Trim Audio to Video Length - ios

Question

I have a video that is 5 secs long. I have an audio file that is 35 secs long. When I use this code to add audio to Video it makes a resulting video that is 35 secs long.
How can I modify this code so that the audio plays the lenght of the video and stops resulting in a video that is only 5 secs long?
I took this code from this post
problem using UIImage and caf to create video file
-(void) addAudioToFileAtPath:(NSString *)vidoPath andAudioPath:(NSString *)audioPath{
AVMutableComposition* mixComposition = [AVMutableComposition composition];
NSURL* audio_inputFileUrl = [NSURL fileURLWithPath:audioPath];
NSURL* video_inputFileUrl = [NSURL fileURLWithPath:vidoPath];
NSString *outputFilePath = FinalVideoPath;
NSURL* outputFileUrl = [NSURL fileURLWithPath:outputFilePath];
if ([[NSFileManager defaultManager] fileExistsAtPath:outputFilePath])
[[NSFileManager defaultManager] removeItemAtPath:outputFilePath error:nil];
AVURLAsset* audioAsset = [[AVURLAsset alloc]initWithURL:audio_inputFileUrl options:nil];
CMTimeRange audio_timeRange = CMTimeRangeMake(kCMTimeZero, audioAsset.duration);
AVMutableCompositionTrack *b_compositionAudioTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];
[b_compositionAudioTrack insertTimeRange:audio_timeRange ofTrack:[[audioAsset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0] atTime:kCMTimeZero error:nil];
AVURLAsset* videoAsset = [[AVURLAsset alloc]initWithURL:video_inputFileUrl options:nil];
CMTimeRange video_timeRange = CMTimeRangeMake(kCMTimeZero,videoAsset.duration);
AVMutableCompositionTrack *a_compositionVideoTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
[a_compositionVideoTrack insertTimeRange:video_timeRange ofTrack:[[videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] atTime:kCMTimeZero error:nil];
//nextClipStartTime = CMTimeAdd(nextClipStartTime, a_timeRange.duration);
[audioAsset release];audioAsset = nil;
[videoAsset release];videoAsset = nil;
AVAssetExportSession* _assetExport = [[AVAssetExportSession alloc] initWithAsset:mixComposition presetName:AVAssetExportPresetHighestQuality];
_assetExport.outputFileType = AVFileTypeQuickTimeMovie;
_assetExport.outputURL = outputFileUrl;
[_assetExport exportAsynchronouslyWithCompletionHandler:
^(void ) {
switch (_assetExport.status)
{
case AVAssetExportSessionStatusCompleted:
//export complete
NSLog(#"Export Complete");
break;
case AVAssetExportSessionStatusFailed:
NSLog(#"Export Failed");
NSLog(#"ExportSessionError: %#", [_assetExport.error localizedDescription]);
//export error (see exportSession.error)
break;
case AVAssetExportSessionStatusCancelled:
NSLog(#"Export Failed");
NSLog(#"ExportSessionError: %#", [_assetExport.error localizedDescription]);
//export cancelled
break;
}
}];
}

Answer 1

_assetExport.timeRange = CMTimeRangeMake(kCMTimeZero, videoAsset.duration);