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• Catch if the Java process crashed

  10 mai 2018, par Victor Sheyanov

  I run java process to convert video using ffmpeg.exe.

  Runtime rt = Runtime.getRuntime();
  
  String cmd = FFMPEGFULLPATH + " -y -i " + '"' + mpeg4File + '"' + " -vcodec libx264 -vsync 2 " + '"' + H264file + '"';
  
  
  
  Process pr = rt.exec(cmd);
  
  
  
  ThreadedTranscoderIO errorHandler = new ThreadedTranscoderIO(pr.getErrorStream(), "Error Stream");
  
  errorHandler.start();
  
  ThreadedTranscoderIO inputHandler = new ThreadedTranscoderIO(pr.getInputStream(), "Output Stream");
  
  inputHandler.start();
  
  
  
  try {
  
        pr.waitFor();
  
  } catch (InterruptedException e) {
  
        LiveApplication.logger.info("Some shit happens during convertation 2 ");
  
        throw new IOException("UseTranscoderBlocking - Run_FFMPEG - process interrupted " + e);                  
  
  }

  But when the process started, sometimes especially with big files, but not always i get this windows message :

  

  This happens only on Windows server 2008 and didn’t happened on Windows 7.

  I have 2 questions :

  1. Why this process fails ?
  2. Can I catch this fail in Java, close
     this window and continue thread execution (maybe I’ll restart this
     proccess).

• How to fetch both live video frame and timestamp from ffmpeg to python on Windows

  8 mai 2018, par vijiboy

  Searching for an alternative as OpenCV would not provide timestamps for live camera stream (on Windows), which are required in my computer vision algorithm, I found ffmpeg and this excellent article https://zulko.github.io/blog/2013/09/27/read-and-write-video-frames-in-python-using-ffmpeg/
  The solution uses ffmpeg, accessing its standard output (stdout) stream. I extended it to read the standard error (stderr) stream as well.

  Working up the python code on windows, while I received the video frames from ffmpeg stdout, but the stderr freezes after delivering the showinfo videofilter details (timestamp) for first frame.

  I recollected seeing on ffmpeg forum somewhere that the video filters like showinfo are bypassed when redirected. Is this why the following code does not work as expected ?

  Expected : It should write video frames to disk as well as print timestamp details.
  Actual : It writes video files but does not get the timestamp (showinfo) details.

  Here’s the code I tried :

  import subprocess as sp
  
  import numpy
  
  import cv2
  
  
  
  command = [ 'ffmpeg', 
  
              '-i', 'e:\sample.wmv',
  
              '-pix_fmt', 'rgb24',
  
              '-vcodec', 'rawvideo',
  
              '-vf', 'showinfo', # video filter - showinfo will provide frame timestamps
  
              '-an','-sn', #-an, -sn disables audio and sub-title processing respectively
  
              '-f', 'image2pipe', '-'] # we need to output to a pipe
  
  
  
  pipe = sp.Popen(command, stdout = sp.PIPE, stderr = sp.PIPE) # TODO someone on ffmpeg forum said video filters (e.g. showinfo) are bypassed when stdout is redirected to pipes??? 
  
  
  
  for i in range(10):
  
      raw_image = pipe.stdout.read(1280*720*3)
  
      img_info = pipe.stderr.read(244) # 244 characters is the current output of showinfo video filter
  
      print "showinfo output", img_info
  
      image1 =  numpy.fromstring(raw_image, dtype='uint8')
  
      image2 = image1.reshape((720,1280,3))  
  
  
  
      # write video frame to file just to verify
  
      videoFrameName = 'Video_Frame{0}.png'.format(i)
  
      cv2.imwrite(videoFrameName,image2)
  
  
  
      # throw away the data in the pipe's buffer.
  
      pipe.stdout.flush()
  
      pipe.stderr.flush()

  So how to still get the frame timestamps from ffmpeg into python code so that it can be used in my computer vision algorithm...

• Async Javascript function returns undefined

  14 avril 2018, par Leon Wright

  I am trying to run this function but the it keeps returning undefined when I explicitly hardcode the return value.

  const splitVideo = async (sid, video, part) => {
  
      let framesLocation =`${process.cwd()}/${dirs.videoFrames}/${sid}_${part}`;
  
  
  
      console.log(fs.existsSync(framesLocation));
  
  
  
      if(!fs.existsSync(framesLocation)) {
  
          console.log("making dir");
  
          f.s.mkdirSync(framesLocation);
  
      }
  
  
  
      ffmpeg(video)
  
          .on('end', () => {
  
               return "done";
  
           })
  
           .on('error', (err) => {
  
               throw err;
  
           })
  
           .screenshots({
  
                timestamps: [1,2],
  
                filename: `${sid}_${part}/frame-%s.png`,
  
                folder: `${process.cwd()}/${dirs.videoFrames}`
  
           });
  
  };

  Please help this is very frustrating.