| With the rapid development of wireless communication technology, as well as the improvement of CPU processing power,and the maturity of video coding technolog, video applications for mobile Internet has become future trend of multimedia systems. Video data acquisition and compression technology are the key technologies of multimedia system.In order to realize transmission of video data wirelessly, in this paper, video acquisition and coding technology are studied. FFmpeg video solutions is selected to realize the acquisition and compression of video signal. Video is captured from USB2.0 camera, on Windows platform, by using VFW technology. H.264 video coding standard is used to realize real-time compression. The system is tested to have good real-time performance. People with handheld mobile devices can watch CIF format video images continuously, with 1-3 seconds' delay.The system can be applied to medical monitoring, enterprise security, etc. The work of this paper mainly has the following several aspects:Firstly,this paper illustrates frame format and sample format,when capturing video using USB camera.This paper also carries research on key techniques of H.264 video coding standard,including selection of various prediction modes and calculation methods in intra prediction, sub-macroblock partition, sub-pixel motion vectors, motion estimation,motion estimation in interframe prediction, processes of transform and quantization,adaptive CAVLC entropy coding and CABAC entropy coding technologies.Sencondly, to design and realize real-time video capture and compression system,FFmpeg audio/video solution is used and transplanted from Linux to Windows platform. Each module is designed.Video is captured by VFW technology,and compressed by H.264 video coding standard, by open source library libx264. RTP streaming protocol is used for data transmission, ffserver is used as a streaming media server waiting for users' requests.Finally, the performance of the system is tested. H.264, H.263 and MPEG4 compression standards are selected to make a comparison. A third-party playback software named MXplayer is used to watch remote video. The experiment result shows that the system has good real-time performance, continuous performance and good image quality,which meets the needs of real-time video capture and compression for the mobile Internet.At last ,methods of subjective and objective video quality assessment are studied. Single Stimulus Methods and Peak Signal to Noise Ratio are used to evaluate image quality. |
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