如何在 WPF 中预览 Windows Media Encoder 会话？

Question

此代码适用于 Windows 窗体应用程序（它显示预览），但不适用于 WPF 应用程序。

WMEncoder _encoder;
WMEncDataView _preview;
_encoder = new WMEncoder();

IWMEncSourceGroupCollection SrcGrpColl = _encoder.SourceGroupCollection;
IWMEncSourceGroup2 sourceGroup = (IWMEncSourceGroup2)SrcGrpColl.Add("SG_1");
IWMEncVideoSource2 videoDevice = (IWMEncVideoSource2)sourceGroup.AddSource(WMENC_SOURCE_TYPE.WMENC_VIDEO);
videoDevice.SetInput("Default_Video_Device", "Device", "");
IWMEncAudioSource audioDevice = (IWMEncAudioSource)sourceGroup.AddSource(WMENC_SOURCE_TYPE.WMENC_AUDIO);
audioDevice.SetInput("Default_Audio_Device", "Device", "");

IWMEncProfile2 profile = new WMEncProfile2();
profile.LoadFromFile("Recording.prx");
sourceGroup.set_Profile(profile);

_encoder.PrepareToEncode(true);

_preview = new WMEncDataView();
int lpreviewStream = videoDevice.PreviewCollection.Add(_preview);

_encoder.Start();

_preview.SetViewProperties(lpreviewStream, (int)windowsFormsHost1.Handle);
_preview.StartView(lpreviewStream);

我尝试使用 WindowsFormsHost 控件来获取要传递的句柄（如示例中所示），但仍然没有成功。

Answer 1

我最近做了一些类似的事情，将现有的 DirectShow 视频组件与新的 WPF UI 集成。有多种方法可以做到这一点，但最简单的方法可能是从HwndHost 派生一个新类。然后，您只需覆盖几个方法，将窗口句柄提供给您的预览流，它应该都能正常工作。根据您的要求，您可能需要在 WndProc 中处理几条 Windows 消息，以便在视频未播放时处理显示更改和重绘。

using System;
using System.Runtime.InteropServices;
using System.Windows;
using System.Windows.Interop;

namespace SOQuestion
{
    public class VideoHost : HwndHost
    {
        protected override HandleRef BuildWindowCore(HandleRef hwndParent)
        {
            IntPtr hwndHost = IntPtr.Zero;
            int hostHeight = (int) this.ActualHeight;
            int hostWidth = (int) this.ActualWidth;

            hwndHost = CreateWindowEx(0, "static", "",
                WS_CHILD | WS_VISIBLE,
                0, 0,
                hostHeight, hostWidth,
                hwndParent.Handle,
                (IntPtr)HOST_ID,
                IntPtr.Zero,
                0);

            return new HandleRef(this, hwndHost);
        }

        protected override void DestroyWindowCore(HandleRef hwnd)
        {
            DestroyWindow(hwnd.Handle);
        }

        protected override void OnWindowPositionChanged(Rect rcBoundingBox)
        {
            base.OnWindowPositionChanged(rcBoundingBox);

            _preview.SetViewProperties(lpreviewStream, (int)this.Handle);
        }

        protected override IntPtr WndProc(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled)
        {
            // Handle a couple of windows messages if required - see MSDN for details

            return base.WndProc(hwnd, msg, wParam, lParam, ref handled);
        }

        [DllImport("user32.dll", EntryPoint = "CreateWindowEx", CharSet = CharSet.Auto)]
        internal static extern IntPtr CreateWindowEx(int dwExStyle,
        string lpszClassName,
        string lpszWindowName,
        int style,
        int x, int y,
        int width, int height,
        IntPtr hwndParent,
        IntPtr hMenu,
        IntPtr hInst,
        [MarshalAs(UnmanagedType.AsAny)] object pvParam);

        [DllImport("user32.dll", EntryPoint = "DestroyWindow", CharSet = CharSet.Auto)]
        internal static extern bool DestroyWindow(IntPtr hwnd); 

        internal const int WS_CHILD = 0x40000000;
        internal const int WS_VISIBLE = 0x10000000;
        internal const int HOST_ID = 0x00000002;
    }
}