基于局域网的H.263视频数据流的实时传输

介绍了一种在局域网上利用RTP技术实时传输H.263图像数据的方法，并对其性能进行了测试，给出了C语言编程实例。通过RTP及RTCP提供的信息对编码端进行码率调整等方法，成功地实现了基于局域网的图像监控系统中的H.263图像数据的实时传送。     

基于i.MX27的3G无线视频监控系统的设计与实现

为解决传统无线视频监控系统存在的问题,介绍了一种基于H.264视频压缩标准和CDMA2000技术标准的嵌入式3G无线视频监控系统.给出了系统的总体结构和硬软件模块设计,重点阐述了视频采集、编码的过程和RTP/RTCP协议下H.264视频流的实时传输.客户端通过RTP数据包的接收、去封装和H.264码流的解码和显示,可以...     

H.261视频数据流的RTP封装

H.261视频编解码标准广泛应用于IP网络的视频通信中,一般采用实时传输协议(RTP)保证H.261视频数据流的实时传输和质量监测.本文在分析H.261帧结构和RTP协议的基础上,基于H.261数据RTP封装的三层结构,此提出了一种新的适用于低带宽高效的封装算法和具体实现方法.     

基于H.264视频通信的交织保护算法

根据H．264中NALU（网络适配层单元）结构和实时视频通信的特点，提出了一种在分组网络上传输H1264码流的交织保护算法。该算法结合前向纠删保护，可以对具有不同重要程度的H．264视频数据进行不等保护。另外，基于该算法提出了一种新的支持交织保护的RTP载荷结构和封装方法。实验结果表明，在5％的丢包环境下，与使用简单误码掩盖算法相比，恢复图像PSNR可以提高8dB以上，且信道传输速率基本没有变化，可以提高H.264视频通信的QoS。     

H.263与MPEG-4视频码流相互转换的实现

分析了H．263与MPEG-4视频编码标准的不同之处，分别阐述H．263视频码流转换为MPEG-4视频码流以及MPEG-4视频码流转换为H．263视频码流的实现方法，给出了码流转换的结果，并分析说明其有效性和实用性。     

基于ARM-Linux嵌入式系统的流媒体服务器实现

简要介绍了嵌入式开发的软硬件平台,针对H.263格式视频流和G.729格式音频流的多媒体数据实时传输要求,设计并实现了ARM-Linux嵌入式平台下基于RTP/RTCP协议的实时流媒体服务器.     

视频编码标准H．263码流结构的分析

视频编码标准H.263视频复用规定为四层分级结构,从顶向下依次为:图像层、块组层、宏块层和块层。视频编码标准H.263关键技术包含有:图像的帧结构、运动补偿加DCT的混合编码方法以及宏块统一使用同样的量化步长进行量化等。视频编码标准H.263标准的比特流功能、大小和语法在其协议中做了详细的规定,但是产生这些必选码流分支和可选码流分支的条件却很复杂。重点对H.263码流结构中比特流语法里面必选码流分支和可选码流分支的条件进行全面详细的分析。     

基于H.264的流媒体服务器的工作机制和实现方法

在H.264视频压缩编码标准的框架下,对H.264编码数据的流式服务机制进行了研究。然后以H.264编码视频数据为研究对象,在RTP/UDP传输协议的网络和基于“推”的达尔文视频流服务系统上,实现了基于RTP的H.264编码数据的封装和传输。     

基于RTP协议的移动视频监控系统的设计

无线移动网络环境稳定性较差,需要研究如何自适应有效带宽的动态变化,以获得最佳的视频监控效果。H．264是高压缩比的视频编解码标准,相同条件下需要的传输带宽更少。RTP/RTCP协议专为实时数据的传输而设计。本系统中,视频采集终端用RTP协议封装和发送H．264数据,用RTCP协议接收网络传输质量信息,自适应调整发送速率;监控平台对收到的数据进行整理和过滤,确保视频图像的正确播放。实验表明该设计在无线移动网络环境下,视频监控效果良好。     

基于B/S架构实时高清音视频监控系统

高清视频监控画面范围广同时产生巨大数据使得在网络传输中造成时延,也存在音频数据有限的问题。针对上述问题,文中设计一种基于B/S架构的实时高清音视频监控系统。USB摄像头基于V4L2接口采集图像,基于ALSA声卡驱动采集音频,结合H.265视频编解码技术和FAAC音频编码技术,以RTP协议打包封装H.265视频码流和AAC音频码流经网络同步传输到Web服务器,利用CGI,JavaScrict技术实现多种智能终端登录浏览器显示监控画面。经测试该监控系统画面清晰无抖动,音视频吻合效果明显满足实验要求。     

视频通信抗误码方法研究的新进展

本文比较全面地总结了视频通信中抗误码方法的研究及其新进展.首先,详细评述了结合信源特点的前向差错控制、码流变换、解码端的误码掩盖和防误码扩散等视频抗误码新方法;然后,介绍视频编码标准H.263+/H.263++和MPEG-4中提出的抗误码算法;接下来,讨论多种视频抗误码系统的设计方案;最后,对视频抗误码今后研究的重点和方向提出了展望.     

