ViewController.m

//
//  ViewController.m
//  SimpleAudioTest
//
//  Created by Sam Tarakajian on 8/24/15.
//  Copyright © 2015 Sam Tarakajian. All rights reserved.
//

#import "ViewController.h"
@import AudioToolbox;

enum {
    kMIDIMessage_NoteOn    = 0x9,
    kMIDIMessage_NoteOff   = 0x8,
};

@interface ViewController () {
    AUGraph _audioUnitGraph;
    MusicTrack _rawMusicTrack;
    AUNode _remoteAUNode;
    AUNode _mixerAUNode;
    AUNode _samplerAUNode;
    
    MusicPlayer _player;
    MusicSequence _sequence;
    MusicTrack _track;
    
    MIDIClientRef _client;
    MIDIEndpointRef _endpoint;
}
@property (nonatomic, strong) NSTimer *pollStateTimer;

- (void)createAudioGraph;
- (void)createRemoteAUNode;
- (void)createMixerAUNode;
- (void)createSamplerAUNode;
- (void)pollState;
- (void)setMusicTrackLength:(MusicTrack *)track length:(MusicTimeStamp)length;
- (void)setMusicTrackLoopDuration:(MusicTrack *)track loopDuration:(MusicTimeStamp)loopDuration;
@end

@implementation ViewController

- (void)createAudioGraph
{
    __unused OSStatus status = NewAUGraph(&_audioUnitGraph);
    NSAssert(status == noErr, @"Assert: NewAUGraph failed: %d", (int)status);
}

- (void)createRemoteAUNode
{
    AudioComponentDescription description;
    description.componentType = kAudioUnitType_Output;
    description.componentSubType = kAudioUnitSubType_RemoteIO;
    description.componentManufacturer = kAudioUnitManufacturer_Apple;
    description.componentFlags = 0;
    description.componentFlagsMask = 0;
    AUGraphAddNode(_audioUnitGraph, &description, &_remoteAUNode);
}

- (void)createMixerAUNode
{
    AudioComponentDescription description;
    description.componentType = kAudioUnitType_Mixer;
    description.componentSubType = kAudioUnitSubType_MultiChannelMixer;
    description.componentManufacturer = kAudioUnitManufacturer_Apple;
    description.componentFlags = 0;
    description.componentFlagsMask = 0;
    AUGraphAddNode(_audioUnitGraph, &description, &_mixerAUNode);
}

- (void)createSamplerAUNode
{
    AudioComponentDescription description;
    description.componentType = kAudioUnitType_MusicDevice;
    description.componentSubType = kAudioUnitSubType_Sampler;
    description.componentManufacturer = kAudioUnitManufacturer_Apple;
    description.componentFlags = 0;
    description.componentFlagsMask = 0;
    AUGraphAddNode(_audioUnitGraph, &description, &_samplerAUNode);
}

- (void)setMusicTrackLength:(MusicTrack *)t length:(MusicTimeStamp)length
{
    MusicTimeStamp trackLength = length;
    
    __unused OSStatus status = MusicTrackSetProperty(*t, kSequenceTrackProperty_TrackLength, &trackLength, sizeof(trackLength));
    NSAssert(status == noErr, @"Assert: MusicTrackSetProperty failed: %d", (int)status);
}

- (void)setMusicTrackLoopDuration:(MusicTrack *)t loopDuration:(MusicTimeStamp)loopDuration
{
    // Setting numberOfLoops to 0.0 will make the track loop forrreevvverrrr
    MusicTrackLoopInfo loopInfo;
    loopInfo.loopDuration = loopDuration;
    loopInfo.numberOfLoops = 0.0;
    
    __unused OSStatus status = MusicTrackSetProperty(*t, kSequenceTrackProperty_LoopInfo, &loopInfo, sizeof(loopInfo));
    NSAssert(status == noErr, @"Assert: MusicTrackSetProperty failed: %d", (int)status);
}

- (void)viewDidLoad {
    [super viewDidLoad];
    __unused OSStatus status;

    // Setup audio graph
    [self createAudioGraph];
    [self createRemoteAUNode];
    [self createSamplerAUNode];
    
    AUGraphOpen(_audioUnitGraph);
    
    AUGraphConnectNodeInput(_audioUnitGraph, _samplerAUNode, 0, _remoteAUNode, 0);
    
    // Create the MusicPlayer
    status = NewMusicPlayer(&_player);
    status = MusicPlayerSetTime(_player, 0.0);
    
    // Create the MusicSequence
    status = NewMusicSequence(&_sequence);
    MusicPlayerSetSequence(_player, _sequence);
    
    // Add a track
    status = MusicSequenceNewTrack(_sequence, &_track);
     NSAssert(status == noErr, @"Assert: MusicSequenceNewTrack failed: %d", (int)status);
    
    // Add a single note
    MIDINoteMessage message;
    message.note = 60;
    message.velocity = 127;
    message.releaseVelocity = 127;
    message.duration = 0.5;
    message.channel = 0;
    MusicTrackNewMIDINoteEvent(_track, 1.0, &message);
    MusicTrackNewMIDINoteEvent(_track, 2.0, &message);
    MusicTrackNewMIDINoteEvent(_track, 3.0, &message);
    
    // Setup Looping
    [self setMusicTrackLoopDuration:&_track loopDuration:4.0];
    [self setMusicTrackLength:&_track length:4.0];
    
    // Attach it to the AUGraph
    MusicSequenceSetAUGraph(_sequence, _audioUnitGraph);
    
    // Start Everything
    AUGraphStart(_audioUnitGraph);
    MusicPlayerPreroll(_player);
    MusicPlayerStart(_player);
    
    // Start polling for status
    self.pollStateTimer = [NSTimer scheduledTimerWithTimeInterval:0.1 target:self selector:@selector(pollState) userInfo:nil repeats:YES];
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (void)pollState
{
    MusicTimeStamp ts = 0.0;
    __unused OSStatus status = MusicPlayerGetTime(_player, &ts);
    NSLog(@"Progress: %f", ts);
}

@end