How to place video(use DirectShow) on an transparent window?

video's owner window is an irregular dialog with png background can be semi-transparent.

I found this:

http://www.ureader.com/msg/14711693.aspx


Re: DirectShow and Transparency
On Tue, 29 Nov 2005 10:44:21 -0600, "Ranna" wrote:

>Hello All!
>I am working on a DiretShow video application. What I would like to know (I
>am new to this, and I know almost nothing about DirectDraw/3D) is will DShow
>always render video as a topmost window? Or is it some specific
>characteristic of VMR-7's windowless controls? I would like to a have a
>layered window on top of the video with transparency key set
>(GDI+/SetLayeredWindowAttributes). In my experience, the video tends to
>paint new frames on top of my layered window, and then my layered window
>then refreshes itself, leading to flickering of my layered window.
>Thanks in advance for your time and effort!

Renderer windows aren't topmost (you can hide them with other windows),
but I don't believe you can have a transparent window on top of them
since they're using DirectX to blit directly to the screen. If you want
to put something on top of it you should use the mixer mode of the VMRs,
or write a transform filter that does the mixing.

In any case, putting a window on top of a renderer is a bad idea, since
the DirectX blits will be split into regions to prevent it from
overwriting the window that is on top of the renderer. The blits are not
done with subpixel accuracy, so it can be very obvious that the blits
are split up if you're doing any kind of stretching.

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date: Tue, 29 Nov 2005 10:57:59 -0600 author: Thore Karlsen [MVP DX]