Pitch Shifter test

Pitch Shifter test

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    
    NSError *error = nil;
    
    // Get the URL of the file
    NSURL *url = [[NSBundle mainBundle] URLForResource:@"Audio File" withExtension:@"m4a"];
    
    if (!url) {
        NSLog(@"Invalid file URL");
        abort();
    }
    
    // Create the file object for reading
    self.file = [[AVAudioFile alloc] initForReading:url error:&error];
    if (error) {
        NSLog(@"%@", error);
        abort();
    }
    
    // Create engine and player and effect nodes
    self.engine = [[AVAudioEngine alloc] init];
    self.player = [[AVAudioPlayerNode alloc] init];
    self.pitchEffect = [[AVAudioUnitTimePitch alloc] init];
    
    // Set the pitch-shift amount (100 cents = 1 semitone)
    self.pitchEffect.pitch = 100.0; // +1 semitone
    self.pitchEffect.overlap = 16.0; // more overlapping windows
    
    // Add nodes to engine
    [self.engine attachNode:self.player];
    [self.engine attachNode:self.pitchEffect];

    // Connect the player's output to the effect's input
    [self.engine connect:self.player to:self.pitchEffect format:self.file.processingFormat];
    // Connect the effect's output to the main mixer's input
    [self.engine connect:self.pitchEffect to:[self.engine mainMixerNode] format:self.file.processingFormat];
    
    // Schedule the file and start the engine
    [self.player scheduleFile:self.file atTime:nil completionHandler:nil];
    [self.engine startAndReturnError:&error];
    if (error) {
        NSLog(@"%@", error);
        abort();
    }
    
    // Play the file
    [self.player play];
}