Sur d’autres sites (4638)

• ClassX installation "codec not found" due to dependencies [migrated]

  25 mars 2014, par khateeb

  ClassX is an interactive lecture streaming system developed in the Electrical Engineering Department at Stanford University.
  Unlike conventional lecture capturing systems, ClassX requires very simple consumer-grade equipment and minimal human operation.

  I faced problems during installing it, I hope you have a solution.

  BTW : I successfully installed it 2 years ago, but now I think the problem as the dependencies and Ubuntu versions are different than the versions we used two years ago.

  Detailed description of the problem :

  • I'm using Ubuntu 12.04
  • I followed the instructions @ ClassX installation guide, and all steps till step 4 are successfully done (the encoder bin file generated).
  • When trying to encode the video using the classX web system, it shows the encoding completed after few seconds.However, there are no tiles generated.

  • I tried to execute the command at CX_log.txt, and the following error appears.

    mahmoud@Mahmoud-HP-Pavilion-dv5-Notebook-PC : $ sudo perl /var/www/ClassXWebSystem/system/publishers/web/actions/encode.pl "/var/www/ClassXWebSystem/content/encoding/FALL_2013_2014/CS106A_FALL_2013_2014/lecSEven" "/var/www/ClassXWebSystem/content/encoding/FALL_2013_2014/CS106A_FALL_2013_2014/.encoding_1372706251" "/var/www/ClassXWebSystem/content/streaming/FALL_2013_2014/CS106A_FALL_2013_2014/lecSEven" "/var/www/ClassXWebSystem/system/publishers/bin" classx y n n
    [sudo] password for mahmoud :
    00068.jpg
    ..
    .
    00068.mp4
    Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/var/www/ClassXWebSystem/content/encoding/FALL_2013_2014/CS106A_FALL_2013_2014/.encoding_1372706251/00068.mp4' :
    Metadata :
    major_brand : isom
    minor_version : 512
    compatible_brands : isomiso2avc1mp41
    encoder : Lavf52.39.0
    Duration : 00:02:30.05, start : 0.000000, bitrate : 8141 kb/s
    Stream #0.0(und) : Video : h264, yuv420p, 1920x1080 [PAR 1:1 DAR 16:9], 8007 kb/s, 29.95 fps, 29.97 tbr, 2997 tbn, 59.94 tbc
    Stream #0.1(und) : Audio : aac, 44100 Hz, stereo, s16, 128 kb/s
    Output #0, mp4, to '/var/www/ClassXWebSystem/content/encoding/FALL_2013_2014/CS106A_FALL_2013_2014/.encoding_1372706251/stream0.mp4' :
    Stream #0.0 : Video : [0][0][0][0] / 0x0000, yuv420p, 640x360, q=32-36, 64 kb/s, 90k tbn, 14.99 tbc
    codec not found

• Writing frames from camera using skvideo.io.FFmpegWriter

  28 juin 2018, par Liam Deacon

  I’m trying to finely control the video encoding of camera image frames captured on the fly using skvideo.io.FFmpegWriter and cv2.VideoCapture, e.g.

  from skvideo import io
  
  import cv2
  
  
  
  fps = 60
  
  stream = cv2.VideoCapture(0)                    # 0 is for /dev/video0
  
  print("fps: {}".format(stream.set(cv2.CAP_PROP_FPS, fps)))
  
  
  
  stream.set(cv2.CAP_PROP_FRAME_WIDTH, 1920)
  
  stream.set(cv2.CAP_PROP_FRAME_HEIGHT, 1080)
  
  print("bit_depth: {}".format(stream.set(cv2.CAP_PROP_FORMAT, cv2.CV_8U)))
  
  
  
  video = io.FFmpegWriter('/tmp/test_ffmpeg.avi', 
  
              inputdict={'-r': fps, '-width': 1920, '-height': 1080},
  
              outputdict={'-r': fps, '-vcodec': 'libx264', '-pix_fmt': 'h264'}
  
  )
  
  
  
  try:
  
      for i in range(fps*10):  # 10s of video
  
          ret, frame = stream.read()
  
          video.writeFrame(frame)
  
  finally:
  
      stream.release()
  
  
  
  try:
  
      video.close()
  
  except:
  
      pass

  However, I get the following exception (in Jupyter notebook) :

  ---------------------------------------------------------------------------
  
  TypeError                                 Traceback (most recent call last)
  
