李伟

Oops! Will fix the indentations when I can. Good point with passing `sub` instead of an arbitrary number. I'll see how full screen looks when I can. Only thing is,...

@fsphil With what you said, i think sections inside `av_test_open()` for `Overlay the logo` and `Generate a basic test pattern` should be done only if `sub == NULL` or `strncmp("test")`...

I think it is better to leave playlist to ffmpeg pipe. Although for the user it might be a little complicated, example can be given easily, and ffmpeg has already...