Design And Implementation Of Outdoor Live Media System Based On Automatic Rate-variation

Live video broadcasts have currently penetrated into various industries.The real-time,interesting and highly-interactive outdoor video live broadcasts provide more possibilities for the field of live broadcasts.The mobile feature of an outdoor video live broadcast system usually shows a live broadcast in the outdoor mobile state,requiring continuous real-time wireless transmission of audio and video data,and high stability of network bandwidth.However,the network varies with the existing environment due to the mobile feature.Unstable network bandwidth degrades the transmission of video stream data,causing serious latency of live broadcasts and weakening the experience of users' real-time viewing and interaction.Low-latency video live broadcasts,and smooth and clear images are the core issues for using video live broadcast systems,and also determine the development of outdoor video live broadcast systems.This paper studies the adaptive rate control technologies of streaming media in an outdoor video broadcast system.Considering the factors,such as client buffer and network bandwidth,for unsmooth playback arising from unstable bandwidth and limited length of the client buffer,this paper proposes a method of automatic rate control and free rate switching by reading the strategic,dynamic and adaptive rate data based on the ring buffer threshold adjustment.The time of transmitting streaming media is predicted and the rate is selected in line with the transmission rate of the streaming media,uplink rate,and mobile network bandwidth.The video rate is selected for each stage throughout the process of video playback.When the client buffer reaches the critical value for usage,the dynamic parameters of the buffer threshold are adjusted in time,the buffer length is increased to minimize switching the bit rate and ensure smooth video playback.This paper also studies and expounds the rate switching in connection with the method of processing real-time and strategic frame loss to overcome unstable network bandwidth in an outdoor video live broadcast system and guarantee the smoothness of video playback.As shown in the test results,this algorithm can maximize the playback rate of video streaming media to ensure the stability,smoothness and picture quality of video playback,reduce the waiting time for booting the live broadcast screen,and bring users a favorable sensory experience for video playback.It plays an important role in the applications,such as motorcycles,extreme challenges,outdoor events,and real-time meetings,which require high video smoothness and real-time performance.This paper designs and implements an outdoor video live broadcast system with adaptive bit rates.The acquisition device can be used for configuration,acquisition,coding,encapsulation and transmission.It is integrated with a WIFI module to support wireless transmission between the device and the AP/hotspot and users.This system adopts the AAC encoding format for the collected audio files,and the H.264 encoding mode for the collected video files.It calls the key technologies of strategic frame loss and adaptive bit rate through the FLV encapsulation specification,and interfaces with users' players through the RTMP standard.