I want to change the container of a .mov video files that I pick using  UIImagePickerController and compressed them via AVAssetExportSession with AVAssetExportPresetMediumQuality and  shouldOptimizeForNetworkUse = YES to .mp4 container. I need programmatically way/sample code to perform a fastest 'trans-wrap' on iPhone/iPad application I tried to set AVAssetExportSession.outputFileType property to AVFileTypeMPEG4 but it not supported and I got exception I tried to do this transform using AVAssetWriter by specifying fileType:AVFileTypeMPEG4, actually I got .mp4 output file, but it was not 'wrap-trans', the output file was  3x bigger than source, and the convert process took 128 sec for video with 60 sec duration. I need solution that will run quickly and will keep the file size  please help