On Apr 24, 2008, at 4:03 PM, Uli Kusterer wrote:
Am 24.04.2008 um 22:14 schrieb Bob Smith:
In my case all I want to do is be able to add a scrolling text
overlay to whatever video is being played. My app is an
informational video kiosk display driver, it's meant to run mostly
unattended from playlists of images and pre-recorded video, but
with occasional scheduled live segments from streaming video
cameras on the local network. I'll take a look at Core Animation,
however one of my limitations is the app has to run under Tiger,
and I thought most of the CA stuff was new to Leopard.
Have you considered rendering your text in a separate layer (not
CA layer) on top of the movie? Several options:
1) borderless overlay window. Could be a child window if the window
with the movie in it can be moved around, so they stick together.
If your Macs are recent enough, the Quartz Compositing engine in
Quartz Extreme will take care of using the GPU to composite the two
windows on top of each other
2) IIRC movies can be rendered into OpenGL polygons. You could try
doing that and then rendering your text into a separate OpenGL
surface on top
3) I think QuickTime movies can contain layers, layered sprites
etc. You might be able to modify the movie before playing it,
adding such a track to it.
4) I think there's a sample on Apple's web site somewhere that
draws pushbuttons etc. on top of a movie (or maybe it was an OpenGL
scene?). Anyway, that approach might work for your movie, too.
Just some avenues to explore. HTH.
I did try the overlay window approach and the problem was performance
on older G5 systems. I expected the GPU to take care of the
compositing, but it seems as if the higher-level window gets rendered
in software if the lower-level window is using OpenGL directly, which
I assume is what QTMovieView is doing. The result was the video
would play fine, but the frame rate on the scrolling text overlay was
very low. It may work on a faster system or with a better graphics
card; unfortunately this app has to run on older Macs.
But your other suggestions sound like good possibilities, I'll
investigate those further.
Thanks!
Bob
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