在Windows Phone Silverlight 8.1上打开使用MediaCapture的手电筒 [英] Turn on torch with MediaCapture on Windows Phone Silverlight 8.1
问题描述
我的问题很简单，我无法打开闪光灯与MediaCapture API从Windows Phone 8.1。 （我用8.0 API成功）
我创建了一个非常简单的项目，有两个按钮，一个用于切换FlashControl，另一个用于切换TorchControl。
没有崩溃，也没有异常。我的手机支持FlashControl和TorchControl。
这是我的代码：
b $ b
MediaCapture m_captureManager;
public MainPage（）
{
InitializeComponent（）;
}
private static async Task< DeviceInformation> GetCameraID（Windows.Devices.Enumeration.Panel desiredCamera）
{
DeviceInformation deviceID =（await DeviceInformation.FindAllAsync（DeviceClass.VideoCapture））
.FirstOrDefault（x => x.EnclosureLocation！= null&& x.EnclosureLocation.Panel == desiredCamera）;
if（deviceID！= null）return deviceID;
else throw new Exception（string.Format（Camera {0} does not exist，desiredCamera））;
}
protected async override void OnNavigatedTo（NavigationEventArgs e）
{
var cameraID = await GetCameraID（Windows.Devices.Enumeration.Panel.Back）;
m_captureManager = new MediaCapture（）;
await m_captureManager.InitializeAsync（new MediaCaptureInitializationSettings
{
StreamingCaptureMode = StreamingCaptureMode.Video，
PhotoCaptureSource = PhotoCaptureSource.VideoPreview，
AudioDeviceId = string.Empty，
VideoDeviceId = cameraID.Id
}）;
}
private void button_ClickTorch（object sender，RoutedEventArgs e）
{
var torch = m_captureManager.VideoDeviceController.TorchControl;
if（torch.Supported）
{
if（torch.Enabled）
torch.Enabled = false;
else
torch.Enabled = true;
}
}
private void button_ClickFlash（object sender，RoutedEventArgs e）
{
if（captureManager.VideoDeviceController.FlashControl.Supported）
{
if（captureManager.VideoDeviceController.FlashControl.Enabled）
captureManager.VideoDeviceController.FlashControl.Enabled = false;
else
captureManager.VideoDeviceController.FlashControl.Enabled = true;
}
}
这是一段简单的代码，工作...我非常绝望，所以我试图切换使用一个中间对象和没有，你可以看到，但它没有改变结果（这是一致的）。
我终于找到了什么问题。为了能够使用摄像头服务，我们必须开始预览。
从Silverlight我们不能使用CaptureElement，我们必须使用CustomPreviewSink与VideoBrush
这是怎么做的（从 microsoft doc ）
private async void StartPreview（）
{
previewSink = new Windows.Phone.Media.Capture.MediaCapturePreviewSink ;
//默认预览格式选择器使用的支持的视频预览格式列表。
var supportedVideoFormats = new List< string> {nv12，rgb32};
//查找支持的预览格式
var availableMediaStreamProperties = mediaCaptureManager.VideoDeviceController.GetAvailableMediaStreamProperties（
Windows.Media.Capture.MediaStreamType.VideoPreview）
.OfType< Windows .Media.MediaProperties.VideoEncodingProperties>（）
.Where（p => p！= null
&&！String.IsNullOrEmpty（p.Subtype）
&& supportedVideoFormats .Contains（p.Subtype.ToLower（）））
.ToList（）;
var previewFormat = availableMediaStreamProperties.FirstOrDefault（）;
//开始预览流
await mediaCaptureManager.VideoDeviceController.SetMediaStreamPropertiesAsync（
Windows.Media.Capture.MediaStreamType.VideoPreview，previewFormat）;
await mediaCaptureManager.StartPreviewToCustomSinkAsync（
new Windows.Media.MediaProperties.MediaEncodingProfile {Video = previewFormat}，previewSink）;
//设置用于预览的VideoBrush的源代码
Microsoft.Devices.CameraVideoBrushExtensions.SetSource（viewfinderBrush，previewSink）;
}
将这段代码添加到以前的代码中，它会工作。重要的一点是在更改任何参数之前开始预览
My problem is quite simple, I cannot turn on the flash light with the MediaCapture API from windows phone 8.1. (I succedded with the 8.0 API)
I built a very simple project with 2 buttons, one to toggle the FlashControl and the other one to toggle TorchControl.
