The iPhone HDMI adapter work a little different on the iPad and iPad 2 as it mirrors the iPad and iPad 2 display on your high definition TV. There is no iPad jailbreak required, you simply connect the HDMI adapter to your iPad/iPad2 dock and you are all set.
The iPhone HDMI Adapter has two slots. One slot is used to connect an HDMI cable to an HD TV, while the other slot is a regular 30pin dock connector which makes it easy to charge your iPhone battery while using the HDMI video out display.
I have tried to connect my iPhone and iPhone 4 video out using an AV video out cable and a component video cable. However, none of those iPhone video cables is comparable to the iPhone HDMI adapter display clarity.
The picture on a high definition TV is so clear that I immediately removed my component video cable and started using the HDMI adapter all the time. There are two ways you can view your iPhone display on an HD TV using the iPhone HDMI adapter.
The other way of displaying your iPhone screen on an HDTV using the iPhone HDMI video adapter requires iPhone jailbreak and it has some advantages over the default one.
First, the whole iPhone screen will be mirrored, therefore, you don't have to worry about an iPhone movie player supporting video out or not. It will automatically be mirrored. There are a couple iPhone hacks that will allow you to mirror your iPhone display to an HDTV taking advantage of the iPhone HDMI video out.
iPhone HD Video Out Hacks:
You can still use some iPhone hacks to display full screen video and bypass the default video display. The advantage of doing this is that you will have more control of your iPhone video out. Not only you can display the default iPhone movie players on an HDTV but also you can mirror any iPhone application whether or not it supports video out.
TVOut2 Mirror TV Out is one of the best iPhone hacks in Cydia that gives you the ability to adjust your display to exactly fit your TV screen.
The other great iPhone video out hack is called Display Out which does the same thing as TVOut2 but has no way to adjust your display. Therefore, you will find that there are 2 black vertical bars displayed on the left and right of the HDTV as shown below by the red rectangles.
Those two black bars can be removed using the TVOut Tuner to fill your whole TV screen as shown below.
Although I wished that there was one simpler connection to iPhone HDMI video out cable which plugs to the iPhone and is built in USB just like the Component video cable. But I think that would increase the cost from $29 to maybe $59 and this is how Apple managed to keep the cost down.
Since the iPhone is a small device, connecting an HDMI cable and a 30 pin iPhone cable to charge the iPhone battery all together seem to be a little too heavy. Therefore, be careful when you leave the iPhone on a table so that the weight of the cables doesn't pull the iPhone 4 and drop it.