无法使用ffmpeg保存Matplotlib动画 [英] Cannot save matplotlib animation with ffmpeg

问题描述

我正在尝试从 Jake保存一个简单的matplotlib动画范德普拉斯(Vanderplas)，但我一直得到OSError: [Errno 13] Permission denied.

I am trying to save a simple matplotlib animation from Jake Vanderplas, but I keep getting OSError: [Errno 13] Permission denied.

我应该注意，我对Jake Vanderplas的示例进行了两个小修改.我从MacPorts安装了ffmpeg，因此我添加了plt.rcParams['animation.ffmpeg_path'] = '/opt/local/bin'行，并且遇到了(

I should note that I made two small modifications to Jake Vanderplas's example. I installed ffmpeg from MacPorts so I added the line plt.rcParams['animation.ffmpeg_path'] = '/opt/local/bin' and I ran into the problem discussed in (Using FFmpeg and IPython), so I added FFwriter = animation.FFMpegWriter().

这是代码:

import numpy as np
from matplotlib import pyplot as plt
from matplotlib import animation
plt.rcParams['animation.ffmpeg_path'] = '/opt/local/bin'

fig = plt.figure()
ax = plt.axes(xlim=(0, 2), ylim=(-2, 2))
line, = ax.plot([], [], lw=2)

def init():
    line.set_data([], [])
    return line,

def animate(i):
    x = np.linspace(0, 2, 1000)
    y = np.sin(2 * np.pi * (x - 0.01 * i))
    line.set_data(x, y)
    return line,

anim = animation.FuncAnimation(fig, animate, init_func=init,
                           frames=200, interval=20, blit=True)

FFwriter = animation.FFMpegWriter()
anim.save('basic_animation.mp4', writer = FFwriter, fps=30, extra_args=['-vcodec', 'libx264'])

这是回溯:

File "ani_debug.py", line 34, in <module>
  anim.save('basic_animation.mp4', writer = FFwriter, fps=30, extra_args=['-vcodec', 'libx264'])
File "/Users/Ben/Library/Enthought/Canopy_64bit/User/lib/python2.7/site- packages/matplotlib/animation.py", line 712, in save
  with writer.saving(self._fig, filename, dpi):
File "/Applications/Canopy.app/appdata/canopy-1.3.0.1715.macosx-x86_64/Canopy.app/Contents/lib/python2.7/contextlib.py", line 17, in __enter__
  return self.gen.next()
File "/Users/Ben/Library/Enthought/Canopy_64bit/User/lib/python2.7/site-packages/matplotlib/animation.py", line 169, in saving
  self.setup(*args)
File "/Users/Ben/Library/Enthought/Canopy_64bit/User/lib/python2.7/site-packages/matplotlib/animation.py", line 159, in setup
  self._run()
File "/Users/Ben/Library/Enthought/Canopy_64bit/User/lib/python2.7/site-packages/matplotlib/animation.py", line 186, in _run
  stdin=subprocess.PIPE)
File "/Applications/Canopy.app/appdata/canopy-1.3.0.1715.macosx-x86_64/Canopy.app/Contents/lib/python2.7/subprocess.py", line 709, in __init__
  errread, errwrite)
File "/Applications/Canopy.app/appdata/canopy-1.3.0.1715.macosx-x86_64/Canopy.app/Contents/lib/python2.7/subprocess.py", line 1326, in _execute_child
  raise child_exception
OSError: [Errno 13] Permission denied

我还尝试使用Spyder的内置python并收到了类似的回溯.有什么建议吗?

I have also tried using Spyder's built-in python and received a similar traceback. Any suggestions?

我意识到我没有给出ffmpeg的正确路径.显然，plt.rcParams['animation.ffmpeg_path']的工作方式不同于PYTHONPATH.您必须使用plt.rcParams['animation.ffmpeg_path'] = '/opt/local/bin/ffmpeg'告诉动画模块ffmpeg的确切位置.

I realized that I did not give the proper path to ffmpeg. Apparently, plt.rcParams['animation.ffmpeg_path'] does not work similar to PYTHONPATH. You must tell the animation module exactly where ffmpeg is with plt.rcParams['animation.ffmpeg_path'] = '/opt/local/bin/ffmpeg'.

现在，我得到了一个可以播放的电影文件，但是内容完全乱码了.我不知道自己在看什么.

Now, I get a movie file that will play, but the content is completely garbled. I can't tell what I am looking at.

