Simplify ffmpeg commands in readme to make it more friendly demo.
Simplify ffmpeg commands in readme to make it more friendly demo.

The original ffmpeg sample contains 2-pass process. It is good to
demostrate the ability of multiple actions, but it would also create
some entry effort for people to get understand the demo. Therefore, I
remove these 2-pass process.

KKBOX/mass,badboy99tw/mass,badboy99tw/mass,KKBOX/mass,badboy99tw/mass,KKBOX/mass