[sugar] video bleeds through somewhat between sessions

[Albert Cahalan]

Jordan Crouse writes:

> Video is muxed to the visible screen through the use of a color key -
> given a rectangle of some size, the hardware compares all of the pixels
> in that rectangle against a set color - if they match, then a pixel of
> the video frame is shown, otherwise not.

That should have gone out of style with those ISA VGA cards that
had a ribbon connector on top to accept video from a tuner card.
The hack almost made sense with a palette.

If a 32-bit framebuffer were used, would the use of the top 8 bits
fix this problem? (valid colors are 0 to 0xffffff, so use 0x1000000)

> The color is specified by the video application - most applications
> use very saturated colors similar to those used in "green" or "blue"
> screens. My favorite is hot pink (0xFF00FF).  IIRC, mplayer uses an
> off-shade color of grey, so it is easier to run into the possibility
> that other applications will match the color key, especially with
> automatic shading such as anti-aliasing.

Better would be 0xff00fe or 0xfe00ff, appropriately adjusted to
deal with 16-bit color. (0xf81e or 0xf01f I think) Decrement either
the red value or blue value to avoid being perfect magenta.

> Nothing to worry about - just a fun little side effect of video
> acceleration.

Well, it does detract from the overall appearance.