How to stop the capture source of AudioVideoCaptureDevice

Question

Hi. I capture video with the AudioVideoCaptureDevice API and I'm not sure if I followed the right steps to implement it. If I record a video for the first time everything works in the emulator but when I tap the record button for the second
time the app crash. I think it's because I have to disconnect the file stream from the capture source but I can't because passed an instance of  AudioVideoCaptureDevice as the source of the video recorder brush. Here's my code + - in the order of
execution:
private async Task InitializeVideoRecorder()
try
if (vcDevice != null)
vcDevice = null;
CameraSensorLocation location = CameraSensorLocation.Back;
captureResolutions =
AudioVideoCaptureDevice.GetAvailableCaptureResolutions(location);
vcDevice = await AudioVideoCaptureDevice.OpenAsync(location, captureResolutions[0]);
vcDevice.RecordingFailed += OnCaptureFailed;
vcDevice.VideoEncodingFormat = CameraCaptureVideoFormat.H264;
vcDevice.AudioEncodingFormat = CameraCaptureAudioFormat.Aac;
// Initialize the camera if it exists on the phone.
if (vcDevice != null)
//initialize fileSink
await InitializeFileSink();
// Create the VideoBrush for the viewfinder.
videoRecorderBrush = new VideoBrush();
videoRecorderBrush.SetSource(vcDevice);
// Display the viewfinder image on the rectangle.
viewfinderRectangle.Fill = videoRecorderBrush;
//_cs.Start();
// Set the button state and the message.
UpdateUI(ButtonState.Initialized, "Tap record to start recording...");
else
// Disable buttons when the camera is not supported by the phone.
UpdateUI(ButtonState.CameraNotSupported, "A camera is not supported on this phone.");
catch(Exception ex)
MessageBox.Show("InitializeVideoRecorder Error:\n" + ex.Message);
private void OnCaptureFailed(AudioVideoCaptureDevice sender, CaptureFailedEventArgs args)
MessageBox.Show(args.ToString());
//setup iClips video file creation
private async Task InitializeFileSink()
StorageFolder isoStore = await ApplicationData.Current.LocalFolder.GetFolderAsync("Shared");
sfVideoFile = await isoStore.CreateFileAsync(
isoVideoFileName+".mp4",
CreationCollisionOption.ReplaceExisting);
// Set the recording state: display the video on the viewfinder.
private void StartVideoPreview()
try
// Display the video on the viewfinder.
if (vcDevice != null)
// Create the VideoBrush for the viewfinder.
videoRecorderBrush = new VideoBrush();
videoRecorderBrush.SetSource(vcDevice);
// Display the viewfinder image on the rectangle.
viewfinderRectangle.Fill = videoRecorderBrush;
// Set the button states and the message.
UpdateUI(ButtonState.Ready, "Ready to record.");
txtRecTime.Visibility = Visibility.Collapsed;
// If preview fails, display an error.
catch (Exception e)
MessageBox.Show("Start Video Preview Exception:\n " + e.Message.ToString());
// Set recording state: start recording.
private async void StartVideoRecording()
try
if (vcDevice != null)
MessageBox.Show("1");
s = await sfVideoFile.OpenAsync(FileAccessMode.ReadWrite);
MessageBox.Show("2");
await vcDevice.StartRecordingToStreamAsync(s);
MessageBox.Show("3");
rState = 1;
logo.Opacity = 1.0; //brighten logo to indicate that the recording started
StartTimer(); //show time ellapsed on UI
// Set the button states and the message.
UpdateUI(ButtonState.Recording, "Recording...");
// If recording fails, display an error.
catch (Exception e)
MessageBox.Show("Start Video Recording Error:\n" + e.Message.ToString());
// Set the recording state: stop recording.
private async void StopVideoRecording()
try
await vcDevice.StopRecordingAsync();
sfVideoFile = null;
rState = 0;
logo.Opacity = 0.1;
StopTimer();
// Set the button states and the message.
UpdateUI(ButtonState.Stopped, "Preparing viewfinder...");
StartVideoPreview();
// If stop fails, display an error.
catch (Exception e)
MessageBox.Show("Stop Video Recording:\n " + e.Message.ToString());
// Start the video recording.
private void StartRecording_Click(object sender, EventArgs e)
// Avoid duplicate taps.
StartRecording.IsEnabled = false;
StartVideoRecording();
private void DisposeVideoRecorder()
if (_cs != null)
// Stop captureSource if it is running.
if (_cs.VideoCaptureDevice != null
&& _cs.State == CaptureState.Started)
_cs.Stop();
// Remove the event handler for captureSource.
_cs.CaptureFailed -= OnCaptureFailed;
// Remove the video recording objects.
