Re: [Fwd: Re: Journey in cheese code;]

[Filippo Argiolas <fargiolas gnome org>]

On Thu, Feb 25, 2010 at 1:08 PM, Nicolas Bertrand <nico inattendu org> wrote:

[cut]

> gst-launch-0.10 v4l2src ! video/x-raw-yuv, framerate=30/1 ! videorate !
> video/x-raw-yuv, framerate=5/1 ! ffmpegcolorspace ! autovideosink   70 %
>
>
> So, I a first conlcusion ffmpegcolospace use a lot of CPU. In second the
> videorate filter before ffmpegcolorspace has no effect on CPU load. Only
> changing the framerate on v4l2src seems effective for CPU load . Weird ....

Thanks for taking time to do those tests.
My conclusion is that those values of cpu usage just don't make any sense :)
And they are completely different from what I see here.
So, there *must be* something hidden we're not considering. I have
some guess, well actually a single one, about what's happening.
Do you by chance have a jpeg camera? If so, that high cpu usage may be
caused by libv4l jpeg decoding, and indeed you would be right, the
only way to reduce it would be to set the framerate directly in
v4l2src.

> And it's true getting framerate from v4l2src and gstreamer is hassle. I
> write a  python piece of code for that, if you are interested.

I'll look at it as soon as I have some spare time, probably in the
2.32 time frame though, we're past all the GNOME freezes for 2.30.

> Other point, does somebody or know somebody on how gnome python bindings
> work ? I read out bindings for pygtk and  pygst.  they use the same
> principle with .defs and .override files, but this method looks like un
> documented, and "slightly" different from the python documented one.

I know almost nothing about python, after a quick google search I
found this http://www.ibm.com/developerworks/linux/library/l-wrap/
It's a bit old but probably still valid. As far as I know (but I could
be wrong) there should be a tool that autogenerates .defs files then
you just need to edit them to suits your needs and add .overrides if
you need to have an adhoc behavior in python for some function (like
using python lists and tuples instead of glist, etc). Probably
something has been moved from pygtk to pygobject since that article,
I'd suggest to look for a python binded gobject library and see how
they do it.
Also, you could ask for help to #pygtk guys on irc.gimpnet.org.

Hope this helps,
Ciao,

Filippo