Energy-efficient wireless video coding and delivery

Transmitting video over wireless channels from mobile devices has gained increased popularity in a wide range of applications. A major obstacle in these types of applications is the limited energy supply in mobile device batteries. For this reason, efficiently utilizing energy is a critical issue in designing wireless video communication systems. This article highlights recent advances in joint source coding and optimal energy allocation. We present a general framework that takes into account multiple factors, including source coding, channel resource allocation, and error concealment, for the design of energy-efficient wireless video communication systems. This framework can take various forms and be applied to achieve the optimal trade-off between energy consumption and video delivery quality during wireless video transmission.     

基于MPEG-4的无线视频通信

目前，人们对处理话音的能力已经非常强大，而且其无线传输也已十分普及，那么下一个无线传输的目标是什么呢？我们很自然地想到了图像信息，尽管仍有许多技术问题有待解决，但视频信息依然会成为无线传输的下一个热点，并且带动一系列新的无线应用。现在迫切需要建立的是，既具有实用性，又能为市场所接受的无线视频传输系统。无线视频传输当前，用于视频信号的主要传输网络有PSTN、ISDN、广播网以及Internet。最初，视频会议使用PSTN和ISDN传输，这两种网络的误码率都十分低。与此类似，有些采用广播方式的系统也设计成能在一定服…     

Rate-distortion based real-time wireless video streaming

This paper presents wireless video streaming techniques that exploit the characteristics of video content, transmission history, and physical layer channels to enable real-time efficient video streaming over wireless networks to a wireless client. The key contribution of the proposed video streaming techniques is the use of rate-distortion based, but simplified, low complexity packet scheduling as well as forward error correction (FEC) rate selection. To this end, we develop an optimization framework that jointly schedules the packets and selects the FEC rates. The rate-distortion optimized packet scheduling and FEC rate selection provides the optimum quality video on the receiver side albeit at a high computational cost. By some intelligent approximations, rate distortion optimized packet scheduling and FEC rate selection technique is transformed into two sub-optimal but low complexity video streaming techniques that can provide high video quality. We perform extensive simulations to understand the performance of our proposed techniques under different scenarios. Results show that, the proposed techniques improve video quality on the average by 4 dB. We conclude that significant benefits to end-user experience can be obtained by using such video streaming methods.     

Per-packet rate adaptation for wireless video

Streaming video over error-prone wireless channels is a challenge as the dynamic network conditions and slow adaptation to channel degradations may affect the quality of the streamed video. Unequal error protection (UEP) can potentially address this issue by considering the importance of each video packet and its impact on the quality of reconstructed video. This paper proposes a cross-layer UEP solution for wireless video streaming over IEEE 802.11 networks. Video packets are prioritized based on the relative importance of the video packet. UEP is achieved by adapting the link layer parameters on a per-packet basis, using inherent forward error correction and adaptive modulation capabilities of the 802.11n network. Experimental results revealed that the proposed solution achieves comparable performance to the state-of-the-art methods at a lower complexity.     

视频监控和无线网络的融合

值金秋时节，《中国无线电》杂志诞生了一个新的栏目——“行业之窗”。 随着我国经济社会的发展，随着近年来无线领域的创新繁荣，在我国各行各业，无线电技术和应用发挥着日益重要的作用。我国无线电管理事业在推动经济社会发展，满足各行业无线电应用需求和保障良好的空中电波秩序等方面，作着不懈的努力并作出了重要的贡献。而各行业无线电技术的推广应用，也促进了我国无线产业的繁荣。“行业之窗”栏目的开设，即期望能够推动行业无线应用发展，进一步促进行业无线电管理工作。该栏目的内容包括行业无线电应用，行业无线电管理研究等，衷心希望得到各行业专家的大力支持。[编者按]     

Error-resilient image and video coding for wireless communicationsystems

Current techniques for coding images and video sources with resilience to channel errors can remove much of the need for complex high-redundancy channel coding and provide a graceful degradation of performance with decreasing channel quality. The main function of these error-resilient techniques is to reduce the propagation of errors within the decoded data. Two main techniques are discussed in detail: the error-resilient entropy code (EREC) and pyramid vector quantisation (PVQ). The paper concludes with a comparison of the relative merits of these systems and areas for further consideration     

QoE in video streaming over wireless networks: perspectives and research challenges

The deployment of 3G/LTE networks and advancements in smart mobile devices had led to high demand for multimedia streaming over wireless network. The rapid increasing demand for multimedia content poses challenges for all parties in a multimedia streaming system, namely, content providers, wireless network service providers, and smart device makers. Content providers and mobile network service providers are both striving to improve their streaming services while utilizing advancing technologies. Smart device makers endeavor to improve processing power and displays for better viewing experience. Ultimately, the common goal shared by content providers, network service providers, and smart device manufactures is to improve the QoE for users. QoE is both an objective and a subjective metric measuring the streaming quality experience by end users. It may be measured by streaming bitrate, playback smoothness, video quality metrics like Peak to Signal Noise Ratio, and other user satisfaction factors. There have been efforts made to improve the streaming experiences in all these aspects. In this paper, we conducted a survey on existing literatures on QoE of video streaming to gain a deeper and more complete understanding of QoE quality metrics. The goal is to inspire new research directions in defining better QoE and improving QoE in existing and new streaming services such as adaptive streaming and 3D video streaming.     

