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• Although ffmpeg installed, unable to save mp4 file on disk

  2 janvier 2020, par yannis

  Although I have installed ffmpeg, matplotlib reports that MovieWriter ffmpeg is unavailable and the MP4 file created is empty.

  import numpy as np
  
  from matplotlib import pyplot as plt
  
  from matplotlib import animation
  
  
  
  # First set up the figure, the axis, and the plot element we want to animate
  
  fig = plt.figure()
  
  ax = plt.axes(xlim=(0, 2), ylim=(-2, 2))
  
  line, = ax.plot([], [], lw=2)
  
  
  
  # initialization function: plot the background of each frame
  
  def init():
  
      line.set_data([], [])
  
      return line,
  
  
  
  # animation function.  This is called sequentially
  
  def animate(i):
  
      x = np.linspace(0, 2, 1000)
  
      y = np.sin(2 * np.pi * (x - 0.01 * i))
  
      line.set_data(x, y)
  
      return line,
  
  
  
  # call the animator.  blit=True means only re-draw the parts that have changed.
  
  anim = animation.FuncAnimation(fig, animate, init_func=init,
  
                                 frames=200, interval=20, blit=True)
  
  
  
  # save the animation as an mp4.  This requires ffmpeg or mencoder to be
  
  # installed.  The extra_args ensure that the x264 codec is used, so that
  
  # the video can be embedded in html5.  You may need to adjust this for
  
  # your system: for more information, see
  
  # http://matplotlib.sourceforge.net/api/animation_api.html
  
  anim.save('basic_animation.mp4', fps=30, extra_args=['-vcodec', 'libx264'])
  
  
  
  plt.show()

  I have even added the line plt.switch_backend('TkAgg') proposed in another post, nothing changed. Here is my matplotlib :

  Name: matplotlib
  
  Version: 2.1.0
  
  Summary: Python plotting package
  
  Home-page: http://matplotlib.org

  my ffmpeg :

  Name: ffmpeg
  
  Version: 1.4
  
  Summary: ffmpeg python package url [https://github.com/jiashaokun/ffmpeg]
  
  Home-page: https://github.com/jiashaokun/ffmpeg

  and my Python version :

  Python 3.6.5

  The error I get is :

  /usr/local/lib/python3.6/site-packages/matplotlib/animation.py:1218: UserWarning: MovieWriter ffmpeg unavailable
  
    warnings.warn("MovieWriter %s unavailable" % writer)

  This error has been reported many times on stackoverflow, each time the solution is either to install ffmpeg (mine is installed) or to add that extra line about the backend, which hasn’t changed anything for me.

  Curiously enough the plt.show()command works and I do preview an animation, but the only file format to save it is (nonanimated) PNG.

• ffmpeg streaming to rtmp at 30fps

  19 janvier 2018, par user6326558

  I am trying to stream my desktop to facebook rtmp server using screen-capture-recorder :

   -re  -rtbufsize 256M -f dshow -i audio="Mikrofon (Realtek Audio)" 
  
  -rtbufsize 256M -f dshow -i audio="virtual-audio-capturer"  
  
  -rtbufsize 1024M -f dshow -i video=screen-capture-recorder -r 30  
  
  -filter:v scale=1280:720 -c:v  h264_nvenc -pix_fmt yuv420p -preset fast 
  
  -b:v 8M -maxrate:v 10M  -c:a aac -b:a 128k -ar 44100 
  
  -f flv rtmp://live-api.facebook.com:80/rtmp/..............

  I am using h264_nvenc codec for gpu acceleration, but I can stream at only 12-18 fps. However, when I stream into a file :

   -re  -rtbufsize 256M -f dshow -i audio="Mikrofon (Realtek Audio)" 
  
  -rtbufsize 256M -f dshow -i audio="virtual-audio-capturer"  
  
  -rtbufsize 1024M -f dshow -i video=screen-capture-recorder -r 30  
  
  -filter:v scale=1280:720 -c:v  h264_nvenc -pix_fmt yuv420p -preset fast 
  
  -b:v 8M -maxrate:v 10M  -c:a aac -b:a 128k -ar 44100 
  
  D:\test.mp4 -y

  I get 30 fps without problem, even when playing game (eg. Call of duty 6, pretty HW draining). Is it also possible to stream to rtmp at 30 fps with my command configuration ? Thank you

  If needed, my ffmpeg build config is :

  ffmpeg version 3.3.3 Copyright (c) 2000-2017 the FFmpeg developers

  built with gcc 7.1.0 (GCC)
  configuration : —disable-static —enable-shared —enable-gpl —enable-version3 —enable-cuda —enable-cuvid —enable-d3d11va —enable-dxva2 —enable-libmfx —enable-nvenc —enable-avisynth —enable-bzlib —enable-fontconfig —enable-frei0r —enable-gnutls —enable-iconv —enable-libass —enable-libbluray —enable-libbs2b —enable-libcaca —enable-libfreetype —enable-libgme —enable-libgsm —enable-libilbc —enable-libmodplug —enable-libmp3lame —enable-libopencore-amrnb —enable-libopencore-amrwb —enable-libopenh264 —enable-libopenjpeg —enable-libopus —enable-librtmp —enable-libsnappy —enable-libsoxr —enable-libspeex —enable-libtheora —enable-libtwolame —enable-libvidstab —enable-libvo-amrwbenc —enable-libvorbis —enable-libvpx —enable-libwavpack —enable-libwebp —enable-libx264 —enable-libx265 —enable-libxavs —enable-libxvid —enable-libzimg —enable-lzma —enable-zlib

• How do I create a 360 [stereo] panorama video of a virtual scene using OpenGL or DirectX ?

  14 novembre 2015, par Prashant Raina

  Like many of you, I have seen the magical 360 degree videos doing the rounds on Facebook right now. I would really like to know how to programmatically create such a video using OpenGL or DirectX, but I found surprisingly little information about it.
  There are several issues I am not clear on :

  1. How do I set up my vertex and fragment shaders to render a frame of 360 video ?
  2. Do I have to generate one image per frame, or a cubemap, or something else ?
  3. Once I have the frames, how do I combine them into a single video file for upload ? My Googling suggests that I should use ffmpeg, but I couldn’t figure out which parameters to use, or what sort of input it expects for 360 video.
  4. What additional steps are needed to make a stereo 360 video ?

  I am not asking how to render an existing video onto the screen, or how to use physical cameras for 360 video.

  Thanks in advance !