Let ffmpeg handle image rescaling for h264

Nathan Goldbaum · Nathan Goldbaum · commit e0c212b5efb2 · 2017-03-09T17:09:17.000-08:00
diff --git a/lib/matplotlib/animation.py b/lib/matplotlib/animation.py
@@ -61,12 +61,6 @@
 # how-to-encode-series-of-images-into-h264-using-x264-api-c-c )
 
 
-def adjusted_figsize(w, h, dpi, n):
-    wnew = int(w * dpi / n) * n / dpi
-    hnew = int(h * dpi / n) * n / dpi
-    return wnew, hnew
-
-
 # A registry for available MovieWriter classes
 class MovieWriterRegistry(object):
     '''Registry of available writer classes by human readable name.'''
@@ -269,18 +263,6 @@ def frame_size(self):
         w, h = self.fig.get_size_inches()
         return int(w * self.dpi), int(h * self.dpi)
 
-    def _adjust_frame_size(self):
-        if self.codec == 'h264':
-            wo, ho = self.fig.get_size_inches()
-            w, h = adjusted_figsize(wo, ho, self.dpi, 2)
-            if not (wo, ho) == (w, h):
-                self.fig.set_size_inches(w, h, forward=True)
-                verbose.report('figure size (inches) has been adjusted '
-                               'from %s x %s to %s x %s' % (wo, ho, w, h),
-                               level='helpful')
-        verbose.report('frame size in pixels is %s x %s' % self.frame_size,
-                       level='debug')
-
     def setup(self, fig, outfile, dpi=None):
         '''
         Perform setup for writing the movie file.
@@ -301,7 +283,6 @@ def setup(self, fig, outfile, dpi=None):
         if dpi is None:
             dpi = self.fig.dpi
         self.dpi = dpi
-        self._adjust_frame_size()
 
         # Run here so that grab_frame() can write the data to a pipe. This
         # eliminates the need for temp files.
@@ -434,7 +415,6 @@ def setup(self, fig, outfile, dpi=None, frame_prefix='_tmp',
         if dpi is None:
             dpi = self.fig.dpi
         self.dpi = dpi
-        self._adjust_frame_size()
 
         self.clear_temp = clear_temp
         self.temp_prefix = frame_prefix
@@ -557,8 +537,14 @@ def output_args(self):
         # with quicktime (and others). Specifying yuv420p fixes playback on
         # iOS,as well as HTML5 video in firefox and safari (on both Win and
         # OSX). Also fixes internet explorer. This is as of 2015/10/29.
-        if self.codec == 'h264' and '-pix_fmt' not in self.extra_args:
-            args.extend(['-pix_fmt', 'yuv420p'])
+        if self.codec == 'h264':
+            if '-pix_fmt' not in self.extra_args:
+                args.extend(['-pix_fmt', 'yuv420p'])
+            # The h264 codec requires that frames passed to it must have a
+            # a width and height that are even numbers of pixels. This tells
+            # ffmpeg to rescale the frames to the nearest even number of pixels
+            # see https://stackoverflow.com/a/20848224/1382869
+            args.extend(['-vf', 'scale=trunc(iw/2)*2:trunc(ih/2)*2'])
         # The %dk adds 'k' as a suffix so that ffmpeg treats our bitrate as in
         # kbps
         if self.bitrate > 0:
