使用AVAudioEngine解决AVAudioUnitEffect问题

Question

我一直在寻找AVAudioEngine,我在整合AVAudioUnitEffect类时遇到了麻烦.例如,使用AVAudioUnitDelay ...

@implementation ViewController {
AVAudioEngine *engine;
AVAudioPlayerNode *player;
}

...

- (IBAction)playButtonHit:(id)sender {
if (!player){
    NSURL *bandsURL = [[NSBundle mainBundle] URLForResource:@"Bands With Managers" withExtension:@"mp3"];
    AVAudioFile *file = [[AVAudioFile alloc] initForReading:bandsURL error:nil];

    engine = [[AVAudioEngine alloc] init];
    player = [[AVAudioPlayerNode alloc] init];
    [engine attachNode:player];

    AVAudioUnitDelay *delay = [[AVAudioUnitDelay alloc] init];
    delay.wetDryMix = 50;

    [engine connect:player to:delay format:file.processingFormat];
    [engine connect:delay to:[engine outputNode] format:file.processingFormat];

    [player scheduleFile:file atTime:nil completionHandler:nil];
    [engine prepare];
    [engine startAndReturnError:nil];
}
[player play];  

}

当调用该方法时,应用程序崩溃,我收到此错误:" *因未捕获的异常而终止应用程序'com.apple.coreaudio.avfaudio',原因:'必需条件为false:[_ node containsObject:node1] && [_nodes containsObject :node2]'"

我是在WWDC的"AVAudioEngine in Practice"会议中的一些例子之后对此进行建模的.我知道可能有一些显而易见的东西我不知道但是无法弄清楚......

Answer 1

在链接之前,您忘记将AvAudioUnitDelay对象附加到AvAudioEngine节点;)

这是工作代码:

- (IBAction)playMusic:(id)sender {
    if (!player){
        NSURL *bandsURL = [[NSBundle mainBundle] URLForResource:@"Bands With Managers" withExtension:@"mp3"];
        AVAudioFile *file = [[AVAudioFile alloc] initForReading:bandsURL error:nil];

        engine = [[AVAudioEngine alloc] init];
        player = [[AVAudioPlayerNode alloc] init];
        [engine attachNode:player];

        AVAudioUnitDelay *delay = [[AVAudioUnitDelay alloc] init];
        delay.wetDryMix = 50;
        [engine attachNode:delay]; 

        [engine connect:player to:delay format:file.processingFormat];
        [engine connect:delay to:[engine outputNode] format:file.processingFormat];

        [player scheduleFile:file atTime:nil completionHandler:nil];
        [engine prepare];
        [engine startAndReturnError:nil];
    }
    [player play]; 
}