How to make the video play in background in iPhone?

Each time I play a video and lock the iPhone by pushing the power button, the video is automatically stopped. If I want to play a MTV and just listen to the music when I walking, I’d like the video play in the background. Is there a method to make this happen?

I can do this with AcePlayer:

First, play the video in AcePlayer.

Then, push the “power” button of iPhone to lock it. The video is AcePlayer is paused.

Now, to continue the playing of the video in Aceplayer:

Push the “play” button (the center button) of the “remote adapter” on the earphone and the video continues play again.

Of course, you must use the earphone with this method.