On Jun 25, 10:56 am, Chris Rutherford
<chrismrutherf...@googlemail.com> wrote:
> 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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