[MPlayer-dev-eng] [PATCH] RFC: xv, composition managers and translucent windows

[Paul TT]

On Thu, 22 Mar 2007 17:49:52 +0200
"Ivan Kalvachev" <ikalvachev at gmail.com> wrote:

...
> 
> There are generally 2 types of video output surfaces.
> 
> One is called overlay and it operates as second stream. It is produced
> from another memory region by another color-creation-engine and is
> switched to be visible only if given color (called key-color or
> colorkey) is present in the primary memory region.
> 
> The second type one is usually referred as blitter. It uses 2D/3D
> operations to convert the color format to the desktop one and place it
> in the visible primary memory region (aka desktop or framebuffer).
> 
> 
> The blue color you are seeing is actually this  key-color. The thing
> is that very few (and practically nearly non of the cheap cards)
> support alpha-coded key-color. Even these that support it have rather
> limited alpha channel.

i knew :)

> My guess is that in your case the composite manager operates only in
> the primary desktop, when there is transparency it combines the
> key-color changing it to another blue color that doesn't trigger the
> second stream.
> 
> Now, I donno what this attribute "XV_ALPHA_MODE" does, but it is not
> visible on my video card (I don't see it with xvinfo). Is it present
> only when composite stuff is running or it is available only on you
> video card?
available on the video card

> A little google search indicates it is something available on Radeon
> cards (r300+).
> There is also attribute "XV_OVERLAY_ALPHA" (range 0 to 255).

ies, playing with this it's possible to change alpha status of the
xvimages

> The thing is that this option may make the overlay stay always-on-top,
> as it may allow transparency control through  the second attribute,
> but without any way to indicate zones, so overlapping non-transparent
> windows would look like they are bellow the video.

ies, i could make some test and i could see this, as i wrote in the
other mail, sigh :(

> Oh, well if you have somewhere documentation what these radeon options
> do, I'd like to get a URL.
> 
> Anyway, the preferred solution seems to be using video bitters because
> s 2d/3d operations allow transparency.

so vo gl/gl2 or the like? or what?
thanx, Paul