Guillermo S. Romero / Familia Romero wrote:
> I tried video, and I got a blue image... fun. I run with depth 24 and
> fbbpp 32, so I guess this has something to do about it, cos when
> moving the video window, I get blue areas (I am still discovering the
> nice and bad things of the new driver for my card).

A modern video card includes hardware optimised for playing back YUV
video data such as "Motion JPEG", MPEG, MPEG2 etc.

Rather than doing YUV -> RGB -> framebuffer in software these cards contain
additional buffers and logic for displaying YUV data as chroma-keyed
overlay onto the "real" RGB framebuffer.

In X11 this is expressed through the Xv video port extension to the X11
protocol, in Windows there is an equivalent mechanism presumably. You
draw a window in the chromakey color (often ~ #0000fe which is "blue")
and the video card paints your YUV data into the blue space!

This has two visible effects

1. Video runs faster and more smoothly even on slower hardware
2. The video data is not "in" the framebuffer, so you can't screenshot
it, and will see weird artifacts if you drag the video window too quickly

This is perfectly normal. If you don't like it it's possible to disable
the support for this feature on some hardware, but IMHO you don't know
what you're missing :)

So long as you only use Free Software you need not fear losing the ability
to get frames out of movies, because the YUV data can be captured and
re-processed to make a screenshot "after the fact" :)

Nick.
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