蓝牙实时视频传输系统设计与实现

文中设计了一种基于蓝牙技术的嵌入式视频传输系统。该系统采用了多种数据缓存机制使MPEG-4视频码流能适应蓝牙信道要求，实现了高质量实时视频的无线传输。实验测试表明，该系统在图像质量、时延上都达到了应用要求。     

基于802．11网络的无线视频传输系统设计

提出一种基于S3C2440A硬件平台和嵌入式Linux操作系统的无线视频传输系统设计方案,介绍系统的总体设计和主要功能模块的设计与实现,主要包括视频采集模块、无线视频传输模块的硬件设计,嵌入式Linux的驱动程序移植、MPEG-4数字视频软件压缩以及应用程序实现等。该系统实现了802．11无线局域网内的视频传输,实时监测网络的数据流量和拥塞状况,自动调节视频的压缩比,提高网络传输质量,保证视频播放流畅性,可靠性高且易于使用。     

无线网桥在视频监控中的研究与应用

为满足在恶劣条件下对基建现场进行视频监控的需求,采用了5．8GHz频段高速无线以太网桥对无线局域网与有线局域网进行系统组网,通过点对点传输技术及MPEG-4视频图像压缩技术实现远端视频监控功能,并利用有线对等加密算法对视频信号进行128b加密,保证了视频信号传输的流畅度、清晰度及安全性,并对该系统的硬件实现进行了详细说明。经过实际测试,该系统具备移动灵活、易于组建、高速率、高稳定性等特点。     

一种信道自适应的无线视频流差错控制机制

提出了一种自适应的无线视频流差错保护方法。该方法充分考虑MPEG-4FGS码流细粒度可扩展的特性,根据码流的重要性程度采用不等的保护措施,同时能够自适应地根据无线信道的具体状况,将信道带宽在MPEG-4FGS信源编码速率和信道编码速率之间进行最优化分配,使得接收端能获得最佳的重建视频质量。实验结果表明,在各种不同信道状况下,与均等错误保护和固定的不等错误保护方法相比,该方法均可获得更好的性能。     

视频通信中MPEG-4的误码弹性

多媒体业务在BER较高的移动网络上实时传输视频数据时，由于编码视频数据对信息损失和信道误码非常敏感，解码质量会受到显著影响。由于MPEG-4所采用的是空间预测，使得差错会迅速传播，重构视频质量会严重降级。为了减轻无线信道差错对解码质量的影响，需对编解码器采用有效的差错处理机制，本文就MPEG-4的误码弹性作了详细的讨论，并对各种差错恢复机制的组合给出了分析。     

基于流媒体技术的移动视频服务器的设计

针对3G无线互联网技术的迅猛发展和人们生活、工作中对手机实时视频的需求,应用MPEG-4视频编码标准和RTP/RTCP流媒体传输协议为基础,设计了一个流媒体传输的解决方案的移动实时视频服务器,服务器完成了对实时视频数据的采集和压缩,对实时源Filter传输和处理过程和服务器与客户端RTP/RTCP通信过程,实现服务器视频实时传输的编码设计和对视频传输的测试.     

实时流媒体业务在未来移动通信中的应用前景

本文介绍了未来移动通信网络流媒体系统结构及主要无线流媒体编码的传输标准，并以基于MPEG-4视频编解码标准的无线实时流媒体通信解决方案为例，着重阐述了在未来移动网络上提供实时多媒体业务将面临的诸多挑战及应对办法。     

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。     

基于蓝牙技术的MPEG-4视频流传输性能分析

提出了一种基于蓝牙技术和MPEG-4视频标准的短距离无线视频传输方案(MPEG4-BT),应用于室内数字视频信号的无线传输,同时分析了MPEG-4比特流在蓝牙HCI层的传输特性,以及同一环境多个蓝牙piconet进行视频通信的吞吐量.该方案可以大大拓宽蓝牙的应用范围,为进一步利用蓝牙实现无线视频通信提供参考.     

