Mike Pan has successfully modified system files on the iPhone 3GS to record HD video at 30fps.
The video is recorded at 1080×800 at up to 20Mbps, this is a big improvement from the default 640×480 at 3Mbps. The unusual size is used to keep the video at the right aspect ratio when recording. You can also change the resolution to 960×720 if you so prefer.
It does take a little longer for the 3GS to focus and the quality won’t be as good as that on the iPhone 4 but it’s a nice improvement especially if you’re not moving the phone a lot.
First of all make sure you have a jailbroken iPhone 3GS on iOS 4.1, then ensure you install OpenSSH and you know your iPhone’s IP Address. Next download the relevant patch files, depending on your resolution prefenrence.
Once you have downloaded the relevant patch extract it. In the extracted folder you should have the following files:
Launch your favourite SSH client and connect to your iPhone. Once you’ve connected navigate to /System/Library/CoreServices/SpringBoard.app/
Now locate the file N88AP.plist, rename it and add .bak to the end of the filename, this will act as a backup file so that you can revert to the original setting.
Now drag the N88AP.plist that you downloaded and put it in the same folder as the original was in.
Now navigate to /System/Library/PrivateFrameworks/Celestial.framework/N88/
Now locate the files:
Rename them all and add .bak to the end of the filenames.
Now drag the AVCapture.plist, CameraRollValidator.plist, and MediaValidator.plist files that you downloaded and put it in the same folder as you just navigated to.
Now just restart your iPhone 3GS and your HD video recording will be enabled.