Q:

Trouble saving matplotlib animation with ffmpeg

I installed ffmpeg and would like to save an animation. 
My code is
#evo is the dataset composed of sequence of images

evo = np.load('bed_evolution_3000iter_2.npy')
fig = plt.figure(figsize=(15,15*2*width/length))
# make axesimage object
# the vmin and vmax here are very important to get the color map correct
im = plt.imshow(np.transpose(evo[0]), cmap=plt.get_cmap('jet'), vmin=0, vmax=1300)
cbar_ax = fig.add_axes([0.85, 0.15, 0.05, 0.7])
fig.colorbar(im, cax=cbar_ax)
fig.subplots_adjust(right=0.8)

def updatefig(j):    
    # set the data in the axesimage object
    im.set_array(np.transpose(evo[j]))
    # return the artists set
    return im,
# kick off the animation
ani = animation.FuncAnimation(fig, updatefig, frames=range(len(evo)), 
                          interval=100, blit=True)

#now just need to get the ability to save... this uses 

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

The animation runs and it looks good, but I just can't get it to save. The error message (at this stage) is

I am not sure what's going wrong. Any help is appreciated. 
EDIT: 
Following Can't save matplotlib animation I added
plt.rcParams['animation.ffmpeg_path'] ='C:\\Program Files\\ffmpeg  \\bin\\ffmpeg.exe'

Which returns 
    Warning: Cannot change to a different GUI toolkit: qt. Using qt4 instead.
    ERROR: execution aborted

A:

Providing my comment as an answer: 
I think you should specify the arguments to FFMpegWriter directly in the initialization of that instance instead of supplying some of them to the animation save method.
FFwriter = animation.FFMpegWriter(fps=30, extra_args=['-vcodec', 'libx264'])
ani.save('basic_animation.mp4', writer = FFwriter)

