python/gst-trick-mode.py

   1 #!/usr/bin/env python3
   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 GLib
  16
  17
  18 class Player:
  19     def __init__(self, uri, rate):
  20         self._rate = rate
  21
  22         self._player = Gst.ElementFactory.make("playbin", "player")
  23         self._player.set_property("uri", uri)
  24
  25         bus = self._player.get_bus()
  26         bus.add_signal_watch()
  27         bus.connect('message::eos', self.on_eos)
  28         bus.connect('message::error', self.on_error)
  29         bus.connect('message::state-changed', self.on_state_changed)
  30
  31     def run(self):
  32         self._player.set_state(Gst.State.PLAYING)
  33         self.loop = GLib.MainLoop()
  34         self.loop.run()
  35
  36     def quit(self):
  37         self._player.set_state(Gst.State.NULL)
  38         self.loop.quit()
  39
  40     def on_eos(self, bus, msg):
  41         self.quit()
  42
  43     def on_error(self, bus, msg):
  44         (err, debug) = msg.parse_error()
  45         print("Error: %s" % err, debug)
  46         self.quit()
  47
  48     def on_state_changed(self, bus, msg):
  49         if msg.src != self._player:
  50             return
  51
  52         print('on_state_changed')
  53         old_state, new_state, pending = msg.parse_state_changed()
  54         print("%s -> %s" % (old_state, new_state))
  55         if old_state == Gst.State.READY and new_state == Gst.State.PAUSED:
  56             self.set_rate(self._rate)
  57
  58     def set_rate(self, rate):
  59         self._rate = rate
  60         position = self._player.query_position(Gst.Format.TIME)[1]
  61
  62         # Create the seek event
  63         seek_event = Gst.Event.new_seek(rate,
  64                                         Gst.Format.TIME,
  65                                         Gst.SeekFlags.FLUSH | Gst.SeekFlags.ACCURATE,
  66                                         Gst.SeekType.SET, position,
  67                                         Gst.SeekType.SET, -1)
  68
  69         if seek_event:
  70             self._player.send_event(seek_event)
  71             Gst.info("rate set to %s" % rate)
  72         else:
  73             Gst.warining("change rate failed")
  74
  75
  76 def main(args):
  77     def usage():
  78         sys.stdout.write("usage: %s <filename> <speedrate>\n" % args[0])
  79
  80     if len(args) != 3:
  81         usage()
  82         sys.exit(1)
  83
  84     uri = Gst.filename_to_uri(args[1])
  85     rate = float(args[2])
  86
  87     player = Player(uri, rate)
  88     player.run()
  89
  90 if __name__ == '__main__':
  91     sys.exit(main(sys.argv))