音声だけのファイルに字幕を付ける方法をメモる。基本的には、字幕の付いたビデオを保存すると同じだが、字幕を入れるには映像トラックが必要なので、それを準備するところが面倒なことになっているので、別の項目としてみた。まずは、そちらに目を通してから、こちらを見てください。
まずは、音声ファイルを読み込んで、AVMutableComposition オブジェクトを作り、読み込んだ音声を入れる。
asset = AVAsset.assetWithURL(url)
composition = AVMutableComposition.composition
composition.insertTimeRange(CMTimeRangeMake(KCMTimeZero,asset.duration),ofAsset:asset,atTime:KCMTimeZero,error:nil)
ここが、ちょっとめんどい。
videoTrack = composition.addMutableTrackWithMediaType(AVMediaTypeVideo,preferredTrackID:KCMPersistentTrackID_Invalid)
blankAsset = AVAsset.assetWithURL(NSURL.fileURLWithPath(pathToBlankMovFile)
blankVideoTrack = blankAsset.tracksWithMediaType(AVMediaTypeVideo)[0]
videoTrack.insertTimeRange(CMTimeRangeMake(KCMTimeZero,blankAsset.duration),ofTrack:blankVideoTrack,atTime:KCMTimeZero,error:nil)
videoTrack.scaleTimeRange(CMTimeRangeMake(KCMTimeZero,blankAsset.duration),toDuration:composition.duration)
何をしているかというと、一秒くらいの、ブランク映像（黒いだけ）の mov ファイルを用意しておいて、それを読み込んで処理している。まずは、空の videoTrack を作る。そしたら、ブランク映像ファイルを読み込んで、映像トラックを取り出す。取り出したら、空の videoTrack に追加して、それを引き延ばして、音声ファイル全体の長さと一致するようにしている。
次に、AVMutableVideoComposition の準備。ここでは、出力したい映像の大きさを指定して、フレームレートは 30 fps にしている。
videoSize = CGSizeMake(480,200)
videoComposition = AVMutableVideoComposition.videoComposition
videoComposition.frameDuration = CMTimeMake(1, 30)
videoComposition.renderSize = videoSize
同期させる AVPlayerItem を作って、synchLayer を用意する。
playerItem = AVPlayerItem.playerItemWithAsset(composition)
synchLayer = AVSynchronizedLayer.synchronizedLayerWithPlayerItem(playerItem)
synchLayer.setFrame(CGRectMake(0, 0, videoSize.width, videoSize.height))
synchLayer.setMasksToBounds(false)
synchLayer.bounds = CGRectMake(0, 0, videoSize.width, videoSize.height)
synchLayer.anchorPoint = CGPointMake(0,0)
synchLayer.position = CGPointMake(0,0)
そして、字幕の layer の準備。
overlayLayer = CALayer.layer
overlayLayer.frame = CGRectMake(0, 0, @maxWidth, @maxHeight)
overlayLayer.anchorPoint = CGPointMake(0.5,0.5)
overlayLayer.position = CGPointMake(videoSize.width/2,videoSize.height/2)
overlayLayer.contentsGravity = KCAGravityResizeAspect
anim = CAKeyframeAnimation.animationWithKeyPath("contents")
anim.beginTime = AVCoreAnimationBeginTimeAtZero
anim.duration = CMTimeGetSeconds(playerItem.duration)
anim.values = subTImages.map{|x| x.CGImage}
anim.keyTimes = subtitleTimes
anim.calculationMode = KCAAnimationDiscrete
anim.removedOnCompletion = false
anim.fillMode = KCAFillModeForwards
overlayLayer.addAnimation(anim,forKey:"contents")
synchLayer に直接 overlayLayer を入れてもいいのだが、字幕の背景色を決めたいときは、overlayLayer の範囲だけでなく、全体を同じ色にしたいので、その色を指定するためだけの layer を用意した。そして、この layer に overlayLayer を追加して、この layer を synchLayer に追加する。
aLayer = CALayer.layer
aLayer.frame = synchLayer.frame
aLayer.backgroundColor = NSColor.blackColor.CGColor
aLayer.addSublayer(overlayLayer)
aLayer.anchorPoint = CGPointMake(0,0)
aLayer.position = CGPointMake(0,0)
synchLayer.addSublayer(aLayer)
字幕を含む layer を videoLayer に合成する処理。この辺りも、字幕の付いたビデオを保存すると同じ。
parentLayer = CALayer.layer
videoLayer = CALayer.layer
parentLayer.bounds = CGRectMake(0, 0, videoSize.width, videoSize.height)
videoLayer.bounds = CGRectMake(0, 0, videoSize.width, videoSize.height)
parentLayer.addSublayer(videoLayer)
parentLayer.addSublayer(synchLayer)
parentLayer.anchorPoint = CGPointMake(0,0)
videoLayer.anchorPoint = CGPointMake(0,0)
parentLayer.position = CGPointMake(0,0)
videoLayer.position = CGPointMake(0,0)
videoComposition.animationTool = AVVideoCompositionCoreAnimationTool.videoCompositionCoreAnimationToolWithPostProcessingAsVideoLayer(videoLayer,inLayer:parentLayer)
ここから先も、特に変わったことはないので、説明は省略。
instruction = AVMutableVideoCompositionInstruction.videoCompositionInstruction
instruction.timeRange = CMTimeRangeMake(KCMTimeZero, composition.duration)
layerInstruction = AVMutableVideoCompositionLayerInstruction.videoCompositionLayerInstructionWithAssetTrack(videoTrack)
instruction.layerInstructions = [layerInstruction]
videoComposition.instructions = [instruction]
