Hi Hanchao3c,

   I just compare the overlay Android will support with Windows DDraw
interface. Just wonder whether it is possible that Android will
provided one feature as DDraw in overlay surface.
In DDraw, Overlay Surface can be created with several surfaces buffer
attach to, which are called as backup surfaces. And provide function
to swap the backup surfaces with Overlay surface. It will do some good
in video decoding. There are some codecs which need more than two
frame buffers for output. In that case , it can directly reuse the
overlay surface buffer with backup surfaces, so no memcpy needed.
So that need createOverlay can take some extra parameters to create
the backup surfaces. And swapBuffers with parameter to point to swap
specific surface.

Thanks
Guoyin Chen

> =========================================================
> It seems swapBuffers just for using double-buffer. like current
> PostBuffer method/
> Whether it can overlay  more than 2 buffers  depends on HW.
> Most Display HW only can support no more than 2 video plane.
> You can refer S3C24A0/PXA/OMAP data sheet.
>
> But I seems there needn't  using 2 HW overlay (for video ) at same
> time.

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