Abstract: The paper focused on research and implement of realtime of Linux The paper proposed a method taking advantage of RTHAL(Real Time Hardware Abstract Layer) , which run between hardware and Linux The method made only a few of modification on Linux and had a schedule delay of only about 3μs. hhe paper discussed how to modify Linux and RTHAL for hard realtime. In addition the paper proposed an effective method to take advantage of buffer between them. Lastly an example of rcaltime MPEG4 stream system was cited, which applied the method and proved it could add to hard realtime of Linux effectively and concisely.

Key words: RTHAL, Rcaltime, Linux, Video stream coding