Only call reformat if necessary

Author: lgeiger

av/video/frame.py

@@ -750,7 +750,7 @@ def to_ndarray(self, channel_last=False, **kwargs):
                 frames_ctx.sw_format, self.ptr.width, self.ptr.height
             ).name
 
-        frame: VideoFrame = self.reformat(**kwargs)
+        frame: VideoFrame = self.reformat(**kwargs) if len(kwargs) > 0 else self
         if frame.ptr.hw_frames_ctx:
             raise ValueError("Cannot convert a hardware frame to numpy directly.")