video bleeds through somewhat between sessions

[Jim Gettys]

On Wed, 2008-08-06 at 01:43 -0400, Benjamin M. Schwartz wrote:
> Quoting Martin Langhoff <martin.langhoff at gmail.com>:
> > There is probably a bug in the mplayer wrapper (are you using an
> > mplayer 'activity' wrapper?) in that it's not getting rid of the
> > overlay setup when it loses focus or is minimized.
> 
> This is not a bug, at least in the case of losing focus.  Color-keyed video
> acceleration is designed specifically for the case of playing video in a
> background window that is partially obscured by a window in front of it.  This
> works correctly so long as the chosen key color isn't present in the foreground
> window, and so the favored key color is hot pink because it is so rarely used.
> 
> The problem here appears to be that mplayer has chosen a key color that is a
> shade of gray.  That's a poor choice, and arguably a bug.
> 
> However, Mikus has a good point here.  Insofar as XVideo's color keying is
> designed to overlap windows correctly with live video, it is unnecessary in our
> single-window UI.  The GPU is doing a great deal of unnecessary work to blit a
> video that we already know to be completely occluded.  Minimizing Activity
> windows might be a good way to start fixing this.  We should also consider what
> happens when two running Activities both want to use XVideo.  Can we multiplex
> access to XVideo, knowing that only one Activity is ever actually visible at a
> time?

There is no blitting going on....

The video unit takes the yuv data, scales it, and puts it where you tell
it to.  The color key determines if it is visible.
                            - Jim

-- 
Jim Gettys <jg at laptop.org>
One Laptop Per Child