在我的应用程序中，我将合成渲染尺寸固定为 1280 x 720。因此，如果要导入任何纵向视频，那么我必须在中心显示视频的填充和宽高比帧的模糊背景。同样是这样的:

https://www.youtube.com/watch?v=yCOrqUA0ws4

我使用 AVMtableComposition 播放了两个视频，但我不知道如何模糊特定的背景轨道。我在我的代码中做了以下操作:

self.composition = [AVMutableComposition composition];
AVAsset *firstAsset = [AVAsset assetWithURL:[NSURL fileURLWithPath:[[NSBundle mainBundle] pathForResource:@"ScreenFlow_Blend" ofType:@"mp4"]]];


[self addAsset:firstAsset toComposition:self.composition withTrackID:1];
[self addAsset:firstAsset toComposition:self.composition withTrackID:2];
//  [self addAsset:ThirdAsset toComposition:self.composition withTrackID:3];

AVAssetTrack *backVideoTrack = [firstAsset tracksWithMediaType:AVMediaTypeVideo][0];;

self.videoComposition = [AVMutableVideoComposition videoComposition];
self.videoComposition.renderSize = CGSizeMake(1280, 720);
self.videoComposition.frameDuration = CMTimeMake(1, 30);

AVMutableVideoCompositionInstruction *instruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
instruction.timeRange = [backVideoTrack timeRange];

CGFloat scale = 1280/backVideoTrack.naturalSize.width;
CGAffineTransform t = CGAffineTransformMakeScale(scale, scale);
t = CGAffineTransformTranslate(t, 0, -backVideoTrack.naturalSize.height/2 + self.videoComposition.renderSize.height/2);

AVMutableVideoCompositionLayerInstruction *frontLayerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstruction];
frontLayerInstruction.trackID = 1;
[frontLayerInstruction setTransform:t atTime:kCMTimeZero];

CGFloat scaleSmall = 720/backVideoTrack.naturalSize.height;

CGAffineTransform  translate = CGAffineTransformMakeTranslation(self.videoComposition.renderSize.width/2 - ((backVideoTrack.naturalSize.width/2)*scaleSmall),0);

CGAffineTransform  scaleTransform = CGAffineTransformMakeScale(scaleSmall,scaleSmall);

CGAffineTransform finalTransform = CGAffineTransformConcat(scaleTransform, translate);


CGAffineTransform t1 = CGAffineTransformMakeScale(scaleSmall,scaleSmall);
t1 = CGAffineTransformTranslate(t1,1280, 0);

AVMutableVideoCompositionLayerInstruction *backLayerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstruction];
backLayerInstruction.trackID = 2;
[backLayerInstruction setTransform:finalTransform atTime:kCMTimeZero];


//    AVMutableVideoCompositionLayerInstruction *maskLayerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstruction];
//    maskLayerInstruction.trackID = 3;
//    [maskLayerInstruction setTransform:t atTime:kCMTimeZero];


instruction.layerInstructions = @[backLayerInstruction,frontLayerInstruction];

self.videoComposition.instructions = @[ instruction ];

AVPlayerItem *playerItem = [AVPlayerItem playerItemWithAsset:self.composition];
playerItem.videoComposition = self.videoComposition;
self.player = [AVPlayer playerWithPlayerItem:playerItem];

AVPlayerLayer *newPlayerLayer = [AVPlayerLayer playerLayerWithPlayer:[self player]];
[newPlayerLayer setFrame:[[[self playerView] layer] bounds]];
// [newPlayerLayer setHidden:YES];

[[[self playerView] layer] addSublayer:newPlayerLayer];
[self setPlayerLayer:newPlayerLayer];

使用上面的代码我可以实现这个:

https://drive.google.com/open?id=0B2jCvCt5fosyOVNOcGZ1MU1laEU

我知道 customVideoCompositor 类可以过滤合成帧。我试过了，但如果我使用 customVideoCompositor，那么我将失去对合成层的转换。另外，从 customVideoCompositor 我不知道如何过滤特定的轨道 ID。

如果有人有任何文档链接或建议，那么我们将不胜感激。

最佳答案

在添加位于屏幕中央的第二个视频层之前，添加此代码

UIVisualEffect *blurEffect;
blurEffect = [UIBlurEffect effectWithStyle:UIBlurEffectStyleExtraLight];//Change the effect which you want.

UIVisualEffectView *visualEffectView;
visualEffectView = [[UIVisualEffectView alloc] initWithEffect:blurEffect];

visualEffectView.frame = self.view.bounds;
[self.view addSubview:visualEffectView];

在 swift

    let blurEffect = UIBlurEffect(style: UIBlurEffectStyle.Light) //Change the style which suites you
    let blurEffectView = UIVisualEffectView(effect: blurEffect)
    blurEffectView.frame = view.bounds
    blurEffectView.autoresizingMask = [.FlexibleWidth, .FlexibleHeight] // for supporting device rotation
    view.addSubview(blurEffectView)

关于ios - AVfoundation 模糊视频中的背景，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/39313688/