我一直在努力为视频添加文字字幕。我添加了一些我详细介绍的链接，但它们没有帮助。
在下面的代码中，我正在尝试为视频添加字幕。输出文件路径如下：
file:///var/mobile/Applications/03E49B29-1070-4541-B7CB-B1366732C179/Documents/output_movie.mov
此外，输入文件是在同一个应用程序中通过调用UIPickerView记录的，位于以下临时路径：
file:///private/var/mobile/Applications/03E49B29-1070-4541-B7CB-B1366732C179/tmp/capture/capturedvideo.MOV
我得到的错误如下，
Error:-
Domain=AVFoundationErrorDomain Code=-11841 "Operation Stopped" UserInfo=0x15ebcfb0 {NSLocalizedDescription=Operation Stopped, NSLocalizedFailureReason=The video could not be composed.}
Description:-
<AVAssetExportSession: 0x15d97c80, asset = <AVMutableComposition: 0x15d788d0 tracks = ("<AVMutableCompositionTrack: 0x15d86910 trackID = 1, mediaType = vide, editCount = 1>")>, presetName = AVAssetExportPresetHighestQuality, outputFileType = com.apple.quicktime-movie
Completed merging the video with status code 4
我使用的代码如下。我在iPhone 4s上的iOS 7.1.2上运行它。
class func mergeVideoWithTheme(outputUrl: NSURL, inputVideoUrl videoUrl: NSURL!, onComplete completionHandler: ((Int) -> ())!) -> Void {
// 1. mergeComposition adds all the AVAssets
var mergeComposition : AVMutableComposition = AVMutableComposition()
var trackVideo : AVMutableCompositionTrack = mergeComposition.addMutableTrackWithMediaType(AVMediaTypeVideo, preferredTrackID: CMPersistentTrackID())
//var trackAudio : AVMutableCompositionTrack = mergeComposition.addMutableTrackWithMediaType(AVMediaTypeAudio, preferredTrackID: CMPersistentTrackID())
// 2. Add a bank for theme insertion later
//trackVideo.insertTimeRange(range, ofTrack: VideoHelper.Static.blankTrack, atTime: kCMTimeZero, error: nil)
// 3. Source tracks
let sourceAsset = AVURLAsset(URL: videoUrl, options: nil)
let sourceDuration = CMTimeRangeMake(kCMTimeZero, sourceAsset.duration)
let vtrack: AVAssetTrack? = sourceAsset.tracksWithMediaType(AVMediaTypeVideo)[0] as? AVAssetTrack
let atrack: AVAssetTrack? = sourceAsset.tracksWithMediaType(AVMediaTypeAudio)[0] as? AVAssetTrack
if (vtrack == nil) {
return
}
let renderWidth = vtrack?.naturalSize.width
let renderHeight = vtrack?.naturalSize.height
let insertTime = kCMTimeZero
let endTime = sourceAsset.duration
let range = sourceDuration
// append tracks
trackVideo.insertTimeRange(sourceDuration, ofTrack: vtrack, atTime: insertTime, error: nil)
//if(atrack > 0){
// trackAudio.insertTimeRange(sourceDuration, ofTrack: atracks[0] as AVAssetTrack, atTime: insertTime, error: nil)
//}
// 4. Add subtitles (we call it theme)
var themeVideoComposition : AVMutableVideoComposition = AVMutableVideoComposition(propertiesOfAsset: sourceAsset)
// 4.1 - Create AVMutableVideoCompositionInstruction
let mainInstruction: AVMutableVideoCompositionInstruction = AVMutableVideoCompositionInstruction()
mainInstruction.timeRange = range
// 4.2 - Create an AVMutableVideoCompositionLayerInstruction for the video track and fix the orientation.
let videolayerInstruction : AVMutableVideoCompositionLayerInstruction = AVMutableVideoCompositionLayerInstruction()
videolayerInstruction.setTransform(trackVideo.preferredTransform, atTime: insertTime)
videolayerInstruction.setOpacity(0.0, atTime: endTime)
// 4.3 - Add instructions
mainInstruction.layerInstructions = NSArray(array: [videolayerInstruction])
themeVideoComposition.renderScale = 1.0
themeVideoComposition.renderSize = CGSizeMake(renderWidth!, renderHeight!)
