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• Use ffmpeg to modify single frame without remux ?

  6 février 2017, par 1337GameDev

  I am curious of a fast way to modify a video, slightly, as to force the video to hash differently than the source. I want to avoid changes to meta tags, as these are parsed from the container file and not the video data itself.

  I will be using a process to compare videos for analytical work, but the process requires the 2 inputs to have differing hashes for the video content (otherwise the analytical process yields odd results). I am testing an improvement on this process, and need to have very similar videos.

  I have currently just used a ffmpeg bash script and filtered a VERY light 2x2 pixel for the first second of the video (90% transparent) and this seems to do the trick as they hash differently, but it requires demux / remux of the video, which takes forever if I want to analyze a lot of videos.

  Is there a way, using ffmpeg, to simple modify a single frame (specified by a time value) and change a single pixel and just copy the rest of the video contents ?

• java.lang.NoClassDefFoundError : Could not initialize class on Linux (Works fine on Windows)

  26 décembre 2016, par Jake Miller

  I’m using a C++ FFmpeg wrapper for Java (org.bytedeco.javacpp). This works perfectly on a Windows machine (my development machine) but throws this error when ran on Linux (Amazon Web Services Elastic Beanstalk) :

  java.lang.NoClassDefFoundError: Could not initialize class org.bytedeco.javacpp.avutil
  
      at java.lang.Class.forName0(Native Method) ~[na:1.8.0_111]
  
      at java.lang.Class.forName(Class.java:348) ~[na:1.8.0_111]
  
      at org.bytedeco.javacpp.Loader.load(Loader.java:472) ~[javacpp-1.2.1.jar!/:1.2.1]
  
      at org.bytedeco.javacpp.Loader.load(Loader.java:417) ~[javacpp-1.2.1.jar!/:1.2.1]
  
      at org.bytedeco.javacpp.avformat$AVFormatContext.<clinit>(avformat.java:2819) ~[ffmpeg-3.2.1-1.3.jar!/:1.2.1]
  
      at org.bytedeco.javacv.FFmpegFrameGrabber.startUnsafe(FFmpegFrameGrabber.java:391) ~[javacv-1.3.jar!/:1.3]
  
      at org.bytedeco.javacv.FFmpegFrameGrabber.start(FFmpegFrameGrabber.java:385) ~[javacv-1.3.jar!/:1.3]
  
  </clinit>

  I’ve been troubleshooting for the past 2 days and have tried the following to fix the issue :

  • upgrade to Linux to 2.4
  • downgrading javacpp to 1.2.1
  • running mvn clean
  • running mvn -U
  • deleting contents of /.m2/ and redownloading dependencies
  • various combinations of dependency versions
  • git clone on a Linux VM & running mvn install there

  When looking further into the issue, I stumbled upon documentation for avformat$AVFormatContext as it’s in the stack trace posted above (6th line). The documentation for a C++ class named AVFormatContext. Whenever I attempt to view the class in Eclipse, it says Source Not Found.

  My question : could this problem possibly be caused by the C++ libraries on my Linux VM ? None of the above solutions fixed it so this is my only hypothesis as of now.

  Here’s my other Stack Overflow question regarding this subject : Java.lang.NoClassDefFoundError caused by FFmpeg when deployed on Linux as a packaged .war (Works on development machine)

• Using OpenCV on 32-bit XP

  14 novembre 2016, par Aleksandar Rakić

  Is it possible to run OpenCV version 3.0.0 on 32-bit XP ?

  I have successfully compiled code on Win 8.1 64-bit platform but it won’t run on the other computer.

  The code I run is below (it’s only for testing purposes)

  package opencvtest;
  
  
  
  import java.awt.Image;
  
  import java.awt.image.BufferedImage;
  
  import java.awt.image.DataBufferByte;
  
  import javax.swing.ImageIcon;
  
  import javax.swing.JFrame;
  
  import javax.swing.JLabel;
  
  import org.opencv.core.*;
  
  import org.opencv.videoio.VideoCapture;
  
  import org.opencv.videoio.Videoio;
  
  
  
  public class OpenCVtest {
  
  
  
  
  
    private JFrame frame;
  
    private JLabel imageLabel;
  
  
  
   public static void main(String[] args) {
  
      OpenCVtest app = new OpenCVtest();
  
      app.initGUI();
  
      app.runMainLoop(args);
  
    }
  
  
  
    private void initGUI() {
  
      frame = new JFrame("Camera Input Example");  
  
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);  
  
      frame.setSize(400,400);  
  
      imageLabel = new JLabel();
  
      frame.add(imageLabel);
  
      frame.setVisible(true);       
  
    }
  
  
  
    public static BufferedImage bufferedImage(Mat m) {
  
  
  
  
  
      int type = BufferedImage.TYPE_BYTE_GRAY;
  
      if (m.channels() > 1) {
  
          type = BufferedImage.TYPE_3BYTE_BGR;
  
      }
  
      BufferedImage image = new BufferedImage(m.cols(), m.rows(), type);
  
  
  
      m.get(0, 0, ((DataBufferByte)image.getRaster().getDataBuffer()).getData());
  
      return image;
  
  
  
    }
  
  
  
    private void runMainLoop(String[] args) {
  
      //ImageProcessor imageProcessor = new ImageProcessor();
  
      System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
  
      System.out.println("Welcome to OpenCV version " + Core.VERSION);
  
      Mat webcamMatImage = new Mat();
  
      System.out.println("Mat " + webcamMatImage);
  
      Image tempImage;
  
      VideoCapture capture = new VideoCapture("Highway.mp4");
  
      System.out.println("Capture " + capture);
  
      if(!capture.isOpened()){
  
          System.out.println(capture.open("D:\\AleksandarRakic\\Java Projects\\mavenproject1\\Highway.mp4")?"Otvorio":"Nije otvorio");
  
      }
  
      capture.set(Videoio.CAP_PROP_FRAME_WIDTH,320);
  
      capture.set(Videoio.CAP_PROP_FRAME_HEIGHT,240);
  
  
  
      if( capture.isOpened()){  
  
          while (true){  
  
              capture.read(webcamMatImage);
  
                  if( !webcamMatImage.empty() ){
  
                      int type = BufferedImage.TYPE_BYTE_GRAY;
  
                      if (webcamMatImage.channels() > 1) {
  
                          type = BufferedImage.TYPE_3BYTE_BGR;
  
                      }
  
                      BufferedImage image = new BufferedImage(webcamMatImage.cols(), webcamMatImage.rows(), type);
  
  
  
                      webcamMatImage.get(0, 0, ((DataBufferByte)image.getRaster().getDataBuffer()).getData());
  
  
  
                      tempImage= image;
  
                      ImageIcon imageIcon = new ImageIcon(tempImage, "Captured video");
  
                      imageLabel.setIcon(imageIcon);
  
                      frame.pack();  //this will resize the window to fit the image
  
                  }  
  
                  else{
  
                      System.out.println(" -- Frame not captured -- Break!");
  
                      break;  
  
                  }
  
          }
  
      }
  
      else{
  
          System.out.println("Couldn't open capture.");
  
      }
  
    }
  
  
  
  }

  When I run it on XP, VideoCapture constructor fails to open the video designated. From my understanding, opencv uses it’s own ffmpeg .dll as a codec. Is this true ?

  If not, is it using the codec I have from K-Lite cp ?

  Finally, could anything else be wrong ?

  My %path% variable contains the locations to opencv_ffmpeg300.dll and openvc_java300.dll on WinXP. I also added the following to NetBeans run parameter

  -Djava.library.path="C :\opencv\build\x86\vc12\bin ;C :\opencv\build\java\x86"