  
  
   in <module>()
  
       18     while range(fps*10):
  
       19         ret, frame = stream.read()
  
  ---> 20         video.writeFrame(frame)
  
       21 except BaseException as err:
  
       22     raise err
  
  
  
  /usr/local/lib/python3.6/site-packages/skvideo/io/ffmpeg.py in writeFrame(self, im)
  
      446         T, M, N, C = vid.shape
  
      447         if not self.warmStarted:
  
  --> 448             self._warmStart(M, N, C)
  
      449 
  
      450         # Ensure that ndarray image is in uint8
  
  
  
  /usr/local/lib/python3.6/site-packages/skvideo/io/ffmpeg.py in _warmStart(self, M, N, C)
  
      412         cmd = [_FFMPEG_PATH + "/" + _FFMPEG_APPLICATION, "-y"] + iargs + ["-i", "-"] + oargs + [self._filename]
  
      413 
  
  --> 414         self._cmd = " ".join(cmd)
  
      415 
  
      416         # Launch process
  
  
  
  TypeError: sequence item 3: expected str instance, int found
  
  </module>

  Changing this to video.writeFrame(frame.tostring()) results in ValueError: Improper data input, leaving me stumped.

  How should I go about writing each frame (as returned by OpenCV) to my FFmpegWriter instance ?

  EDIT

  The code works fine if I remove inputdict and outputdict from the io.FFmpegWriter call, however this defeats the purpose for me as I need fine control over the video encoding (I am experimenting with lossless/near-lossless compression of the raw video captured from the camera and trying to establish the best compromise in terms of compression vs fidelity for my needs).

• Saving the openGL context as a video output

  16 septembre 2016, par activatedgeek

  I am currently trying to save the animation made in openGL to a video file. I have tried using openCV’s videowriter but to no advantage. I have successfully been able to generate a snapshot and save it as bmp using the SDL library. If I save all snapshots and then generate the video using ffmpeg, that is like collecting 4 GB worth of images. Not practical.
  How can I write video frames directly during rendering ?
  Here the code i use to take snapshots when I require :

  void snapshot(){
  
  SDL_Surface* snap = SDL_CreateRGBSurface(SDL_SWSURFACE,WIDTH,HEIGHT,24, 0x000000FF, 0x0000FF00, 0x00FF0000, 0);
  
  char * pixels = new char [3 *WIDTH * HEIGHT];
  
  glReadPixels(0, 0,WIDTH, HEIGHT, GL_RGB, GL_UNSIGNED_BYTE, pixels);
  
  
  
  for (int i = 0 ; i <height>pixels) + snap->pitch * i, pixels + 3 * WIDTH * (HEIGHT-i - 1), WIDTH*3 );
  
  
  
  delete [] pixels;
  
  SDL_SaveBMP(snap, "snapshot.bmp");
  
  SDL_FreeSurface(snap);
  
  }
  
  </height>

  I need the video output. I have discovered that ffmpeg can be used to create videos from C++ code but have not been able to figure out the process. Please help !

  EDIT : I have tried using openCV CvVideoWriter class but the program crashes ("segmentation fault") the moment it is declared.Compilation shows no errors ofcourse. Any suggestions to that ?

  SOLUTION FOR PYTHON USERS (Requires Python2.7,python-imaging,python-opengl,python-opencv, codecs of format you want to write to, I am on Ubuntu 14.04 64-bit) :

  def snap():
  
      pixels=[]
  
      screenshot = glReadPixels(0,0,W,H,GL_RGBA,GL_UNSIGNED_BYTE)
  
      snapshot = Image.frombuffer("RGBA",W,H),screenshot,"raw","RGBA",0,0)
  
      snapshot.save(os.path.dirname(videoPath) + "/temp.jpg")
  
      load = cv2.cv.LoadImage(os.path.dirname(videoPath) + "/temp.jpg")
  
      cv2.cv.WriteFrame(videoWriter,load)

  Here W and H are the window dimensions (width,height). What is happening is I am using PIL to convert the raw pixels read from the glReadPixels command into a JPEG image. I am loading that JPEG into the openCV image and writing to the videowriter. I was having certain issues by directly using the PIL image into the videowriter (which would save millions of clock cycles of I/O), but right now I am not working on that. Image is a PIL module cv2 is a python-opencv module.