Fucking AV Foundation code with audio and video mixing

FuckingAVFoundation.m

- (void)buildTransitionCompositionAUDIO:(AVMutableComposition *)composition andVideoComposition:(AVMutableVideoComposition *)videoComposition andAudioMix:(AVMutableAudioMix *)audioMix
{
    
	CMTime nextClipStartTime = kCMTimeZero;
	
	// Add two video tracks and two audio tracks.
	AVMutableCompositionTrack *compositionVideoTracks[2];
	AVMutableCompositionTrack *compositionAudioTracks[2];
	compositionVideoTracks[0] = [composition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
	compositionVideoTracks[1] = [composition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
	compositionAudioTracks[0] = [composition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];
	compositionAudioTracks[1] = [composition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];
	
//	CMTimeRange *passThroughTimeRanges = alloca(sizeof(CMTimeRange) * clipsCount);
//	CMTimeRange *transitionTimeRanges = alloca(sizeof(CMTimeRange) * clipsCount);
	
    
    AVURLAsset *asset;
    NSInteger alternatingIndex;
    CMTimeRange timeRangeInAsset;
    AVAssetTrack *clipVideoTrack;
    AVAssetTrack *clipAudioTrack;
    const CMTime duration = CMTimeMakeWithSeconds(18, 60000);

    NSError *error;

    alternatingIndex = 0;
    asset = [self.clips objectAtIndex:0];
    timeRangeInAsset = CMTimeRangeMake(kCMTimeZero, duration);
    clipVideoTrack = [[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];
    [compositionVideoTracks[alternatingIndex] insertTimeRange:timeRangeInAsset ofTrack:clipVideoTrack atTime:nextClipStartTime error:&error];
    clipAudioTrack = [[asset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0];
    [compositionAudioTracks[alternatingIndex] insertTimeRange:timeRangeInAsset ofTrack:clipAudioTrack atTime:nextClipStartTime error:&error];
    
    alternatingIndex = 1;
    asset = [self.clips objectAtIndex:1];
    timeRangeInAsset = CMTimeRangeMake(kCMTimeZero, duration);
    clipVideoTrack = [[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];
    [compositionVideoTracks[alternatingIndex] insertTimeRange:timeRangeInAsset ofTrack:clipVideoTrack atTime:nextClipStartTime error:&error];
    clipAudioTrack = [[asset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0];
    [compositionAudioTracks[alternatingIndex] insertTimeRange:timeRangeInAsset ofTrack:clipAudioTrack atTime:nextClipStartTime error:&error];

    
	// Set up the video composition if we are to perform crossfade transitions between clips.
    alternatingIndex = 0;

	NSMutableArray *instructions = [NSMutableArray array];
    AVMutableVideoCompositionInstruction *transitionInstruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
    transitionInstruction.timeRange = CMTimeRangeMake(kCMTimeZero, duration);
    AVMutableVideoCompositionLayerInstruction *fromLayer = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:compositionVideoTracks[alternatingIndex]];
    AVMutableVideoCompositionLayerInstruction *toLayer = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:compositionVideoTracks[1-alternatingIndex]];
    // Fade in the toLayer by setting a ramp from 0.0 to 1.0.
    [fromLayer setOpacityRampFromStartOpacity:1.0 toEndOpacity:0.0 timeRange:CMTimeRangeMake(kCMTimeZero, duration)];
    [toLayer setOpacityRampFromStartOpacity:0.0 toEndOpacity:1.0 timeRange:CMTimeRangeMake(kCMTimeZero, duration)];
    
    transitionInstruction.layerInstructions = [NSArray arrayWithObjects:toLayer, fromLayer, nil];
    [instructions addObject:transitionInstruction];


    // Add X audio mix
    NSMutableArray *trackMixArray = [NSMutableArray array];

    AVMutableAudioMixInputParameters *audioMixInputParameters[2];
    audioMixInputParameters[0] = [AVMutableAudioMixInputParameters audioMixInputParametersWithTrack:compositionAudioTracks[0]];
    audioMixInputParameters[1] = [AVMutableAudioMixInputParameters audioMixInputParametersWithTrack:compositionAudioTracks[1]];
    
    AVMutableAudioMixInputParameters *trackMix1 = [AVMutableAudioMixInputParameters audioMixInputParametersWithTrack:compositionAudioTracks[0]];
    [trackMix1 setVolumeRampFromStartVolume:0.0 toEndVolume:1.0 timeRange:CMTimeRangeMake(kCMTimeZero, duration)];
    [trackMixArray addObject:trackMix1];
    
    AVMutableAudioMixInputParameters *trackMix2 = [AVMutableAudioMixInputParameters audioMixInputParametersWithTrack:compositionAudioTracks[1]];
    [trackMix2 setVolumeRampFromStartVolume:5.0 toEndVolume:5.0 timeRange:CMTimeRangeMake(kCMTimeZero, duration)];
    [trackMixArray addObject:trackMix2];

	audioMix.inputParameters = trackMixArray;
	videoComposition.instructions = instructions;
}