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• Superimpose audio track on plot animation

  17 février 2023, par Antoine101

  I plot a matrix in a standard matplotlib figure with imshow. Each matrix is the result of a signal processing calculation on a time signal snapshot (0.2s). I plot each snapshot one after the other (the signal is several seconds long) in a loop and record the animation with FFMPegWriter, setting the FPS so that it matches real time. The output is an MP4 file.

  


  Now, I'd like to add a soundtrack on top of it, of the time signal that was used to calculate the matrices.

  


  How would you do that ? I scrolled a lot but didn't find any suitable solution.
Any idea of libraries or packages ?

  


  Many thanks in advance.

  


• Shell script works fine from shell but doesn’t work as expected when executed via PHP “shell_exec” code

  9 décembre 2019, par Eric Feillant

  This record.sh script shell is here and works fine on command line to record an MP4 file from a local flv live stream :

  DATE=`date +"%d-%m-%Y-%T"`
  
  if [ -s NAMESTREAM ]
  
  then
  
  cat config.php | dos2unix | grep auth | grep username | \
  
  awk -F ' ' '{print $3}' | sed "s/'//g" | sed "s/;//g" | while read VAR
  
  do echo $VAR > RECSTREAM
  
  echo "Starting recording ..."
  
  ffmpeg -i "rtmp://localhost/hls/$VAR" -crf 19 videos/"$VAR"_"$DATE".mp4
  
  done
  
  else
  
  echo "Streaming is not started, please start it before"
  
  fi

  I send a shell_exec to call the last shell script in a php script like this :

  $old_path = getcwd();
  
  chdir('/usr/local/nginx/html/mydir');
  
  $output = shell_exec('nohup ./record.sh >/dev/null 2>/dev/null &');
  
  chdir($old_path);

  The MP4 video files are generated but unreadable with VLC, etc… It seems that the problem is due to my PHP script but I am not able to know why.

  When executing from the shell command line : PHP myphpscript.php works fine, MP4 video files are OK. But from the PHP web page, the MP4 video files are corrupted.

  Any ideas ? Any param to test in FFmpeg to have a good mp4 video file ?

• Matplotlib use Ffmpeg to save plot to be mp4 not include full step

  21 décembre 2020, par 昌翰余

  I use ffmpeg to store the dynamic graph drawn on matplotlib, but the output file is only 2 seconds
but It should have been 30 seconds.
I set a graph to run three curves, a total of 30 seconds of data,
the graph that ran on the py file is normal,
but the output is only the first two seconds of the output.
May I ask if I missed something

  


  Below is my code

  


  import matplotlib.pyplot as plt
from matplotlib import animation
from numpy import random 
import pandas as pd
from matplotlib.animation import FFMpegWriter

FFwriter=animation.FFMpegWriter(fps=30, extra_args=['-vcodec', 'libx264'])
data = pd.read_csv('apple1.csv', delimiter = ',', dtype = None)
data = data.values
AccX1=[]
AccY1=[]
AccZ1=[]
AccX2=[]
AccY2=[]
AccZ2=[]

time = []

for i in range(600):
        AccX1.append(data[i][8])
        AccY1.append(data[i][9])
        AccZ1.append(data[i][10])
        AccX2.append(data[i][24])
        AccY2.append(data[i][25])
        AccZ2.append(data[i][26])
        
        time.append(data[i][0])
        
fig = plt.figure()
ax1 = plt.axes(xlim=(0,3000), ylim=(6,-6))
line, = ax1.plot([], [], lw=2)
plt.xlabel('ACC')
plt.ylabel('Time')

plotlays, plotcols = [3], ["r","g","b"]
lines = []
for index in range(3):
    lobj = ax1.plot([],[],lw=2,color=plotcols[index])[0]
    lines.append(lobj)


def init():
    for line in lines:
        line.set_data([],[])
    return lines

x1,y1 = [],[]
x2,y2 = [],[]
x3,y3 = [],[]



i=0

def animate(frame):
    global i
    
    i+=1
    x = i
    y = AccX1[i]

    x1.append(x)
    y1.append(y)

    x = i
    y = AccY1[i]
    x2.append(x)
    y2.append(y)

    x = i
    y = AccZ1[i]
    x3.append(x)
    y3.append(y)
    

    xlist = [x1, x2,x3]
    ylist = [y1, y2,y3]


    for lnum,line in enumerate(lines):
        line.set_data(xlist[lnum], ylist[lnum]) 


    return lines


anim = animation.FuncAnimation(fig, animate,
                    init_func=init, blit=True,interval=10)
anim.save('test.mp4',writer=FFwriter)
plt.show()


  


  The dynamic picture ran out using plt.show is correct.
And I don't think I have set the length of storage. Did I add something ?