【作者】 施佳子；

【导师】 夏涛；

【作者基本信息】 华中科技大学 ， 计算机系统结构， 2009， 硕士

【摘要】 随着移动网络的迅猛发展以及第三代移动通信业务的推陈出新,使用移动流媒体业务的用户也日益增多。与此同时,市场的急剧扩大也加速了移动流媒体技术的进步。在参照了第三代合作伙伴计划的分组交换流媒体服务技术规范的基础上,介绍移动流媒体网络体系中使用的网络协议,论述H.264视频解码技术和AMR-NB(Adaptive Multi-Rate Speech Codec Narrow Band)及AAC(Advanced Audio Coding)音频解码技术以及承载音视频媒体数据的容器3GPP(3rd Generation Partnership Project)文件结构,针对iPhone平台自身特点,重点研究在iPhone平台上移动流媒体播放器的实现。播放器由四大模块组成:网络模块、缓冲模块和音视频解码播放模块。顺序流式传输采用HTTP(Hypertext Transfer Protocol)协议实现网络模块,从服务器接收3GPP文件流,通过解析索引区数据,分别请求音视频媒体数据后,将其送入缓冲区;实时流式传输通过使用RTSP/RTP/RTCP(Real-time Streaming Protocol/ Real-time Transport Protocol/ Real-time Transport Control Protocol)协议栈进行会话建立、媒体数据传输和网络状况反馈。缓冲模块把从网络模块接收到的音视频数据包进行处理,然后将处理后的数据存储在循环队列中,以此来缓解网络丢包、抖动和乱序引起的问题。音视频解码播放模块从缓冲模块取得AMR-NB/AAC音频帧和H.264视频帧,将其送入相应的解码器解码后,播放声音显示图像,并通过时间戳信息进行音视频同步。比较了移动流媒体网络体系中的两种流式传输体系的优缺点。在采取码率适配技术、大文件传输优化、内网穿透技术和图像缩放技术优化等措施后,在真实的移动网络环境中测试,实现了移动网络下流媒体的流畅播放,达到了设计要求。更多还原

【Abstract】 With the rapid development of the mobile network and the 3rd Generation network service, the numbers of the mobile streaming service subscribers have increased dramatically, and the extension of the market has also speed up the improvement of the mobile streaming technology.On the basis of the Packet Switched Streaming Service technology specifications of the 3rd Generation Partnership Project, the network protocols in the mobile streaming network system are presented, and the H.264 video decoding technology and the AMR-NB/AAC audio decoding technology as well as the configuration of the 3GPP files that acting as a container bearing the audio-video media data are analyzed. According to the iPhone platform’s self-characteristics, enough emphasis has been put on the implementation of the mobile streaming media player in the iPhone platform. The player consists of four modules, which include network module, buffer module, audio-video decoding and playing module. Each part of the player is respectively responsible for accepting media data from the network, audio/video decoding and playback. Progressive streaming uses the HTTP protocol to implement the network module, receive the 3GPP file stream from the servers and acquire the audio-video media data through analyzing data in the index area, then put the media data into the buffer respectively. Real-time streaming makes use of the RTSP/RTP/RTCP protocol stack for session establishment, media data transmission and the feedback. Buffer module stores audio-video packets which received and processed by the network module to the circular buffering queue to solve the problem which caused by packets loss, jitter and packets reordering. Audio-video decoding and playing module fetch AMR-NB/AAC audio data and H.264 video data from buffer module and send to corresponding decoder and finally play back.The using conditions of the two different kinds of stream transmission in the mobile streaming media network system are analyzed. After taking the measures such as rate adaption, the optimization on the transmission of large files, network address translation technology and the optimization of image scaling, the player is tested in real GPRS/EDGE network and meets the requirements of the design.更多还原