. Using multimedia services, there are more and more users in end-system over wireless networking environment. H.264/AVC is now the standard for video streaming because of its high compression efficiency, robustness against errors and network-friendly features. However, providing the desired quality of service or improving the transmission efficiency for H.264 video transmissions over wireless networks present numbers of challenges. In this paper, we consider those challenges and survey existing mechanisms based on the protocol layers they work on. Finally, we address some open research issues concerning for H.264 video transmission in wireless networks.     

Idempotent H.264 intraframe compression

This paper studies H.264 intraframe multi-generation characteristics and presents four mechanisms that contribute to the generation degradation. We analyze the H.264 transform and quantization and reveal that for some quantization parameters there always exists at least one clipping compensation matrix to make the H.264 intraframe multi-generation coding idempotent as long as the same prediction mode and the same quantization parameter are selected for each coding generation. In addition, an idempotent H.264 intraframe multi-generation coding procedure is presented. The procedure has three additional steps to achieve idempotence: Prediction Mode and QP Restriction, Prediction Mode and QP Identification, and Clipping Compensation. Experiment results show that the proposed idempotent coding produces no generation PSNR loss and the rate-distortion efficiency is almost same as that of traditional H.264.     

基于H.264标准的无线局域网视频传输系统实现方案

近年来,无线移动终端PDA(personal digital assistant)以其体积小、重量轻、功能完善等诸多特点在移动办公领域发挥了重要作用,而新一代视频编码标准H.264标准的提出又为无线信道等环境下的视频传输提供了更多技术保证.根据H.264编码标准的特点和PDA平台的基本特性,提出了一种无线局域网环境下的视频传输系统方案,该方案采用H.264作为视频编码方法,PDA作为移动终端,RTP/UDP/IP作为网络传输协议,并在此基础上构建了系统的演示平台.测试结果表明,该系统可以在无线局域网环境下实现视频的实时传输,显示帧率10帧/s以上(CIF格式).     

Cross-Layer prioritized H.264 video packetization and error protection over noisy channels

Video transmission over wireless channels is affected by channel-induced packet losses. Distortion due to channel errors can be alleviated by applying forward error correction. Aggregating H.264/AVC slices to form video packets with sizes adapted to their importance can also improve transmission reliability. Larger packets are more likely to be in error but smaller packets require more overhead. We present a cross-layer dynamic programming (DP) approach to minimize the expected received video distortion by jointly addressing the priority-adaptive packet formation at the application layer and rate compatible punctured convolutional (RCPC) code rate allocation at the physical layer for prioritized slices of each group of pictures (GOP). Some low priority slices are also discarded to improve protection to more important slices and meet the channel bit-rate limitations. We propose two schemes. Our first scheme carries out joint optimization for all slices of a GOP at a time. The second scheme extends our cross-layer DP-based approach to slices of each frame by predicting the expected channel bit budget per frame for live streaming. The prediction uses a generalized linear model developed over the cumulative mean squared error per frame, channel SNR, and normalized compressed frame bit budget. The parameters are determined over a video dataset that spans high, medium and low motion complexity. The predicted frame bit budget is used to derive the packet sizes and corresponding RCPC code rates for live transmission using our DP-based approach. Simulation results show that both proposed schemes significantly improve the received video quality over contemporary error protection schemes.     

H.264软件编码器的优化

为降低编码复杂度以满足实时应用的需求,以联合专家组（JVT）发布的H．264参考模型JM9．4为基础,分析H．264软件编码器的结构,指出影响编码速度的瓶颈所在,给出具体的优化方案,并结合MMX／SSE技术,对H．264软件编码器进行全面优化,其编码速度完全可以满足实时性应用的要求,而图像的重建质量基本不变。     

H.264的视频编码技术初探

H.264频编码是今年来多媒体信息技术领域出现的又一项关键技术,本文首先分析了H.264的分层结构和主要编码技术,并探讨了其在性能改进方面的研究成果,最后展望了其在多个领域中的应用前景。     

改进的H.264视频编码方案

提出了一种改进的H264视频编码方案。针对H264中具有7种不同块模式运动估值的特点,在帧间预测过程中使用一种扩展的变换编码概念——自适应块变换,把运动估值的块大小和变换块大小联系起来,通过限制最大的变换块尺寸对自适应块变换做了简化,以适应实际应用的需要;通过扩展帧内预测的块模式,将简化的自适应块变换也应用到帧内预测编码中：鉴于不同块尺寸的变换系数矩阵的概率分布不同,提出在熵编码过程中采用自适应通用变长编码对码表进行动态重组,以进一步提高编码效率。比较了与现有H．264视频编码方案的性能差异。     

基于ZigBee和H.264的无线视频传输系统的设计与实现

ZigBee是以IEEE 802.15.4标准为基础的一种低成本、低功耗的无线网络技术,通过ZigBee协议栈,可将各ZigBee节点形成一个节点容量大、通信范围广的ZigBee网络。而H.264是当今最好的视频压缩标准,具有码流率低、图像质量高、容错能力强等优点。使用ZigBee网络来传输H.264视频码流,是实现无线视频传输系统的一种好方案。通过具体开发实例,从硬件和软件两个方面讨论了该方案的设计与实现。     

基于H.264的误码隐藏技术

为了在高误码环境下提高视频通信质量,提出一种改进的基于H.264的误码隐藏技术。对于帧内编码图像,根据图像直方图信息计算图像的光滑特性,然后自适应地选择线性插值的方法。对于帧间编码图像,根据不同大小块编码类型和多参考帧的特性,能够更准确地估计出丢失的MV,进行时域误码隐藏。实验表明,此方法同H.264参考软件JM11.0方法相比,具有更好的主客观图像恢复质量。     

实时高清H.264编码中CAVLC的流式实现

CAVLC是H.264中熵编码的一种重要实现方式,具有可挖掘的数据级并行特征,但同时具有较强的串行特点。本文分析了CAVLC的程序特征,提出了CAVLC的流式实现方法,并在流处理器STORM-1上进行了实现。实验结果表明本方法能够满足实时高清H.264编码的性能需求。     

用于高清视频传输的Linux无线路由卡的设计

城市中存在不便布线的或者布线成本较高的高清视频监控点,可以使用基于嵌入式Linux的无线路由卡的网络摄像机配备,通过Wifi将视频传到另一台布线方便的摄像机,经过网线传到监控中心。由于一路1080P的视频需要带宽6 M-10 M,采用雷凌RT5350设计一款基于嵌入式的Linux无线路由器以满足高带宽的要求,并同时传输多路视频。通过创造性使用Linux的无线路由卡,减少了施工量,降低了成本,使高清视频监控点得以快速投入使用。     

多路嵌入式H．264视频服务器的设计

介绍了一种基于Linux操作系统的多路嵌入式H．264视频服务器的设计方案。该方案给出了系统的硬件组成和软件设计框架．然后说明了发送端和接收端的实现过程，并对网络传输中利用RTP实现QoS机制做了说明。实验结果表明，上述设计的多路嵌入式视频服务器在不影响图象质量的前提下，能够比以往的视频服务器占用更低的带宽。     

Efficient hybrid framework for transmission enhancement of composite 3D H.264 and H.265 compressed video frames

Multimedia Tools and Applications - Three-Dimensional Multi-View Video (3D-MVV) transmission over wireless networks suffers from losses. Therefore, the robust performance of 3D-MVV transmission...