examples: add an example to show looping using segments

Fixes #339772.

examples/segments.py

@@ -0,0 +1,198 @@
+#! /usr/bin/env python
+# -*- coding: utf-8 -*-
+
+# Segments.py
+# Copyright (C) 2006 Artem Popov <artfwo@gmail.com>
+#
+# This example demonstrates segment seeking
+# and seamless looping within playbin.
+
+import pygst
+pygst.require ("0.10")
+import gst
+
+import pygtk
+pygtk.require ("2.0")
+import gobject
+
+class Looper (gobject.GObject):
+	__gproperties__ = {
+		"loop": (gobject.TYPE_BOOLEAN,
+			"loop",
+			"Whether to loop the segment",
+			False,
+			gobject.PARAM_READWRITE),
+		"start-pos": (gobject.TYPE_UINT64,
+			"start position",
+			"The segment start marker",
+			0,
+			0xfffffffffffffff, # max long possible
+			0,
+			gobject.PARAM_READWRITE),
+		"stop-pos": (gobject.TYPE_UINT64,
+			"stop position",
+			"The segment stop marker",
+			0,
+			0xfffffffffffffff, # max long possible
+			0,
+			gobject.PARAM_READWRITE),
+	} # __gproperties__
+	
+	__gsignals__ = {
+		"stopped": (gobject.SIGNAL_RUN_LAST, gobject.TYPE_NONE, ()),
+		"position-updated": (gobject.SIGNAL_RUN_LAST, gobject.TYPE_NONE, (gobject.TYPE_FLOAT,)),
+		"error": (gobject.SIGNAL_RUN_LAST, gobject.TYPE_NONE, (gobject.TYPE_PYOBJECT,))
+	} # __gsignals__
+	
+	def __init__ (self, location = None):
+		gobject.GObject.__init__ (self)
+		
+		self.__playbin = gst.element_factory_make ("playbin")
+		self.__playbin.props.video_sink = gst.element_factory_make ("fakesink")
+		
+		bus = self.__playbin.get_bus ()
+		bus.add_watch (self.__on_bus_message)
+		
+		self.__loop = False
+		self.__start_pos = 0
+		self.__stop_pos = 0
+		
+		self.__timeout_id = 0
+		
+		if location:
+			self.load (location)
+	
+	def load (self, location):
+		self.__playbin.props.uri = location
+		self.__start_position = 0
+		self.__stop_position = 0
+	
+	def set_segment (self, start, stop):
+		self.props.start_pos = start
+		self.props.stop_pos = stop
+	
+	def play (self):
+		if not (self.__start_pos or self.__stop_pos):
+			raise RuntimeError, "Cannot start playback, segment was not set!"
+		
+		self.__playbin.set_state (gst.STATE_PLAYING)
+	
+	def stop (self, silent = False):
+		self.__playbin.set_state (gst.STATE_NULL)
+		if not silent:
+			self.emit ("stopped")
+	
+	def do_get_property (self, property):
+		if property.name == "loop":
+			return self.__loop
+		elif property.name == "start-pos":
+			return self.__start_pos
+		elif property.name == "stop-pos":
+			return self.__stop_pos
+		else:
+			raise AttributeError, "Unknown property %s" % property.name
+	
+	def do_set_property (self, property, value):
+		if property.name == "loop":
+			self.__loop = value
+		elif property.name == "start-pos":
+			self.__start_pos = value
+		elif property.name == "stop-pos":
+			self.__stop_pos = value
+		else:
+			raise AttributeError, "Unknown property %s" % property.name
+	
+	def do_stopped (self):
+		if self.__timeout_id:
+			gobject.source_remove (self.__timeout_id)
+			self.__timeout_id = 0
+	
+	def __seek (self, start, stop, flush):
+		flags = gst.SEEK_FLAG_SEGMENT | gst.SEEK_FLAG_ACCURATE
+		if flush:
+			flags = flags | gst.SEEK_FLAG_FLUSH
+		self.__playbin.seek (1.0, gst.FORMAT_TIME, flags,
+			gst.SEEK_TYPE_SET, start,
+			gst.SEEK_TYPE_SET, stop)
+	
+	def __on_timeout (self):
+		position = self.__playbin.query_position (gst.FORMAT_TIME) [0]
+		self.emit ("position-updated", float (position))
+		return True
+	
+	def __on_bus_message (self, bus, message):
+		if message.type == gst.MESSAGE_ERROR:
+			error, debug = message.parse_error ()
+			self.stop () # this looks neccessary here
+			self.emit ("error", (error, debug))
+		
+		elif message.type == gst.MESSAGE_NEW_CLOCK:
+			# we connect the timeout handler here to be sure that further queries succeed
+			interval = int ((self.__stop_position - self.__start_position) / (2 * gst.SECOND) + 50)
+			self.__timeout_id = gobject.timeout_add (interval, self.__on_timeout)
+		
+		elif message.type == gst.MESSAGE_STATE_CHANGED:
+			old_state, new_state, pending = message.parse_state_changed ()
+			if old_state == gst.STATE_READY and new_state == gst.STATE_PAUSED and message.src == self.__playbin:
+				self.__seek (self.__start_pos, self.__stop_pos, True)
+		
+		elif message.type == gst.MESSAGE_SEGMENT_DONE:
+			if self.__loop:
+				self.__seek (self.__start_pos, self.__stop_pos, False)
+			else:
+				src = self.__playbin.get_property ("source")
+				pad = src.get_pad ('src')
+				pad.push_event (gst.event_new_eos ())
+				
+				# this is the good old way:
+				#
+				# pads = src.src_pads ()
+				# while True:
+				# 	try:
+				# 		pad = pads.next ()
+				# 		pad.push_event (gst.event_new_eos ())
+				# 	except:
+				# 		break
+		
+		elif message.type == gst.MESSAGE_EOS:
+			self.stop ()
+		
+		return True
+
+mainloop = gobject.MainLoop ()
+
+def on_looper_stopped (looper):
+	mainloop.quit ()
+
+def on_looper_pos_updated (looper, position):
+	print round (position / gst.SECOND, 2)
+
+def on_looper_error (looper, error_tuple):
+	error, debug = error_tuple
+	print "\n\n%s\n\n%s\n\n" % (error, debug)
+	mainloop.quit ()
+
+if __name__ == "__main__":
+	import sys
+	if len (sys.argv) != 5:
+		print "Usage: %s <filename|uri> <start_seconds> <stop_seconds> <loop = 0|1>" % sys.argv [0]
+		sys.exit (1)
+	
+	if "://" in sys.argv [1]:
+		uri = sys.argv [1]
+	else:
+		import os.path
+		uri = "file://" + os.path.abspath (sys.argv [1])
+	
+	looper = Looper (uri)
+	
+	looper.props.start_pos = long (sys.argv [2]) * gst.SECOND
+	looper.props.stop_pos = long (sys.argv [3]) * gst.SECOND
+	looper.props.loop = int (sys.argv [4])
+	
+	looper.connect ("stopped", on_looper_stopped)
+	looper.connect ("position-updated", on_looper_pos_updated)
+	looper.connect ("error", on_looper_error)
+	
+	looper.play ()
+	mainloop.run ()