How to Record video using AVCaptureVideoDataOutput

Question

Am using AVCaptureSession to get the camera output and have added successfully the audio and video inputs and outputs.

{

    var captureDevice = AVCaptureDevice.defaultDeviceWithMediaType(AVMediaTypeVideo) as AVCaptureDevice

    var error: NSError? = nil

    do {

        //remove the previous inputs
        let inputs = cameraSession.inputs as! [AVCaptureDeviceInput]
        for oldInput:AVCaptureDeviceInput in inputs {
            cameraSession.removeInput(oldInput)
        }
        cameraSession.beginConfiguration()

        if cameraPosition.isEqualToString("Front") {
            captureDevice = cameraWithPosition(.Front)!
        }
        else {
            captureDevice = cameraWithPosition(.Back)!
        }

        let deviceInput = try AVCaptureDeviceInput(device: captureDevice)

        if (cameraSession.canAddInput(deviceInput) == true) {
            cameraSession.addInput(deviceInput)
        }

        let dataOutput = AVCaptureVideoDataOutput()
        dataOutput.videoSettings = [(kCVPixelBufferPixelFormatTypeKey as NSString) : NSNumber(unsignedInt: kCVPixelFormatType_420YpCbCr8BiPlanarFullRange)]
        dataOutput.alwaysDiscardsLateVideoFrames = true

        if (cameraSession.canAddOutput(dataOutput) == true) {
            cameraSession.addOutput(dataOutput)
        }

        let audioCheck = AVCaptureDevice.devicesWithMediaType(AVMediaTypeAudio)
        if audioCheck.isEmpty {
            print("no audio device")
            return
        }

        let audioDevice: AVCaptureDevice! = audioCheck.first as! AVCaptureDevice

        var audioDeviceInput: AVCaptureDeviceInput?

        do {
            audioDeviceInput = try AVCaptureDeviceInput(device: audioDevice)
        } catch let error2 as NSError {
            error = error2
            audioDeviceInput = nil
        } catch {
            fatalError()
        }

        if error != nil{
            print(error)
            let alert = UIAlertController(title: "Error", message: error!.localizedDescription
                , preferredStyle: .Alert)
            alert.addAction(UIAlertAction(title: "OK", style: .Default, handler: nil))
            self.presentViewController(alert, animated: true, completion: nil)
        }
        if cameraSession.canAddInput(audioDeviceInput){
            cameraSession.addInput(audioDeviceInput)
        }

        cameraSession.commitConfiguration()

        let queue = dispatch_queue_create("com.invasivecode.videoQueue", DISPATCH_QUEUE_SERIAL)
        dataOutput.setSampleBufferDelegate(self, queue: queue)

    }
    catch let error as NSError {
        NSLog("\(error), \(error.localizedDescription)")
    }
}

Using AVCaptureMovieFileOutput am able to save the output video in the photo library using

movieFileOutput.startRecordingToOutputFileURL( outputFilePath, recordingDelegate: self)

but i use AVCaptureVideoDataOutput as output for doing extra work on the meta data i get from the delegates and try to record the video, but am unable to get any methods to start and stop recording the video.

Suggest how to record the video using AVCaptureVideoDataOutput

Answer 1

You need an AVCaptureSession to do it:

//First add AVCaptureVideoDataOutput to AVCaptureSession 
AVCaptureSession *_captureSession;
_captureSession = [[AVCaptureSession alloc] init];
......Configuration......

AVCaptureVideoDataOutput *videoOut = [[AVCaptureVideoDataOutput alloc] init];
......Configuration......
if ( [_captureSession canAddOutput:videoOut] ) {
    [_captureSession addOutput:videoOut];
}

//Then use captureSession to start and stop recording
[_captureSession startRunning];
[_captureSession stopRunning];

Please look through RosyWriterCapturePipeline.m, this is a very good example:

RosyWriter

Answer 2

I found that the Rosy Writer is a good example for the working of AVCaptureSession. So here is the Rosy Writer2.1 Swift version. It should help those who struggle with AVCaptureSession.