stevenhuey

@implementation CBCosmDatastream

#pragma mark - Mantle

+ (NSDictionary *)externalRepresentationKeyPathsByPropertyKey
{
   return [super.externalRepresentationKeyPathsByPropertyKey mtl_dictionaryByAddingEntriesFromDictionary:@{
           @"datastreamId": @"id",
           @"updated": @"at",
           @"value": @"current_value",

stevenhuey

@implementation CBCosmDatastream

- (id)initWithAttributes:(NSDictionary*)attributes
{
   self = [super init];
   
   if (self)
   {
      if (!attributes)
      {

stevenhuey

// Build and apply an audio mix using our volume values
- (void)applyAudioMix
{
   AVMutableAudioMix* mix = [AVMutableAudioMix audioMix];
   
   NSMutableArray* inputParameters = [[NSMutableArray alloc] initWithCapacity:0];
   
   [_audioMixTrackIDs enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL*stop) {
      AVAssetTrack* track = [self trackWithId:(CMPersistentTrackID)[(NSNumber*)obj integerValue]];
      

stevenhuey

// Set the volumne (0.0 - 1.0) for the given track
- (void)setVolume:(float)volume forTrack:(NSString*)audioTrackName
{
   [_audioMixValues setValue:[NSNumber numberWithFloat:volume] forKey:audioTrackName];
}

stevenhuey

// Action for our 4 sliders
- (IBAction)mix:(id)sender
{
   UISlider* slider = (UISlider*)sender;
   
   [self setVolume:slider.value
          forTrack:[NSString stringWithFormat:@"track%d", slider.tag]];
   [self applyAudioMix];
}

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- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
   if ([keyPath isEqualToString:@"status"])
   {
      if (AVPlayerItemStatusReadyToPlay == _player.currentItem.status)
      {
         [_player play];
      }
   }
}

stevenhuey

// Setup
   _composition = [AVMutableComposition composition];
   
   _audioMixValues = [[NSMutableDictionary alloc] initWithCapacity:0];
   _audioMixTrackIDs = [[NSMutableDictionary alloc] initWithCapacity:0];
   
   // Insert the audio tracks into our composition
   NSArray* tracks = [NSArray arrayWithObjects:@"track1", @"track2", @"track3", @"track4", nil];
   NSString* audioFileType = @"wav";