How can I set a graph in graphedit to capture both audio and video to mp4 file ? I know how ot capture the audio to wave file.

To start with, learn about those files, streams, codecs and so on. You cannot ask about nothing. There is no such thing as "mp4" file. This is just naming convention, and, behind it, there are many different things. Files formats are formats of containers. And each container can host several streams. And "MPEG-4" is a whole class of standards for some of those streams. And "AVI" is badly obsolete, I never hear that anyone still use it. And so on...
—SA