IOS 4.2.1 video feature removal?

Question

I have noticed that after upgrading to iOS 4.2.1, I am no
longer able to play videos in the background (i.e. Play a video and
then lock my iPhone, double tap the home button and then press play).
This method had always allowed me to listen to the audio track from a video.
Has this been removed on purpose or is it a bug? It looks like a bug,
because it attempts to play the video and the video thumbnail flashes
up momentarily, then disappears.
I also can't see any reason why it would be removed. I'd just like to
know one way or another as I use it all the time.
Thanks

Answer 1

Topic:  Listen to IPhone Movie Audio with Screen Locked and Backlighting Off
Hello All,
I too have been wishing for, and searching for, a way to listen to movie audio on my iPhone 4, with the screen locked and backlighting off.  In this way, you could listen to movie audio, instead of music, as background while doing other things during the day, and conserving battery power versus having the screen lit.
I'm happy to say I've just discovered a way to make this work with iOS 5 on my iPhone 4!  I don't know if this is a published technique somewhere, but I happened upon it through experimentation.
Here are the steps:
Select the Videos application from the Home screen
Select a movie
Press Play for the movie (if the movie doesn't autoplay)
Double Click the Home button to bring up the "Application Chooser" (the movie will pause on its own at this point)
Swipe Right in the Application Chooser (to move the view to the left) so you see what would normally be the iPod controls within the Application Chooser
The Music icon normally seen to the far right of the iPod controlswithin the Application Chooser is not visible, but the Videos icon is!
Press the Play button in the middle of the iPod controls within the Application Chooser.  The Movie will begin playing again
Click the Lock Screen button.  The screen locks and the backlighting clicks off, but the movie audio continues playing!
I'm guessing this is actually functionality that was created by design, but is not being communicated openly to users for some reason.  Here's why I think this:
   +  When you click the Lock/Unlock Screen button again, or click the Home button, and the screen re-lights, you actually see the movie splash/poster page (I bought this particular move through iTunes), vs. your Lock screen image
   +  With the screen being off, when you double click the Home button, or click the Lock/Unlock Screen button, the media controls that appear (Back Chapter, Play/Pause, Forward Chapter, and Volume) do in fact control the movie audio.
Let me know if this solves the problem for you too!