Simplification of VLC Tables With Application to ML and MAP Decoding Algorithms

Many source coding standards (JPEG, H263+, H264), rely heavily on entropy coding with variable-length codes (VLC). However, bitstreams made of VLC-encoded data are particularly sensitive to transmission errors. Recent results tend to use knowledge of the VLC structure in order to perform an efficient decoding of the bitstream. These techniques use a trellis describing the structure of the VLC codebook and assume that some a priori information is available at decoder side. Significant improvements, compared with prefix decoding of bitstreams are achieved. However, the complexity of these techniques may become intractable when realistic VLC codebooks are considered. This paper presents an algorithm for compacting VLC tables. The codewords are grouped into a minimum number of classes. Decoding algorithms may then work on a reduced number of classes, instead of working on the whole set of codewords. A proof of optimality is provided for the VLC table-compaction algorithm. The algorithm is applied to the H263+ VLC codebook and merges the 204 codewords into 25 classes. The resulting compact tables are shown to be exactly equivalent to the initial ones when used with hard decoding algorithms. The properties of the associated soft decoding algorithms using these compact tables are also evaluated.     

Efficient Media Synchronization Mechanism for SVC Video Transport over IP Networks

The scalable extension of H.264, known as scalable video coding (SVC) has been the main focus of the Joint Video Team's work and was finalized at the end of 2007. Synchronization between media is an important aspect in the design of a scalable video streaming system. This paper proposes an efficient media synchronization mechanism for SVC video transport over IP networks. To support synchronization between video and audio bitstreams transported over IP networks, a real‐time transport protocol/RTP control protocol (RTP/RTCP) suite is usually employed. To provide an efficient mechanism for media synchronization between SVC video and audio, we suggest an efficient RTP packetization mode for inter‐layer synchronization within SVC video and propose a computationally efficient RTCP packet processing method for inter‐media synchronization. By adopting the computationally simple RTCP packet processing, we do not need to process every RTCP sender report packet for inter‐media synchronization. We demonstrate the effectiveness of the proposed mechanism by comparing its performance with that of the conventional method.     

基于DirectX的音频视频无线传输系统设计与实现

主要介绍一种基于微软DirectX平台实现音频视频无线传输的系统,该系统利用Direct Play Voice实现音频传输,利用DirectShow实现视频传输。针对音频传输过程中延时、抖动现象,利用RTP协议包头时间戳和建立缓冲池的方法进行消除,提高音质;利用RTP/RTCP协议传输MPEG-4码流,提高视频质量。探讨了该系统的基本结构和实现细节,实际测试表明该系统音频和视频质量令人满意,具有稳定性好、占用带宽低等优点。     

一种基于AES算法的流媒体加密方法

总结基于H．263的流媒体加密方式，提出一种采用高级加密标准AES加密流媒体RTP数据包的方法，实验表明该算法既保证了流媒体加密系统的实时性，又使其有相当高的安全性，能够抵抗现有的所有攻击。     

基于无线局域网的实时视频传输与控制

针对无线局域网,研究实现了一种基于RTP/UDP/IP协议的端到端H.263实时视频传输系统.针对无线QoS机制系统应用了一种RTCP反馈友好码率控制算法TFRC,根据丢包率来动态调整发送码率实现拥塞控制.实验表明该传输方案能获得较好的视频传输质量.     

A scalable and format-compliant encryption scheme for H.264/SVC bitstreams

SVC (Scalable Video Coding) is designed to adapt to heterogeneous networks and various terminal devices. This paper presents an encryption scheme for SVC bitstreams which retains the valuable scalability properties of SVC. To this end, we explore PACSI (Payload Content Scalability Information) and RTP (Real-time Transport Protocol) payload format such that encrypted bitstreams are SVC format-compliant. Specifically, the proposed scheme processes the base layer and enhancement layers in different ways. For the base layer, the scheme encrypts VCL (video coding layer) NALU (Network Abstract Layer Unit) into either SEI (Supplement Enhancement Information) NALU or PACSI NALU. For an enhancement layer, the scheme replaces a coded slice in scalable extension NALU with an encryption of PACSI NALU. Thus, the proposed encryption scheme preserves SVC scalability and format-compliance. It produces encrypted bitstreams which have the original SVC structure without emulation markers or illegal codewords for any standard decoder. The analysis and experiments indicate that our algorithm is cost-effective and secure against chosen plaintext attack.     

Fast Inverse Motion Compensation Algorithms for MPEG and for Partial DCT Information

In prior work, we developed a fast inverse motion compensation method that can be implemented directly on the DCT domain representation derived from the compressed bitstreams conforming to MPEG, H.261, and H.263 standards. That work was restricted to compressed-domain representations wherein the motion-vectors have integer pel accuracy. Here, we extend this work to fractional-pel accurate motion-vectors. We also extend the prior work to speed up the inverse motion compensation process in the DCT domain by explicitly exploiting the sparseness of the DCT domain representation. Using partial DCT information, we show that the DCT domain method has substantially lower operation count than the conventional spatial domain approach which requires decompression followed by inverse motion-compensation.