Combining two .caf files on iPhone

Question

I've looked and looked for an answer, but can't seem to find one. Lots have asked, but none have gotten answers. I have an app that records audio using AVAudioRecorder. Now I just want to merge two or more recordings into one file that can be sent out via email. Does anyone have any clue as to how this can be done?

(This answer suggests using something called Audio Service Queues, but I don't know anything about that)

Answer 1

It's not quite as easy as you would think. I used the AVFoundation framework to do exactly what you're asking about to create iAmRingtones. It required creating AVAssets from the audio files and setting up an AVExportSession. The end result was great, but it certainly took a bit of work. Here's more or less how we created the export functionality in our app:

- (void) setUpAndAddAudioAtPath:(NSURL*)assetURL toComposition:(AVMutableComposition *)composition {

    AVURLAsset *songAsset = [AVURLAsset URLAssetWithURL:assetURL options:nil];  

    AVMutableCompositionTrack *track = [composition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];
    AVAssetTrack *sourceAudioTrack = [[songAsset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0];

    NSError *error = nil;
    BOOL ok = NO;

    CMTime startTime = CMTimeMakeWithSeconds(0, 1);
    CMTime trackDuration = songAsset.duration;
    CMTime longestTime = CMTimeMake(848896, 44100); //(19.24 seconds)
    CMTimeRange tRange = CMTimeRangeMake(startTime, trackDuration);

    //Set Volume
    AVMutableAudioMixInputParameters *trackMix = [AVMutableAudioMixInputParameters audioMixInputParametersWithTrack:track];
    [trackMix setVolume:0.8f atTime:startTime];
    [audioMixParams addObject:trackMix];

    //Insert audio into track
    ok = [track insertTimeRange:tRange ofTrack:sourceAudioTrack atTime:CMTimeMake(0, 44100) error:&error];
}   

The above method gets called twice (once for each audio track) from the following method:

- (void) exportAudio {

    AVMutableComposition *composition = [AVMutableComposition composition];
    audioMixParams = [[NSMutableArray alloc] initWithObjects:nil];

    //Add Audio Tracks to Composition
    NSString *URLPath1 = pathToYourAudioFile1;
    NSURL *assetURL1 = [NSURL fileURLWithPath:URLPath1];
    [self setUpAndAddAudioAtPath:assetURL1 toComposition:composition];

    NSString *URLPath2 = pathToYourAudioFile2;
    NSURL *assetURL2 = [NSURL fileURLWithPath:URLPath2];
    [self setUpAndAddAudioAtPath:assetURL2 toComposition:composition];

    AVMutableAudioMix *audioMix = [AVMutableAudioMix audioMix];
    audioMix.inputParameters = [NSArray arrayWithArray:audioMixParams];

    //If you need to query what formats you can export to, here's a way to find out
    NSLog (@"compatible presets for songAsset: %@",
            [AVAssetExportSession exportPresetsCompatibleWithAsset:composition]);

    AVAssetExportSession *exporter = [[AVAssetExportSession alloc]
                                  initWithAsset: composition
                                  presetName: AVAssetExportPresetAppleM4A];
    exporter.audioMix = audioMix;
    exporter.outputFileType = @"com.apple.m4a-audio";
    NSString *fileName = @"someFilename";
    NSString *exportFile = [[util getDocumentsDirectory] stringByAppendingFormat: @"/%@.m4a", fileName];    

    // set up export 
    myDeleteFile(exportFile);
    NSURL *exportURL = [NSURL fileURLWithPath:exportFile];
    exporter.outputURL = exportURL; 

    // do the export
    [exporter exportAsynchronouslyWithCompletionHandler:^{
            int exportStatus = exporter.status;
            switch (exportStatus) {
                case AVAssetExportSessionStatusFailed: 
                    NSError *exportError = exporter.error;
                    NSLog (@"AVAssetExportSessionStatusFailed: %@", exportError);
                    break;

                case AVAssetExportSessionStatusCompleted: NSLog (@"AVAssetExportSessionStatusCompleted"); break;
                case AVAssetExportSessionStatusUnknown: NSLog (@"AVAssetExportSessionStatusUnknown"); break;
                case AVAssetExportSessionStatusExporting: NSLog (@"AVAssetExportSessionStatusExporting"); break;
                case AVAssetExportSessionStatusCancelled: NSLog (@"AVAssetExportSessionStatusCancelled"); break;
                case AVAssetExportSessionStatusWaiting: NSLog (@"AVAssetExportSessionStatusWaiting"); break;
                default:  NSLog (@"didn't get export status"); break;
    }
}];