_cs = null;
vcDevice = null;
//fileSink = null;
videoRecorderBrush = null;
InitializeVideoRecorder() is called in OnNavigatedTo the when I tap the record button StartVideoRecording() is then called like wise StopVideoRecording() and when I tap the record button( or call StartVideoRecording) for the second time an error
is thrown. What am I missing? (I bet it's something to do with how I implemented the capture source.) Thaanks in advance.
 

Answer 1

Thank you that answer is very helpful. I got the recording to work and it's playing the video back too, however, when I record for the second time and tries to playback that file the screen is just black. Can you kindly take a look at my methods
and see where I'm missing up?
// Constructor
public MainPage()
try
InitializeComponent();
//setup recording
// Prepare ApplicationBar and buttons.
PhoneAppBar = (ApplicationBar)ApplicationBar;
PhoneAppBar.IsVisible = true;
StartRecording = ((ApplicationBarIconButton)ApplicationBar.Buttons[0]);
StopPlaybackRecording = ((ApplicationBarIconButton)ApplicationBar.Buttons[1]);
StartPlayback = ((ApplicationBarIconButton)ApplicationBar.Buttons[2]);
PausePlayback = ((ApplicationBarIconButton)ApplicationBar.Buttons[3]);
//SetScreenResolution();
//Sign_Client();
catch (Exception ex)
MessageBox.Show("Constructor Error:\n"+ ex.Message);
//Life Cycle
protected async override void OnNavigatedTo(NavigationEventArgs e)
base.OnNavigatedTo(e);
// Initialize the video recorder.
await InitializeVideoRecorder();
//prepare shutter hot keys
CameraButtons.ShutterKeyHalfPressed += OnButtonHalfPress;
CameraButtons.ShutterKeyPressed += OnButtonFullPress;
CameraButtons.ShutterKeyReleased += OnButtonRelease;
protected override void OnNavigatedFrom(NavigationEventArgs e)
// Dispose of camera and media objects.
DisposeVideoPlayer();
DisposeVideoRecorder();
base.OnNavigatedFrom(e);
CameraButtons.ShutterKeyHalfPressed -= OnButtonHalfPress;
CameraButtons.ShutterKeyPressed -= OnButtonFullPress;
CameraButtons.ShutterKeyReleased -= OnButtonRelease;
// Update the buttons and text on the UI thread based on app state.
private void UpdateUI(ButtonState currentButtonState, string statusMessage)
try
// Run code on the UI thread.
Dispatcher.BeginInvoke(delegate
switch (currentButtonState)
// When the camera is not supported by the phone.
case ButtonState.CameraNotSupported:
StartRecording.IsEnabled = false;
StopPlaybackRecording.IsEnabled = false;
StartPlayback.IsEnabled = false;
PausePlayback.IsEnabled = false;
break;
// First launch of the application, so no video is available.
case ButtonState.Initialized:
StartRecording.IsEnabled = true;
StopPlaybackRecording.IsEnabled = false;
StartPlayback.IsEnabled = false;
PausePlayback.IsEnabled = false;
break;
// Ready to record, so video is available for viewing.
case ButtonState.Ready:
StartRecording.IsEnabled = true;
StopPlaybackRecording.IsEnabled = false;
StartPlayback.IsEnabled = true;
PausePlayback.IsEnabled = false;
break;
// Video recording is in progress.
case ButtonState.Recording:
StartRecording.IsEnabled = false;
StopPlaybackRecording.IsEnabled = true;
StartPlayback.IsEnabled = false;
PausePlayback.IsEnabled = false;
break;
// Video Recording Stopped.
case ButtonState.Stopped:
StartRecording.IsEnabled = true;
StopPlaybackRecording.IsEnabled = false;
StartPlayback.IsEnabled = true;
PausePlayback.IsEnabled = false;
break;
// Video playback is in progress.
case ButtonState.Playback:
StartRecording.IsEnabled = false;
StopPlaybackRecording.IsEnabled = true;
StartPlayback.IsEnabled = false;
PausePlayback.IsEnabled = true;
break;
// Video playback has been paused.
case ButtonState.Paused:
StartRecording.IsEnabled = false;
StopPlaybackRecording.IsEnabled = true;
StartPlayback.IsEnabled = true;
PausePlayback.IsEnabled = false;
break;
default:
break;
// Display a message.
txtDebug.Text = statusMessage;
// Note the current application state.
