Add alpha channel to a video using a PNG mask

[GianniRusso86]

How can I set a .png mask as a vlc player property?

There are two instances of vlc one superimposed on the other.
The first instance of vlc start the video "background_video.mp4"

The second instance of vlc start the video "foreground_video.mp4"

I would like to apply a transparent mask (mask.png) like this to the second instance of vlc

So I get this result:

How do I apply a transparent mask to the second vlc player?

I tried to do:
player2.LoadMediaWithOptions(@"C:\foreground_video.mp4", new String[] { "--alphamask-mask=mask.png" });

Not Working.

Visual studio 2013 - WPF Application

Any ideas?
Thanks in advance.

[devkanro]

There are too many options for Vlc
As I know, some option is different for new Vlc() and new VlcMedia()
Maybe you can try :alphamask-mask but not --alphamask-mask, it just a example, maybe other something

[GianniRusso86]

unfortunately it does not work.
Can you give me a suggestion to reach my goal?

[peter-wwj]

Is the problem solved?