    // start up the export progress bar
    progressView.hidden = NO;
    progressView.progress = 0.0;
    [NSTimer scheduledTimerWithTimeInterval:0.1
                                 target:self
                               selector:@selector (updateExportProgress:)
                               userInfo:exporter
                                repeats:YES];

}

Answer 2

How to merge any number of Audio Files sequentially whose path is contained by an array called as recordingsArray

# pragma mark  mergeRecording

- (void) mergeRecording
{
        AVMutableComposition *composition = [AVMutableComposition composition];
        [self buildSequenceComposition:composition];   //given Below 

        NSLog (@"compatible presets for songAsset: %@",[AVAssetExportSession exportPresetsCompatibleWithAsset:composition]);

        AVAssetExportSession *exporter = [[AVAssetExportSession alloc] initWithAsset: composition presetName: AVAssetExportPresetAppleM4A];
        exporter.outputFileType = @"com.apple.m4a-audio";

        //File Name

        NSString *recordingFileName = [self setRecordingFileName];
        self.recordingTimeLbl.text = @"00:00:00";
        NSString *exportFile = [NSTemporaryDirectory() stringByAppendingFormat: @"/%@.m4a", recordingFileName];

        // set up export 
        BOOL yes = [[NSFileManager defaultManager] removeItemAtPath:exportFile error:NULL];
        NSURL *exportURL = [NSURL fileURLWithPath:exportFile];
        exporter.outputURL = exportURL; 
        NSData *sound1Data = [[NSData alloc] initWithContentsOfURL: exportURL];
        NSLog(@"Length %i",sound1Data.length);

        [exporter exportAsynchronouslyWithCompletionHandler:^{
            int exportStatus = exporter.status;
            switch (exportStatus) {
                case AVAssetExportSessionStatusFailed: 
                    NSLog (@"AVAssetExportSessionStatusFailed:");
                    break;

                case AVAssetExportSessionStatusCompleted: NSLog (@"AVAssetExportSessionStatusCompleted"); break;
                case AVAssetExportSessionStatusUnknown: NSLog (@"AVAssetExportSessionStatusUnknown"); break;
                case AVAssetExportSessionStatusExporting: NSLog (@"AVAssetExportSessionStatusExporting"); break;
                case AVAssetExportSessionStatusCancelled: NSLog (@"AVAssetExportSessionStatusCancelled"); break;
                case AVAssetExportSessionStatusWaiting: NSLog (@"AVAssetExportSessionStatusWaiting"); break;
                default:  NSLog (@"didn't get export status"); break;
            }
        }];

        // start up the export progress bar
        [NSTimer scheduledTimerWithTimeInterval:0.1 target:self selector:@selector (updateProgress:) userInfo:exporter repeats:NO];
}


- (NSString *) setRecordingFileName
{
    NSDate *todaysDate = [NSDate date];

    NSDateFormatter *dateFormat = [[NSDateFormatter alloc] init];
    [dateFormat setDateFormat:@"dd-MM-yyyy"];
    NSString *dateString11 = [dateFormat stringFromDate:todaysDate];

    NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
    NSDateComponents *dateComponents = [gregorian components:(NSHourCalendarUnit  | NSMinuteCalendarUnit | NSSecondCalendarUnit) fromDate:todaysDate];
    NSInteger hour = [dateComponents hour];
    NSInteger minute = [dateComponents minute];
    NSInteger second = [dateComponents second];
    [gregorian release];

    NSLog(@"Date: %@  \n Time : %@-%@-%@",dateString11,[NSString stringWithFormat:@"%i",hour],[NSString stringWithFormat:@"%i",minute],[NSString stringWithFormat:@"%i",second]);


    NSString *recordingFileName = @"Any Name";
    if(recordingFileName.length > 0)
    {
            recordingFileName = [NSString stringWithFormat:@"%@AND%@AND%@-%@-%@", recordingFileName, dateString11, [NSString stringWithFormat:@"%i",hour], [NSString stringWithFormat:@"%i",minute], [NSString stringWithFormat:@"%i",second]];
    }
    else
    {
            recordingFileName = [NSString stringWithFormat:@"%@AND%@-%@-%@",dateString11,[NSString stringWithFormat:@"%i",hour],[NSString stringWithFormat:@"%i",minute],[NSString stringWithFormat:@"%i",second]];
    }
    return recordingFileName;
}


