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• Transcoding to webm with ffmpeg audio problems

  9 novembre 2011, par Max A.

  For the past few days, I have been trying to get my lossless .mov video(that has an audio track) to a .webm format.

  Some info on the video & audio is that the fps is 30. Also the audio track has about 3-5 seconds of silence/blank audio before you start hearing some music.

  My problem is that is seems during the transcoding to webm, it strips away this blank audio because when I go to play the video, the audio starts right away.I've also notice that it jumps right away to 4 seconds in the video. When i play it on the browser, it jumps to that moment in the timeline. If I try to scrub to the beginning, the video ends.

  I've have figured somethings out.

  1. This is just a webm problem. This does not happen with ogv or mp4
  2. It only happens if they is blank audio in the beginning of the audio track.

  I am using ffmpeg with the libvpx and libvorbis librarys and I am doing just the basic command line setup

  ffmpeg -i "infile" "outfile.webm"

• Start/Stop Ffmpeg video capture

  2 novembre 2011, par Dasas

  I'm currently using ffmpeg for recording video from a webcam source.

  At the moment i use java to call for ffmpeg to execute.

  The code is pretty straightforward

  ffmpeg -f dshow -i video="Dualpix HD720p for Notebooks" -s cif -r 20 -f flv TEST.FLV
  
  Runtime.getRuntime().exec("rundll32 SHELL32.DLL,ShellExec_RunDLL " + cmd);

  and it works fine.

  The only real issue occour when when i need to stop the recording process.

  I know that i can press q or even ctrl+c in the CMD but i need to stop the process without keyboard input.

  That would be pretty easy to achive by killing the process but in this case ffmpeg do not finalize the video leaving me with a corrupt, need to fix, output.

  Is there any way to trigger the finalizing process "remotely".

  Thx,
  D.

  *******EDIT**********

  Thx for the prompt answer, i think you're referring to

  Process.getOutputStream()

  As for this case i have tried with this code :

  public Process doCommand(String cmd) throws Exception {
  
  
  
      rt = Runtime.getRuntime();
  
      Process proc = rt.exec(cmd);
  
      recOS= proc.getOutputStream();
  
      regcIS= proc.getInputStream();
  
  
  
      return proc;
  
  
  
  }
  
  
  
     receOS.write(("q/n".getBytes()));
  
     recOS.flush();

  I'm still getting an error, to be more specific, java.io.ioexception The pipe is being closed ...

• Multiple video sources combined into one

  28 septembre 2011, par Oded

  I am looking for an efficient way to do the following :

  Using several source videos (of approximately the same length), I need to generate an output video that is composed of all of the original sources each running in its own area (like a bunch of PIPs in several different sizes). So, the end result is that all the original are running side-by-side, each in its own area/box.

  The source and output need to be flv and the platform I am using is Windows (dev on Windows 7 64bit, deployment to Windows server 2008).

  I have looked at avisynth but unfortunately it can't handle flv and non of the plugins and flv splitters I have tried worked.

  My current process uses ffmpeg in the following manner :

  1. Use ffmpeg to generate 25 png's per second per video, resizing the original as needed.
  2. Use the System.Drawing namespace to combine each set of frames into a new image, starting with a static background, then loading each frame into an Image and drawing to the background Graphics object - this gives me the combined frames.
  3. Use ffmpeg to combine the generated images to a video.

  All this is very IO intensive (which is my processing bottleneck at the moment) and I feel there must be a more efficient way to reach my goal. I do not have much experience with video processing, and don't know what options are out there.

  Can anyone suggest a more efficient way of processing these ?