tso,
haha, i forgot to paste a link, sorry
http://n8xx.com/topic2874-gstreamer.html

auouymous,
Yes, DBE will have 800x480 buffer. I just tried to test it in order to measure its memory consumption. But it seems that it will not give any advantage.

The trick that made rotated scrolling work fast is blitting window→window because in this case we don't need to rotate whole list contents each time.
Even if slider widget will lie at some floating layer there will be flickering because this blitting will override it and only after it slider will draw itself back. To make your suggestion work we need one more buffer that will store rotated content. While scrolling we will blit its content on itself, then draw the slider on this buffer and then blit it to window (with no rotation, this buffer already rotated). But this means one more fullscreen buffer that will increase X memory use...