Download HDEnable3GS : Official

I found this great tweak from Mike Pan. Similar to enabling HDR photos on your iPhone 3GS, with a few simple changes to some plist files, you can have 720p video recording on your iPhone 3GS.



The Easy Way:

• Download the pre-edited files HDVideo3GS.zip.
• Jailbreak your device and install OpenSSH
• Copy N88AP.plist to /System/Library/CoreServices/SpringBoard.app/
• Copy the 3 other plist files to /System/Library/PrivateFrameworks/Celestial.framework/N88/
• Reboot your iPhone 3Gs

The Hard Way:

• Via SSH, open /System/Library/PrivateFrameworks/Celestial.framework/N88/AVCapture.plist with a Plist editor
• Under the AVCaptureMode_AudioVideoRecording key, set the width and height for the capture key to 1080×800, respectively.  This value controls the dimension of the video it is encoded at.
• Set the width and height for the preview key to 440×320.  This value controls the size of the on-screen preview.  It does not have any effect on the final video.
• Set the width and height for the sensor key to 1920×1080.  This value controls the active region of the sensor, so basically, we want to use the entire sensor.  This source will be automatically downscaled to the proper resolution at encoding time.
• Increase the encoding average bitrate to 20Mbps (20000000bps), this records a much larger video file (~ 2MB for every second of video)
• Increase the encoding bitrate cap to 40Mbps.  Also, lower the minimum quantizer from 19 to 15 or something, just for the heck of it.
• Set the H264 profile from 3_0 to 3_1  (because  wikipedia says so)
• Save and close this file.
• To make the phone playback the recorded HD video. Simply edit CameraRollValidator.plist and MediaValidator.plist, they can be found in the same place as AVCapture.plist. (If you don’t do this, the file can only be played back on your computer)
• Replace 768 with 1280
• And replace:

MaxLevel
30

with

MaxLevel
31

• Save these two files.
• Open /System/Library/CoreServices/SpringBoard.app/N88AP.plist with a Plist editor, and add the following under the capability node, this will enable HD recording from the camera app:

720p

hd-video-capture

• Reboot your iPhone 3Gs.