Question: I am using Avplayer to show video clips and when i go back (app in background) video stop. How can i keep playing the video? 

I have search about background task & background thread ,IOS only support music in background (Not video)
 <http://developer.apple.com/library/ios/#documentation/iphone/conceptual/iphoneosprogrammingguide/ManagingYourApplicationsFlow/ManagingYourApplicationsFlow.html>

here is some discussion about play video in background 

1) <https://discussions.apple.com/thread/2799090?start=0&tstart=0>

2) <http://www.cocoawithlove.com/2011/04/background-audio-through-ios-movie.html> 

But there are many apps in AppStore, that play video in Background like 

Swift Player : <https://itunes.apple.com/us/app/swift-player-speed-up-video/id545216639?mt=8&ign-mpt=uo%3D2>

SpeedUpTV : <https://itunes.apple.com/ua/app/speeduptv/id386986953?mt=8>

Answer: 
If you try to change the background mode:
Sorry, App store wont approve it.[MPMoviePlayerViewController playback video after going to background for youtube](https://stackoverflow.com/questions/15389989/mpmovieplayerviewcontroller-playback-video-after-going-to-background-for-youtube)

In my research, someone would take the sound track out to play in te background when it goes into background as the video would be pause and get the playbacktime for resume playing when go into foreground
In addition to fattomhk's response, here's what you can do to achieve video forwarding to the time it should be after your application comes in foreground:

* Get `currentPlaybackTime` of playing video when go to background and store it in `lastPlayBackTime`
* Store the time when application goes to background (in `userDefault` probably)
* Again get the time when application comes in foreground
* Calculate the `duration` between background and foreground time
* Set current playback time of video to `lastPlayBackTime` + `duration`