问题
I'm working on a custom video player using the Media Foundation framework. Currently, I can play, pause, stop or change the rate of the playback using an IMFMediaSession. I can also retrieve a single frame using an IMFSourceReader.
I am currently able to render a frame (IMFSample) to a window area (a HWND) but only when the media session is stopped. My goal is to be able to render a frame while the media session is paused. (= doing frame-stepping using a source reader and not the media session)
I'm using GetDC, CreateBitmap, SelectObject and BitBlt to render my frame. I tried using directd3d interfaces to fill it with a solid color (I'm really new to direct3d so followed a basic tutorial) but it didn't work. Here is what I did : retrieving an IDirect3DDeviceManager9 with MR_VIDEO_ACCELERATION_SERVICE, doing OpenDeviceHandle, LockDevice, Clear, Begin/EndScene and Present.
None of these calls fail but I suspect the EVR is still painting the last frame. So basically, I want the EVR to stop repainting its frame when I want and of course, I need to re-enable its painting process.
Any idea how to do that ? Thanks
回答1:
I finally got it working. If you're interested, do the following:
- retrieve IMFVideoDisplayControl and IMFVideoMixerBitmap from the media session using MFGetService
- set up MFVideoAlphaBitmap structure and feed it to IMFVideoMixerBitmap::SetAlphaBitmap (there is a working example at the dedicated MSDN page)
- call IMFVideoDisplayControl::RepaintVideo to update the output
To hide the previous content, don't set the alpha so that it's opaque. Call IMFVideoMixerBitmap::ClearAlphaBitmap to get the previous content back.
And voilà !
来源：https://stackoverflow.com/questions/27623912/painting-frames-while-media-session-is-paused