The Design And Implementation Of A Media Stream Real-time Player System

With the wildly spread of the embedded terminal products such as Smart phone,and PDA in public,the application of Multimedia on embedded system has become more and more universal,and the real-time media stream play-back support based on 3GPP also become more and more important. The implementation of the play-back support to media stream file on embedded system is the main aim in this article.Referenced to 3GPP mobile streaming media system framework, bassed on analysis of the transport characteristic of wireless streaming media and h.264 video encoding and decoding technology, with the carefull consideration of symbian os, this project implements the real-time media stream play system on Symbian platform.The real-time stream media system is composed of network module, decoder, display module and Graphical User Interface, and these modules are implemented as Active Objects in Symbian OS.The network module uses RTP/RTCP/RTSP protocol to implement the request and receiving of network data: RTP receives and splices streaming data asynchronously by using UDP active object; RTSP uses TCP active object to control the real-time transmission in application layer; RTCP transmits status report periodically by means of UDP active object to control the flow and congestion. Syncretic module restores the lost and disorder video frame and audio frame from the UDP package and output the correct one.The audio-video decoding module decodes AAC/AMR-NB audio frame and H.264 video frame that syncretized by RTP. The direct screen access technology and multimedia framework technology are adopted by audio-video playback module to output audio and video, whose speed are adjusted according to timestamp to realize audio-video synchronization.Finally,it is discussed that fulfillment of all GUIs are also developed on different user interfaces .