Hi,
I am planning to write code similar to "XAWTV" and "fbtv" to capture the video stream and store the same in the hard disk. For this i am planning to use to use MPEG compression methodoly like that in fbtv. since the compression is done by software coding will the recording of dynamic video input from cable be in correct sequence? i.e., will there be any problem in synchronization or will the recorded video will be in slow motion pictures compared to that of the original? Is the idea of doing MPEG compression using software is correct? Or to record video stream using MPEG compression by software in correct sequence what are the hardware requirements? i.e., the processor and all.

Maybe it's me but I don't understand exactly what you mean in your post, especially the last part. But it is possible to record tv input and compress it at the same time before writing it to harddisk.
It's very easy to do this with mencoder. Just read the documentation, they have examples how to get this done. So maybe you should look at their code, and see how it's done there so you can create the same in your application.