Cannot save animation in matplotlib: Windows permi

I've been trying for a day long to sort this out, checking similar threads but with no success. Stretch's Cannot save matplotlib animation with ffmpeg helped with previous errors (I had ffmpeg path wrong), but I kept getting Access denied after fixing it.

My ffmpeg binary is on C:\ffmpeg\bin

A nice alternative would be to able to export gif files, but I keep getting an ascii error with imagemagick. I think both problems are related, so I wanted to sort out the ffmpeg first.

I think the problem might have to do with the fact I'm working with Canopy (in Windows 8 64bit), which pretty much hegemonized my path variable and broke some things along the way (e.g. I can't open IDLE since I installed Canopy, didn't tried to fix that yet). As I fixed things along the way I found at least 3 distinct path variables, all of which I updated: windows advanced settings path (set manually), windows console path (set via console with setx), and sys.path (set or checked at runtime), adding ";C:\ffmpeg\bin", where ffmpeg effectively is. Regardless I sort out the problem or not, I would like to learn which of these environment variables are relevant for what, I find it very confusing.

The code is the following:

# -*- coding: utf-8 -*-
import sys
import numpy as np
from matplotlib import pyplot as plt
from matplotlib import animation
plt.rcParams['animation.ffmpeg_path'] = r'C:\ffmpeg\bin'
if r'C:\ffmpeg\bin' not in sys.path: sys.path.append(r'C:\ffmpeg\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)
plt.show()

# This case generates Windows err: Access Denied
FFwriter = animation.FFMpegWriter()
# anim.save(r'C:\basic_animation.mp4', writer = FFwriter, fps=30)

# This case generates UnicodeDecodeError:'ascii' codec can't decode byte 0xa0 in position 3
# anim.save(r'C:\animation.gif', writer='imagemagick', fps=30)

The traceback for anim.save(r'C:\basic_animation.mp4', writer = FFwriter, fps=30):

%run "C:\Users\Yahveh\Documents\Vlad\Investigacion\animation saving.py"
---------------------------------------------------------------------------
WindowsError                              Traceback (most recent call last)
C:\Users\Yahveh\Documents\Vlad\Investigacion\animation saving.py in <module>()
     27 # This case generates Windows err: Access Denied
     28 FFwriter = animation.FFMpegWriter()
---> 29 anim.save(r'C:\basic_animation.mp4', writer = FFwriter, fps=30)
     30 
     31 # This case generates UnicodeDecodeError:'ascii' codec can't decode byte 0xa0 in position 3

C:\Users\Yahveh\AppData\Local\Enthought\Canopy\User\lib\site-packages\matplotlib\animation.pyc in save(self, filename, writer, fps, dpi, codec, bitrate, extra_args, metadata, extra_anim, savefig_kwargs)
    759         # since GUI widgets are gone. Either need to remove extra code to
    760         # allow for this non-existant use case or find a way to make it work.
--> 761         with writer.saving(self._fig, filename, dpi):
    762             for data in zip(*[a.new_saved_frame_seq()
    763                               for a in all_anim]):

C:\Users\Yahveh\AppData\Local\Enthought\Canopy\App\appdata\canopy-1.5.2.2785.win-x86_64\lib\contextlib.pyc in __enter__(self)
     15     def __enter__(self):
     16         try:
---> 17             return self.gen.next()
     18         except StopIteration:
     19             raise RuntimeError("generator didn't yield")

C:\Users\Yahveh\AppData\Local\Enthought\Canopy\User\lib\site-packages\matplotlib\animation.pyc in saving(self, *args)
    184         '''
    185         # This particular sequence is what contextlib.contextmanager wants
--> 186         self.setup(*args)
    187         yield
    188         self.finish()

C:\Users\Yahveh\AppData\Local\Enthought\Canopy\User\lib\site-packages\matplotlib\animation.pyc in setup(self, fig, outfile, dpi, *args)
    174         # Run here so that grab_frame() can write the data to a pipe. This
    175         # eliminates the need for temp files.
--> 176         self._run()
    177 
    178     @contextlib.contextmanager

C:\Users\Yahveh\AppData\Local\Enthought\Canopy\User\lib\site-packages\matplotlib\animation.pyc in _run(self)
    202                                       stdout=output, stderr=output,
    203                                       stdin=subprocess.PIPE,
--> 204                                       creationflags=subprocess_creation_flags)
    205 
    206     def finish(self):

C:\Users\Yahveh\AppData\Local\Enthought\Canopy\App\appdata\canopy-1.5.2.2785.win-x86_64\lib\subprocess.pyc in __init__(self, args, bufsize, executable, stdin, stdout, stderr, preexec_fn, close_fds, shell, cwd, env, universal_newlines, startupinfo, creationflags)
    707                                 p2cread, p2cwrite,
    708                                 c2pread, c2pwrite,
--> 709                                 errread, errwrite)
    710         except Exception:
    711             # Preserve original exception in case os.close raises.

