[Kdenlive-devel] blue screen during plaback

[Dan Dennedy]

On Thu, Jul 31, 2008 at 8:18 PM, Johannes Wilm <j at indymedia.no> wrote:
>>> Also, what X extensions are used? XV and if that fails X11? Nothing else?
>>> It uses SDL and this is exactly the behavior. What else are you looking
>>> for, opengl? directx :-P
>
> Ok, yeah opengl and there seem to be a bunch of fancy extensions used these
> days. Ok, so how do I see which one it uses? (the point is in the end to
> discover why the screen remains blue duing playback)

I'll an opengl output to the MLT TODO list, but it won't be anything
ready for the next release. If you are using some decent 3d hardware
with a good driver (like NVIDIA and its binary driver), it will
emulate XV on its GPU. I am not sure of a good, hard way to see what
SDL is using at run time. However, there is a general rule that an Xv
port can only be used by one process, and it is typical for there to
be only one Xv port. Then, you can just be aware of what applications
are running that might have the Xv port allocated. However, some
applications may release the port when they are idle; others may not.
For example, I have seen Kaffeine with xine backend has the xv port
allocated even when its not playing. Then, when you close it, it
defaults to remain loaded in the system tray, keeping that port
allocated. (That might have changed in some version.) Sometimes, if
you know a program's behavior like this, you can take advantage of it
to, e.g., force another app to not use Xv.

Since you are getting blue, it seems to indicate that it is attempting
to use Xv, but failing for some reason. This can fail because the
images are too big for the Xv port, and you are using HD, so this
might be the case. Another reason can be a pixel format mismatch. MLT
wants YUY2, which is quite common. However, run 'xvinfo' to see what
the max res and pixel formats your system supports. Also, you can
request not to use Xv with an environment var:

http://www.libsdl.org/faq.php?action=listentries&category=3#33

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