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• Making animations by matplotlib and saving the video files

  20 janvier 2016, par Richard.L

  I have been studying the 1D wave equations and making the animation of the equation. But there are some problems when using the anim.save of animation to save the video file. I have already installed ffmpeg on my computer (a Windows machine) and set the environment variables. But it keeps telling me this :

  UserWarning: MovieWriter ffmpeg unavailable
  
  ...
  
  RuntimeError: Error creating movie, return code: 4 Try running with --verbose-debug

  

  Here is my code :

  from numpy import zeros,linspace,sin,pi
  
  import matplotlib.pyplot as mpl
  
  from matplotlib import animation
  
  mpl.rcParams['animation.ffmpeg_path'] = 'C:\\ffmpeg\\bin\\ffmpeg.exe'
  
  
  
  def I(x):
  
      return sin(2*x*pi/L)
  
  
  
  def f(x,t):
  
      return sin(0.5*x*t)
  
  
  
  def solver0(I,f,c,L,n,dt,t):
  
      # f is a function of x and t, I is a function of x
  
      x = linspace(0,L,n+1)
  
      dx = L/float(n)
  
      if dt <= 0:
  
          dt = dx/float(c)
  
      C2 = (c*dt/dx)**2
  
      dt2 = dt*dt
  
      up = zeros(n+1)
  
      u = up.copy()
  
      um = up.copy()
  
      for i in range(0,n):
  
          u[i] = I(x[i])
  
      for i in range(1,n-1):
  
          um[i] = u[i]+0.5*C2*(u[i-1] - 2*u[i] + u[i+1]) + dt2*f(x[i],t)
  
      um[0] = 0
  
      um[n] = 0    
  
      while t <= tstop:
  
          t_old = t
  
          t += dt
  
          #update all inner points:
  
          for i in range(1,n-1):
  
              up[i] = -um[i] + 2*u[i] + C2*(u[i-1] - 2*u[i] + u[i+1]) + dt2*f(x[i],t_old)    
  
          #insert boundary conditions:
  
          up[0] = 0
  
          up[n] = 0
  
          #update data structures for next step
  
          um = u.copy()
  
          u = up.copy()   
  
      return u
  
  
  
  c = 1.0 
  
  L = 10
  
  n = 100
  
  dt = 0
  
  tstop = 40
  
  
  
  fig = mpl.figure()
  
  ax = mpl.axes(xlim=(0,10),ylim=(-1.0,1.0))
  
  line, = ax.plot([],[],lw=2)
  
  
  
  def init():
  
      line.set_data([],[])
  
      return line,
  
  
  
  def animate(t):
  
      x = linspace(0,L,n+1)
  
      y = solver0(I, f, c, L, n, dt, t)
  
      line.set_data(x,y)
  
      return line,
  
  
  
  anim = animation.FuncAnimation(fig, animate, init_func=init,
  
                                 frames=200, interval=20, blit=True)
  
  
  
  anim.save('seawave_1d_ani.mp4',writer='ffmpeg',fps=30)
  
  mpl.show()

  I believe the problem is in the part of the animation instead of the three functions above. Please help me find what mistake I have made.

• Any working example recording a (e.g. rtsp) stream to a local MP4 file with ffmpeg/libav ?

  15 novembre 2017, par ggs

  I’m looking for a working and not-out-dated script how to record an e.g. rtsp input stream to a local file (mp4) with ffmpeg/libav. If you could point me to one or post one, many thanks in advance. I’m searching for many hours and I haven’t got any experience with this topic.

  A lot of examples, libs, etc. are outdated, but I want to use ffmpeg >= v3.3.

  Any special things I have to consider (when compiling ffmpeg, or when saving local file to iOS device) ?

• FFmpeg dosn't listen on RTP port in debian

  26 juin 2021, par MSS

  I compose a command to encode my HLS audio stream to a mp3 stream :

  


  ffmpeg -re -i "http://cdn1.live.irib.ir:1935/channel-live/smil:r-payam/chunklist_b307200_slFa.m3u8" -acodec libmp3lame   -f rtp rtp://127.0.0.1:9434/


  


  When I run the command on windows 10 machine FFmpeg start to listen on port 9434 and works perfectly :

  


  

  


  But when I run it on my Debian machine it doesn't bind to specified port and also any of bind ports doesn't work :

  


  

  


  Running out put :

  


  

  


  FFmpeg version info :

  


  ffmpeg version N-57736-ga501d55905-static https://johnvansickle.com/ffmpeg/  Copyright (c) 2000-2021 the FFmpeg developers
built with gcc 6.3.0 (Debian 6.3.0-18+deb9u1) 20170516
configuration: --enable-gpl --enable-version3 --enable-static --disable-debug --disable-ffplay --disable-indev=sndio --disable-outdev=sndio --cc=gcc --enable-fontconfig --enable-frei0r --enable-gnutls --enable-gmp --enable-libgme --enable-gray --enable-libfribidi --enable-libass --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-librubberband --enable-libsoxr --enable-libspeex --enable-libsrt --enable-libvorbis --enable-libopus --enable-libtheora --enable-libvidstab --enable-libvo-amrwbenc --enable-libvpx --enable-libwebp --enable-libx264 --enable-libxml2 --enable-libxvid --enable-libzimg
libavutil      57.  0.100 / 57.  0.100
libavcodec     59.  1.101 / 59.  1.101
libavformat    59.  3.100 / 59.  3.100
libavdevice    59.  0.100 / 59.  0.100
libavfilter     8.  0.102 /  8.  0.102
libswscale      6.  0.100 /  6.  0.100
libswresample   4.  0.100 /  4.  0.100
libpostproc    56.  0.100 / 56.  0.100


  


  Does any body knows the correct way of stream rtp on debian ?