cleanup

mp4/demuxer.py

@@ -2,7 +2,7 @@
 
 from . import libav
 from .codec import Codec
-from .stream import NullStream, Stream
+from .stream import Stream
 from .packet import Packet
 
 class Demuxer:
@@ -20,7 +20,11 @@ class Demuxer:
             libav.format_close_input(self._context)
             raise Exception("Failed to find stream info")
         self.video_stream = self._find_stream(libav.AVMEDIA_TYPE_VIDEO)
+        if self.video_stream is None:
+            raise Exception("Failed to find a video stream")
         self.audio_stream = self._find_stream(libav.AVMEDIA_TYPE_AUDIO)
+        if self.audio_stream is None:
+            raise Exception("Failed to find an audio stream")
 
     @property
     def nb_streams(self):
@@ -31,7 +35,7 @@ class Demuxer:
     def _find_stream(self, type):
         index, codec_ref = libav.format_find_best_stream(self._context, type)
         if index < 0 or not codec_ref:
-            return NullStream()
+            return None
         parameters = self._context.contents.streams[index].contents.codecpar
         return Stream(index, Codec(codec_ref), parameters)