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, filename, rate):
  21         self._filename = filename
  22         self._rate = rate
  23
  24         self._player = Gst.ElementFactory.make("playbin", "player")
  25         self._player.set_property("uri", filename)
  26
  27         bus = self._player.get_bus()
  28         bus.add_signal_watch()
  29         bus.connect('message::state-changed', self.on_state_changed)
  30
  31     def run(self):
  32         self._player.set_state(Gst.State.PLAYING)
  33         loop = GObject.MainLoop()
  34         loop.run()
  35
  36     def on_state_changed(self, bus, msg):
  37         if msg.src != self._player:
  38             return
  39
  40         print 'on_state_changed'
  41         old_state, new_state, pending = msg.parse_state_changed()
  42         print "%s -> %s" % (old_state, new_state)
  43         if old_state == Gst.State.READY and new_state == Gst.State.PAUSED:
  44             self.set_rate(self._rate)
  45
  46     def set_rate(self, rate):
  47         self._rate = rate
  48         try:
  49             position, fmt = self._player.query_position(Gst.Format.TIME)
  50         except:
  51             position = 0
  52
  53         # Create the seek event
  54         if rate > 0:
  55             seek_event = Gst.Event.new_seek(rate,
  56                     Gst.Format.TIME,
  57                     Gst.SeekFlags.FLUSH | Gst.SeekFlags.ACCURATE,
  58                     Gst.SeekType.SET, position,
  59                     Gst.SeekType.NONE, 0)
  60         else:
  61             seek_event = Gst.Event.new_seek(rate,
  62                     Gst.Format.TIME,
  63                     Gst.SeekFlags.FLUSH | Gst.SeekFlags.ACCURATE,
  64                     Gst.SeekType.SET, 0,
  65                     Gst.SeekType.SET, position)
  66
  67         if seek_event:
  68             self._player.send_event(seek_event)
  69             Gst.info("rate set to %s" % rate)
  70         else:
  71             Gst.warining("change rate failed")
  72
  73
  74 def main(args):
  75     def usage():
  76         sys.stdout.write("usage: %s <URI-OF-MEDIA-FILE>\n" % args[0])
  77
  78     if len(args) != 2:
  79         usage()
  80         sys.exit(1)
  81
  82     if not Gst.uri_is_valid(args[1]):
  83         sys.stderr.write("Error: Invalid URI: %s\n" % args[1])
  84         sys.exit(1)
  85
  86     player = Player(args[1], 3.0)
  87     player.run()
  88
  89 if __name__ == '__main__':
  90     sys.exit(main(sys.argv))