themeVideoComposition.frameDuration = CMTimeMake(1, 30)
themeVideoComposition.instructions = NSArray(array: [mainInstruction])
// add the theme
// setup variables
// add text
let title = String("Testing this subtitle")
var titleLayer = CATextLayer()
titleLayer.string = title
titleLayer.frame = CGRect(x: 0, y: 0, width: renderWidth!, height: renderHeight!)
let fontName: CFStringRef = "Helvetica-Bold"
let fontSize = CGFloat(36)
titleLayer.font = CTFontCreateWithName(fontName, fontSize, nil)
titleLayer.alignmentMode = kCAAlignmentCenter
titleLayer.foregroundColor = UIColor.whiteColor().CGColor
var backgroundLayer = CALayer()
backgroundLayer.frame = CGRect(x: 0, y: 0, width: renderWidth!, height: renderHeight!)
backgroundLayer.masksToBounds = true
backgroundLayer.addSublayer(titleLayer)
// 2. set parent layer and video layer
var parentLayer = CALayer()
var videoLayer = CALayer()
parentLayer.frame = CGRect(x: 0, y: 0, width: renderWidth!, height: renderHeight!)
videoLayer.frame = CGRect(x: 0, y: 0, width: renderWidth!, height: renderHeight!)
parentLayer.addSublayer(backgroundLayer)
parentLayer.addSublayer(videoLayer)
// 3. make animation
themeVideoComposition.animationTool = AVVideoCompositionCoreAnimationTool(postProcessingAsVideoLayer: videoLayer, inLayer: parentLayer)
// Remove the file if it already exists (merger does not overwrite)
let fileManager = NSFileManager.defaultManager()
fileManager.removeItemAtURL(outputUrl, error: nil)
// export to output url
var exporter = AVAssetExportSession(asset: mergeComposition, presetName: AVAssetExportPresetHighestQuality)
exporter.outputURL = outputUrl
exporter.videoComposition = themeVideoComposition
exporter.outputFileType = AVFileTypeQuickTimeMovie
exporter.shouldOptimizeForNetworkUse = true
exporter.exportAsynchronouslyWithCompletionHandler({
if (exporter.error != nil) {
println("Error")
println(exporter.error)
println("Description")
println(exporter.description)
}
completionHandler(exporter.status.rawValue)
})
}
非常感谢你的帮助。我没有找到任何向视频添加动画的快速示例。想知道它对swift的人是否有用。
参考文献：（1）https://gist.github.com/SheffieldKevin/c01789ccff2b2a87f5ea（2）http://www.raywenderlich.com/30200/avfoundation-tutorial-adding-overlays-and-animations-to-videos
答案 0 :(得分：1)
创建图层指令时无法插入trackID。试试：
Signal (Signal something)答案 1 :(得分：0)
When I tried this the subtitle did not appear. I fixed it by swapping the order of the sublayers.
i.e
parentLayer.addSublayer(videoLayer)
parentLayer.addSubLayer(backgroundLayer)
答案 2 :(得分：0)
我更新了它以使用Swift 3 +添加Deepak建议的修复程序。
func mergeVideoWithTheme(outputUrl: NSURL, inputVideoUrl videoUrl: NSURL!, onComplete completionHandler: ((Int) -> ())!) -> Void {
do {
// 1. mergeComposition adds all the AVAssets
var mergeComposition : AVMutableComposition = AVMutableComposition()
var trackVideo : AVMutableCompositionTrack = mergeComposition.addMutableTrack(withMediaType: AVMediaTypeVideo, preferredTrackID: CMPersistentTrackID())
//var trackAudio : AVMutableCompositionTrack = mergeComposition.addMutableTrackWithMediaType(AVMediaTypeAudio, preferredTrackID: CMPersistentTrackID())
// 2. Add a bank for theme insertion later
//trackVideo.insertTimeRange(range, ofTrack: VideoHelper.Static.blankTrack, atTime: kCMTimeZero, error: nil)
// 3. Source tracks
let sourceAsset = AVURLAsset(url: videoUrl as URL, options: nil)
let sourceDuration = CMTimeRangeMake(kCMTimeZero, sourceAsset.duration)
let vtrack: AVAssetTrack? = sourceAsset.tracks(withMediaType: AVMediaTypeVideo)[0] as? AVAssetTrack
let atrack: AVAssetTrack? = sourceAsset.tracks(withMediaType: AVMediaTypeAudio)[0] as? AVAssetTrack
if (vtrack == nil) {
return
}
let renderWidth = vtrack?.naturalSize.width
let renderHeight = vtrack?.naturalSize.height
let insertTime = kCMTimeZero
let endTime = sourceAsset.duration
let range = sourceDuration
// append tracks
try trackVideo.insertTimeRange(sourceDuration, of: vtrack!, at: insertTime)
//if(atrack > 0){
// trackAudio.insertTimeRange(sourceDuration, ofTrack: atracks[0] as AVAssetTrack, atTime: insertTime, error: nil)
//}
// 4. Add subtitles (we call it theme)
var themeVideoComposition : AVMutableVideoComposition = AVMutableVideoComposition(propertiesOf: sourceAsset)
// 4.1 - Create AVMutableVideoCompositionInstruction
let mainInstruction: AVMutableVideoCompositionInstruction = AVMutableVideoCompositionInstruction()
mainInstruction.timeRange = range
// 4.2 - Create an AVMutableVideoCompositionLayerInstruction for the video track and fix the orientation.
