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• Revision 56730 : On tente une fonction de normalisation des données. Il faudra mieux ...

  6 janvier 2012, par marcimat@… — Log

  On tente une fonction de normalisation des données.
  Il faudra mieux définir ce genre de chose, mais ça va permettre de tester un peu.
  La fonction normaliser(valeur, type, options) retourne un tableau avec
   erreur
   valeur
   changement
  Changement vaut true s’il n’y a pas d’erreur et que la valeur a été modifiée.

• Pipe raw OpenCV images to FFmpeg

  15 février 2017, par BrianTheLion

  Here’s a fairly straightforward example of reading off a web cam using OpenCV’s python bindings :

  '''capture.py'''
  
  import cv, sys
  
  cap = cv.CaptureFromCAM(0)                    # 0 is for /dev/video0
  
  while True :
  
      if not cv.GrabFrame(cap) : break
  
      frame = cv.RetrieveFrame(cap)
  
      sys.stdout.write( frame.tostring() )

  Now I want to pipe the output to ffmpeg as in :

  $ python capture.py | ffmpeg -f image2pipe -pix_fmt bgr8 -i - -s 640x480 foo.avi

  Sadly, I can’t get the ffmpeg magic incantation quite right and it fails with

    libavutil     50.15. 1 / 50.15. 1
    libavcodec    52.72. 2 / 52.72. 2
    libavformat   52.64. 2 / 52.64. 2
    libavdevice   52. 2. 0 / 52. 2. 0
    libavfilter    1.19. 0 /  1.19. 0
    libswscale     0.11. 0 /  0.11. 0
    libpostproc   51. 2. 0 / 51. 2. 0
  Output #0, avi, to ’out.avi’ :
      Stream #0.0 : Video : flv, yuv420p, 640x480, q=2-31, 19660 kb/s, 90k tbn, 30 tbc
  [image2pipe @ 0x1508640]max_analyze_duration reached
  [image2pipe @ 0x1508640]Estimating duration from bitrate, this may be inaccurate
  Input #0, image2pipe, from ’pipe :’ :
    Duration : N/A, bitrate : N/A
      Stream #0.0 : Video : 0x0000, bgr8, 25 fps, 25 tbr, 25 tbn, 25 tbc
  swScaler : 0x0 -> 640x480 is invalid scaling dimension
  

  • The captured frames are definitely 640x480.
  • I’m pretty sure the pixel order for the OpenCV image type (IplImage) is GBR, one byte per channel. At least, that’s what seems to be coming off the camera.

  I’m no ffmpeg guru. Has anyone done this successfully ?

• Using FFMpeg with Runtime.exec() to do a simple transcoding

  1er novembre 2011, par Adam Ingmansson

  I know there are many questions touching this subject, but none have helped me solve my issue.

  Purpose :

  Transcoding a video taken,from a queue, from .mov to h.264 (for now only that)

  Solution :

  Building a java application that gets the next in the queue, transcodes it then repeat

  Problem :

  Running ffmpeg using Runtime.exec() is not working.
  Im using the StreamGobbler from this tutorial to capturing the output from the process.

  This code shows how i start my process :

  String[] command = new String[]{"./ffmpeg/ffmpeg","-i",videoFile.getPath(),"-vcodec","libx264","-fpre",preset,folder + recID + ".flv"};
  
  System.out.println("Running command..");
  
  Process p = r.exec(command);
  
  
  
   // any error message?
  
  StreamGobbler errorGobbler = new 
  
  StreamGobbler(p.getErrorStream(), "ERROR");            
  
  
  
  // any output?
  
  StreamGobbler outputGobbler = new 
  
  StreamGobbler(p.getInputStream(), "OUT");
  
  
  
  // kick them off
  
  errorGobbler.start();
  
  outputGobbler.start();
  
  
  
  //logProcessOutputAndErrors(p);
  
  
  
  int res = p.waitFor();
  
  if (res != 0) {
  
      throw new Exception("Encoding error: "+String.valueOf(res));
  
  }

  and this is the current modified version of StreamGobbler (the important part)

  InputStreamReader isr = new InputStreamReader(is);
  
  BufferedReader br = new BufferedReader(isr);
  
  String line=null;
  
  int c = 0;
  
  StringBuilder str = new StringBuilder();
  
  
  
  while (true) {
  
      c = br.read();
  
  }

  Sometimes ffmpeg just stalls, maybe waiting for my input (although there is no indication on screen).

  Sometimes it just ends.

  Sometimes (when I added the line "System.out.print((char) c) ;" in the while-loop above) i got loads of "¿¿ï" repeated over and over again, wich might be the actual encoding of the video wich I managed to capture instead of to a file.

  For those who wonders why i dont just go with a commandline or maybe even php :

  The purpose is an application that will run 24/7 transcoding anything and everything from a queue. The files are pretty large to begin with and takes about 15 min to transcode.