The Construction Of Embedded Mobile Streaming Media Player System And QoS Optimization

With the rapid upgrading of network bandwidth, by making use of mobile devices to receive and view multimedia information has become the people's urgent needs. Traditional multimedia files usually have a very heavy volume, downloading them takes a long time and can only be downloaded, stored in memory and then played, time-consuming and laborious, and should not be suitable for mobile devices such embedded device systems which have weak CPU and small capacity storage. The appearance of Streaming Media has changed this situation, it does not need to be downloaded entirely and can start to be played while being transmitted to the players, it's this feature, which greatly reduces the required waiting time to start to play and the required storage capacity on the receiving end, very much in line with embedded systems which have CPU with poor ability and small capacity storage. And along with the in-depth research and widening application of the electronic technology, wireless communications and computer network, the application of wireless LAN function based on embedded systems increasingly widespreads. From the web browser, network message, IP phone to real-time video communications, mobile streaming media, wireless LAN applications gradually become research and application focus of embedded systems.This article describes the embedded mobile streaming media player system which implemented a portable software and hardware equipment system which can play the streaming media among the wireless LAN, contains a detailed account of the embedded mobile streaming media player system's hardware modules and software modules construction. The system used advanced USB interface wireless card which is in line with the IEEE802.11b/g standard, can achieve Infrastructure and Ad-Hoc two working mode, has adaptive transmission rate up to 54Mbps, supports the wireless roaming function, can move between different AP and the network connection is not interrupted, has the transmission distance for the farthest interior 100 meters, outdoor 300 meters far away.From the hardware, the mobile streaming media player system used advanced ARM processor S3C2440A as a core, which has rich interface modules, including the substantial GPIO port, IIS digital audio interface, LCD controller interface, USB interface and Touch Panel interface without needing the external circuit which are used in the system, the external part included audio player subsystem, video player subsystem, people-machine interactive subsystem and wireless network subsystem four modules, respectively, comprised the audio codec, TFT LCD display, wireless card with USB interface, four-wire resistive touch screen and the corresponding interface module of S3C2440A, this article describes in detail the hardware connection, the configuration of control register, program and transplant drivers in embedded operating system Linux of each subsystem.Streaming media protocols comprise Real-Time Streaming Protocol RTSP, Real-time Transport Protocol RTP, Real-time Transport Control Protocol RTCP and Session Description Protocol SDP, in the streaming media player system separately to serve as the role of remote control, data transmission, monitoring and feedback, information description. The streaming media is packaged in the streaming media file, the main ASF, RM, such as streaming media file format, packet-style architecture of the streaming media file formats makes streaming media file can be downloaded while being played. The majority of streaming media contains audio and video, such as multimedia data, without going through the process of coding, it is difficult to complete the real-time network transmission, so prior to being played the video and audio data should be decoded and decompressed. From the software, based on MiniGUI embedded user interface system, which packaged video player subsystem and interactive subsystem, we programmed the mobile streaming media player system which packaged the audio player subsystem and SOCKET programming interface based on the wireless card network interface, and which realized the above protocols of streaming media,streaming media file formats analysis,audio and video decoding by multi-threaded approach, and, audio and video streaming finally achieved synchronous playback. And based on the original (data buffer length measurement method, we added the condition factor decoding rate, so that streaming media can be played more fluent.