gstreamer Python and cairooverlay

[Olivier Aubert]

Indeed, it does not work when passing the data directly in single quotes
in gst_parse_launch. It is because of quote handling which, in the
command line, is in part handled by the shell and hides this issue (I
guess).

If you change your python into
pipeline = gst.parse_launch('''videotestsrc ! ffmpegcolorspace !
rsvgoverlay data="<svg><circle cx='100' cy='100' r='50'
fill='red' /></svg>" ! ffmpegcolorspace ! autovideosink''')

(note the "double quote" to pass the parameter value) it works. The same
goes for filename: it works from python as well as from the command
line, if you use either no quote or double quotes to pass the parameter.

However, from my experience in my own python-based app (www.advene.org),
it is more convenient to pass the SVG value after pipeline
initialization, especially if you want to dynamically modify the
overlayed graphics:

import gst

pipeline = gst.parse_launch('''videotestsrc ! ffmpegcolorspace !
        rsvgoverlay name=overlay ! ffmpegcolorspace ! autovideosink''')

pipeline.set_state(gst.STATE_PLAYING)

overlay = pipeline.get_by_name('overlay')

overlay.props.data = "<svg><circle cx='100' cy='100' r='50'
fill='red' /></svg>"

# And if you need to clear the overlay after some time :
overlay.props.data = None

Best regards,
Olivier


On Sat, 2013-01-05 at 22:26 -0800, Roy Wiggins wrote:
> I can't get a single svg element to show up using the python bindings :(
> 
> The command line 
> 
> gst-launch-0.10 -v videotestsrc ! ffmpegcolorspace ! rsvgoverlay data =
> '<svg><circle cx="100" cy="100" r="50" fill="red" /></svg>' !
> ffmpegcolorspace ! autovideosink
> 
> works as expected. I tried doing the same thing in Python, and while it
> doesn't error, it also doesn't display the overlay (though the videotestsrc
> does show up):
> 
> pipeline = gst.parse_launch('videotestsrc ! ffmpegcolorspace ! rsvgoverlay
> data = \'<svg><circle cx="100" cy="100" r="50" fill="red" /></svg>\' !
> ffmpegcolorspace ! autovideosink')
> 
> I also tried building the pipeline by creating each pad in turn and linking
> them, but that didn't work either; neither does using an svg file which
> works just find at the command line.
> 
> 
> Olivier Aubert-2 wrote
> > Hello
> > 
> > Given your requirements, did you give the rsvgoverlay element a try? It
> > is cross-platform, and allows you to overlay arbitrary SVG graphics on
> > top of the video. You do not have to write any cairo code, just generate
> > on-the-fly SVG code and feed it to the element.
> > 
> > Olivier
> 
> 
> 
> 
> 
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