Error resilience video transcoding for wireless communications

Video communication through wireless channels is still a challenging problem due to the limitations in bandwidth and the presence of channel errors. Since many video sources are originally coded at a high rate and without considering the different channel conditions that may be encountered later, a means to repurpose this content for delivery over a dynamic wireless channel is needed. Transcoding is typically used to reduce the rate and change the format of the originally encoded video source to match network conditions and terminal capabilities. Given the existence of channel errors that can easily corrupt video quality, there is also the need to make the bitstream more resilient to transmission errors. In this article we provide an overview of the error resilience tools found in today's video coding standards and describe a variety of techniques that may be used to achieve error-resilient video transcoding.     

Prediction of transmission distortion for wireless video communication: Algorithm and application

In this paper, we develop algorithms for estimating transmission distortion in wireless video communication systems. By leveraging the analytical results obtained in our previous works, we design low complexity algorithms that are capable of estimating transmission distortion accurately. We also extend our algorithm for pixel-level transmission distortion estimation to pixel-level end-to-end distortion estimation. Furthermore, we apply our pixel-level end-to-end distortion estimation algorithm to prediction mode decision in H.264 encoder. Experimental results show that (1) our transmission distortion estimation algorithm is more accurate and more robust against inaccurate channel estimation than existing distortion estimation algorithms; (2) our mode decision algorithm achieves remarkable PSNR gain over the existing algorithms for prediction mode decision in H.264 encoder, e.g., an average PSNR gain of 1.44 dB for ‘foreman’ sequence when Packet Error Probability (PEP) equals 5%.     

Error-resilient transcoding for video over wireless channels

We describe a method to maintain quality for video transported over wireless channels. The method is built on three fundamental blocks. First, we use a transcoder that injects spatial and temporal resilience into an encoded bitstream. The amount of resilience is tailored to the content of the video and the prevailing error conditions, as characterized by bit error rate. Second, we derive analytical models that characterize how corruption propagates in a video that is compressed using motion-compensated encoding and subjected to bit errors. Third, we use rate distortion theory to compute the optimal allocation of bit rate among spatial resilience, temporal resilience, and source rate. Furthermore, we use the analytical models to generate the resilience rate distortion functions that are used to compute the optimal resilience. The transcoder then injects this optimal resilience into the bitstream. Simulation results show that using a transcoder to optimally adjust the resilience improves video quality in the presence of errors while maintaining the same input bit rate     

Distributed video coding in wireless sensor networks

This paper addresses the important aspect of compressing and transmitting video signals generated by wireless broadband networks while heeding the architectural demands imposed by these networks in terms of energy constraints as well as the channel uncertainty related to the wireless communication medium. Driven by the need to develop light, robust, energy-efficient, and low delay video delivery schemes, a distributed video coding based framework dubbed PRISM is introduced. PRISM addresses the wireless video sensor network requirements far more effectively than current state-of-the-art standards like MPEG. This paper focuses on the case of a single video camera and use it as a platform to describe the theoretical principles and practical aspects underlying distributed video coding.     

“两客一危”车载无线视频监控系统研究

为全面提升"两客一危"车辆的行驶安全和客运服务质量,利用加载了3G模块的无线视频监控车载终端系统,实现对车辆行驶记录、视频取证、远程视频监控的管理。车内安装摄像机、拾音器、紧急报警按钮和车载信息显示屏,分别作为视频图像、音频数据、紧急报警信息、GPS等信息的采集设备,采集后的信息经过车载硬盘录像机的处理之后,由车载硬盘录像机自带的3G无线通信模块发送给监控中心。     

无线视频监控系统中的安全机制研究

无线视频监控系统的安全不能单纯依靠加密来保证,从信息系统安全体系的角度,对无线视频监控系统的安全进行了分析,并对系统中主要应用的鉴权、密钥管理、空中接口加密、端到端加密等安全机制进行了重点研究。     

无线视频监控系统研究及应用

无线视频监控已经广泛应用于各个行业,包括医院、银行、建筑工地等,文中首先主要介绍了无线视频监控的发展历程,然后介绍了无线视频监控中所涉及的一些主要技术,包括:一是无线传输方式,二是视频压缩技术。最后,通过几个实例来说明了无线视频监控在生活各方面的应用。     

基于ARM的嵌入式家用无线视频监控系统

介绍了一种基于ARM的室内无线视频系统设计方法,该系统的主要构成模块包括：主控模块、图像处理模块、无线传输模块三模块。该系统通过将删改过的linux内核以及文件系统移植到ARM芯片中来完成主控芯片对各硬件系统的支持。通过测试表明,该系统设计方案合理、有效能够较好的达到设计目的和要求。