currentAppState = currentButtonState;
catch (Exception ex)
MessageBox.Show("UpdateUI Error:\n" + ex.Message.ToString());
private async Task InitializeVideoRecorder()
try
CameraSensorLocation location = CameraSensorLocation.Back;
captureResolutions =
AudioVideoCaptureDevice.GetAvailableCaptureResolutions(location);
vcDevice = await AudioVideoCaptureDevice.OpenAsync(location, captureResolutions[0]);
vcDevice.RecordingFailed += OnCaptureFailed;
vcDevice.VideoEncodingFormat = CameraCaptureVideoFormat.H264;
vcDevice.AudioEncodingFormat = CameraCaptureAudioFormat.Aac;
//Set a perfect orientation to capture with
int encodedOrientation = 0;
int sensorOrientation = (Int32)this.vcDevice.SensorRotationInDegrees;
switch (this.Orientation)
// Camera hardware shutter button up.
case PageOrientation.LandscapeLeft:
encodedOrientation = -90 + sensorOrientation;
break;
// Camera hardware shutter button down.
case PageOrientation.LandscapeRight:
encodedOrientation = 90 + sensorOrientation;
break;
// Camera hardware shutter button right.
case PageOrientation.PortraitUp:
encodedOrientation = 0 + sensorOrientation;
break;
// Camera hardware shutter button left.
case PageOrientation.PortraitDown:
encodedOrientation = 180 + sensorOrientation;
break;
vcDevice.SetProperty(KnownCameraGeneralProperties.EncodeWithOrientation, sensorOrientation + 90);
// Initialize the camera if it exists on the phone.
if (vcDevice != null)
//initialize fileSink
await CreateAndOpenNewVideoFile();
// Create the VideoBrush for the viewfinder.
videoRecorderBrush = new VideoBrush();
videoRecorderBrush.SetSource(vcDevice);
// Display the viewfinder image on the rectangle.
viewfinderRectangle.Fill = videoRecorderBrush;
//_cs.Start();
// Set the button state and the message.
UpdateUI(ButtonState.Initialized, "Tap record to start recording...");
else
// Disable buttons when the camera is not supported by the phone.
UpdateUI(ButtonState.CameraNotSupported, "A camera is not supported on this phone.");
catch(Exception ex)
MessageBox.Show("InitializeVideoRecorder Error:\n" + ex.Message);
private void OnCaptureFailed(AudioVideoCaptureDevice sender, CaptureFailedEventArgs args)
MessageBox.Show(args.ToString());
//setup iClips video file creation
private async Task CreateAndOpenNewVideoFile()
StorageFolder isoStore = await ApplicationData.Current.LocalFolder.GetFolderAsync("Shared");
sfVideoFile = await isoStore.CreateFileAsync(isoVideoFileName+".mp4",
CreationCollisionOption.ReplaceExisting);
s = await sfVideoFile.OpenAsync(FileAccessMode.ReadWrite);
// Set the recording state: display the video on the viewfinder.
private void StartVideoPreview()
try
// Display the video on the viewfinder.
if (vcDevice != null)
// Create the VideoBrush for the viewfinder.
videoRecorderBrush = new VideoBrush();
videoRecorderBrush.SetSource(vcDevice);
// Display the viewfinder image on the rectangle.
viewfinderRectangle.Fill = videoRecorderBrush;
// Set the button states and the message.
UpdateUI(ButtonState.Ready, "Ready to record.");
txtRecTime.Visibility = Visibility.Collapsed;
// If preview fails, display an error.
catch (Exception e)
MessageBox.Show("Start Video Preview Exception:\n " + e.Message.ToString());
// Set recording state: start recording.
private async void StartVideoRecording()
try
if (vcDevice != null)
await vcDevice.StartRecordingToStreamAsync(s);
rState = 1;
logo.Opacity = 1.0; //brighten logo to indicate that the recording started
StartTimer(); //show time ellapsed on UI
// Set the button states and the message.
UpdateUI(ButtonState.Recording, "Recording...");
// If recording fails, display an error.
catch (Exception e)
MessageBox.Show("Start Video Recording Error:\n" + e.Message.ToString());
// Set the recording state: stop recording.
private async void StopVideoRecording()
try
await vcDevice.StopRecordingAsync();
//sfVideoFile = null;
rState = 0;
logo.Opacity = 0.1;
StopTimer();
// Set the button states and the message.
UpdateUI(ButtonState.Stopped, "Preparing viewfinder...");
//StartVideoPreview();
// If stop fails, display an error.
catch (Exception e)
MessageBox.Show("Stop Video Recording:\n " + e.Message.ToString());
// Start the video recording.
private void StartRecording_Click(object sender, EventArgs e)
// Avoid duplicate taps.
