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::state-changed', self.on_state_changed)
  29
  30     def run(self):
  31         self._player.set_state(Gst.State.PLAYING)
  32         loop = GObject.MainLoop()
  33         loop.run()
  34
  35     def on_state_changed(self, bus, msg):
  36         if msg.src != self._player:
  37             return
  38
  39         print 'on_state_changed'
  40         old_state, new_state, pending = msg.parse_state_changed()
  41         print "%s -> %s" % (old_state, new_state)
  42         if old_state == Gst.State.READY and new_state == Gst.State.PAUSED:
  43             self.set_rate(self._rate)
  44
  45     def set_rate(self, rate):
  46         self._rate = rate
  47         try:
  48             position, fmt = self._player.query_position(Gst.Format.TIME)
  49         except:
  50             position = 0
  51
  52         # Create the seek event
  53         if rate > 0:
  54             seek_event = Gst.Event.new_seek(rate,
  55                     Gst.Format.TIME,
  56                     Gst.SeekFlags.FLUSH | Gst.SeekFlags.ACCURATE,
  57                     Gst.SeekType.SET, position,
  58                     Gst.SeekType.NONE, 0)
  59         else:
  60             seek_event = Gst.Event.new_seek(rate,
  61                     Gst.Format.TIME,
  62                     Gst.SeekFlags.FLUSH | Gst.SeekFlags.ACCURATE,
  63                     Gst.SeekType.SET, 0,
  64                     Gst.SeekType.SET, position)
  65
  66         if seek_event:
  67             self._player.send_event(seek_event)
  68             Gst.info("rate set to %s" % rate)
  69         else:
  70             Gst.warining("change rate failed")
  71
  72
  73 def main(args):
  74     def usage():
  75         sys.stdout.write("usage: %s <filename> <speedrate>\n" % args[0])
  76
  77     if len(args) != 3:
  78         usage()
  79         sys.exit(1)
  80
  81     uri = Gst.filename_to_uri(args[1])
  82     rate = float(args[2])
  83
  84     player = Player(uri, rate)
  85     player.run()
  86
  87 if __name__ == '__main__':
  88     sys.exit(main(sys.argv))