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• FFmpeg screencast recording : which codecs to use ?

  24 avril 2013, par mkaito

  I've been experimenting with recording screencasts using FFmpeg's X11grab module, which has worked more or less fine so far. I understand that a/v encoding is a complex process with many fine details, but I'm doing my best to learn.

  I'd like to do "lightweight" recording of a video stream, that puts as little strain as possible on the system while the stream is being recorded. I record two audio streams separately with pacat and sox. Later, the whole thing is filtered, normalized, encoded, and combined into a Matroska container.

  Right now, I'm having ffmpeg record a rawvideo stream to be fed to x264's yuv4 demuxer. I experimented with ffv1 and straight x264 recording before. My system can't handle real time encoding with x264 on the settings I want for the final stream, so I have to recompress separately once the recording is done. I've found that ffv1 gives me terrible frame dropping, and yuv4 too, but less so. I suspect this is due to hard drive speed, even if I'm sitting in a SATA3 Caviar Black that's being used exclusively to hold the recorded data.

  The question is, which combination of video codecs should I look at ? Record straight in x264 and recompress to "better" x264 later ? Raw video, then compress ? How would I go about pinpointing issues such as the frame drops I've been experiencing ?

  EDIT : This is the ffmpeg line I currently use.

  ffmpeg -v warning -f x11grab -s 1920x1080 -r 30000/1001 -i :0.0\
  
  -vcodec rawvideo -pix_fmt yuv420p -s 1280x720\
  
  -threads 0\
  
  recvideo.y4m

• FFMPEG in Java (runtime error)

  4 juillet 2012, par Eric

  I want to write a program that converts video into frames using FFMPEG. When I use it on the Ubuntu terminal, it works fine. But when I try to put it into the Java code, it gives me a runtime error. Did I make a mistake in my code below ?

  import java.util.*;
  
  import java.awt.*;
  
  import java.lang.*;
  
  import java.lang.Runtime;
  
  import java.io.*;
  
  import java.io.IOException;
  
  
  
  public class ConvertVideoToImage
  
  {
  
      private SingletonServer ss = null;
  
  
  
      public ConvertVideoToImage(SingletonServer ss)
  
      {
  
          this.ss = ss;
  
      }
  
  
  
      public void run()
  
      {
  
          convertVideo();
  
      }
  
  
  
      public void convertVideo()
  
      {
  
          try
  
          {
  
              Runtime rt = Runtime.getRunTime().exec("ffmpeg" + "-i" +         "display.wmv" + "image%d.jpg");
  
          }
  
          catch(Exception e){}
  
      }
  
  
  
  }

  Edit :

  I have changed the code like you suggested, but it also doesn't work. And when I Googled it, I found out that someone put the full path inside the executable and it became like this :

  Runtime.getRuntime().exec("/home/pc3/Documents/ffmpeg_temp/ffmpeg -i display.wmv image%d.jpg")

  BTW, thanks for the reply. I have another question. Is it possible to make a counter for FFMPEG ? I used this command in the Ubuntu terminal to make it convert a video to 30 frames/1seconds :

  ffmpeg -i display.wmv image%d.jpg

  This will automatically generate numbers like image1.jpg, image2.jpg, to image901.jpg. Is it possible to make a counter for this ? Because I need to count the files and control the number.

  Thanks in advance.

• vmr9 surface with ffmpeg codec

  7 janvier 2013, par Vipul

  I am a multimedia newbie, so pardon me if I am asking a stupid question.

  I want to use VMR9 surface while using the codec's from FFMPEG library.
  So far my search result tells that VMR9 has it's own codec. And I am not able to find any VMR9 related API change the codec to use to one of those provided by FFMPEG library.

  Can anyone tell if there is some way to do that ?
  Maybe an exaplme will help me understand better.

  Thanks