objective-c - iPhone 上的音频混合：需要建议

Question

我正在使用 AudioQueue 服务在我的应用程序中播放音频。我需要一起播放几个音频文件。我现在所做的只是创建尽可能多的音频队列来播放文件。即我为两个音频文件创建两个音频队列并同时启动它们以获得音频混合效果。

所以基本上我想知道这是一种“优雅”的方式。

请注意，我知道音频单元服务及其 MixerHost 示例，请不要建议该选项，我需要专门使用音频队列服务进行声音混合。

Answer 1

- (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];
}


- (BOOL) exportAudio {

    if (defaultSoundPath == nil || recordingSoundPath == nil) {

        [actvityIdicatiorView stopAnimating];
        [actvityIdicatiorView setHidden:YES];


        UIAlertView *alertView=[[UIAlertView alloc]initWithTitle:@"Select Sound" message:@"Both Sound is selected" delegate:self cancelButtonTitle:@"Ok" otherButtonTitles:nil];
        [alertView show];
        return NO;



    }

    AVMutableComposition *composition = [AVMutableComposition composition];
    if (audioMixParams) {
        [audioMixParams release];
        audioMixParams=nil;
    }
    audioMixParams = [[NSMutableArray alloc] initWithObjects:nil];

    //Add Audio Tracks to Composition

    NSString *sourceA= [[NSBundle mainBundle] pathForResource:@"Beach Soundscape" ofType:@"mp3"];

    //NSString *URLPath1 = pathToYourAudioFile1;

    NSURL *assetURL1 = [NSURL fileURLWithPath:sourceA];
    [self setUpAndAddAudioAtPath:assetURL1 toComposition:composition];

    NSString *sourceB = [[NSBundle mainBundle] pathForResource:@"DrumsMonoSTP" ofType:@"aif"];
    // NSString *URLPath2 = pathToYourAudioFile2;
    NSURL *assetURL2 = [NSURL fileURLWithPath:sourceB];
    [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";

    //    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    //
    //    NSString *fileName = @"someFilename";

    //NSString *exportFile = [[paths objectAtIndex:0] stringByAppendingFormat: @"/%@.m4a", fileName];

    mixingSoundPath= [[self mixingSoundFolder] stringByAppendingFormat: @"/Mixing%@.m4a", [self dateString]];
    [mixingSoundPath retain];

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

    static BOOL isComplete;

    // do the export
    [exporter exportAsynchronouslyWithCompletionHandler:^{

        int exportStatus = exporter.status;

        NSLog(@"exporter.......%i",exportStatus);


        switch (exportStatus) {

            case AVAssetExportSessionStatusFailed:
                //    NSError *exportError =exporter.error;
                isComplete=NO;
                NSLog (@"AVAssetExportSessionStatusFailed");


                NSLog (@"Error == %@", exporter.error);
                break;

            case AVAssetExportSessionStatusCompleted:
                [self mixingDidFinshing];

                isComplete=YES;
                break;
            case AVAssetExportSessionStatusUnknown:
                NSLog (@"AVAssetExportSessionStatusUnknown");
                isComplete=NO;

                break;
            case AVAssetExportSessionStatusExporting:
                isComplete=NO;

                NSLog (@"AVAssetExportSessionStatusExporting");

                break;
            case AVAssetExportSessionStatusCancelled:
                isComplete=NO;

                NSLog (@"AVAssetExportSessionStatusCancelled");

                break;
            case AVAssetExportSessionStatusWaiting:
                isComplete=NO;

                NSLog (@"AVAssetExportSessionStatusWaiting"); 

                break;
            default:  
                NSLog (@"didn't get export status"); 
                isComplete=NO;
                break;
        }


    }];

    return isComplete;

}