Swift 视频缩放器 AVAsset

Question

我有这段代码可以将视频从 1280 x 720 调整为 640 x 360 但我想要一个没有裁剪的调整大小。

有没有办法完全调整不裁剪的大小？

这是代码

class func resizer(inputURL : NSURL , completion: (outPutURL : NSURL?) -> Void ){
        let videoAsset = AVAsset(URL: inputURL) as AVAsset
        let clipVideoTrack = videoAsset.tracksWithMediaType(AVMediaTypeVideo).first! as AVAssetTrack

        let composition = AVMutableComposition()
        composition.addMutableTrackWithMediaType(AVMediaTypeVideo, preferredTrackID: CMPersistentTrackID())

        let videoComposition = AVMutableVideoComposition()
        videoComposition.renderSize = CGSizeMake(360,640)
        videoComposition.frameDuration = CMTimeMake(1, 30)

        let instruction = AVMutableVideoCompositionInstruction()
        instruction.timeRange = CMTimeRangeMake(kCMTimeZero, CMTimeMakeWithSeconds(180, 30))

        let transformer : AVMutableVideoCompositionLayerInstruction = AVMutableVideoCompositionLayerInstruction(assetTrack: clipVideoTrack)

        let t1 = CGAffineTransformMakeTranslation(360, 0)
        let t2 = CGAffineTransformRotate(t1, CGFloat(M_PI_2))
//        let t2 = CGAffineTransformMakeRotation(CGFloat(M_PI_2))
        transformer.setTransform(t2, atTime: kCMTimeZero)
        instruction.layerInstructions = [transformer]
        videoComposition.instructions = [instruction]


        let formatter = NSDateFormatter()
        formatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss'Z'"
        let date = NSDate()

        let tempDir = NSTemporaryDirectory().stringByAppendingString(formatter.stringFromDate(date))
        let d = "\(tempDir).mp4"
        let outputURL = NSURL(fileURLWithPath: d)

        let exporter = AVAssetExportSession(asset: videoAsset, presetName: AVAssetExportPresetHighestQuality)
        exporter!.videoComposition = videoComposition
        exporter!.outputURL = outputURL
        exporter!.outputFileType = AVFileTypeQuickTimeMovie

        exporter?.exportAsynchronouslyWithCompletionHandler({ () -> Void in
            dispatch_async(dispatch_get_main_queue(), {
                completion(outPutURL: outputURL)
            })
        })
    }

Answer 1

我认为您正在寻找的（不裁剪调整大小）也是缩放视频。也尝试使用 CGAffineTransformScale / MakeScale。

https://developer.apple.com/library/ios/documentation/GraphicsImaging/Reference/CGAffineTransform/#//apple_ref/c/func/CGAffineTransformMakeScale

鉴于您的比率为 0.5 (1280 / 640)，您可以试试这个：

let t3 = CGAffineTransformScale(t2, 0.5, 0.5)
transformer.setTransform(t3, atTime: kCMTimeZero)

如果看起来不对，您可能还需要通过比例调整平移。

Answer 2

在Swift4

let playerLayer = AVPlayerLayer(player: player)
let transform = CGAffineTransform.init(scaleX: 0.5, y: 0.5)
playerLayer.setAffineTransform(transform)

Doc

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