make get_frame return None when no more frame to decode

PyDemux/Video.py

@@ -6,12 +6,14 @@ def __init__(self, filename):
         self.ctx = _demux.open(filename)
 
     def get_frame(self):
-        frame, w, h = _demux.get_frame(self.ctx)
+        result = _demux.get_frame(self.ctx)
 
-        if frame is not None:
-            return Image.frombytes("RGB", (w, h), frame)
-        else:
-            return None
+        if result is None:
+            return none
+
+        frame, w, h, = result
+
+        return Image.frombytes("RGB", (w, h), frame)
 
     def __del__(self):
         if self.ctx is not None:

_py.c

@@ -70,8 +70,12 @@ static PyObject* get_frame_wrapper(PyObject* self, PyObject* args)
     if (!PyArg_ParseTuple(args, "l", &ctx))
         return NULL;
 
+    // demux frame
     frame = demux_get_frame(ctx);
 
+    if (!frame)
+        Py_RETURN_NONE;
+
     // convert RGB array to python string
     width = demux_get_width(ctx);
     height = demux_get_height(ctx);