纵向模式下的 AVVideoCompositionCoreAnimationTool 和 CALayer？

我正在尝试使用 iOS 4.3 上的 AVMutableComposition、AVMutableVideoComposition 和 AVVideoCompositionCoreAnimationTool 将 CALayer 烘焙为纵向模式视频（导出时）。这一切都适用于风景。但是，如果我以纵向方式捕获视频，AVVideoCompositionCoreAnimationTool 将忽略视频轨道上的转换。也就是说，对于纵向模式视频，我将 AVMutableCompositionTrack.preferredTransform 设置为原始资源视频轨道中的 PreferredTransform 值。只要我不使用 AVVideoCompositionCoreAnimationTool，它就可以工作，并且视频会以纵向模式显示。然而，一旦我添加 AVVideoCompositionCoreAnimationTool 和 CALayer，该文件就会以横向方式显示。 （CALayer 显示正确，但其后面的视频在其一侧，并且文件的宽高比关闭）。我尝试将变换应用于 CALayer，并在 ACVideoComposition 中设置变换。这些都不会改变生成的文件的方向（它仍然是 480x369，而不是 360x480）。有没有办法使用 AVVideoCompositionCoreAnimationTool 渲染纵向模式视频？

首先我设置了 AVMutableComposition 和 AVMutableVideoComposition

AVMutableComposition *composition = [AVMutableComposition composition];
AVMutableCompositionTrack *compositionVideoTrack = [composition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
AVURLAsset *videoAsset = [AVURLAsset URLAssetWithURL:url options:nil];
CMTimeRange timeRange = CMTimeRangeMake(kCMTimeZero, [videoAsset duration]);
AVAssetTrack *clipVideoTrack = [[videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];

CGSize videoSize = CGSizeApplyAffineTransform(clipVideoTrack.naturalSize, clipVideoTrack.preferredTransform);
videoSize.width = fabs(videoSize.width);
videoSize.height = fabs(videoSize.height);

CMTime titleDuration = CMTimeMakeWithSeconds(5, 600);
CMTimeRange titleRange = CMTimeRangeMake(kCMTimeZero, titleDuration);

[compositionVideoTrack insertTimeRange:titleRange ofTrack:nil atTime:kCMTimeZero error:nil];
[compositionVideoTrack insertTimeRange:timeRange ofTrack:clipVideoTrack atTime:titleDuration error:nil];
compositionVideoTrack.preferredTransform = clipVideoTrack.preferredTransform;

AVMutableVideoComposition *videoComposition = [AVMutableVideoComposition videoComposition];
AVMutableVideoCompositionInstruction *passThroughInstruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
passThroughInstruction.timeRange = CMTimeRangeMake(kCMTimeZero, [composition duration]);
AVAssetTrack *videoTrack = [[composition tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];
AVMutableVideoCompositionLayerInstruction *passThroughLayer = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:videoTrack];    
passThroughInstruction.layerInstructions = [NSArray arrayWithObject:passThroughLayer];
videoComposition.instructions = [NSArray arrayWithObject:passThroughInstruction];       
videoComposition.frameDuration = CMTimeMake(1, 30); 
videoComposition.renderSize = videoSize;
videoComposition.renderScale = 1.0;

和一个带有标题的 CALayer

CALayer *animationLayer = [CALayer layer];
animationLayer.bounds = CGRectMake(0, 0, videoSize.width, videoSize.height);

CATextLayer *titleLayer = [CATextLayer layer];
titleLayer.string = [effect valueForKey:@"title"];
titleLayer.font = [effect valueForKey:@"font"];
titleLayer.fontSize = 30;

titleLayer.alignmentMode = kCAAlignmentCenter;
titleLayer.bounds = CGRectMake(0, 0, videoSize.width, videoSize.height / 6);

[animationLayer addSublayer:titleLayer];
titleLayer.anchorPoint =  CGPointMake(0.5, 0.5);
titleLayer.position = CGPointMake(CGRectGetMidX(layer.bounds), CGRectGetMidY(layer.bounds));    

CABasicAnimation *fadeAnimation = [CABasicAnimation animationWithKeyPath:@"opacity"];
fadeAnimation.fromValue = [NSNumber numberWithFloat:1.0];
fadeAnimation.toValue = [NSNumber numberWithFloat:0.0];
fadeAnimation.additive = NO;
fadeAnimation.removedOnCompletion = NO;
fadeAnimation.beginTime = 3.5;
fadeAnimation.duration = 1.0;
fadeAnimation.fillMode = kCAFillModeBoth;
[titleLayer addAnimation:fadeAnimation forKey:nil];

最后我将 CALayer 添加到 AVMutableVideoComposition

CALayer *parentLayer = [CALayer layer];
CALayer *videoLayer = [CALayer layer];

parentLayer.bounds = CGRectMake(0, 0, videoSize.width, videoSize.height);
parentLayer.anchorPoint =  CGPointMake(0, 0);
parentLayer.position = CGPointMake(0, 0);

videoLayer.bounds = CGRectMake(0, 0, videoSize.width, videoSize.height);
[parentLayer addSublayer:videoLayer];
videoLayer.anchorPoint =  CGPointMake(0.5, 0.5);
videoLayer.position = CGPointMake(CGRectGetMidX(parentLayer.bounds), CGRectGetMidY(parentLayer.bounds));
[parentLayer addSublayer:layer];    
animationLayer.anchorPoint =  CGPointMake(0.5, 0.5);
animationLayer.position = CGPointMake(CGRectGetMidX(parentLayer.bounds), CGRectGetMidY(parentLayer.bounds));
videoComposition.animationTool = [AVVideoCompositionCoreAnimationTool videoCompositionCoreAnimationToolWithPostProcessingAsVideoLayer:videoLayer inLayer:parentLayer];

并出口！

AVAssetExportSession *exportSession = [[[AVAssetExportSession alloc] initWithAsset:composition presetName:AVAssetExportPresetMediumQuality] autorelease];
exportSession.videoComposition = videoComposition; 

NSURL *segmentFileURL = //some local URL
exportSession.outputFileType = @"com.apple.quicktime-movie";
exportSession.outputURL = segmentFileURL;


[exportSession exportAsynchronouslyWithCompletionHandler:^{
    switch ([exportSession status]) {
        case AVAssetExportSessionStatusFailed:
            Log(@"Export failed: %@", [exportSession error]);
            break;
        case AVAssetExportSessionStatusCancelled:
            Log(@"Export canceled");
            break;
        case AVAssetExportSessionStatusCompleted:
            Log(@"Export done");
            break;
    }
}]; 

该代码适用于横向模式，如果我删除该行，也适用于纵向模式videoComposition.animationTool = [AVVideoCompositionCoreAnimationTool videoCompositionCoreAnimationToolWithPostProcessingAsVideoLayer:videoLayer inLayer:parentLayer];

尝试这个并添加您的其他说明。

///turn video 90 degrees
AVMutableVideoCompositionLayerInstruction *passThroughLayer = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:clipVideoTrack];
CGAffineTransform rotationTransform = CGAffineTransformMakeRotation(degreesToRadians(90.0));
CGAffineTransform rotateTranslate = CGAffineTransformTranslate(rotationTransform,320,0);
[passThroughLayer setTransform:rotateTranslate atTime:kCMTimeZero];

让我知道事情的后续！

MacMike