Use 'proc.poll()' to make sure that processes should be terminated (#…

…1296)

* fix to terminate the process that has ended

check if the process exists before using teminate() to stop the process.

* Update readers.py

* fix to terminate the process which has been killed

* Use proc.poll() is video reader 'close()'

moviepy/audio/io/readers.py

@@ -257,10 +257,11 @@ def buffer_around(self, frame_number):
 
     def close(self):
         if self.proc:
-            self.proc.terminate()
-            self.proc.stdout.close()
-            self.proc.stderr.close()
-            self.proc.wait()
+            if self.proc.poll() is None:
+                self.proc.terminate()
+                self.proc.stdout.close()
+                self.proc.stderr.close()
+                self.proc.wait()
             self.proc = None
 
     def __del__(self):

moviepy/video/io/ffmpeg_reader.py

@@ -225,10 +225,11 @@ def get_frame_number(self, t):
 
     def close(self, delete_lastread=True):
         if self.proc:
-            self.proc.terminate()
-            self.proc.stdout.close()
-            self.proc.stderr.close()
-            self.proc.wait()
+            if self.proc.poll() is None:
+                self.proc.terminate()
+                self.proc.stdout.close()
+                self.proc.stderr.close()
+                self.proc.wait()
             self.proc = None
         if delete_lastread and hasattr(self, "last_read"):
             del self.last_read