Use -framerate to set ffmpeg input framerate

This is about the input frame rate, and as noted in ffmpeg docs, should
be preferred over `-r` for input.

Author: QuLogic

lib/matplotlib/animation.py

@@ -559,7 +559,7 @@ def _args(self):
         # ffmpeg to create a movie using a pipe.
         args = [self.bin_path(), '-f', 'rawvideo', '-vcodec', 'rawvideo',
                 '-s', '%dx%d' % self.frame_size, '-pix_fmt', self.frame_format,
-                '-r', str(self.fps)]
+                '-framerate', str(self.fps)]
         # 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.
@@ -590,9 +590,8 @@ def _args(self):
                 '-f', 'image2', '-vcodec', 'rawvideo',
                 '-video_size', '%dx%d' % self.frame_size,
                 '-pixel_format', 'rgba',
-                '-framerate', str(self.fps),
             ]
-        args += ['-r', str(self.fps), '-i', self._base_temp_name(),
+        args += ['-framerate', str(self.fps), '-i', self._base_temp_name(),
                  '-vframes', 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