Support videos with rotation

sigal/video.py

@@ -67,11 +67,15 @@ def video_size(source):
     ret, stdout, stderr = call_subprocess(['ffmpeg', '-i', source])
     pattern = re.compile(r'Stream.*Video.* ([0-9]+)x([0-9]+)')
     match = pattern.search(stderr)
+    rot_pattern = re.compile(r'rotate\s*:\s*-?(90|270)')
+    rot_match = rot_pattern.search(stderr)
 
     if match:
         x, y = int(match.groups()[0]), int(match.groups()[1])
     else:
         x = y = 0
+    if rot_match:
+        x, y = y, x
     return x, y