Create Movie Using AVFoundation

Steps to Create Movie Using AVFoundation:-
1. Create a AVMutableComposition
CFAbsoluteTime currentTime = CFAbsoluteTimeGetCurrent(); //Debug purpose – used to calculate the total time taken
NSError *error = nil;
AVMutableComposition *saveComposition = [AVMutableComposition composition];
2. Get the video and audio file path
NSString *tempPath = NSTemporaryDirectory();
NSString *videoPath = nil ;//<Video file path>;
NSString *audioPath = nil ;//<Audio file path>;;
3. Create the video asset 
NSURL * url1 = [[NSURL alloc] initFileURLWithPath:videoPath];
AVURLAsset *video = [AVURLAsset URLAssetWithURL:url1 options:nil];
[url1 release];
4. Get the AVMutableCompositionTrack for video and add the video track to it.
The method insertTimeRange: ofTrack: atTime: decides the what portion of the video to be added and also where the video track should appear in the final video created.
AVMutableCompositionTrack *compositionVideoTrack = [ addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
AVAssetTrack *clipVideoTrack = [ objectAtIndex:0];
[compositionVideoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, )  ofTrack:clipVideoTrack atTime:kCMTimeZero error:nil];
NSLog(@”%f %@”,CMTimeGetSeconds(),error);
5. Create the Audio asset 
NSURL * url2 = [[NSURL alloc] initFileURLWithPath:audioPath];
AVURLAsset *audio = [AVURLAsset URLAssetWithURL:url2 options:nil];
[url2 release];
6. Get the AVMutableCompositionTrack for audio and add the audio track to it.
AVMutableCompositionTrack *compositionAudioTrack = [saveComposition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];
AVAssetTrack *clipAudioTrack = [ objectAtIndex:0];
[compositionAudioTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, http://duration)  ofTrack:clipAudioTrack atTime:kCMTimeZero error:nil];
NSLog(@”%f %@”,CMTimeGetSeconds(http://duration),error);
7. Get file path for of the final video.
NSString *path = [tempPath stringByAppendingPathComponent:@”mergedvideo.mov”];
if([[NSFileManager defaultManager] fileExistsAtPath:path])
{
[[NSFileManager defaultManager] removeItemAtPath:path error:nil];
}
NSURL *url = [[NSURL alloc] initFileURLWithPath: path];
8. Create the AVAssetExportSession and set the preset to it.
The completion handler will be called upon the completion of the export.
AVAssetExportSession *exporter = [[[AVAssetExportSession alloc] initWithAsset:saveComposition presetName:AVAssetExportPresetHighestQuality] autorelease];
exporter.outputURL=url;
exporter.outputFileType=[[exporter supportedFileTypes] objectAtIndex:0];
[exporter exportAsynchronouslyWithCompletionHandler:^{
NSLog(@”export completed : %lf”,CFAbsoluteTimeGetCurrent()-currentTime);
}];
The above technique can be used to merge N number of video and audio tracks and create a movie. I hope this tutorial helps to create movie using AVFoundation.