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[directfb-dev] Video overlay questions



Hi guys,

I'm working on overlays, and a couple of problems have come up. Can someone
please straighten out some of the question marks for me? Thanks!

/Andreas

-------Question #1--------

Does the VESA fb-driver support the FBIO_WAITFORVSYNC ioctl?
If not, i'm thinking of using code from waitretrace() in fbdev.c instead.

Does this line of code wait for the VBI to happen, or wait until the VBI is
over?

while (!(inb (0x3da) & 0x8));

-------Problem #2--------

I'm running this test program from DFB examples v0.9.18:

./df_layer test.mpg

test.mpg is a short mpeg2 stream I found here:
http://teco.emg.hu/tdmpeg120.mpv
(Website: http://www.tecoltd.com/enctest/enctest.htm)

First, the default buffer mode is set to DLBM_FRONTONLY (by my InitLayer
function in the driver)
Result: Works nicely, (although with lots of framedrops)

Then, the default buffer mode is changed to DLBM_BACKVIDEO, and the driver
is recompiled.
Result: No video - the overlay is black.

It turns out that df_layer doesn't call the layer's FlipBuffers function...

So, what could be missing?

-------Problem #3--------

The hardware supports a kind of alpha blending, where the video engine takes
the alpha channel in the graphics layer and uses it as the alpha channel for
the video overlay. For example, if the alpha in a graphics pixel is 255, the
video pixel on top of it is 100% opaque. If the alpha is 0, video is
transparent.

Is there support for this in the framework? Could I use DLCAPS_ALPHACHANNEL
for example?



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