StartRecording.IsEnabled = false;
StartVideoRecording();
private void DisposeVideoRecorder()
if (vcDevice != null)
// Remove the video recording objects.
vcDevice = null;
// Remove the event handler for captureSource.
vcDevice.RecordingFailed -= OnCaptureFailed;
s = null;
sfVideoFile = null;
videoRecorderBrush = null;
private void OnCaptureFailed(object sender, ExceptionRoutedEventArgs e)
MessageBox.Show("Recording Failed!");
private void SaveThumbnail()
Deployment.Current.Dispatcher.BeginInvoke(() =>
var w = (int)vcDevice.PreviewResolution.Width;
var h = (int)vcDevice.PreviewResolution.Height;
var argbPx = new Int32[w * h];
vcDevice.GetPreviewBufferArgb(argbPx);
var wb = new WriteableBitmap(w, h);
argbPx.CopyTo(wb.Pixels, 0);
wb.Invalidate();
using (var isoStore = IsolatedStorageFile.GetUserStoreForApplication())
var fileName = isoVideoFileName + "_iThumb.jpg";
if (isoStore.FileExists(fileName))
isoStore.DeleteFile(fileName);
var file = isoStore.CreateFile(fileName);
wb.SaveJpeg(file, w, h, 0, 20);
file.Close();
//STOP WATCH
private void StartTimer()
dispatcherTimer = new System.Windows.Threading.DispatcherTimer();
dispatcherTimer.Tick += new EventHandler(dispatcherTimer_Tick);
dispatcherTimer.Interval = new TimeSpan(0, 0, 1);
dispatcherTimer.Start();
startTime = System.DateTime.Now;
private void StopTimer()
dispatcherTimer.Stop();
private void dispatcherTimer_Tick(object sender, EventArgs e)
System.DateTime now = System.DateTime.Now;
this.Dispatcher.BeginInvoke(delegate()
txtRecTime.Visibility = Visibility.Visible;
txtRecTime.Text = now.Subtract(startTime).ToString().Substring(0, now.Subtract(startTime).ToString().LastIndexOf("."));
// ICLIPS THEATRE - VIDEO PLAYER
private void StopPlaybackRecording_Click(object sender, EventArgs e)
try
if (rState == 1)
// Avoid duplicate taps.
StopPlaybackRecording.IsEnabled = false;
// Stop during video recording.
StopVideoRecording();
// Set the button state and the message.
UpdateUI(ButtonState.NoChange, "Recording stopped.");
if (rState == 0)
// Stop during video playback.
// Remove playback objects.
DisposeVideoPlayer();
StartVideoPreview();
// Set the button state and the message.
UpdateUI(ButtonState.NoChange, "Playback stopped.");
catch (Exception ex)
MessageBox.Show("Stop playback recording Exception:\n" + ex.Message.ToString());
private void StartPlayback_Click(object sender, EventArgs e)
PlayVideo();
private async void PlayVideo()
try
// Avoid duplicate taps.
StartPlayback.IsEnabled = false;
// Start video playback when the file stream exists.
if (VideoPlayer.Source != null)
VideoPlayer.Play();
// Start the video for the first time.
else
//vcDevice.Dispose();
// Remove VideoBrush from the tree.
viewfinderRectangle.Fill = null;
//get the path of iClips-video
StorageFolder isoStore = await ApplicationData.Current.LocalFolder.GetFolderAsync("Shared");
iclip = await isoStore.GetFileAsync(isoVideoFileName + ".mp4");
// Create the file stream and attach it to the MediaElement.
VideoPlayer.Source = new Uri(iclip.Path);
// Add an event handler for the end of playback.
VideoPlayer.MediaEnded += new RoutedEventHandler(VideoPlayerMediaEnded);
// Start video playback.
VideoPlayer.Play();
// Set the button state and the message.
UpdateUI(ButtonState.Playback, "Playback started.");
catch (Exception ex)
MessageBox.Show("Play Video Exception:\n" + ex.Message.ToString());
private void PausePlayback_Click(object sender, EventArgs e)
PauseVideo();
private void PauseVideo()
// Avoid duplicate taps.
PausePlayback.IsEnabled = false;
// If mediaElement exists, pause playback.
if (VideoPlayer != null)
VideoPlayer.Pause();
// Set the button state and the message.
UpdateUI(ButtonState.Paused, "Playback paused.");
private void DisposeVideoPlayer()
if (VideoPlayer != null)
// Stop the VideoPlayer MediaElement.
VideoPlayer.Stop();
// Remove playback objects.
VideoPlayer.Source = null;
iclip = null;
// Remove the event handler.
VideoPlayer.MediaEnded -= VideoPlayerMediaEnded;
// Display the viewfinder when playback ends.
public void VideoPlayerMediaEnded(object sender, RoutedEventArgs e)
// Remove the playback objects.
DisposeVideoPlayer();
StartVideoPreview();
I'm using StorageFile to create the file to save the video to. I think my Stop and Start Video Recording logic is causing ether the video not to write to the file the second time or something else. If you can see something that's not right kindly tell me. Thank
you in advance.