Dynamically update duration if it changes while playing (closes #15)

Strange thing - GStreamer sometimes can't query the duration of a file. The only
workaround I found is to just play the file and it normally updates after some
time automatically.

bin/gtranscribe

@@ -98,6 +98,7 @@ class gTranscribeWindow:
         self.player = gTranscribePlayer()
         self.player.connect('ready', self.on_file_ready)
         self.player.connect('ended', self.on_file_ended)
+        self.player.connect('duration_changed', self.on_duration_changed)
 
         if audiofile:
             # Open a file passed as command-line parameter.
@@ -220,6 +221,21 @@ class gTranscribeWindow:
         logger.debug('received signal "ready"')
         GLib.idle_add(self.update_file, audiofile)
 
+    # pylint: disable=unused-argument
+    def on_duration_changed(self, sig):
+        if sig is not None:
+            logger.debug('received signal "duration_changed"')
+        duration = ns_to_time(self.player.duration)
+        if duration.hour:
+            self.time_str = '%H:%M:%S.%f'
+        else:
+            self.time_str = '%M:%S.%f'
+        # set duration
+        dur_str = trim(duration.strftime(self.time_str))
+        self.dur_label.set_text(dur_str)
+        # set position
+        self.set_position_label(time_to_ns(duration))
+
     def update_file(self, audiofile):
         self.position = 0
         fileinfo = MetaData(audiofile, self.md5)
@@ -231,16 +247,8 @@ class gTranscribeWindow:
         if fileinfo.speed:
             logger.debug('Resuming with speed %s', fileinfo.speed)
             self.speedscale.set_value(fileinfo.speed)
-        duration = ns_to_time(self.player.duration)
-        if duration.hour:
-            self.time_str = '%H:%M:%S.%f'
-        else:
-            self.time_str = '%M:%S.%f'
-        # set duration
-        dur_str = trim(duration.strftime(self.time_str))
-        self.dur_label.set_text(dur_str)
-        # set position
-        self.set_position_label(time_to_ns(duration))
+        # Query duration once before we start playing
+        self.on_duration_changed(None)
         # set window title
         filename = os.path.basename(audiofile)
         self.window.set_title(u'gTranscribe \u2013 %s' % filename)
@@ -331,6 +339,8 @@ class gTranscribeWindow:
                 self.slider.set_value(scalepos)
             pos_str = trim(ns_to_time(self.position).strftime(self.time_str))
             self.pos_label.set_text(pos_str)
+        else:
+            logger.warning("Can't update position, don't know the duration")
 
     def dec_speed(self, action):
         self.speedscale.set_value(self.speedscale.get_value() - 0.1)

gtranscribe/player.py

@@ -30,14 +30,16 @@ class gTranscribePlayer(Gst.Bin):
 
     __gsignals__ = {
         'ready': (GObject.SignalFlags.RUN_LAST, None, (GObject.TYPE_STRING,)),
-        'ended': (GObject.SignalFlags.RUN_LAST, None, ())
+        'ended': (GObject.SignalFlags.RUN_LAST, None, ()),
+        'duration_changed': (GObject.SignalFlags.RUN_LAST, None, ())
     }
 
     def __init__(self):
         super(gTranscribePlayer, self).__init__()
 
         self._rate = 1
         self._duration = None
+        self._messageType = Gst.MessageType.UNKNOWN
         self.init_pipeline()
 
     def init_pipeline(self):
@@ -89,10 +91,13 @@ def filename(self):
     def duration(self):
         """Return the duration of the current stream."""
         success = False
-        if self._duration is None:
+        if self._duration is None or self._messageType == Gst.MessageType.DURATION_CHANGED:
             success, self._duration = self.pipeline.query_duration(Gst.Format.TIME)
-            logger.debug('Query was successful: %s, Duration is: "%s"', success, self._duration)
-        return self._duration if success else 0
+            if not success:
+                self._duration = 0
+            logger.debug('Query was successful: %s, Duration is: "%s"',
+                         success, self._duration)
+        return self._duration
 
     def _get_position(self):
         """Return the position of the current stream."""
@@ -175,12 +180,15 @@ def on_new_decoded_pad(self, element, pad):
     # pylint: disable=unused-argument
     def on_message(self, bus, message):
         """Handle message and react accordingly."""
+        self._messageType = message.type
         if message.type == Gst.MessageType.EOS:
             self.state = Gst.State.NULL
             self.emit('ended')
         elif message.type == Gst.MessageType.ERROR:
             logger.debug("%s", print(message.parse_error()))
             self.state = Gst.State.NULL
+        elif message.type == Gst.MessageType.DURATION_CHANGED:
+            self.emit('duration_changed')
 
     def open(self, filepath, duration=True):
         """Open audio file and optionally query duration."""