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• ffmpeg - concatenate several videos with xfade transition

  8 mai 2021, par ilim

  I have N videos, and I'm using ffmpeg to concatenate them with xfade transitions between them. The video files are named as positive integers representing their order in the concatenated output, and none of them have any audio. In fact, each file just includes a different image with no animation that stays on screen all through that video's duration.

  


  I'm using a simple command I found in a response to an existing question to concatenate the first 2 videos :

  


  ffmpeg -i 1.mp4 -i 2.mp4 -y
       -filter_complex "xfade=transition=fade:offset=3.5:duration=0.5"
       1-2.mp4


  


  I planned to employ that same command for all the videos, each time appending a single video to the cumulative one produced so far, and producing an intermediary output to be used later.

  


  Specifically, I first concatenated files 1.mp4 and 2.mp4, and recorded the result into 1-2.mp4, which was produced correctly. Videos had the respective duration of 4 and 8 seconds, and the resulting 1-2.mp4 was 12 seconds long, with the transition occurring when it should.

  


  The problem started when I tried concatenating 1-2.mp4 and 3.mp4. I used the following command to generate a concatenation of videos [1-3].

  


  ffmpeg -i 1-2.mp4 -i 3.mp4 -y
       -filter_complex "xfade=transition=fade:offset=11.5:duration=0.5"
       1-3.mp4


  


  The video produced seems to be an exact copy of 1-2.mp4, and contents of 3.mp4 are not present at all in the resulting 1-3.mp4. Video file 3.mp4 was 3 seconds long, but the resulting 1-3.mp4 was 12 seconds long, just like 1-2.mp4 was.

  


  Apart from the input and output file names, both commands are the same. I was suspicious of having set the offset parameter of the transition incorrectly, but the first 2 files were merged successfully.

  


  I am at a loss as to what I'm doing incorrectly here. Is there a particular caveat of the xfade filter that gets problematic when used among 2 files with one of them already having that filter ?

  


  Any suggestions as to how I may debug or fix this behavior ? I'd welcome any alternative means of concatenating these (i.e., with some transition effects) in a simple fashion as well.

  


  I'm planning to use these commands in a Python script, so I'd appreciate any alternative solution not involving any gigantic commands or parameters.

  


  Just to be thorough, I should mention that I have ffmpeg version 4.3.1 installed via snap.

  


• AttributeError while saving an animation using celluloid, Python 3.9

  26 juillet 2021, par rafael gf

  I'm trying to create a simple animation using the celluloid library, but I'm getting an attribute error when trying to save it. I'm not familiar with ffmpeg, but I read I should install it and point to its executable file for the saving to work, not sure what's going wrong. The massage I'm getting is :

  


  Exception has occurred: AttributeError&#xA;type object &#x27;FuncAnimation&#x27; has no attribute &#x27;_first_draw_id&#x27;&#xA; File "C:\Users\Fernando\Documents\Circulos\circulos.py", line 102, in <module>  anim.save(anim, filename="my_animation.gif", writer=FFwriter)&#xA;</module>

  


  I'll out the simplification version of the code below - I'm suppressing the part where I do some tucking with the circles, but I've done some testing plot by plot and it is working fine.

  


  import smtplib, os
import matplotlib.pyplot as plt
from matplotlib import animation
import math
from celluloid import Camera

plt.rcParams['animation.ffmpeg_path'] = os.getcwd() + '\\Circulos\\ffmpeg\\bin\\ffmpeg.exe'


#axes
figure, axes = plt.subplots()
axes.set_aspect(1)
axes.set_xlim((-xmax(C)),(xmax(C)))
axes.set_ylim((-ymax(C)),(ymax(C)))

b = 0

#add initial circles
for a in range 5:
    draw_circle = plt.Circle((a, a), 2, fc = 'None', ec = 'r')
    axes.add_artist(draw_circle)


#create figure and camera
figure, axes = plt.subplots()
axes.set_aspect(1)
axes.set_xlim((-xmax(C)),(xmax(C)))
axes.set_ylim((-ymax(C)),(ymax(C)))
camera = Camera(figure) 

Frame_time = 10

for b in range(Frame_time):

     #add circles
     for a in range 5:
        draw_circle = plt.Circle((a, a), 2, fc = 'None', ec = 'r')
        axes.add_artist(draw_circle)

    #Frame Picture
    camera.snap()


#create animation
anim = camera.animate()
anim = animation.FuncAnimation
FFwriter = animation.FFMpegWriter()
anim.save(anim, filename="my_animation.gif", writer=FFwriter)


  


  I'm working on VS code, the latest version I just updated it, and python 3.9

  


• Anomalie #2025 (Nouveau) : Surlignage intempestif

  8 avril 2011, par r o m y

  Le surlignage des résultats de recherche tel qu’actuellement géré par SPIP, pose plusieurs soucis, dont des surlignements, souvent plus surprenants qu’utiles, lorsqu’on arrive sur un site après une requête en moteur de recherche Google.

  le surlignage devrait être inactif par défaut (poser la class (...)