Question

在Windows手机silverlight中，我在启动预览视频时使用PhotoCamera获取缓冲帧，在通用应用中我使用MediaCapture，但我不知道如何获取预览缓冲区。

由于

Answer 1

由于Windows运行时没有Silverlight的PhotoCaptureDevice类，因此无法使用非常有用的GetPreviewBufferARGB()和GetPreviewBufferYCbCr()方法。

您正在寻找的解决方案是使用MediaCapture.StartPreviewToCustomSinkAsync()方法，但这需要比我的C ++技能更好。似乎没有人解决问题并分享他们的代码。

现在有一个非常漂亮的解决方案，使用Lumia Imaging SDK，不使用MediaCapture类，但可能会更好地解决您的问题。

首先查看Microsoft的example on Github。这很好用但很复杂，因为它同时针对Windows 8.1和Windows Phone 8.1。

为了我自己的理解，我写了一些更简单的代码，只针对Windows Phone。这可能有所帮助。

从新的C＃Windows Phone 8.1（商店）应用开始，通过NuGet PM安装Lumia Imaging SDK。此示例在x:Name="previewImage"中绘制了MainPage.xaml的图像元素，因此请务必添加该元素。您还需要将相关的导入设为MainPage.xaml.cs，我认为这是。

using Lumia.Imaging;
using System.Threading.Tasks;
using Windows.UI.Xaml.Media.Imaging;
using Windows.UI.Core;
using System.ComponentModel;

然后，您只需在MainPage.xaml.cs中的正确位置添加以下内容即可。

private CameraPreviewImageSource _cameraPreviewImageSource; // Using camera as our image source
private WriteableBitmap _writeableBitmap;
private FilterEffect _effect;
private WriteableBitmapRenderer _writeableBitmapRenderer; // renderer for our images
private bool _isRendering = false; // Used to prevent multiple renderers running at once

public MainPage()
{
    this.InitializeComponent();
    this.NavigationCacheMode = NavigationCacheMode.Required;
    startCameraPreview();
}

private async Task startCameraPreview()
{
    // Create a camera preview image source (from the Lumia Imaging SDK)
    _cameraPreviewImageSource = new CameraPreviewImageSource();
    await _cameraPreviewImageSource.InitializeAsync(string.Empty); // use the first available camera (ask  me if you want code to access other camera)
    var previewProperties = await _cameraPreviewImageSource.StartPreviewAsync();
    _cameraPreviewImageSource.PreviewFrameAvailable += drawPreview; // call the drawPreview method every time a new frame is available

    // Create a preview bitmap with the correct aspect ratio using the properties object returned when the preview started.
    var width = 640.0;
    var height = (width / previewProperties.Width) * previewProperties.Height;
    var bitmap = new WriteableBitmap((int)width, (int)height);
    _writeableBitmap = bitmap;

    // Create a BitmapRenderer to turn the preview Image Source into a bitmap we hold in the PreviewBitmap object
    _effect = new FilterEffect(_cameraPreviewImageSource);
    _effect.Filters = new IFilter[0]; // null filter for now
    _writeableBitmapRenderer = new WriteableBitmapRenderer(_effect, _writeableBitmap);
}

private async void drawPreview(IImageSize args)
{
    // Prevent multiple rendering attempts at once
    if (_isRendering == false)
    {
        _isRendering = true;
        await _writeableBitmapRenderer.RenderAsync(); // Render the image (with no filter)
        // Draw the image onto the previewImage XAML element
        await Windows.ApplicationModel.Core.CoreApplication.MainView.CoreWindow.Dispatcher.RunAsync(CoreDispatcherPriority.High,
            () =>
            {
                previewImage.Source = _writeableBitmap; // previewImage is an image element in MainPage.xaml
                _writeableBitmap.Invalidate(); // force the PreviewBitmap to redraw
            });
        _isRendering = false;
    }
}

你可能想知道......我如何抓住previewBuffer？你不需要！

_writeableBitmap对象始终保持相机中的最新帧，因此您可以随意执行任何操作。

Answer 2

我的其他答案对于针对Windows 8.1的通用应用仍然有效 - 但对于那些使用UWP应用定位Windows 10的应用，现在有一个更简单的答案。

Grabbing a preview frame in UWP is easy and well-documented - 从现有的MediaCapture对象可以用三行完成。

// Get information about the preview
var previewProperties = _mediaCapture.VideoDeviceController.GetMediaStreamProperties(MediaStreamType.VideoPreview) as VideoEncodingProperties;

// Create a video frame in the desired format for the preview frame
VideoFrame videoFrame = new VideoFrame(BitmapPixelFormat.Bgra8, (int)previewProperties.Height, (int)previewProperties.Width);

// Grave a preview frame        
VideoFrame previewFrame = await _mediaCapture.GetPreviewFrameAsync(videoFrame);

如何获取MediaCapture的预览缓冲区 - 通用应用程序

2 个答案: