Recherche avancée

Sur d’autres sites (6286)

• Can you stream video with ffmpeg and opencv without long buffers

  13 septembre 2019, par steve

  I’m successfully getting a video stream using ffmpeg, and displaying with opencv, but the video starts and stops very often and is not as smooth as when played on a browser. Is there a way to get the video stream to be as smooth as on a browser ?

  I’ve tried playing with ffmpeg parameters as well as having multiple pipes to stitch together a single video.

  import cv2
  
  import numpy as np
  
  import subprocess as sp
  
  import time
  
  
  
  
  
  # Playlist manifest for video from Nevada DOT traffic camera
  
  VIDEO_URL = "https://wowza1.nvfast.org/bmw3/charleston_and_fremont_public.stream/playlist.m3u8"
  
  
  
  width = 360
  
  height = 240
  
  
  
  pipe = sp.Popen([ 'ffmpeg', "-i", VIDEO_URL,
  
              "-loglevel", "quiet", # no text output
  
              "-an",   # disable audio
  
              "-f", "image2pipe",
  
              "-pix_fmt", "bgr24",
  
              "-r", "15", # FPS
  
              "-hls_list_size", "3", 
  
              #"-hls_time", "8" 
  
              "-vcodec", "rawvideo", "-"],
  
              stdin = sp.PIPE, stdout = sp.PIPE)
  
  
  
  while True:
  
  
  
          # Convert bytes to image
  
          raw_image = pipe.stdout.read(width*height*3) # read 432*240*3 bytes (= 1 frame)
  
          img =  np.fromstring(raw_image, dtype='uint8').reshape((height,width,3))
  
          raw_image = np.copy(img)
  
  
  
          # Show image
  
          cv2.imshow('pipe', img)
  
          cv2.waitKey(1)
  
          time.sleep(0.05) # This is to slow down the video so it plays more naturally

  The expected output is a opencv window that displays the video just like in https://cctv.nvfast.org/

  I assume the problem lies in ffmpeg not getting the video chunks.

• Evolution #3015 : Joindre document sur article, par défaut

  17 octobre 2013, par guytarr °

  Samuel Delacre a écrit :

  [...] N’étant pas encore totalement rodé aux nouveautés de SPIP3, et pas encore familier aux différences "spipienne" entre images et documents, je ne pensais pas que cette option de contenu concernait les images également. Enfin les documents dans le cas présent.
  [...]

  Hello,
  En fait, ce n’est pas une nouveauté de SPIP3 mais de SPIP2.
  Si l’on regarde comment est renseignée la méta (pour les documents sur les articles) en 1.9.2 :
  http://core.spip.org/projects/spip/repository/entry/branches/spip-1.9.2/ecrire/inc/config.php#L65
  C’est à partir de SPIP 2.0 qu’elle change :
  http://core.spip.org/projects/spip/repository/entry/branches/spip-2.0/ecrire/inc/config.php#L86

  Le commit qui explique le pourquoi du comment et les tickets liés est notre cher r9462
  Bien sûr on peut défaire pour refaire puis redéfaire, il faudrait juste se mettre d’accord à un moment.

• Cannot play video created by OpenCV (using Ubuntu 12.04)

  2 février 2015, par mcExchange

  I tried to write a video from a sequence of images created by OpenCV. However I cannot open the videos after writing them. I guess there is a codec issue. I find it extremely difficult where the error exactly comes from. Here is my code :

      Size size = Size(vecOfMats[0].rows,vecOfMats[0].cols);
  
      int codec = CV_FOURCC('D', 'I', 'V', 'X');
  
  
  
      VideoWriter videoWriter;
  
      videoWriter.open(outputFilename,codec,15.0,size,true);
  
  
  
      for(int z=0; z < vecOfMats.size(); z++)
  
      {
  
          videoWriter.write(vecOfMats[z]);
  
      }
  
      videoWriter.release();

  I also tried all of these codecs without success (either OpenCv could not find the codec or the video could not be opened) :

  int codec = CV_FOURCC('P','I','M','1');   // = MPEG-1 codec
  
  int codec = CV_FOURCC('M','J','P','G');   // = motion-jpeg codec - cannot be played by VLC
  
  int codec = CV_FOURCC('M', 'P', '4', '2');// = MPEG-4.2 codec - not found
  
  int codec = CV_FOURCC('D', 'I', 'V', '3');// = MPEG-4.3 codec - not found
  
  int codec = CV_FOURCC('D', 'I', 'V', 'X');// = MPEG-4 codec - cannot be played by VLC
  
  int codec = CV_FOURCC('U', '2', '6', '3');// = H263 codec - must have w/h = 4
  
  int codec = CV_FOURCC('I', '2', '6', '3');// = H263I codec - not found

  I even took the codec of a video opened via OpenCV previously (without success) :

  string filename = "/path/to/the/video/myVideo.avi";
  
  VideoCapture capture(filename);
  
  int ex = static_cast<int>(capture.get(CV_CAP_PROP_FOURCC));             // Get Codec Type- Int form
  
  char EXT[] = {(char)(ex &amp; 0XFF) , (char)((ex &amp; 0XFF00) >> 8),(char)((ex &amp; 0XFF0000) >> 16),(char)((ex &amp; 0XFF000000) >> 24), 0};// Transform from int to char via Bitwise operators
  
  cout&lt;&lt;"Codec: "&lt;code></int>

  I’m not even sure if the problem lies with my OpenCV or my Ubuntu :/.
  (I tried to open them using the default video player and vlc)