Python Matplotlib FuncAnimation + Saving

Question

I am new to python and I'm trying to make an animation and save it into some video format using matplotlibs FuncAnimation. If I run the following code:

import numpy as np
import matplotlib.animation as ani
import matplotlib.pyplot as plt

azimuths = np.radians(np.linspace(0, 360, 360))
zeniths = np.arange(0, 8, 0.2)
rho, psi = np.meshgrid(zeniths, azimuths)


fig = plt.figure()
ax = fig.add_subplot(1, 1, 1, polar=True)
ax.set_yticks([])
plt.grid()


def frame(i):
    values_i = prob_density(rho ** 2, psi, i)
    ax.contourf(psi, rho, values_i)

animation = ani.FuncAnimation(fig, frame, np.linspace(0, 1000, 10))
animation.save('video.mp4', writer='ffmpeg')

There is an error that says:

ValueError: outfile must be *.htm or *.html

As this seems to have something to do with the ffmpeg files - these are located in

/anaconda3/bin/ffmpeg

I have been on this for quite some time now but can't seem to figure out a solution though it seems to be common issue. Thankful for any suggestions.

Solution

I have never worked with FuncAnimation bevore, but the matplotlib-example states, you have to initialize ffmpeg first. Like this:

import numpy as np
import matplotlib
matplotlib.use("Agg")
import matplotlib.pyplot as plt
import matplotlib.animation as animation


def update_line(num, data, line):
    line.set_data(data[..., :num])
    return line,

# Set up formatting for the movie files
Writer = animation.writers['ffmpeg']
writer = Writer(fps=15, metadata=dict(artist='Me'), bitrate=1800)


fig1 = plt.figure()

data = np.random.rand(2, 25)
l, = plt.plot([], [], 'r-')
plt.xlim(0, 1)
plt.ylim(0, 1)
plt.xlabel('x')
plt.title('test')
line_ani = animation.FuncAnimation(fig1, update_line, 25, fargs=(data, l),
                                   interval=50, blit=True)
line_ani.save('lines.mp4', writer=writer)

Maybe, you could give this a try.

Comments

[Apostolos]

Thanks for the advice but I got "Requested MovieWriter (ffmpeg) not available". Any idea? (Saving aw MP4 is great, in contrast to saving as HTML which is nice but .. crap (e.g. 300 PNG files are created for a simple animation!)

[dudakl]

To me it sounds like you are missing ffmpeg (even though, you say, it is already installed). Did you try updating anaconda? Are you using Windows or Linux? Maybe try this: stackoverflow.com/questions/13316397/…

[Apostolos]

Right, ffmpeg should be installed (I didn't say it is already installed). Thanks.