multiplayer screen has black bars on R and L sides

Could you try changing the output resolution on the 360 to 480p just to try to see if that resolves the initial issue? We can then further troubleshoot.  What is the make and model # of the tv?

Unfortunately, when playing in split screen almost all games are like this. There is no way to fix this, it is simply made that way to compensate for the compression of the screen.

As far as i am aware a lot of games have these bars, its to do with the compression of the screen i believe as someone else has said. There is no way to fix it or change it i am afraid.

It's so both players can get the same aspect ratio.

There are games like Warriros Orochi that will simply divide the screen in half but the viewing angle suffers a lot.

When a game shrinks the size of the picture, it's so that both players can still have the same field of view they would have while playing alone...just in a smaller screen.

You need to just readjust your game to your screen, which should be found in options>video>screen adjust. Or something of that nature.

I have the same problem and adjusting the screen size doesn't fix it.

You can't fix it...as mentioned, the game was created that way.  Nothing you will do will change it.

I have this same problem...all of a sudden! Those of you saying this is how it is suppose to be are wrong...I have been playing Halo 4 for months in split screen multiplayer and the black bars were not there!  About 6 weeks ago they appeared on the screen for the first time and now I cannot get rid of them.

Hey there Flea! Go ahead and make a new thread detailing your issue and any steps you've taken so far to fix it. That is how these forums work best as it lets us tailor our support to your specific issue. Thanks! ^_^