PySide (Qt) + PyGst (GStreamer) on Microsoft Windows

pyside_pygst_on_windows.py

import sys

# needed for casting PyCObject to void pointer
from ctypes import pythonapi, c_void_p, py_object

from PySide.QtCore import *
from PySide.QtGui import *

import gobject
import pygst
pygst.require('0.10')
import gst


class Form(QDialog):
    def __init__(self, parent=None):
        super(Form, self).__init__(parent)
        self.setWindowTitle('PySide+GStreamer on Microsoft Windows')

        # create widgets and set properties
        self.videoWidget = QWidget(self)
        self.videoWidget.setMinimumSize(640, 480)
        self.numBuffersSpinBox = QSpinBox()
        self.numBuffersSpinBox.setMinimum(-1)
        self.numBuffersSpinBox.setValue(-1)
        self.button = QPushButton('Start')

        # build layout
        layout = QVBoxLayout()
        layout.addWidget(self.videoWidget)
        layout.addWidget(QLabel('num-buffers'))
        layout.addWidget(self.numBuffersSpinBox)
        layout.addWidget(self.button)
        self.setLayout(layout)

        # connect signals
        self.button.clicked.connect(self.on_start_stop)

        # build pipeline
        self.pipeline = gst.Pipeline()
        self.source = gst.element_factory_make('videotestsrc')
        self.sink = gst.element_factory_make('dshowvideosink')
        self.pipeline.add(self.source, self.sink)
        gst.element_link_many(self.source, self.sink)

        # connect sync-message from gst.Bus
        self.bus = self.pipeline.get_bus()
        self.bus.add_signal_watch()
        self.bus.enable_sync_message_emission()
        self.bus.connect('sync-message::element', self.on_sync_message)

        # create timer for checking gst.Bus messages
        self.timer = QTimer()
        self.timer.timeout.connect(self.on_timer)

        # we can't call winId() within the streaming thread (on_sync_message)
        # so we must do it here
        winid = self.videoWidget.winId()

        # convert winId from PyCObject to void pointer (only for PySide on
        # Windows)
        pythonapi.PyCObject_AsVoidPtr.restype = c_void_p
        pythonapi.PyCObject_AsVoidPtr.argtypes = [py_object]
        self.hWnd = pythonapi.PyCObject_AsVoidPtr(self.videoWidget.winId())

    def on_start_stop(self):
        if self.button.text() == 'Stop':
            self.pipeline.set_state(gst.STATE_NULL)
            self.button.setText('Start')
        else:
            self.source.props.num_buffers = self.numBuffersSpinBox.value()
            self.pipeline.set_state(gst.STATE_PLAYING)
            self.button.setText('Stop')
            self.timer.start(30)

    def on_sync_message(self, bus, message):
        if message.structure is None:
            return

        if message.structure.get_name() == 'prepare-xwindow-id':
            # enables video to play in QWidget
            self.sink.set_xwindow_id(self.hWnd)

    def on_timer(self):
        message = self.bus.pop()
        if message == None:
            return

        t = message.type
        if t == gst.MESSAGE_EOS:
            self.on_start_stop()
        elif t == gst.MESSAGE_ERROR:
            err, debug = message.parse_error()
            QMessageBox.critical(self, self.tr('Pipeline error'),
                                 str(err) + '\n' + debug)
            self.on_start_stop()

if __name__ == '__main__':
    gobject.threads_init()
    app = QApplication(sys.argv)
    form = Form()
    form.show()
    sys.exit(app.exec_())