iPhone上的混音: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播放文件所需的音频队列。也就是说，我为两个音频文件创建了两个音频队列，并同时启动它们以产生音频混合效果。

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，请不要建议使用该选项，我需要专门使用音频队列服务进行混音。

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;
}