what is overlay on earth ?
Is it a function of graphic card or a function of
video capture card or both?
Someone told me :
overlay means transfering video from capture card
directly to video memory without cpu’s involvement.
Then according to this explaintion ,it should be the
function of both.
But from doc for SDL, I can also see yuvoverlay api.
Does it mean without capture card ,SDL still can
provide the overlay function.
From this point, overlay should be the function of
video card .
Does overlay means DMA between capture card and video
card or some color space conversion by video card ?
who can give me a answer ?
Any help will be nice ,thanks in advance!__________________________________________________
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Hi!
I think you completely missed the bus. Fewest people have a video capture
card, but overlays are used in many applications. What in my opinion is an
overlay:
You have two surfaces, with different stuff in them. And now you need a
fast function for mixing them together so both surface-contents are
displayed at the same time, maybe even blended. IT has nothing to do with
video capturing … dunno where you caught this, anyhow, doesn’t matter,
hope you’re on the right way by now …
St0fF.
Hello,
i would like to ask, why when i use SDL_DisplayYUVOverlay it doesn't
respect double buffering. I want to have something over the video. But when i
use SDL_DisplayYUVOverlay it repaints screen and Updates it even if it’s double
buffering. And then when i paint over it -> it’s flickering. What shall i do?
I did Overlay not over screen surface but some other and then i paint it into
it and then i use SDL_BlitSurface to the screen. But it takes time.
YUVOverlay -SDL_DisplayYUVOverlay> tempSurface -SDL_BlitSurface> Screen -> (Flip)
but i would like to:
YUVOverlay -SDL_DisplayYUVOverlay> Screen -> (Flip)
Is it possible not to update screen after SDL_DisplayYUVOverlay ?
Overlay doesn’t behave like Surface, but in man i can read:
A SDL_Overlay is similar to a SDL_Surface except it stores a YUV overlay.
milaOn Sun, Mar 10, 2002 at 02:50:20AM +0100, St0fF 64 wrote:
Hi!
I think you completely missed the bus. Fewest people have a video capture
card, but overlays are used in many applications. What in my opinion is an
overlay:
You have two surfaces, with different stuff in them. And now you need a
fast function for mixing them together so both surface-contents are
displayed at the same time, maybe even blended. IT has nothing to do with
video capturing … dunno where you caught this, anyhow, doesn’t matter,
hope you’re on the right way by now …
St0fF.
SDL mailing list
SDL at libsdl.org
http://www.libsdl.org/mailman/listinfo/sdl
i would like to ask, why when i use SDL_DisplayYUVOverlay it doesn’t
respect double buffering. I want to have something over the video. But when i
use SDL_DisplayYUVOverlay it repaints screen and Updates it even if it’s double
buffering. And then when i paint over it -> it’s flickering. What shall i do?
Try displaying the overlay to an SDL surface and then blitting what you want
onto that surface, and then blitting the entire surface to the screen. You
won’t get YUV acceleration that way, but if you don’t do that, it may be that
the video card itself is displaying the overlay over all other video output,
and it may not be possible to display anything over it.
You may also convert what you want to draw into YUV and merge it with the
YUV image before displaying it, but that’s much more difficult.
See ya,
-Sam Lantinga, Software Engineer, Blizzard Entertainment