C:\Users\Yahveh\AppData\Local\Enthought\Canopy\App\appdata\canopy-1.5.2.2785.win-x86_64\lib\subprocess.pyc in _execute_child(self, args, executable, preexec_fn, close_fds, cwd, env, universal_newlines, startupinfo, creationflags, shell, to_close, p2cread, p2cwrite, c2pread, c2pwrite, errread, errwrite)
    955                                          env,
    956                                          cwd,
--> 957                                          startupinfo)
    958             except pywintypes.error, e:
    959                 # Translate pywintypes.error to WindowsError, which is

WindowsError: [Error 5] Acceso denegado

The traceback for anim.save(r'C:\animation.gif', writer='imagemagick', fps=30):

In [8]: %run "C:\Users\Yahveh\Documents\Vlad\Investigacion\animation saving.py"
---------------------------------------------------------------------------
UnicodeDecodeError                        Traceback (most recent call last)
C:\Users\Yahveh\Documents\Vlad\Investigacion\animation saving.py in <module>()
     30 
     31 # This case generates UnicodeDecodeError:'ascii' codec can't decode byte 0xa0 in position 3
---> 32 anim.save(r'C:\animation.gif', writer='imagemagick', fps=30)

C:\Users\Yahveh\AppData\Local\Enthought\Canopy\User\lib\site-packages\matplotlib\animation.pyc in save(self, filename, writer, fps, dpi, codec, bitrate, extra_args, metadata, extra_anim, savefig_kwargs)
    765                     # TODO: Need to see if turning off blit is really necessary
    766                     anim._draw_next_frame(d, blit=False)
--> 767                 writer.grab_frame(**savefig_kwargs)
    768 
    769         # Reconnect signal for first draw if necessary

C:\Users\Yahveh\AppData\Local\Enthought\Canopy\User\lib\site-packages\matplotlib\animation.pyc in grab_frame(self, **savefig_kwargs)
    225             verbose.report('MovieWriter -- Error '
    226                            'running proc:\n%s\n%s' % (out,
--> 227                                                       err), level='helpful')
    228             raise
    229 

UnicodeDecodeError: 'ascii' codec can't decode byte 0xa0 in position 3: ordinal not in range(128)

Stared at them for a while.

Thanks for your time!

UPDATE: I followed the steps in this post for granting access to both C:\ffmpeg and destination folder, but no luck :(

回答1:

Try saving the files somewhere else, for debugging purposes. That is: where you're saving "C:\basic_animation.mp4", try something like "C:\TEMP\basic_animation.mp4".

If i remember it right, win7+ added extra security in "C:\" and other directories. That simple test will tell you if the problem is the destination directory or not.

I'll recomend to always use the system's temp dir for this kind of things, and then moving the file where it should go. You can get tue current system's TEMP dir in Python like this:

import tempfile

print tempfile.gettempdir()

Also, about the "'ascii' codec can't decode" problem: it's an string conversion problem. Happens all the time, specially on Windows.

Check this out: http://nedbatchelder.com/text/unipain/unipain.html#1

But this time seems to be inside FFMPEG's, as "anim" is some instance returned by "FuncAnimation", and i don't see any wrongdoing from you on its use. The best thing you can do is to guarantee all YOUR strings are correctly converted before being used. Like the path strings, for example.

Here's another comment about that: https://stackoverflow.com/a/21129492

For what i can understand of your stack trace, the string conversion error is happening in some verbose/log function inside canopy. Perhaps is trying to log something with non-ascii chars. So, you could also try some canopy flag for log/verbose disabling; maybe that's enough.

回答2:

Perhaps not a surprise. My path to ffmpeg, C:\ffmpeg\bin, was wrong; since it should be the path right down to the exe file, not just the parent folder, as I misunderstood from Stretch's post, and as Daniel pointed out. Notice out I have already tried this before, but just changed the error message at the time. Calm, get some rest and read carefully, not just looking for the piece of code that will suit you. It's just a bug. That's the answer.