let videolayerInstruction : AVMutableVideoCompositionLayerInstruction = AVMutableVideoCompositionLayerInstruction(assetTrack: vtrack!)
videolayerInstruction.setTransform(trackVideo.preferredTransform, at: insertTime)
videolayerInstruction.setOpacity(0.0, at: endTime)
// 4.3 - Add instructions
mainInstruction.layerInstructions = NSArray(array: [videolayerInstruction]) as! [AVVideoCompositionLayerInstruction]
themeVideoComposition.renderScale = 1.0
themeVideoComposition.renderSize = CGSize(width: renderWidth!, height: renderHeight!)
themeVideoComposition.frameDuration = CMTimeMake(1, 30)
themeVideoComposition.instructions = NSArray(array: [mainInstruction]) as! [AVVideoCompositionInstructionProtocol]
// add the theme
// setup variables
// add text
let title = String("Testing this subtitle")
var titleLayer = CATextLayer()
titleLayer.string = title
titleLayer.frame = CGRect(x: 0, y: 0, width: renderWidth!, height: renderHeight!)
let fontName: CFString = "Helvetica-Bold" as CFString
let fontSize = CGFloat(36)
titleLayer.font = CTFontCreateWithName(fontName, fontSize, nil)
titleLayer.alignmentMode = kCAAlignmentCenter
titleLayer.foregroundColor = UIColor.white.cgColor
var backgroundLayer = CALayer()
backgroundLayer.frame = CGRect(x: 0, y: 0, width: renderWidth!, height: renderHeight!)
backgroundLayer.masksToBounds = true
backgroundLayer.addSublayer(titleLayer)
// 2. set parent layer and video layer
var parentLayer = CALayer()
var videoLayer = CALayer()
parentLayer.frame = CGRect(x: 0, y: 0, width: renderWidth!, height: renderHeight!)
videoLayer.frame = CGRect(x: 0, y: 0, width: renderWidth!, height: renderHeight!)
parentLayer.addSublayer(backgroundLayer)
parentLayer.addSublayer(videoLayer)
// 3. make animation
themeVideoComposition.animationTool = AVVideoCompositionCoreAnimationTool(postProcessingAsVideoLayer: videoLayer, in: parentLayer)
// Remove the file if it already exists (merger does not overwrite)
let fileManager = FileManager.default
try fileManager.removeItem(at: outputUrl as URL)
// export to output url
var exporter = AVAssetExportSession(asset: mergeComposition, presetName: AVAssetExportPresetHighestQuality)
exporter?.outputURL = outputUrl as URL
exporter?.videoComposition = themeVideoComposition
exporter?.outputFileType = AVFileTypeQuickTimeMovie
exporter?.shouldOptimizeForNetworkUse = true
exporter?.exportAsynchronously(completionHandler: {
if (exporter?.error != nil) {
print("Error")
print(exporter?.error)
print("Description")
print(exporter?.description)
}
completionHandler((exporter?.status.rawValue)!)
})
}
catch{
}
}