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overlay with two framebuffers

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overlay with two framebuffers

‎12-05-2013 01:50 AM
2,030 Views
tselmeci
Contributor IV

Hi all!

Having the following kernel parameters:

video=mxcdi0fb:RGB24,1920x1080M@60 video=mxcdi2fb:RGB24,1920x1080M@60 hdmi di0_primary

Writing bytes into /dev/fb0, I can see the pixels on the display, that's ok.

Writing bytes into /dev/fb2, I can't see the pixels.

cat /sys/class/graphics/fb0/name

DISP3 BG

cat /sys/class/graphics/fb2/name

DISP3 FG

So fb0 is the background and I suppose it covers the foreground pixels. I suppose somehow the alpha of background should be changed or color keying should be used to make the foreground also visible.

I'd like to implement an OSD and using multiple framebuffers (one with the video data, another one with the OSD itself) seems to be a convenient way.

How can I adjust the color keying/opacity of each framebuffer? Is this possible at all?

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‎12-18-2013 05:49 AM
1,138 Views
tselmeci
Contributor IV

/dev/fb0 and /dev/fb2 can be set to the same resolution, even in different colorspaces. Using Freescale's MXCFB IOCTLs you can have such effects as global alpha or color keying.

The only problem is that it's not functional with resolutions above 1280x768. Does anybody know anything about this? Is it another frustrating limitation of iMX53? Isn't there HW support to put OSD text in full HD resolution?

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