Video rotated after applying AVVideoComposition

问题:

After applying an AVVideoComposition to my AVPlayerItem, the filter I apply does work, but the video gets rotated in the AVPlayerLayer.

I know for a fact that the problem is not with the filtered frame because if I show the frame in a UIImageView, the frame is rendered 100% correctly.

The video shows correctly until I apply a videoComposition. Setting the videoGravity on the AVPlayerLayer does not help.

The video gets rotated 90º clockwise and gets stretched in the layer.

Essentially, the video is displayed perfectly in the AVPlayerLayer before the AVPlayerItem is fed through the AVMutableVideoComposition. Once that happens, the video is rotated -90º, and then scaled to fit the same dimensions as the video before filtering. This suggests to me that it does not realize that its transform is already correct, and so it is reapplying the transform on itself.

Why is this happening, and how can I fix it?

Here is some code:

private func filterVideo(with filter: Filter?) {
    if let player = player, let playerItem = player.currentItem {
        let composition = AVMutableComposition()
        let videoAssetTrack = playerItem.asset.tracks(withMediaType: .video).first
        let videoCompositionTrack = composition.addMutableTrack(withMediaType: .video, preferredTrackID: kCMPersistentTrackID_Invalid)
        try? videoCompositionTrack?.insertTimeRange(CMTimeRange(start: kCMTimeZero, duration: playerItem.asset.duration), of: videoAssetTrack!, at: kCMTimeZero)
        videoCompositionTrack?.preferredTransform = videoAssetTrack!.preferredTransform

        let videoComposition = AVMutableVideoComposition(asset: composition, applyingCIFiltersWithHandler: { (request) in
            let filteredImage = <...>
            request.finish(with: filteredImage, context: nil)
        })

        playerItem.videoComposition = videoComposition
    }
}

回答1:

You have problem in the renderingSize of AVVideoComposition you should apply transform on AVMutableVideoCompositionInstruction (ie. Rotate and translate transform ) .

i have done in Objective-c i am posting my code you can convert the syntax into Swift

Objective-c

        //------------------------------------
        //      FIXING ORIENTATION
        //------------------------------------


        AVMutableVideoCompositionInstruction * MainInstruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
        MainInstruction.timeRange = CMTimeRangeMake(kCMTimeZero, CMTimeAdd(firstAsset.duration, secondAsset.duration));

        AVMutableVideoCompositionLayerInstruction *FirstlayerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:secondTrack]; // second

        AVAssetTrack *FirstAssetTrack = [[firstAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];
        UIImageOrientation FirstAssetOrientation_  = UIImageOrientationUp;
        BOOL  isFirstAssetPortrait_  = NO;
        CGAffineTransform firstTransform = FirstAssetTrack.preferredTransform;
        if(firstTransform.a == 0 && firstTransform.b == 1.0 && firstTransform.c == -1.0 && firstTransform.d == 0)  {FirstAssetOrientation_= UIImageOrientationRight; isFirstAssetPortrait_ = YES;}
        if(firstTransform.a == 0 && firstTransform.b == -1.0 && firstTransform.c == 1.0 && firstTransform.d == 0)  {FirstAssetOrientation_ =  UIImageOrientationLeft; isFirstAssetPortrait_ = YES;}
        if(firstTransform.a == 1.0 && firstTransform.b == 0 && firstTransform.c == 0 && firstTransform.d == 1.0)   {FirstAssetOrientation_ =  UIImageOrientationUp;}
        if(firstTransform.a == -1.0 && firstTransform.b == 0 && firstTransform.c == 0 && firstTransform.d == -1.0) {FirstAssetOrientation_ = UIImageOrientationDown;}
        CGFloat FirstAssetScaleToFitRatio = 320.0/FirstAssetTrack.naturalSize.width;
        if(isFirstAssetPortrait_){
            FirstAssetScaleToFitRatio = 320.0/FirstAssetTrack.naturalSize.height;
            CGAffineTransform FirstAssetScaleFactor = CGAffineTransformMakeScale(FirstAssetScaleToFitRatio,FirstAssetScaleToFitRatio);
            [FirstlayerInstruction setTransform:CGAffineTransformConcat(FirstAssetTrack.preferredTransform, FirstAssetScaleFactor) atTime:kCMTimeZero];
        }else{
            CGAffineTransform FirstAssetScaleFactor = CGAffineTransformMakeScale(FirstAssetScaleToFitRatio,FirstAssetScaleToFitRatio);
            [FirstlayerInstruction setTransform:CGAffineTransformConcat(CGAffineTransformConcat(FirstAssetTrack.preferredTransform, FirstAssetScaleFactor),CGAffineTransformMakeTranslation(0, 160)) atTime:kCMTimeZero];
        }
        [FirstlayerInstruction setOpacity:0.0 atTime:firstAsset.duration];



