How to merge audio in our video file - objective-c

Question

I have an application in which I need to merge an audio file in to the video recorded by AVCapture session, so that both audio of recorded movie and merged audio can be heard.
I am able to merge the audio to video with avcomposition and it does fine . But the problem is that the original audio file can not be heard. Here is my code.
NSString *resourceAudioName = [NSString stringWithFormat:#"%#_audio",getTitle];
NSURL *audio_inputFileUrl = [[NSBundle mainBundle] URLForResource:resourceAudioName withExtension:#"mp3"];
NSString * video_inputFilePath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
video_inputFilePath = [video_inputFilePath stringByAppendingPathComponent:#"movie1.mp4"];
self.outputFilePath = [NSHomeDirectory() stringByAppendingPathComponent:[NSString stringWithFormat:#"/Documents/OutPutMovie-%#.mp4",[NSDate date]]];
NSURL * outputFileUrl = [NSURL fileURLWithPath:self.outputFilePath];
if (audio_inputFileUrl) {
AVMutableComposition* mixComposition = [AVMutableComposition composition];
NSURL * video_inputFileUrl = [NSURL fileURLWithPath:video_inputFilePath];
CMTime nextClipStartTime = kCMTimeZero;
AVURLAsset * videoAsset = [[AVURLAsset alloc]initWithURL:video_inputFileUrl options:nil];
NSArray * videoAssetTracks2 = [videoAsset tracksWithMediaType:AVMediaTypeVideo];
AVAssetTrack * videoAssetTrack2 = ([videoAssetTracks2 count] > 0 ? [videoAssetTracks2 objectAtIndex:0] : nil);
CMTimeRange video_timeRange = CMTimeRangeMake(kCMTimeZero,videoAsset.duration);
AVMutableCompositionTrack * a_compositionVideoTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
[a_compositionVideoTrack insertTimeRange:video_timeRange ofTrack:videoAssetTrack2 atTime:nextClipStartTime error:nil];
AVURLAsset * audioAsset = [[AVURLAsset alloc]initWithURL:audio_inputFileUrl options:nil];
NSArray * videoAssetTracks = [audioAsset tracksWithMediaType:AVMediaTypeAudio];
AVAssetTrack * videoAssetTrack = ([videoAssetTracks count] > 0 ? [videoAssetTracks objectAtIndex:0] : nil);
CMTimeRange audio_timeRange = CMTimeRangeMake(kCMTimeZero, audioAsset.duration);
AVMutableCompositionTrack * b_compositionAudioTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];
[b_compositionAudioTrack insertTimeRange:audio_timeRange ofTrack:videoAssetTrack atTime:nextClipStartTime error:nil];
AVAssetExportSession * _assetExport = [[AVAssetExportSession alloc] initWithAsset:mixComposition presetName:AVAssetExportPresetHighestQuality];
_assetExport.outputFileType = #"com.apple.quicktime-movie";
_assetExport.outputURL = outputFileUrl;
[_assetExport exportAsynchronouslyWithCompletionHandler:
^(void ) {
if (AVAssetExportSessionStatusCompleted == _assetExport.status) {
[videoAsset release];
[audioAsset release];
[_assetExport release];
[self performSelectorOnMainThread:#selector(moveNextView) withObject:nil waitUntilDone:YES];
}
}
];

Answer 1

-(void)mergeAndSave
{
//Create AVMutableComposition Object which will hold our multiple AVMutableCompositionTrack or we can say it will hold our video and audio files.
AVMutableComposition* mixComposition = [AVMutableComposition composition];
//Now first load your audio file using AVURLAsset. Make sure you give the correct path of your videos.
NSURL *audio_url = [NSURL fileURLWithPath:[[NSBundle mainBundle] pathForResource:#"kick" ofType:#"mp3"]];
self.audioAsset = [[AVURLAsset alloc]initWithURL:audio_url options:nil];
CMTimeRange audio_timeRange = CMTimeRangeMake(kCMTimeZero, self.audioAsset.duration);
//Now we are creating the first AVMutableCompositionTrack containing our audio and add it to our AVMutableComposition object.
AVMutableCompositionTrack *b_compositionAudioTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];
[b_compositionAudioTrack insertTimeRange:audio_timeRange ofTrack:[[self.audioAsset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0] atTime:kCMTimeZero error:nil];
//Now we will load video file.
NSURL *video_url = mediaUrl;
self.videoAsset = [[AVURLAsset alloc]initWithURL:video_url options:nil];
CMTimeRange video_timeRange = CMTimeRangeMake(kCMTimeZero,self.audioAsset.duration);
//Now we are creating the second AVMutableCompositionTrack containing our video and add it to our AVMutableComposition object.
AVMutableCompositionTrack *a_compositionVideoTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
[a_compositionVideoTrack insertTimeRange:video_timeRange ofTrack:[[self.videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] atTime:kCMTimeZero error:nil];
//decide the path where you want to store the final video created with audio and video merge.
NSArray *dirPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *docsDir = [dirPaths objectAtIndex:0];
NSString *outputFilePath = [docsDir stringByAppendingPathComponent:[NSString stringWithFormat:#"video.mov"]];
NSURL *outputFileUrl = [NSURL fileURLWithPath:outputFilePath];
if ([[NSFileManager defaultManager] fileExistsAtPath:outputFilePath])
[[NSFileManager defaultManager] removeItemAtPath:outputFilePath error:nil];
//Now create an AVAssetExportSession object that will save your final video at specified path.
AVAssetExportSession* _assetExport = [[AVAssetExportSession alloc] initWithAsset:mixComposition presetName:AVAssetExportPresetHighestQuality];
_assetExport.outputFileType = #"com.apple.quicktime-movie";
_assetExport.outputURL = outputFileUrl;
[_assetExport exportAsynchronouslyWithCompletionHandler:
^(void ) {
dispatch_async(dispatch_get_main_queue(), ^{
[self exportDidFinish:_assetExport];
});
}
];
}
- (void)exportDidFinish:(AVAssetExportSession*)session
{
if(session.status == AVAssetExportSessionStatusCompleted){
NSURL *outputURL = session.outputURL;
ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];
if ([library videoAtPathIsCompatibleWithSavedPhotosAlbum:outputURL]) {
[library writeVideoAtPathToSavedPhotosAlbum:outputURL
completionBlock:^(NSURL *assetURL, NSError *error){
dispatch_async(dispatch_get_main_queue(), ^{
if (error) {
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:#"Error" message:#"Video Saving Failed" delegate:nil cancelButtonTitle:#"Ok" otherButtonTitles: nil, nil];
[alert show];
}else{
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:#"Video Saved" message:#"Saved To Photo Album" delegate:self cancelButtonTitle:#"Ok" otherButtonTitles: nil];
[alert show];
//[self loadMoviePlayer:outputURL];
}
});
}];
}
}
self.audioAsset = nil;
self.videoAsset = nil;
//[activityView stopAnimating];
//[activityView setHidden:YES];
}
try this

Answer 2

I believe you have to use AVMutableAudioMix in order to do a mixing of more than one audio. With your approach only the audioAsset gets added to the composition. There is a video about this in WWDC 2010, which explains how to do this. I have tried to implement without success here. Hopefully someone will help us fix it.