exportSession = AVAssetExportSession.alloc.initWithAsset(composition,presetName:AVAssetExportPresetAppleM4V480pSD)
exportSession.videoComposition = videoComposition
exportSession.outputURL = url
exportSession.outputFileType = AVFileTypeAppleM4V
exportSession.exportAsynchronouslyWithCompletionHandler(Proc.new{
case @exportSession.status
when AVAssetExportSessionStatusCompleted
when AVAssetExportSessionStatusFailed
end
})
こんな感じで、音声だけのファイルに字幕を付けて映像として保存できる（はず）。
composition = AVMutableComposition.composition
composition.insertTimeRange(CMTimeRangeMake(KCMTimeZero,asset.duration),ofAsset:asset,atTime:KCMTimeZero,error:nil)
blankAsset = AVAsset.assetWithURL(NSURL.fileURLWithPath(pathToBlankMovFile)
videoTrack = composition.addMutableTrackWithMediaType(AVMediaTypeVideo,preferredTrackID:KCMPersistentTrackID_Invalid)
blankVideoTrack = blankAsset.tracksWithMediaType(AVMediaTypeVideo)[0]
videoTrack.insertTimeRange(CMTimeRangeMake(KCMTimeZero,blankAsset.duration),ofTrack:blankVideoTrack,atTime:KCMTimeZero,error:nil)
videoTrack.scaleTimeRange(CMTimeRangeMake(KCMTimeZero,blankAsset.duration),toDuration:composition.duration)
playerItem = AVPlayerItem.playerItemWithAsset(composition)
videoSize = CGSizeMake(480,200)
videoComposition = AVMutableVideoComposition.videoComposition
videoComposition.frameDuration = CMTimeMake(1, 30)
videoComposition.renderSize = videoSize
synchLayer = AVSynchronizedLayer.synchronizedLayerWithPlayerItem(playerItem)
synchLayer.setFrame(CGRectMake(0, 0, videoSize.width, videoSize.height))
synchLayer.setMasksToBounds(false)
synchLayer.bounds = CGRectMake(0, 0, videoSize.width, videoSize.height)
synchLayer.anchorPoint = CGPointMake(0,0)
synchLayer.position = CGPointMake(0,0)
overlayLayer = CALayer.layer
overlayLayer.frame = CGRectMake(0, 0, @maxWidth, @maxHeight)
overlayLayer.anchorPoint = CGPointMake(0.5,0.5)
overlayLayer.position = CGPointMake(videoSize.width/2,videoSize.height/2)
overlayLayer.contentsGravity = KCAGravityResizeAspect
overlayLayer.cornerRadius = 10.0
anim = CAKeyframeAnimation.animationWithKeyPath("contents")
anim.beginTime = AVCoreAnimationBeginTimeAtZero
anim.duration = CMTimeGetSeconds(playerItem.duration)
anim.values = subTImages.map{|x| x.CGImage}
anim.keyTimes = subtitleTimes
anim.calculationMode = KCAAnimationDiscrete
anim.removedOnCompletion = false
anim.fillMode = KCAFillModeForwards
overlayLayer.addAnimation(anim,forKey:"contents")
aLayer = CALayer.layer
aLayer.frame = synchLayer.frame
aLayer.backgroundColor = NSColor.blackColor.CGColor
aLayer.addSublayer(overlayLayer)
aLayer.anchorPoint = CGPointMake(0,0)
aLayer.position = CGPointMake(0,0)
synchLayer.addSublayer(aLayer)
parentLayer = CALayer.layer
videoLayer = CALayer.layer
parentLayer.bounds = CGRectMake(0, 0, videoSize.width, videoSize.height)
videoLayer.bounds = CGRectMake(0, 0, videoSize.width, videoSize.height)
parentLayer.addSublayer(videoLayer)
parentLayer.addSublayer(synchLayer)
parentLayer.anchorPoint = CGPointMake(0,0)
videoLayer.anchorPoint = CGPointMake(0,0)
parentLayer.position = CGPointMake(0,0)
videoLayer.position = CGPointMake(0,0)
videoComposition.animationTool = AVVideoCompositionCoreAnimationTool.videoCompositionCoreAnimationToolWithPostProcessingAsVideoLayer(videoLayer,inLayer:parentLayer)
instruction = AVMutableVideoCompositionInstruction.videoCompositionInstruction
instruction.timeRange = CMTimeRangeMake(KCMTimeZero, composition.duration)
layerInstruction = AVMutableVideoCompositionLayerInstruction.videoCompositionLayerInstructionWithAssetTrack(videoTrack)
instruction.layerInstructions = [layerInstruction]
videoComposition.instructions = [instruction]
exportSession = AVAssetExportSession.alloc.initWithAsset(composition,presetName:AVAssetExportPresetAppleM4V480pSD)
exportSession.videoComposition = videoComposition
exportSession.outputURL = @panel.URL
exportSession.outputFileType = AVFileTypeAppleM4V
exportSession.exportAsynchronouslyWithCompletionHandler(Proc.new{
case @exportSession.status
when AVAssetExportSessionStatusCompleted
when AVAssetExportSessionStatusFailed
end
})