AVVideoComposition Failure

As in mine. To use it.

I am string several different video clips together into an AVMutableComposition and attempting to correct their orientation if n开发者_如何学编程eeded.

Here is my code:

composition = [[AVMutableComposition alloc] init];
AVMutableVideoComposition *videoComposition = [AVMutableVideoComposition videoComposition];

AVMutableCompositionTrack *compositionVideoTrack = [composition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
AVMutableCompositionTrack *compositionAudioTrack = [composition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];

CMTime nextClipStartTime = kCMTimeZero;

// orientation compensation vars
AVMutableVideoCompositionInstruction *inst = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
NSMutableArray *compInst = [[NSMutableArray alloc] init];

// get view size
CGSize viewSize = playerView.frame.size;

// generate movie assets
for (NSString* moviePath in [currentBlam valueForKey:@"movies"]) {
    NSURL *movieURL = [NSURL fileURLWithPath:moviePath];
    AVURLAsset *movieAsset = [AVURLAsset URLAssetWithURL:movieURL options:nil];  

    // scale asset to fit screen

    CMTimeRange tr = CMTimeRangeFromTimeToTime(CMTimeMakeWithSeconds(0.0f, 1), CMTimeMakeWithSeconds(0.0f, 1));

    //    create video track
    AVAssetTrack *clipVideoTrack = [[movieAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];
    //    create audio track
    AVAssetTrack *clipAudioTrack = [[movieAsset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0];

    tr = CMTimeRangeFromTimeToTime(CMTimeMakeWithSeconds(0.0f, 1), CMTimeMakeWithSeconds(CMTimeGetSeconds([movieAsset duration]), 1));

    AVMutableVideoCompositionLayerInstruction *layerInst;
    layerInst = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:clipVideoTrack];

    int or = [self orientationForTrack:movieAsset];
    if (or==1) { 
        float rot = (0.0f);
        [layerInst setTransform:CGAffineTransformMakeRotation(rot) atTime:nextClipStartTime];
    } else if (or==2) { 
        float rot = (M_PI);
        [layerInst setTransform:CGAffineTransformMakeRotation(rot) atTime:nextClipStartTime];
    } else if (or==3) { 
        float rot = (M_PI*-0.5f);
        [layerInst setTransform:CGAffineTransformMakeRotation(rot) atTime:nextClipStartTime];
    } else if (or==4) { 
        float rot = (M_PI*0.5f);
        [layerInst setTransform:CGAffineTransformMakeRotation(rot) atTime:nextClipStartTime];
    }

    [layerInst setTransform:clipVideoTrack.preferredTransform atTime:nextClipStartTime];
    [compInst addObject:layerInst];

    //    insert video track
    [compositionVideoTrack insertTimeRange:tr 
                                   ofTrack:clipVideoTrack 
                                    atTime:nextClipStartTime 
                                     error:nil];
    //    insert audio track
    [compositionAudioTrack insertTimeRange:tr 
                                   ofTrack:clipAudioTrack 
                                    atTime:nextClipStartTime 
                                     error:nil];

    nextClipStartTime = CMTimeAdd(nextClipStartTime, tr.duration);
}

//set size and duration
composition.naturalSize = viewSize;
videoComposition.frameDuration = composition.duration;
videoComposition.renderSize = viewSize;
videoComposition.renderScale = 1.0f;

//apply instructions
inst.timeRange = CMTimeRangeMake(kCMTimeZero, composition.duration);
inst.layerInstructions = compInst;
videoComposition.instructions = [NSArray arrayWithObject:inst];

playerItem = [[AVPlayerItem alloc] initWithAsset:composition];
playerItem.videoComposition = videoComposition;
[playerItem addObserver:self forKeyPath:@"status" options:0 context:&ItemStatusContext];
[[NSNotificationCenter defaultCenter] addObserver:self 
                                         selector:@selector(playerItemDidReachEnd:) 
                                             name:AVPlayerItemDidPlayToEndTimeNotification 
                                           object:playerItem];
player = [AVPlayer playerWithPlayerItem:playerItem];

[playerView setPlayer:player];

When I run this and populate with content nothing shows.

This was working previously without the AVVideoComposition being applied to the player. In fact, commenting out the playerItem.videoComposition = videoComposition allows it to work, albeit without correcting the assets rotations.

At this point I know I'm just misunderstanding something here. Can someone please point out what?

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Did you consider that maybe the point the video is being rotated about is not the center and the video is being drawn off screen? This may totally be wrong but its just my first thought.

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I think you are setting each single frame to be the length of the entire clip:

videoComposition.frameDuration = composition.duration;