Creating our own MPE

[brabebhin]

This is a rather unstructured collection of thoughts I had over the years in regards to this topic.

1. MediaPlayer has the frame server mode, which allows rendering of video frames to a directx surface. MediaPlayer continues to do audio-video-subtitle sync in frame server mode, so that's quite cool.
2. We know from the analysis of the MPE source code that Microsoft uses some sort of swap chain to render video with DirectX. We can do the same. In fact I could probably get something going over a weekend if I find the time. The swap chain will also allow us to render video effects more efficiently and avoid bugs within MF (like MediaPlaybackList).
3. The elephant in the room are subtitles. MediaPlayer does have a subtitle rendering method for frame server mode, but I could never get that to work. TBH I never tried this with an actual DirectX swap chain but with win2D canvases, maybe that's the problem. But assuming we cannot relay on Microsoft, we would need to do our own rendering of subtitles. For SRT and Image cues this is pretty straightforward, but it becomes tricky for ASS/SSA with animations. I guess we could draw inspiration from winappsdk code to build our own rendering, although I would prefer to keep things DirectX based and avoid XAML composition.