For instance my close source and commercial application creates a movie file. Can this application with a command line launch an executable GPL viewer ? Can I freely distribute this unmodified GPL executable with my application ? Do I have to add the unmodified GPL source code of this GPL viewer to my distribution ?
thanks
Yes, common understanding of the GPL is that you don't break it if you only communicate with GPL-ed program in some way (provided you don't link with it or use any of its' sources).
So, as long as you only execute GPL-ed it from you program, you don't have to disclose sources of your prioprietary application.
I am not sure about the second part of the question, but I think you only have to distribute the sources upon request. I.e. you distribute only binary of the GPL program and only send the sources if someone asks for them.