The Technology Of Audio And Video Session For The Mobile Handheld Terminals

In recent years, with the the rapid development of computer techology, multimedia technology and network technology, Embedded、digital and networked are the development direction of audio and video session. With the rapid development of mobile networks,audio and video sessions becoming more and more popular in the mobile termials. The purpose of this paper is combination of the enbedded tehnology and mobile network technology,and then build a stable performance with strong real-time features of audio and video session system.First, this paper introduces the status of a technical of audio and video sessions at home and abroad.For the characteristics of a mobile termina session system. We chose the S3C6410,it is a processor of ARM family,made by Sansung,and the necessary peripherals,those constitute the hardware platform.The focus of the article is software on audio and video sessions,in accordance with the process of audio and video sessions,and write it in sub-blocks.In the acquisition aspect, In video capture we first analysis the V4L2driver careful,and combining its features and programming methods with characteristics of the CMOS camera to complete the acquisition of video data.Similarly in the audio capture, difference is that audio capture is used OSS driver.In the Codec aspect,we introduced the purpose and importance of the audio and video codec firstly. Then,we analysis of the mainstream codec methods,binding our system features, we chose the H.264format for video codec and G.729format for audio codec.Since the S3C6410embedded a hardware multimedia process module itself, so it make H.264codec fastly and stably.On the audio side, we transplanted the G.729codec on our system.In the audio and video transmission,we analysis of the TCP and UDP firstly, and it points out that the TCP is not suitable for transimiting transmit real-time data. And the UDP is not unreliable,it also bring the packet disorder、packet lost and other problems.Compared with TCP and UDP,We found UDP is more suitable for the needs of us,but we must introduce the necessary controls.In this,RTP based on the UDP component is proposed by us.RTP brings some necessary controls on the real-time data transimition.A careful analysis of the characteristics of the RTP/RTCP, and get in-depth research of the protocol format. Finally, we used JRTPLIB library and transplant it on embedded Linux platform,then writed useful application programs.Ultimately, we realized the audio and video RTP/RTCP transmission.