How do I preview a Windows Media Encoder session in WPF? - wpf

Question

This code works in a windows forms application (it shows the preview) but not in a WPF application.
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);
I've tried to use the WindowsFormsHost control to get a handle to pass (as shown in the sample), but still no luck.

Answer 1

I've recently done something similar to integrate an existing DirectShow video component with a new WPF UI. There are a variety of ways to do it, but probably the easiest is to derive a new class from HwndHost. You then simply override a couple of methods, give the window handle to your preview stream and it should all just work. depending on your requirements you may need to handle a couple of Windows messages in your WndProc to handle display changes and redrawing when the video's not playing.
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;
}
}