AVFoundation没有在我的视频中添加覆盖。我不确定我做错了什么。我试着把覆盖层做成完全白色，但它没有被放在视频上。播放视频时，它必须播放AVMutableComposition Track，而不是我添加的exporter.videoComposition。我在AVFoundation的经验不足，不知道出了什么问题。
AVMutableComposition *mixComposition = [[AVMutableComposition alloc] init];
// 3 - Video track
AVMutableCompositionTrack *videoTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo
preferredTrackID:kCMPersistentTrackID_Invalid];
// [videoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero,self.videoAsset.duration)
// ofTrack:[[self.videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0]
// atTime:kCMTimeZero error:nil];
CMTime insertTime = kCMTimeZero;
for(AVURLAsset *videoAsset in self.videoArray){
[videoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, videoAsset.duration) ofTrack:[[videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] atTime:insertTime error:nil];
// Updating the insertTime for the next insert
insertTime = CMTimeAdd(insertTime, videoAsset.duration);
}
// 3.1 - Create AVMutableVideoCompositionInstruction
AVMutableVideoCompositionInstruction *mainInstruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
mainInstruction.timeRange = videoTrack.timeRange;
// 3.2 - Create an AVMutableVideoCompositionLayerInstruction for the video track and fix the orientation.
AVMutableVideoCompositionLayerInstruction *videolayerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:videoTrack];
AVAssetTrack *videoAssetTrack = [[videoTrack.asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];
UIImageOrientation videoAssetOrientation_ = UIImageOrientationUp;
BOOL isVideoAssetPortrait_ = NO;
CGAffineTransform videoTransform = videoAssetTrack.preferredTransform;
if (videoTransform.a == 0 && videoTransform.b == 1.0 && videoTransform.c == -1.0 && videoTransform.d == 0) {
videoAssetOrientation_ = UIImageOrientationRight;
isVideoAssetPortrait_ = YES;
}
if (videoTransform.a == 0 && videoTransform.b == -1.0 && videoTransform.c == 1.0 && videoTransform.d == 0) {
videoAssetOrientation_ = UIImageOrientationLeft;
isVideoAssetPortrait_ = YES;
}
if (videoTransform.a == 1.0 && videoTransform.b == 0 && videoTransform.c == 0 && videoTransform.d == 1.0) {
videoAssetOrientation_ = UIImageOrientationUp;
}
if (videoTransform.a == -1.0 && videoTransform.b == 0 && videoTransform.c == 0 && videoTransform.d == -1.0) {
videoAssetOrientation_ = UIImageOrientationDown;
}
[videolayerInstruction setTransform:videoAssetTrack.preferredTransform atTime:kCMTimeZero];
[videolayerInstruction setOpacity:0.0 atTime:videoTrack.timeRange.duration];
// 3.3 - Add instructions
mainInstruction.layerInstructions = [NSArray arrayWithObjects:videolayerInstruction,nil];
AVMutableVideoComposition *mainCompositionInst = [AVMutableVideoComposition videoComposition];
CGSize naturalSize;
if(isVideoAssetPortrait_){
naturalSize = CGSizeMake(videoAssetTrack.naturalSize.height, videoAssetTrack.naturalSize.width);
} else {
naturalSize = videoAssetTrack.naturalSize;
}
float renderWidth, renderHeight;
renderWidth = naturalSize.width;
renderHeight = naturalSize.height;
mainCompositionInst.renderSize = CGSizeMake(renderWidth, renderHeight);
mainCompositionInst.instructions = [NSArray arrayWithObject:mainInstruction];
mainCompositionInst.frameDuration = CMTimeMake(1, 30);
// [self applyVideoEffectsToComposition:mainCompositionInst size:naturalSize];
// 1 - set up the overlay
CALayer *overlayLayer = [CALayer layer];
UIImage *overlayImage = nil;
//overlayLayer.backgroundColor = [UIColor whiteColor].CGColor;
overlayImage = [UIImage imageNamed:@"overlayImage.png"];
[overlayLayer setContents:(id)[overlayImage CGImage]];
overlayLayer.frame = CGRectMake(0, 0, videoTrack.naturalSize.width, videoTrack.naturalSize.height);
[overlayLayer setMasksToBounds:YES];
// 2 - set up the parent layer
CALayer *parentLayer = [CALayer layer];
CALayer *videoLayer = [CALayer layer];
parentLayer.frame = CGRectMake(0, 0, videoTrack.naturalSize.width, videoTrack.naturalSize.height);
videoLayer.frame = CGRectMake(0, 0, videoTrack.naturalSize.width, videoTrack.naturalSize.height);
[parentLayer addSublayer:videoLayer];
[parentLayer addSublayer:overlayLayer];
// 3 - apply magic
mainCompositionInst.animationTool = [AVVideoCompositionCoreAnimationTool
videoCompositionCoreAnimationToolWithPostProcessingAsVideoLayer:videoLayer inLayer:parentLayer];
// 4 - Get path
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *myPathDocs = [documentsDirectory stringByAppendingPathComponent:
[NSString stringWithFormat:@"FinalVideo-%d.mov",arc4random() % 1000]];
NSURL *url = [NSURL fileURLWithPath:myPathDocs];
// 5 - Create exporter
