AVMutableVideoCompositionInstruction是在AVMutableVideoComposition

Question

當我創建使用this tutorial一個視頻，我嘗試移動AVAssetTrack* firstTrack使用AVMutableVideoCompositionInstruction爲包含一些CGAffineTransform個AVMutableVideoCompositionLayerInstruction（不包括動畫，所以我不能使用CAAnimation S），在變換一下就忽略忽略。

有誰知道這個問題，並知道如何解決它？

在此先感謝！

此信息可能有所幫助：在導出時，我使用AVAssetExportPreset1280x720作爲預設。所以我認爲（可能是錯誤的）this不是問題。

編輯：代碼被分割成各種函數，但我試圖把所有東西都合併到一個代碼中。我希望沒有忘記任何東西或弄亂了某些東西。

// The layer I want to move 
CALayer* layerToMove = nil; 
// A layer containing just the black background 
CALayer* backgroundLayer = nil; 
// The videos duration 
double duration = 12.0; 

AVMutableComposition *exportAsset = [[AVMutableComposition alloc] init]; 
[exportAsset setNaturalSize:layerToMove.frame.size]; 

AVMutableCompositionTrack* dstTrack = [self addBlackVideoTrackOfDuration:duration toComposition:exportAsset]; 

AVMutableVideoCompositionInstruction * MainInstruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction]; 

MainInstruction.timeRange = CMTimeRangeMake(kCMTimeZero, exportAsset.duration); 

CGAffineTransform Scale = CGAffineTransformMakeScale(0.1f,0.1f); 
CGAffineTransform Move = CGAffineTransformMakeTranslation(230,230); 
AVMutableVideoCompositionLayerInstruction *FirstlayerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:dstTrack]; 

[FirstlayerInstruction setTransform:CGAffineTransformConcat(Scale,Move) atTime:kCMTimeZero]; 
[MainInstruction setLayerInstructions:@[FirstlayerInstruction]]; 

CALayer* compositionLayer = [CALayer layer]; 

compositionLayer.bounds = layerToMove.frame; 
compositionLayer.anchorPoint = CGPointMake(0, 0); 
compositionLayer.position = CGPointMake(0, 0); 

[compositionLayer setFrame:layerToMove.frame]; 
[compositionLayer setBounds:layerToMove.frame]; 

[compositionLayer addSublayer:backgroundLayer]; 
[compositionLayer addSublayer:layerToMove]; 

AVVideoCompositionCoreAnimationTool *animationTool = [AVVideoCompositionCoreAnimationTool videoCompositionCoreAnimationToolWithPostProcessingAsVideoLayer:layerToMove inLayer:compositionLayer]; 

CMTime frameDuration = CMTimeMakeWithSeconds(1.0/25, 
              1000); 

AVMutableVideoComposition *videoComposition = [AVMutableVideoComposition videoComposition]; 
[videoComposition setFrameDuration:frameDuration]; 
[videoComposition setInstructions:@[MainInstruction]]; 
[videoComposition setAnimationTool:animationTool]; 
[videoComposition setRenderSize:layerToMove.frame.size]; 
[videoComposition setRenderScale:1.0]; 

AVAssetExportSession *exportSession = [AVAssetExportSession exportSessionWithAsset:exportAsset presetName:AVAssetExportPreset1280x720]; 

[exportSession setOutputFileType:AVFileTypeQuickTimeMovie]; 
[exportSession setOutputURL:nil/*Any url*/]; 
[exportSession setVideoComposition:videoComposition]; 
// The export is complete 
[exportSession exportAsynchronouslyWithCompletionHandler:^ 
{ 
    /*Whatever*/ 
}]; 

Answer 1

我發現，我能得到變換，每次工作的唯一方法是使用preferredTransform從AVAssetTrack對象爲出發點，然後CONCAT您所需的變換（S）與：

AVAsset *asset = [AVAsset assetWithURL:videoURL]; 
AVAssetTrack *track = [[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0]; 

[mutableCompositionVideoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero,asset.duration) ofTrack:track atTime:kCMTimeZero error:nil]; 
AVMutableVideoCompositionLayerInstruction* layerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:track]; 
AVMutableVideoCompositionInstruction *instruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction]; 

CGAffineTransform transform = track.preferredTransform; 

CGAffineTransform scale = CGAffineTransformMakeScale(0.1f,0.1f); 
transform = CGAffineTransformConcat(transform, scale); 
[layerInstruction setTransform:transform atTime:kCMTimeZero]; 

我有一些代碼重新定位在視頻中的圖像。這似乎對我有用。我將持續時間設置爲0.01，並立即生成動畫。模擬器中存在一個錯誤，使得它看起來好像動畫不起作用（有時）。如果你在設備上運行它，它將工作：

//animate from the start to end bounds 
CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:@"bounds"]; 
animation.fromValue = [NSValue valueWithCGRect:layerToMove.bounds]; 
animation.toValue = [NSValue valueWithCGRect:CGRectOffset(layerToMove.bounds, 100, 100)]; //change to the desired new position 
animation.duration = 0.01; 
animation.beginTime = 1e-100; 
animation.removedOnCompletion = NO; 
animation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear]; 

//animate from the start to end center points. 
CABasicAnimation *animation2 = [CABasicAnimation animationWithKeyPath:@"position"]; 
animation2.fromValue = [NSValue valueWithCGPoint:CGPointMake(CGRectGetMidX(layerToMove.bounds), CGRectGetMidY(layerToMove.bounds))]; 
animation2.toValue = [NSValue valueWithCGPoint:CGPointMake(CGRectGetMidX(layerToMove.bounds) + 50, CGRectGetMidY(layerToMove.bounds) + 50)]; 
animation2.duration = 0.01; 
animation2.beginTime = 1e-100; 
animation2.removedOnCompletion = NO; 
animation2.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear]; 

//Create an animation group 
CAAnimationGroup *group = [[CAAnimationGroup alloc] init]; 
group.duration = 0.01; 
group.beginTime = 2.0; 
group.removedOnCompletion = NO; 
group.fillMode = kCAFillModeForwards; //causes the values that were animated to remain at their end values 
group.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear]; 
group.animations = @[animation, animation2]; 

//Add the animation group to the layer 
[layerToMove addAnimation:group forKey:@"reposition"];