使用AVCaptureVideoDataOutput或AVCaptureMovieFileOutput使用Swift捕获视频

Question

我需要一些关于如何在不使用UIImagePicker的情况下捕获视频的指导.视频需要在按钮单击时启动和停止,然后将此数据保存到NSDocumentDirectory.我是swift的新手,所以任何帮助都会有用.

我需要帮助的代码部分是启动和停止视频会话并将其转换为数据.我创建了一个运行captureStillImageAsynchronouslyFromConnection的图片,并将此数据保存到NSDocumentDirectory.我已经设置了一个视频捕获会话,并准备好代码保存数据,但不知道如何从会话中获取数据.

var previewLayer : AVCaptureVideoPreviewLayer?
var captureDevice : AVCaptureDevice?
var videoCaptureOutput = AVCaptureVideoDataOutput()

let captureSession = AVCaptureSession()

override func viewDidLoad() {
    super.viewDidLoad()

    captureSession.sessionPreset = AVCaptureSessionPreset640x480
    let devices = AVCaptureDevice.devices()

    for device in devices {
        if (device.hasMediaType(AVMediaTypeVideo)) {
            if device.position == AVCaptureDevicePosition.Back {
                captureDevice = device as? AVCaptureDevice
                if captureDevice != nil {
                    beginSession()
                }
            }   
        }
    }
}

func beginSession() {
    var err : NSError? = nil
    captureSession.addInput(AVCaptureDeviceInput(device: captureDevice, error: &err))

    if err != nil {
        println("Error: \(err?.localizedDescription)")
    }

    videoCaptureOutput.videoSettings = [kCVPixelBufferPixelFormatTypeKey:kCVPixelFormatType_32BGRA]
    videoCaptureOutput.alwaysDiscardsLateVideoFrames = true

    captureSession.addOutput(videoCaptureOutput)

    previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
    self.view.layer.addSublayer(previewLayer)
    previewLayer?.frame = CGRectMake(0, 0, screenWidth, screenHeight)
    captureSession.startRunning()

    var startVideoBtn = UIButton(frame: CGRectMake(0, screenHeight/2, screenWidth, screenHeight/2))
        startVideoBtn.addTarget(self, action: "startVideo", forControlEvents: UIControlEvents.TouchUpInside)
        self.view.addSubview(startVideoBtn)

    var stopVideoBtn = UIButton(frame: CGRectMake(0, 0, screenWidth, screenHeight/2))
        stopVideoBtn.addTarget(self, action: "stopVideo", forControlEvents: UIControlEvents.TouchUpInside)
        self.view.addSubview(stopVideoBtn)
}

如果需要,我可以提供更多代码或解释.

Answer 1

为获得最佳效果,请阅读AV Foundation编程指南中的静止和视频媒体捕获部分.

要处理来自的帧AVCaptureVideoDataOutput,您需要一个采用该AVCaptureVideoDataOutputSampleBufferDelegate协议的委托.captureOutput只要写入新帧,就会调用委托的方法.设置输出的委托时,还必须提供应在其上调用回调的队列.它看起来像这样:

let cameraQueue = dispatch_queue_create("cameraQueue", DISPATCH_QUEUE_SERIAL)
videoCaptureOutput.setSampleBufferDelegate(myDelegate, queue: cameraQueue)
captureSession.addOutput(videoCaptureOutput)

注意:如果您只想将电影保存到文件中,您可能更喜欢使用AVCaptureMovieFileOutput该类而不是AVCaptureVideoDataOutput.在这种情况下,您将不需要队列.但是你仍然需要一个代表,这次采用的是AVCaptureFileOutputRecordingDelegate协议.(相关方法仍然被调用captureOutput.)

以下是AVCaptureMovieFileOutput与上述指南相关的部分摘录:

开始录制

您开始使用录制QuickTime电影startRecordingToOutputFileURL:recordingDelegate:.您需要提供基于文件的URL和委托.URL不得标识现有文件,因为电影文件输出不会覆盖现有资源.您还必须具有写入指定位置的权限.委托必须符合 AVCaptureFileOutputRecordingDelegate协议,并且必须实现该 captureOutput:didFinishRecordingToOutputFileAtURL:fromConnections:error: 方法.

AVCaptureMovieFileOutput *aMovieFileOutput = <#Get a movie file output#>;
NSURL *fileURL = <#A file URL that identifies the output location#>;
[aMovieFileOutput startRecordingToOutputFileURL:fileURL recordingDelegate:<#The delegate#>];

在实现中 captureOutput:didFinishRecordingToOutputFileAtURL:fromConnections:error:,委托可能会将生成的影片写入Camera Roll相册.它还应检查可能发生的任何错误.