斯威夫特：在一个尺寸的视频记录，但在错误的大小呈现斯威夫特：在一个尺寸的视频记录，但在错误的大小呈现

我们的目标是捕捉全屏视频与斯威夫特的设备上。在下面的代码，视频拍摄出现在全屏发生（同时录制的摄像头预览使用全屏幕），但视频的呈现发生在不同的分辨率。对于5S具体地说，它看起来像捕捉发生在320x568 ，但在渲染时320x480 。

你怎么能捕捉并呈现全屏视频？

代码视频拍摄：

private func initPBJVision() {
    // Store PBJVision in var for convenience
    let vision = PBJVision.sharedInstance()

    // Configure PBJVision
    vision.delegate = self
    vision.cameraMode = PBJCameraMode.Video
    vision.cameraOrientation = PBJCameraOrientation.Portrait
    vision.focusMode = PBJFocusMode.ContinuousAutoFocus
    vision.outputFormat = PBJOutputFormat.Preset
    vision.cameraDevice = PBJCameraDevice.Back

    // Let taps start/pause recording
    let tapHandler = UITapGestureRecognizer(target: self, action: "doTap:")
    view.addGestureRecognizer(tapHandler)

    // Log status
    print("Configured PBJVision")
}


private func startCameraPreview() {
    // Store PBJVision in var for convenience
    let vision = PBJVision.sharedInstance()

    // Connect PBJVision camera preview to <videoView>
    // -- Get preview width
    let deviceWidth = CGRectGetWidth(view.frame)
    let deviceHeight = CGRectGetHeight(view.frame)

    // -- Configure PBJVision's preview layer
    let previewLayer = vision.previewLayer
    previewLayer.frame = CGRectMake(0, 0, deviceWidth, deviceHeight)
    previewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill
    ...
}

视频渲染代码：

func exportVideo(fileUrl: NSURL) {
    // Create main composition object
    let videoAsset = AVURLAsset(URL: fileUrl, options: nil)
    let mainComposition = AVMutableComposition()
    let compositionVideoTrack = mainComposition.addMutableTrackWithMediaType(AVMediaTypeVideo, preferredTrackID: CMPersistentTrackID(kCMPersistentTrackID_Invalid))
    let compositionAudioTrack = mainComposition.addMutableTrackWithMediaType(AVMediaTypeAudio, preferredTrackID: CMPersistentTrackID(kCMPersistentTrackID_Invalid))

    // -- Extract and apply video & audio tracks to composition
    let sourceVideoTrack = videoAsset.tracksWithMediaType(AVMediaTypeVideo)[0]
    let sourceAudioTrack = videoAsset.tracksWithMediaType(AVMediaTypeAudio)[0]
    do {
        try compositionVideoTrack.insertTimeRange(CMTimeRangeMake(kCMTimeZero, videoAsset.duration), ofTrack: sourceVideoTrack, atTime: kCMTimeZero)
    } catch {
        print("Error with insertTimeRange. Video error: \(error).")
    }
    do {
        try compositionAudioTrack.insertTimeRange(CMTimeRangeMake(kCMTimeZero, videoAsset.duration), ofTrack: sourceAudioTrack, atTime: kCMTimeZero)
    } catch {
        print("Error with insertTimeRange. Audio error: \(error).")
    }

    // Add text to video
    // -- Create video composition object
    let renderSize = compositionVideoTrack.naturalSize
    let videoComposition = AVMutableVideoComposition()
    videoComposition.renderSize = renderSize
    videoComposition.frameDuration = CMTimeMake(Int64(1), Int32(videoFrameRate))

    // -- Add instruction to  video composition object
    let instruction = AVMutableVideoCompositionInstruction()
    instruction.timeRange = CMTimeRangeMake(kCMTimeZero, videoAsset.duration)
    let videoLayerInstruction = AVMutableVideoCompositionLayerInstruction(assetTrack: compositionVideoTrack)
    instruction.layerInstructions = [videoLayerInstruction]
    videoComposition.instructions = [instruction]

    // -- Define video frame
    let videoFrame = CGRectMake(0, 0, renderSize.width, renderSize.height)
    print("Video Frame: \(videoFrame)")  // <-- Prints frame of 320x480 so render size already wrong here 
    ...

Answer 1:

如果我得到你的权利，你似乎有误解的事实是设备屏幕的宽度is'n等于相机预览（和捕获）大小。

该videoGravity你的财产previewLayer指示如何伸展/适合您的层内的预览。它不影响拍摄输出。

输出的实际帧大小取决于sessionPreset你目前的财产AVCaptureSession 。而且，我可以通过读取PBJVision LIB的GitHub的仓库了解，其单有这个（称为二传手captureSessionPreset ）。您可以在里面更改initPBJVision方法。

这里你可以找到会议预置的可能值。

Answer 2:

尝试SDAVAssetExportSession

您可以指定AVVideoWidthKey和AVVideoHeightKey你也可以指定配置文件， AVVideoProfileLevelKey即AVVideoProfileLevelH264HighAutoLevel支持4K的东西，朋友（迈克尔Lowin）追踪该属性下来，帮助我们提高部分出口品质。