cannot making movie from UIImage Array with AVAssetWriter on iphone 3G

I am working on an iOS app which make a movie using array of UIImages. Everything work well on iphone 3GS, iphone 4, but cannot on iphone 3, I got this in AVAssetWriterInput.h:

Video output settings keys are defined in AVVideoSettings.h. Video output settings with keys from are not currently supported. The only values currently supported for AVVideoCodecKey are AVVideoCodecH264 and AVVideoCodecJPEG. AVVideoCodecH264 is not supported on iPhone 3G.

Please anyone could help me an idea?

The error message is pretty clear. You're trying to encode your video as h264, which is not supported on the iPhone 3G or classic, because it requires special encoding hardware. That's also the reason, the camera app on the 3G can't record videos.