Python GStreamer src element

Glenn Pierce glennpierce at
Mon Jan 16 07:09:55 PST 2012

I didn't want to high jack the thread from Mahendra about writing a
src plugin in Python. However, I sure it would help him as well.

I am also trying to create an element src in Python. I have found the
following code at
This seems to work when placed into a pipeline with a fake sink.

To extend this example and learn more I have decided to try to play a
sine wave.  (Ultimately I wan't to pass data from a text to speech

I cant seem to find any good examples of what's need to be done in do_create.
What I have at the moment is

def do_create(self, offset, length):
       data = [str(math.sin(a)*255.0) for a in numpy.arange(0.0,
2*math.pi, 0.01)]  ? # How am I meant to populate data ?
       buf = gst.Buffer(data)
       caps = gst.caps_from_string('audio/x-raw-float, rate=44100,
channels=1, width=8')
       buf.timestamp = 0 * gst.SECOND
       buf.duration = 4 * gst.SECOND
       return gst.FLOW_OK, buf

I basically need to know how I can populate the Buffer object with
audio data as a string.
Everything I try results in

error: Internal data flow error.

I am using to with the following pipeline to playback.

'acapelasrc ! audioconvert ! audioresample ! autoaudiosink'

Any pointers would be greatly appreciated.


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