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• How do I properly save an animation involving circles with matplotlib.animation and ffmpeg ?

  12 juillet 2020, par bghost

  I recently tried out matplotlib.animation, and it's a wonderful tool. I can now make and save basic animations (ie that only involve straight lines) without any issues. However, when I made an animation involving circles, even though the interactive display was perfect, the saved mp4 file wasn't really satisfying. In the mp4 file, the edges of the circles were blurred, and if the circles were made semi-transparent (ie with an alpha value < 1), they all suddenly became completely opaque after a couple of frames. I suspected it was due to the fact that my bitrate wasn't high enough, but I went up to 10000 kb/s (instead of 1800), and exactly the same phenomenon occurred.

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  What can be done to solve these 2 issues (blurred edges + negated transparency) in the generated mp4 file ?

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  Here is a simple animation that describes what I just said :

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

fig = plt.figure(figsize=(11, 7))
ax = plt.axes(xlim=(-1.2, 1.2), ylim=(-0.7, 0.7))
ax.set_aspect('equal')

dict_circles = {}
dict_circles['ring'] = plt.Circle((-0.5, 0), 0.5, color='b', lw=2, fill=False)
dict_circles['disk'] = plt.Circle((-0.5, 0), 0.5, color='b', alpha=0.2)

def init():
    for circle in dict_circles.values():
        ax.add_patch(circle)
    return(dict_circles.values())

nb_frames = 100
X_center = np.linspace(-0.5, 0.5, nb_frames)

def animate(frame):
    for circle in dict_circles.values():
        circle.center = (X_center[frame], 0)
        ax.add_patch(circle)
    return(dict_circles.values())

ani = animation.FuncAnimation(fig, animate, init_func=init, frames=nb_frames, blit=True, interval=10, repeat=False)
plt.show()

plt.rcParams['animation.ffmpeg_path'] = 'C:\\ffmpeg\\bin\\ffmpeg.exe'
Writer = animation.writers['ffmpeg']
writer_ref = Writer(fps=15, bitrate=1800)

ani.save('Blue circle.mp4', writer=writer_ref)


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• avcodec/alsdec : Limit maximum channels to 512

  20 août 2019, par Michael Niedermayer

  avcodec/alsdec : Limit maximum channels to 512
  There seems to be no limit in the specification and upto 64k could be stored
  
  512 is choosen as limit as thats the maximum in a conformance sample
  An alternative to this patch would be a max_channels variable
  Fixes : OOM
  
  Fixes : 16200/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_ALS_fuzzer-5764788793114624
  Found-by : continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
  
  Suggested-by : Thilo Borgmann <thilo.borgmann@mail.de>
  
  Reviewed-by : Thilo Borgmann <thilo.borgmann@mail.de>
  
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavcodec/alsdec.c

• Anomalie #2015 (Fermé) : validation courriel inscription

  31 mars 2011, par stef dn

  le format de courriel test@mail passe l’inscription