Don't pass vframes to ffmpeg when using a tmpdir

Also, switch to the not-deprecated `frames:v`.

Author: QuLogic

lib/matplotlib/animation.py

@@ -591,8 +591,9 @@ def _args(self):
                 '-video_size', '%dx%d' % self.frame_size,
                 '-pixel_format', 'rgba',
             ]
-        args += ['-framerate', str(self.fps), '-i', self._base_temp_name(),
-                 '-vframes', str(self._frame_counter)]
+        args += ['-framerate', str(self.fps), '-i', self._base_temp_name()]
+        if not self._tmpdir:
+            args += ['-frames:v', str(self._frame_counter)]
         # Logging is quieted because subprocess.PIPE has limited buffer size.
         # If you have a lot of frames in your animation and set logging to
         # DEBUG, you will have a buffer overrun.