AVAssetExportSession *exporter = [[AVAssetExportSession alloc] initWithAsset:mixComposition
presetName:AVAssetExportPresetHighestQuality];
exporter.outputURL=url;
exporter.outputFileType = AVFileTypeQuickTimeMovie;
exporter.shouldOptimizeForNetworkUse = YES;
exporter.videoComposition = mainCompositionInst;
[exporter exportAsynchronouslyWithCompletionHandler:^{
dispatch_async(dispatch_get_main_queue(), ^{
//[self exportDidFinish:exporter];
//do stuff
});
}];
我不是Objective-C方面的专家。我目前正在做一个iOS项目（Swift 3），该项目需要将文本覆盖到特定时间范围的视频上。下面的代码在我的项目中非常有效。你可以试试。你的视频保存在documents目录中。所以导出时必须删除临时视频文件。下面的代码，我正在导出视频到我的照片库。因此，您需要导入照片框架。
let composition = AVMutableComposition()
let asset = AVURLAsset(url: urlVideo!, options: nil)
let track = asset.tracks(withMediaType: AVMediaTypeVideo)
let videoTrack:AVAssetTrack = track[0] as AVAssetTrack
let timerange = CMTimeRangeMake(kCMTimeZero, asset.duration)
let compositionVideoTrack:AVMutableCompositionTrack = composition.addMutableTrack(withMediaType: AVMediaTypeVideo, preferredTrackID: CMPersistentTrackID())
do {
try compositionVideoTrack.insertTimeRange(timerange, of: videoTrack, at: kCMTimeZero)
compositionVideoTrack.preferredTransform = videoTrack.preferredTransform
} catch {
print(error)
}
let compositionAudioTrack:AVMutableCompositionTrack = composition.addMutableTrack(withMediaType: AVMediaTypeAudio, preferredTrackID: CMPersistentTrackID())
for audioTrack in asset.tracks(withMediaType: AVMediaTypeAudio) {
do {
try compositionAudioTrack.insertTimeRange(audioTrack.timeRange, of: audioTrack, at: kCMTimeZero)
} catch {
print(error)
}
}
let size = videoTrack.naturalSize
//print("Size of vieo: (size)")
let textLayer = CATextLayer()
textLayer.string = "Text Overlay Test"
textLayer.fontSize = 35
textLayer.font = "Baskerville-BoldItalic" as CFTypeRef
textLayer.foregroundColor = UIColor.red.cgColor
textLayer.opacity = 0
textLayer.alignmentMode = kCAAlignmentCenter
textLayer.frame = CGRect(x: 0, y: 100, width: size.width, height: size.height / 6)
// making a time range to show text
let fadeInAnimation = CABasicAnimation(keyPath: "opacity")
fadeInAnimation.duration = 10
fadeInAnimation.fromValue = Int(1.0)
fadeInAnimation.toValue = Int(1.0)
fadeInAnimation.beginTime = 3
fadeInAnimation.isRemovedOnCompletion = false
textLayer.add(fadeInAnimation, forKey: "opacity")
// video layer making
let videolayer = CALayer()
videolayer.frame = CGRect(x: 0, y: 0, width: size.width, height: size.height)
let parentlayer = CALayer()
parentlayer.frame = CGRect(x: 0, y: 0, width: size.width, height: size.height)
parentlayer.addSublayer(videolayer)
parentlayer.addSublayer(textLayer)
// adding the magic
let layercomposition = AVMutableVideoComposition()
layercomposition.frameDuration = CMTimeMake(1, 30)
layercomposition.renderSize = size
layercomposition.animationTool = AVVideoCompositionCoreAnimationTool(postProcessingAsVideoLayer: videolayer, in: parentlayer)
let instruction = AVMutableVideoCompositionInstruction()
instruction.timeRange = CMTimeRangeMake(kCMTimeZero, composition.duration)
let videotrack = composition.tracks(withMediaType: AVMediaTypeVideo)[0] as AVAssetTrack
let layerinstruction = AVMutableVideoCompositionLayerInstruction(assetTrack: videotrack)
instruction.layerInstructions = [layerinstruction]
layercomposition.instructions = [instruction]
// create new file to receive data
let mergedVideoURL = NSURL(fileURLWithPath: NSHomeDirectory() + "/Documents/mergedVideo.mp4")
// must delete existing temporary file from file directory, also use try catch
do {
try FileManager.default.removeItem(at: mergedVideoURL as URL)
print("Tyr Excepted")
} catch _ as NSError {
print("Error")
}
// use AVAssetExportSession to export video
guard let assetExport = AVAssetExportSession(asset: composition, presetName:AVAssetExportPresetMediumQuality) else {return}
assetExport.videoComposition = layercomposition
assetExport.outputFileType = AVFileTypeMPEG4
assetExport.outputURL = mergedVideoURL as URL
assetExport.exportAsynchronously(completionHandler: {
switch assetExport.status{
case AVAssetExportSessionStatus.failed:
print("failed")
case AVAssetExportSessionStatus.cancelled:
print("cancelled")
default:
print("Exported")
PHPhotoLibrary.shared().performChanges({
PHAssetChangeRequest.creationRequestForAssetFromVideo(atFileURL: mergedVideoURL as URL)
}) { saved, error in
if saved {
let alertController = UIAlertController(title: "Your video was successfully saved", message: nil, preferredStyle: .alert)
let defaultAction = UIAlertAction(title: "OK", style: .default, handler: nil)
alertController.addAction(defaultAction)
self.present(alertController, animated: true, completion: nil)
}
}
}
})