基于TMS320DM355的MAV机载视频传输系统的设计与实现

为了提高微型飞行器(MAV)无线视频传输的质量、扩大传输距离,设计并实现了一种基于3G WCDMA无线网络的机载视频传输系统。采用TI公司的达芬奇处理器TMS320DM355作为核心处理器,给出了总体设计方案和硬件结构,并阐述了采用PPP协议拨号接入WCDMA网络的方法。采用嵌入式Linux操作系统作为软件开发平台,分析并设计了基于V4L2(Video For Linux Two)驱动的视频采集模块。通过调用TI提供的编解码引擎API,实现了视频MPEG-4压缩编码处理。针对视频传输的实时性要求,采用了实时传输协议RTP和实时传输控制协议RTCP,重点阐述了MPEG-4视频的RTP封包策略,并基于JRTPLIB库文件实现了视频的实时传输功能。实验结果表明,该系统可以满足视频清晰、实时的传输要求。     

基于BF533的MPEG-4解码系统实现

介绍了一种嵌入式MPEG-4视频流解码系统,以ADI公司的BF533 DSP为硬件,嵌入式uClinux为操作系统,采用软解码的方式实现对以太网和USB接口设备输入的MPEG-4码流转换成PAL/NTSC制式的电视信号输出.     

压缩域MPEG-2到MPEG-4视频转码中不匹配宏块的复原算法

作为一种最有应用前景的先进的压缩编码标准，MPEG-4将会很快在视频传输、存储和剪辑等许多领域中得到应用。不过，MPEG-2和MPEG-4这两种优秀的视频系统肯定会在很长一段时间内共存。本文提出了一种基于MC-DCT域的转码方法。重点解决了两种标准视频流中宏块编码模式不匹配的一些关键问题。仿真结果表明，本算法不仅能有效地实现MPEG-2到MPEG-4的转码，满足实时性和低处迟的需求，而且能隐藏或复原编码模式不匹配宏块，明显地改变视觉质量。     

Prediction of MPEG-coded video source traffic using recurrent neural networks

Predicting traffic generated by multimedia sources is needed for effective dynamic bandwidth allocation and for multimedia quality-of-service (QoS) control strategies implemented at the network edges. The time-series representing frame or visual object plane (VOP) sizes of an MPEG-coded stream is extremely noisy, and it has very long-range time dependencies. This paper provides an approach for developing MPEG-coded real-time video traffic predictors for use in single-step (SS) and multistep (MS) prediction horizons. The designed SS predictor consists of one recurrent network for I-VOPs and two feedforward networks for P- and B-VOPs, respectively. These are used for single-frame-ahead prediction. A moving average of the frame or VOP sizes time-series is generated from the individual frame sizes and used for both SS and MS prediction. The resulting MS predictor is based on recurrent networks, and it is used to perform two-step-ahead and four-step-ahead prediction, corresponding to multistep prediction horizons of 1 and 2 s, respectively. All of the predictors are designed using a segment of a single MPEG-4 video stream, and they are tested for accuracy on complete video streams with a variety of quantization levels, coded with both MPEG-1 and MPEG-4. Comparisons with SS prediction results of MPEG-1 coded video traces from the recent literature are presented. No similar results are available for prediction of MPEG-4 coded video traces and for MS prediction. These are considered unique contributions of this research.     

MPEG-2视频码流分解的VHDL描述与验证

本文提出一个ＭＰＥＧ－２视频解码中码流分解的硬件设计,包括解码控制和变长码解码。一些新的硬件设计,如：将宏块和块控制作为主要状态;采用桶形移位缓冲器并行解变长码;将变长码的长度计算和解码分别进行;将码表分割成多个小码表等等,保证ＭＰＥＧ－２ＭＰ＠ＭＬ的实时解码,并为更复杂的应用提供了扩展的余地。本文中的设计是ＭＰＥＧ－２解码ＡＳＩＣ ＶＬＳＩ设计工作的一部分。     

