| As the rapid development of the multimedia technology and networktransmission technology, real-time video transmission is increasingly used inindustrial monitoring, environment monitoring, security monitoring and other fields.Relative to the wire transmission, the huge advantage of wireless transmission makeswireless-based real-time video transmission becoming the trend. However, due to thecharacteristics of wireless channel, such as high error rate, limited bandwidth, andtime-varying, is not suitable for characteristics of real-time video transmission such aslarge volumes of data, delay-sensitive and stable transmission. So how to improve theQoS (Quality of Service) and the transmission efficiency of real-time videotransmission in time-varying wireless environment becomes an important content ofstudy.An end-to-end embedded wireless scalable real-time video transmission systemhas been designed and implemented in this paper. With ARM11(S3C6410) as thehardware platform and Linux as the software platform, the system achieved real-timeH.264video transmission based on RTP. Meanwhile, in order to safeguard the QoS ofthe video transmission, a scalable control module and improved streaming rate controlalgorithm has been designed and implemented.Firstly this thesis investigates the status of real-time wireless video transmissionsystem and analysis the functional requirements of the target system. According to thecorresponding functional requirements, we learned and studied the key technologies,including video decoding standard, streaming media real-time transmission protocol,telescopic video transmission technology and streaming media rate control technology.Then, based on the hardware and software development platform, this paper realizesthe embedded wireless telescopic video real-time transmission system hardware framedesign and software development. This system is composed of video sending side andvideo receiving side. Video sending side completes the functions such as videoacquisition, h.264coding, RTP packets encapsulation and send. Video receiving sidecompletes the functions such as RTP packets receive, h.264decoding and videodisplay. In order to guarantee QoS of video transmission, a scalable control modulehas been designed in target system. This module first gets packet loss rate and business data throughput, then forecasts appropriate transmission rate combined withimproved multiplied by minus (AIMD) rate control algorithm. And then according tothe scalable mode selection strategy, the module determines the corresponding videotransmission parameters. Finally, the indoor time-varying wireless environment hasbeen set to test the performance of wireless scalable video real-time transmissionsystem. Test results show that the system can effectively guarantee the time-varyingwireless environment of real-time video transmission quality of service. |
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