There is no crash, no exception. My phones support FlashControl and TorchControl. I also debug step-by-step and everything looks good, values are changed when buttons are clicked.
Here is my code:
MediaCapture m_captureManager;
public MainPage()
{
InitializeComponent();
}
private static async Task<DeviceInformation> GetCameraID(Windows.Devices.Enumeration.Panel desiredCamera)
{
DeviceInformation deviceID = (await DeviceInformation.FindAllAsync(DeviceClass.VideoCapture))
.FirstOrDefault(x => x.EnclosureLocation != null && x.EnclosureLocation.Panel == desiredCamera);
if (deviceID != null) return deviceID;
else throw new Exception(string.Format("Camera {0} doesn't exist", desiredCamera));
}
protected async override void OnNavigatedTo(NavigationEventArgs e)
{
var cameraID = await GetCameraID(Windows.Devices.Enumeration.Panel.Back);
m_captureManager = new MediaCapture();
await m_captureManager.InitializeAsync(new MediaCaptureInitializationSettings
{
StreamingCaptureMode = StreamingCaptureMode.Video,
PhotoCaptureSource = PhotoCaptureSource.VideoPreview,
AudioDeviceId = string.Empty,
VideoDeviceId = cameraID.Id
});
}
private void button_ClickTorch(object sender, RoutedEventArgs e)
{
var torch = m_captureManager.VideoDeviceController.TorchControl;
if (torch.Supported)
{
if (torch.Enabled)
torch.Enabled = false;
else
torch.Enabled = true;
}
}
private void button_ClickFlash(object sender, RoutedEventArgs e)
{
if (captureManager.VideoDeviceController.FlashControl.Supported)
{
if (captureManager.VideoDeviceController.FlashControl.Enabled)
captureManager.VideoDeviceController.FlashControl.Enabled = false;
else
captureManager.VideoDeviceController.FlashControl.Enabled = true;
}
}
It's a simple piece of code and I cannot make it works... I was quite desperate so I tried to toggle by using an intermediate object and without, as you can see, but it did not change the result (which is in conformity).
I finally found out what was wrong. To be able to use camera services, we have to start a preview. Since with Silverlight we can’t use a CaptureElement, we have to use a CustomPreviewSink with a VideoBrush
This is how to do it ( from microsoft doc)
private async void StartPreview()
{
previewSink = new Windows.Phone.Media.Capture.MediaCapturePreviewSink();
// List of supported video preview formats to be used by the default preview format selector.
var supportedVideoFormats = new List<string> { "nv12", "rgb32" };
// Find the supported preview format
var availableMediaStreamProperties = mediaCaptureManager.VideoDeviceController.GetAvailableMediaStreamProperties(
Windows.Media.Capture.MediaStreamType.VideoPreview)
.OfType<Windows.Media.MediaProperties.VideoEncodingProperties>()
.Where(p => p != null
&& !String.IsNullOrEmpty(p.Subtype)
&& supportedVideoFormats.Contains(p.Subtype.ToLower()))
.ToList();
var previewFormat = availableMediaStreamProperties.FirstOrDefault();
// Start Preview stream
await mediaCaptureManager.VideoDeviceController.SetMediaStreamPropertiesAsync(
Windows.Media.Capture.MediaStreamType.VideoPreview, previewFormat);
await mediaCaptureManager.StartPreviewToCustomSinkAsync(
new Windows.Media.MediaProperties.MediaEncodingProfile { Video = previewFormat }, previewSink);
// Set the source of the VideoBrush used for your preview
Microsoft.Devices.CameraVideoBrushExtensions.SetSource(viewfinderBrush, previewSink);
}
Add this piece of code to previous code and it will work. The important point is to start the preview before changing any parameters
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