MPEG-4: a multimedia compression standard for interactiveapplications and services

The Moving Pictures Experts Group (MPEG), which produced the MPEG-1 and MPEG-2 video and audio compression standards, is developing the MPEG-4 standard. MPEG-4 targets interactive multimedia applications and will become a standard in 1999. As well as an increased compression efficiency, MPEG-4 will also offer content-based functionality, i.e. the possibility of accessing and manipulating individual objects in the picture. Furthermore, MPEG-4 will offer possibilities for efficient video storage and for transmission over poor audio and video channels at bit rates between 5 kbit/s and 4 Mbit/s. This paper gives an overview of the state of the art of MPEG-4 development, concentrating especially on video content-based functionality, which is so important for interactive applications     

基于TMS320C6416的MPEG-2/MPEG-4 视频流转码器设计与实现

目前的视频流转码大致可以分为空域(像素域)转码和压缩域(DCT域)转码两种方法。针对目前最流行的MPEG-2和MPEG-4两个压缩编码标准,采用级联空域转码方案,并且基于TMS320C6416 DSP芯片,探讨了MPEG-2/MPEG-4视频流转码的硬件实现方法。在设计中,通过PCI消息机制,解决了DSP与PC机的数据传输“瓶颈”问题,同时合理分配存储器,并采取各种优化技术,近实时地实现了MPEG视频流转码。     

基于SSE2的MPEG-4视频快速解码研究

离散余弦逆变换是MPEG-4视频纹理解码中运算时间开销最大的部分.本文在快速离散余弦逆变换算法的基础上,引入针对多媒体数据流的SSE2并行计算技术.在保证图像质量的前提下大幅度提高了软件的解码速度.实验结果表明,该方法能有效地降低MPEG-4视频解码的时间开销,适合于NC环境下的视频分发应用.     

MPEG-4 Video Transmission over Wireless Networks: A Link Level Performance Study

With the scalability and flexibility of the MPEG-4 and the emergence of the broadband wireless network, wireless multimedia services are foreseen to become deployed in the near future. Transporting MPEG-4 video over the broadband wireless network is expected to be an important component of many emerging multimedia applications. One of the critical issues for multimedia applications is to ensure that the quality-of-service (QoS) requirement to be maintained at an acceptable level. This is further challenged in that such a service guarantee must be achieved under unreliable and time-varying wireless channels. In this paper we study the link level performance of MPEG-4 video transmission over the uplink of an unreliable wireless channel. We introduce the discrete time batch Markovian arrival process (DBMAP) with two types of arrivals to model the MPEG-4 video source, which takes into account the inherent nature of the adaptiveness of the video traffic. We prove that in a hidden Markov modeled (HMM) wireless channel with probabilistic transmission, the service time for an arbitrary radio link control (RLC) burst follows phase type (PH-type) distribution. We show that the link level performance of a wireless video transmission system can be modeled by a DBMAP/PH/1 priority queue, and present computation algorithm and numerical results for the queueing model. Extensive simulations are carried out on the queueing behavior of the video transmission buffer, as well as on the packet level error behavior of the video data. The results demonstrate that video quality can be substantially improved by preserving the high priority video data during the transmission.     

Rate control for MPEG-2 SNR scalability and stream morphing using codeword estimation and overhead modelling

Many encoder architectures, notably for scalable systems such as MPEG-2 SNR scalability and stream morphing, require DCT-domain techniques for the estimation of the rate-distortion characteristics of a video frame for use in the rate control process. This paper develops a CBR rate control framework that can be used for single-layer MPEG-4 Simple Profile as well as two MPEG-4-based scalable systems, one following the structure described in MPEG-2 and also stream morphing. The framework supports perceptual quantization and also low bit rate operation by modelling macroblock overhead as well as the bits required to code non-zero DCT coefficients. Experimental results demonstrate the performance of stream morphing, in both objective and subjective measures, is in almost all cases superior to the MPEG-2 SNR scalability and MPEG-4 Fine Granularity Scalability.