I have a video with transparent background in .avi format (Made from Adobe After Effects), but the transparent background appears black in mediaelement. Media Player has no background property also.
What should i use so that this media element plays the file and when placed on an image takes that image as its background. (No i cannot embed that image in the avi file as my image keeps changing).
*If my approach is wrong please let me know.
I'm afraid using the normal wpf media player this can't be done.
The mediaplayer ignores the transparent regions, even with video formats that accept it. From memory, i dont think AVI files support transparent regions. MOV files do.
Having said that, and although it could be a very complicated task, it may be possible to enhance the WPFMediaKit mediaplayer to do what you want.
http://wpfmediakit.codeplex.com/
J Morrill the author of wpfmediakit may be able to let you know if it is possible or not.
I might add that i got around this problem in a project once by using a sequence of .png files that played a short 10 second movie. Of course this is not an ideal solution, but it got me out of a jam
Another workaround is to use color keying - assing a color (or more colors) in your video, which you translate to the transparency by a WPF Effect(BitmapEffect or ShaderEffect).
来源：https://stackoverflow.com/questions/8470507/how-to-play-transparent-background-avi-file-in-media-element