python/gst-trick-mode.py

   1 #!/usr/bin/env python
   2 #
   3 # A simple "trick-mode" player to play a file at a given speed rate.
   4 #
   5 # Get a test sample with:
   6 # youtube-dl -t http://www.youtube.com/watch?v=yWa-YXiSk2Y
   7
   8 import sys
   9
  10 import gi
  11 gi.require_version('Gst', '1.0')
  12 from gi.repository import Gst
  13 Gst.init(None)
  14
  15 from gi.repository import GObject
  16 GObject.threads_init()
  17
  18
  19 class Player:
  20     def __init__(self, uri, rate):
  21         self._rate = rate
  22
  23         self._player = Gst.ElementFactory.make("playbin", "player")
  24         self._player.set_property("uri", uri)
  25
  26         bus = self._player.get_bus()
  27         bus.add_signal_watch()
  28         bus.connect('message::eos', self.on_eos)
  29         bus.connect('message::error', self.on_error)
  30         bus.connect('message::state-changed', self.on_state_changed)
  31
  32     def run(self):
  33         self._player.set_state(Gst.State.PLAYING)
  34         self.loop = GObject.MainLoop()
  35         self.loop.run()
  36
  37     def quit(self):
  38         self._player.set_state(Gst.State.NULL)
  39         self.loop.quit()
  40
  41     def on_eos(self, bus, msg):
  42         self.quit()
  43
  44     def on_error(self, bus, msg):
  45         (err, debug) = msg.parse_error()
  46         print "Error: %s" % err, debug
  47         self.quit()
  48
  49     def on_state_changed(self, bus, msg):
  50         if msg.src != self._player:
  51             return
  52
  53         print 'on_state_changed'
  54         old_state, new_state, pending = msg.parse_state_changed()
  55         print "%s -> %s" % (old_state, new_state)
  56         if old_state == Gst.State.READY and new_state == Gst.State.PAUSED:
  57             self.set_rate(self._rate)
  58
  59     def set_rate(self, rate):
  60         self._rate = rate
  61         try:
  62             position, fmt = self._player.query_position(Gst.Format.TIME)
  63         except:
  64             position = 0
  65
  66         # Create the seek event
  67         if rate > 0:
  68             seek_event = Gst.Event.new_seek(rate,
  69                                             Gst.Format.TIME,
  70                                             Gst.SeekFlags.FLUSH | Gst.SeekFlags.ACCURATE,
  71                                             Gst.SeekType.SET, position,
  72                                             Gst.SeekType.NONE, 0)
  73         else:
  74             seek_event = Gst.Event.new_seek(rate,
  75                                             Gst.Format.TIME,
  76                                             Gst.SeekFlags.FLUSH | Gst.SeekFlags.ACCURATE,
  77                                             Gst.SeekType.SET, 0,
  78                                             Gst.SeekType.SET, position)
  79
  80         if seek_event:
  81             self._player.send_event(seek_event)
  82             Gst.info("rate set to %s" % rate)
  83         else:
  84             Gst.warining("change rate failed")
  85
  86
  87 def main(args):
  88     def usage():
  89         sys.stdout.write("usage: %s <filename> <speedrate>\n" % args[0])
  90
  91     if len(args) != 3:
  92         usage()
  93         sys.exit(1)
  94
  95     uri = Gst.filename_to_uri(args[1])
  96     rate = float(args[2])
  97
  98     player = Player(uri, rate)
  99     player.run()
 100
 101 if __name__ == '__main__':
 102     sys.exit(main(sys.argv))