Design And Implementation Of Video Conference Recording And Playback System

Recently, to overcome the expansion restriction of media stream centralized video conference system, some researchers designed media stream distributed architecture. Meanwhile, users in some areas expect recording audio and video from all parties intactly and comprehensively, and require access the recorded files flexibly later. The current video conference recording products do not meet the requirements. On the one hand, due to the widespread use of MCU-based media stream centralized architecture, the dedicated recording and broadcasting equipment cannot record intactly, comprehensively and flexibly; on the other hand, using third-party recorders enables recording of media stream distributed architecture, and also meets the diversity needs, but increase the deployment, management and maintenance difficulties. In this paper, a video conference recording and playback system based on a media stream distributed architecture products is presented. Taking the above-mentioned recording requirements into consideration, a recording server and a multiple stream player are designed and implemented.Firstly, the system architecture is expended, so the recording servers is added. And the model of recording and playback is designed. The procedure is divided into three stages, including recording, storing and playback. When recording, each video stream is recorded as an MP4 file, rather than merge the images from different parties together. A hierarchical organization is carry out to manage the recorded files. To maintain the audio and video synchronization in a single file, the algorithm based on RTP is adopted. And in the absence of a global clock, to determine the time relationship between streams from different parties, we propose a method for estimating the media deriving time based on the receiver clock.Based on the designed model, the recording and playback system is implemented. To achieve the basic recording and information storing function, the original video conference terminal system is reused and its framework is modified to add some parts, including a recording module, a recording control module, the auxiliary function modules and a file management database. In order to improve the I/O performance and achieve recording multiple video simultaneously, a disk write buffer is used. The multiple stream player is for playing the recorded videos at the terminal, designed with the file parsing and playback in separated process to allow further expansion. Multiple streams are synchronized by using timeline synchronization method. And to enhance the playback synchronization, a start delay is introduced to ensure the stream data is fully prepared.The video conference recording and playback system implemented in this paper is aimed at media stream distributed architecture. It is integrated in the video conference system and is easy to be deployed. It will help to achieve management through unified platform. It also records in a flexible way, save intact multimedia data and is capable of playback. The development made reference from research in related fields, and would have much practical value.