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• 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.

• FFmpeg static keyframe rate

  7 novembre 2011, par 2di

  I have a question about ffmpeg usage. Every time when I trying to convert video files into
  some different format, output file getting static keyframe sequence.

  What I mean is that keyframes appear at the distance of 12 frames. I know that its controllerd by parameter -g that you can change to any other number.

  ffmpeg -i 1.avi -vcodec mpeg4 -b 2000000  out.avi

  I believe there should be some way to make keyframes appear on uneven intervals. These interval should be calculated by codec, and it should be based on image changes in the video file. So keyframes should be inserted only when they needed, but not consistently after N frames.

  Can somebody please explain to me how this "smart" encoding can be done with ffmpeg ?
  Thank you

  SOLUTION : ok what I'ev been looking for has very simple solution. If you set -g to zero, ffmpeg will choose keyframes based on the video shots and bitrate

• HLS streaming on Android

  29 mars 2016, par STeN

  The HLS is supported on Android since version 3.0. Until the Honeycomb the H.264 and AAC was supported, but there was only RTSP streaming protocol. The HLS and MPEG-2 TS not (see here) were not supported.

  Porting the ffmpeg to the Android platform could be a solution for that (LGPL sources ara available). I am however looking for a ready made solution with SDK, customizable HLS player, etc. There is one here, but I would like to know if you do not know about other solutions.

  Thanks
  STEN