        AVMutableVideoCompositionLayerInstruction *SecondlayerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:firstTrack];
        AVAssetTrack *SecondAssetTrack = [[secondAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];
        UIImageOrientation SecondAssetOrientation_  = UIImageOrientationUp;
        BOOL  isSecondAssetPortrait_  = NO;
        CGAffineTransform secondTransform = SecondAssetTrack.preferredTransform;
        if(secondTransform.a == 0 && secondTransform.b == 1.0 && secondTransform.c == -1.0 && secondTransform.d == 0)  {SecondAssetOrientation_= UIImageOrientationRight; isSecondAssetPortrait_ = YES;}
        if(secondTransform.a == 0 && secondTransform.b == -1.0 && secondTransform.c == 1.0 && secondTransform.d == 0)  {SecondAssetOrientation_ =  UIImageOrientationLeft; isSecondAssetPortrait_ = YES;}
        if(secondTransform.a == 1.0 && secondTransform.b == 0 && secondTransform.c == 0 && secondTransform.d == 1.0)   {SecondAssetOrientation_ =  UIImageOrientationUp;}
        if(secondTransform.a == -1.0 && secondTransform.b == 0 && secondTransform.c == 0 && secondTransform.d == -1.0) {SecondAssetOrientation_ = UIImageOrientationDown;}
        CGFloat SecondAssetScaleToFitRatio = 320.0/SecondAssetTrack.naturalSize.width;
        if(isSecondAssetPortrait_){
            SecondAssetScaleToFitRatio = 320.0/SecondAssetTrack.naturalSize.height;
            CGAffineTransform SecondAssetScaleFactor = CGAffineTransformMakeScale(SecondAssetScaleToFitRatio,SecondAssetScaleToFitRatio);
            [SecondlayerInstruction setTransform:CGAffineTransformConcat(SecondAssetTrack.preferredTransform, SecondAssetScaleFactor) atTime:firstAsset.duration];
        }else{
            ;
            CGAffineTransform SecondAssetScaleFactor = CGAffineTransformMakeScale(SecondAssetScaleToFitRatio,SecondAssetScaleToFitRatio);
            [SecondlayerInstruction setTransform:CGAffineTransformConcat(CGAffineTransformConcat(SecondAssetTrack.preferredTransform, SecondAssetScaleFactor),CGAffineTransformMakeTranslation(0, 160)) atTime:secondAsset.duration];
        }


        MainInstruction.layerInstructions = [NSArray arrayWithObjects:SecondlayerInstruction,nil];;

        AVMutableVideoComposition *MainCompositionInst = [AVMutableVideoComposition videoComposition];
        MainCompositionInst.instructions = [NSArray arrayWithObject:MainInstruction];
        MainCompositionInst.frameDuration = CMTimeMake(1, 30);
        MainCompositionInst.renderSize = CGSizeMake(320.0, 480.0);


   // Now , you have Orientation Fixed Instrucation layer 
   // add this composition to your video