- (void)updateProgress:(id)timer
{
    AVAssetExportSession *session;
    if([timer isKindOfClass:[NSTimer class]])
        session = (AVAssetExportSession *)[timer userInfo];
    else if([timer isKindOfClass:[AVAssetExportSession class]])
        session = timer;

    if (session.status == AVAssetExportSessionStatusExporting) 
    {

        NSArray *modes = [[[NSArray alloc] initWithObjects:NSDefaultRunLoopMode, UITrackingRunLoopMode, nil] autorelease];
        [self performSelector:@selector(updateProgress:) withObject:session afterDelay:0.5 inModes:modes];

    }
    else if(session.status == AVAssetExportSessionStatusCompleted)
    {
        NSLog(@"Exporting Ended");
        NSURL  *exportURL =  session.outputURL;
        NSData *sound1Data = [[NSData alloc] initWithContentsOfURL: exportURL];
        NSLog(@"Length %i \n Path %@",sound1Data.length,exportURL);

        [self.activityIndicator stopAnimating];
        self.activityIndicator.hidden = YES;
        NSLog(@"Merging Complete");

        for(int x = 0 ; x < [recordingsArray count] ; x++)
        {
                NSURL   *recordingPathUrl = [recordingsArray objectAtIndex:x];
                BOOL yes = [[NSFileManager defaultManager] removeItemAtPath:recordingPathUrl.relativePath error:NULL];
                if (yes) 
                {
                    NSLog(@"File Removed at Path %@",recordingPathUrl.relativePath);
                }
                else
                {
                    NSLog(@"Problem During Removal of Recording At Path %@",recordingPathUrl.relativePath);
                }

        }

        NSString *exportFile = [NSString stringWithFormat:@"%@",exportURL];
        NSString *recordingFileName = [self setRecordingFileName];
        BOOL isInserted = [[DbFile sharedDatabase] insertRecordingDataIntoTable:recordingFileName recordingPath:exportFile];

        if(isInserted)
        {
            NSLog(@"Recording Inserted In Database");
        }
        else
        {
            NSLog(@"Recording Inserted In Database");
        }


         if([timer isKindOfClass:[NSTimer class]])
            [timer invalidate];

    }
    else if(session.status == AVAssetExportSessionStatusFailed)
    {

            [self.activityIndicator stopAnimating];
            NSLog(@"Recording Export Failed");

            UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"Error" message:@"Recording Export Failed" delegate:nil cancelButtonTitle:@"OK" otherButtonTitles: nil];
            [alertView show];
            [alertView release];

            if([timer isKindOfClass:[NSTimer class]])
                [timer invalidate];

    }
    else if(session.status == AVAssetExportSessionStatusCancelled)
    {

            [self.activityIndicator stopAnimating];
            NSLog(@"Recording Export Cancelled");

            UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"Error" message:@"Recording Export Cancelled" delegate:nil cancelButtonTitle:@"OK" otherButtonTitles: nil];
            [alertView show];
            [alertView release];
            if([timer isKindOfClass:[NSTimer class]])
                [timer invalidate];
    }
}


- (void) buildSequenceComposition:(AVMutableComposition *)composition
{
    AVMutableCompositionTrack *audioTrack1 = [composition addMutableTrackWithMediaType:AVMediaTypeAudio 
                                                                      preferredTrackID:kCMPersistentTrackID_Invalid];
    CMTime nextClipStartTime = kCMTimeZero;

    for(NSURL * view in recordingsArray)
    {
        AVURLAsset* audioAsset = [[AVURLAsset alloc]initWithURL:view options:nil];
        CMTimeRange timeRangeInAsset;
        timeRangeInAsset = CMTimeRangeMake(kCMTimeZero, [audioAsset duration]);

        AVAssetTrack *clipVideoTrack = [[audioAsset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0];
        [audioTrack1 insertTimeRange:timeRangeInAsset ofTrack:clipVideoTrack atTime:nextClipStartTime error:nil];
        nextClipStartTime = CMTimeAdd(nextClipStartTime, timeRangeInAsset.duration);
    }
}