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• 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 ?

  


• How to save python compatible audio file from JavaScript blob

  16 septembre 2020, par Talha Anwar

  I am trying to save an audio blob to the backend.
Here is an audio blob

  


   const blob = new Blob(chunks, { 'type' : 'audio/wav; codecs=0' });


  


  Here is the upload function

  


  function uploadAudio( blob ) {
  var reader = new FileReader();
  reader.onload = function(event){
    var fd = {};
    fd["data"] = event.target.result;
    $.ajax({
     // contentType:"application/x-www-form-urlencoded; charset=UTF-8",
      type: 'POST',
      url: 'testing/',
      data: fd,
      dataType: 'text'
    }).done(function(data) {
        console.log(data);
        document.getElementById("response").innerHTML=data;
       // alert(data);
    });
  };


  


  Here is the function to save the file.

  


  def upload_audio(request):
    print('upload_audio')
    if request.is_ajax():
        
        req=request.POST.get('data')
        d=req.split(",")[1]
        print("Yes, AJAX!")
        #print(request.body)
        f = open('./file.wav', 'wb')
        
        f.write(base64.b64decode(d))
        #f.write(request.body)
        f.close()
    return HttpResponse('audio received')


  


  When I try to read it in python for converting to text. I got following error

  


  ValueError: Audio file could not be read as PCM WAV, AIFF/AIFF-C, or Native FLAC; check if file is corrupted or in another format


  


  I tried to convert the file

  


  import ffmpeg
stream = ffmpeg.input('file.wav')
stream = ffmpeg.output(stream, 'filen.wav')
ffmpeg.run(stream)


  


  I got following error

  


  Traceback (most recent call last):&#xA;  File "script.py", line 8, in <module>&#xA;    ffmpeg.run(stream)&#xA;  File "C:\Anaconda3\envs\VA\lib\site-packages\ffmpeg\_run.py", line 320, in run&#xA;    overwrite_output=overwrite_output,&#xA;  File "C:\Anaconda3\envs\VA\lib\site-packages\ffmpeg\_run.py", line 285, in run_async&#xA;    args, stdin=stdin_stream, stdout=stdout_stream, stderr=stderr_stream&#xA;  File "C:\Anaconda3\envs\VA\lib\subprocess.py", line 729, in __init__&#xA;    restore_signals, start_new_session)&#xA;  File "C:\Anaconda3\envs\VA\lib\subprocess.py", line 1017, in _execute_child&#xA;    startupinfo)&#xA;FileNotFoundError: [WinError 2] The system cannot find the file specified&#xA;</module>

  


• In Python, why do 'writer' is considered to be as an unexpected keyword argument for save

  23 mars 2014, par Strömungsmechanik

  I would like to save an animation using the function save in Python. During compilation, I get the following message :

  anim.save('mymovie.mp4',writer="ffmpeg")
  
  TypeError: save() got an unexpected keyword argument 'writer'

  Please note that I have installed successfully FFmpeg. Here is a minimal working environment :

  import numpy as np
  
  from matplotlib import pyplot as plt
  
  from matplotlib import animation
  
  from numpy import pi
  
  
  
  X,Y = np.meshgrid(np.arange(0,2*np.pi,.2),np.arange(0,2*np.pi,.2) )  
  
  U = np.cos(X)
  
  V = np.sin(Y)
  
  
  
  fig,ax = plt.subplots(1,1)
  
  Q = ax.quiver( X, Y, U, V, pivot='mid', color='r', units='inches')
  
  
  
  ax.set_xlim(0, 2*pi)
  
  ax.set_ylim(0, 2*pi)
  
  
  
  def update_quiver(num, Q, X, Y):
  
      U = np.cos(X + num*0.1)
  
      V = np.sin(Y + num*0.1)
  
      Q.set_UVC(U,V)
  
      return Q,
  
  
  
  anim = animation.FuncAnimation(fig, update_quiver, fargs=(Q, X, Y),
  
      interval=10, blit=False)
  
  
  
  anim.save('mymovie.mp4',writer="ffmpeg")