basic-tutorial-7.py

#!/usr/bin/python3

import sys
import gi
gi.require_version('Gst', '1.0')
from gi.repository import Gst

# http://docs.gstreamer.com/display/GstSDK/Basic+tutorial+7%3A+Multithreading+and+Pad+Availability


def main():
    # initialize GStreamer
    Gst.init(sys.argv)

    # create the elements
    audio_source = Gst.ElementFactory.make("audiotestsrc", "audio_source")
    tee = Gst.ElementFactory.make("tee", "tee")
    audio_queue = Gst.ElementFactory.make("queue", "audio_queue")
    audio_convert = Gst.ElementFactory.make("audioconvert", "audio_convert")
    audio_resample = Gst.ElementFactory.make("audioresample", "audio_resample")
    audio_sink = Gst.ElementFactory.make("autoaudiosink", "audio_sink")
    video_queue = Gst.ElementFactory.make("queue", "video_queue")
    visual = Gst.ElementFactory.make("wavescope", "visual")
    video_convert = Gst.ElementFactory.make("videoconvert", "video_convert")
    video_sink = Gst.ElementFactory.make("autovideosink", "video_sink")

    # create the empty pipeline
    pipeline = Gst.Pipeline.new("test-pipeline")

    if (not pipeline or not audio_source or not tee or not audio_queue
            or not audio_convert or not audio_resample or not audio_sink
            or not video_queue or not visual or not video_convert
            or not video_sink):
        print("ERROR: Not all elements could be created.")
        sys.exit(1)

    # configure elements
    audio_source.set_property("freq", 215.0)
    visual.set_property("shader", 0)
    visual.set_property("style", 1)

    # link all elements that can be automatically linked because they have
    # always pads
    pipeline.add(audio_source, tee, audio_queue, audio_convert, audio_resample,
                 audio_sink, video_queue, visual, video_convert, video_sink)

    ret = audio_source.link(tee)
    ret = ret and audio_queue.link(audio_convert)
    ret = ret and audio_convert.link(audio_resample)
    ret = ret and audio_resample.link(audio_sink)
    ret = ret and video_queue.link(visual)
    ret = ret and visual.link(video_convert)
    ret = ret and video_convert.link(video_sink)

    if not ret:
        print("ERROR: Elements could not be linked")
        sys.exit(1)

    # manually link the tee, which has "Request" pads
    tee_src_pad_template = tee.get_pad_template("src_%u")
    tee_audio_pad = tee.request_pad(tee_src_pad_template, None, None)
    print(
        "Obtained request pad {0} for audio branch".format(
            tee_audio_pad.get_name()))
    audio_queue_pad = audio_queue.get_static_pad("sink")
    tee_video_pad = tee.request_pad(tee_src_pad_template, None, None)
    print(
        "Obtained request pad {0} for video branch".format(
            tee_video_pad.get_name()))
    video_queue_pad = video_queue.get_static_pad("sink")

    if (tee_audio_pad.link(audio_queue_pad) != Gst.PadLinkReturn.OK
            or tee_video_pad.link(video_queue_pad) != Gst.PadLinkReturn.OK):
        print("ERROR: Tee could not be linked")
        sys.exit(1)

    # one could use link() to link elements with"Reuest" pads automatically
    # instead of manually (see above), as it will internally
    # request the pads
    # tee.link(audio_queue)
    # tee.link(video_queue)

    # start playing
    pipeline.set_state(Gst.State.PLAYING)

    # wait until error or EOS
    terminate = False
    bus = pipeline.get_bus()
    while True:
        try:
            msg = bus.timed_pop_filtered(
                0.5 * Gst.SECOND,
                Gst.MessageType.ERROR | Gst.MessageType.EOS)
            if msg:
                terminate = True
        except KeyboardInterrupt:
            terminate = True

        if terminate:
            break

    pipeline.set_state(Gst.State.NULL)

if __name__ == '__main__':
    main()