this++
On Jun 24, 3:34 pm, "chrismrutherf...@googlemail.com"
<chrismrutherf...@googlemail.com> wrote:
> http://groups.google.com/group/android-framework/browse_thread/thread...
>
> Sparks..
> For overlay interface, the hardware driver is responsible for scaling,
> rotation, etc. SurfaceFlinger just leaves a whole in the 2D composited
> frame (black pixels with alpha = 0) to allow overlay surface to show
> through the 2D surfaces.
>
> To be clear, this means that the video overlay is behind the 2D
> overlay. I believe there are provisions for chroma-key if the overlay
> doesn't support an alpha channel.
>
> Hi It appears that I can't reply to the discussion above previously
> called 'About the libhardware and overlay hardware interface.' From
> the discussion it appears that a video overlay is displayed behind the
> sufaceflinger's composited frame. When using overlays, the discussion
> states that the surfaceflinger leaves a hole with alpha=0 and pixels =
> black, but the discussion it also implies that an overlay may have an
> alpha channel.
>
> If the surfaceflinger leaves a hole, then what use is the overlay
> alpha because there will be no colors to multiply. Surely the
> surfaceflinger does not always leave a hole? and can have color pixels
> so that the surfaceflinger's composted frame can be alpha blended with
> an overlay frame using hardware?
>
> If this is the case can a composted frame have an alpha value so that
> the hardware knows how to multiply the foreground surface with the
> background video overlay? or does the overlay always have to have the
> alpha?
>
> Thanks
>
> Chris
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