这是回溯:

Exception in Tkinter callback
Traceback (most recent call last):
  File "Tkinter.pyc", line 1470, in __call__
  File "Tkinter.pyc", line 531, in callit
  File "/Applications/Spyder.app/Contents/Resources/lib/python2.7/matplotlib/backends/backend_tkagg.py", line 141, in _on_timer
    TimerBase._on_timer(self)
  File "/Applications/Spyder.app/Contents/Resources/lib/python2.7/matplotlib/backend_bases.py", line 1203, in _on_timer
    ret = func(*args, **kwargs)
  File "/Applications/Spyder.app/Contents/Resources/lib/python2.7/matplotlib/animation.py", line 876, in _step
    still_going = Animation._step(self, *args)
  File "/Applications/Spyder.app/Contents/Resources/lib/python2.7/matplotlib/animation.py", line 735, in _step
    self._draw_next_frame(framedata, self._blit)
  File "/Applications/Spyder.app/Contents/Resources/lib/python2.7/matplotlib/animation.py", line 753, in _draw_next_frame
    self._pre_draw(framedata, blit)
  File "/Applications/Spyder.app/Contents/Resources/lib/python2.7/matplotlib/animation.py", line 766, in _pre_draw
    self._blit_clear(self._drawn_artists, self._blit_cache)
  File "/Applications/Spyder.app/Contents/Resources/lib/python2.7/matplotlib/animation.py", line 806, in _blit_clear
    a.figure.canvas.restore_region(bg_cache[a])
KeyError: <matplotlib.axes.AxesSubplot object at 0x104cfb150>

---

出于某种原因，现在一切正常.我已经在家用计算机和工作计算机上进行了尝试，但是在修复ffmpeg路径问题后，没人能重新创建我收到的乱码视频文件.

---

For some reason, everything is working fine now. I have tried things on my home computer and my work computer, and neither one can recreate the garbled video file I got after I fixed the ffmpeg path issue.

啊！我找到了这个吸盘.有时我会导入其中包含plt.rcParams['savefig.bbox'] = 'tight'的模块. (我永远不会使用该模块，但是rcParams会一直存在，直到您重新启动python解释器为止.)该设置导致视频显示为乱码.我将在下面发布我的解决方案.

Aaaahaaa! I tracked this sucker down. Sometimes I would import a module that had plt.rcParams['savefig.bbox'] = 'tight' in it. (I would never use that module, but rcParams persist, until you restart your python interpreter.) That setting causes the video to come out all garbled. I will post my solution below.

推荐答案

因此，事实证明存在两个问题.

So it turns out there were two issues.

问题1:ffmpeg的路径错误.我以为我需要提供ffmpeg所在目录的路径，但是我需要一直提供到ffmpeg二进制文件的路径.

Issue #1: The path to ffmpeg was wrong. I thought I needed to provide the path to the directory that ffmpeg resides in, but I needed to provide the path all the way to the ffmpeg binary.

问题2:在测试代码以生成视频之前，有时我会导入设置为plt.rcParams['savefig.bbox'] = 'tight'的模块. (我没有考虑太多，因为我没有使用该模块，但是rcParams会一直存在，直到您重新启动python解释器为止.)此plt.rcParams['savefig.bbox'] = 'tight'导致视频文件保存没有任何错误，但是当您使用时，这些帧都是乱码尝试播放视频.尽管我花了一整夜的时间来进行跟踪，但事实证明这是一个已知问题.

Issue #2: Prior to testing out my code to generate videos, I sometimes would import a module with the setting plt.rcParams['savefig.bbox'] = 'tight'. (I did not think much of it, because I did not use the module, but rcParams persist until you restart the python interpreter.) This plt.rcParams['savefig.bbox'] = 'tight' causes the video file to save without any errors, but the frames are all garbled when you try to play the video. Although it took me all evening to track this down, it turns out this is a known issue.

这是更新的解决方案，可以为我创建一个带有平移，正弦波的视频文件.

Here is the updated solution that creates a video file for me with a nice, translating, sine wave.

import numpy as np
from matplotlib import pyplot as plt
from matplotlib import animation
plt.rcParams['animation.ffmpeg_path'] = '/opt/local/bin/ffmpeg'

fig = plt.figure()
ax = plt.axes(xlim=(0, 2), ylim=(-2, 2))
line, = ax.plot([], [], lw=2)

def init():
    line.set_data([], [])
    return line,

def animate(i):
    x = np.linspace(0, 2, 1000)
    y = np.sin(2 * np.pi * (x - 0.01 * i))
    line.set_data(x, y)
    return line,

anim = animation.FuncAnimation(fig, animate, init_func=init, frames=200, interval=20, blit=True)

FFwriter = animation.FFMpegWriter()
anim.save('basic_animation.mp4', writer = FFwriter, fps=30, extra_args=['-vcodec', 'libx264'])

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