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• Using openCV library with Java works well on Linux but not on Windows

  6 août 2016, par user3586330

  I have a method that takes screenshots on absolute intervals (25%, 50%, 75% and 100%) from a video-file and save each of them to a separate .png-file. I use openCV with the JavaCV-Wrapper library to do that. The class/method of interest is :

  package de.stal.videoreporter;
  
  
  
  import org.bytedeco.javacpp.opencv_core;
  
  import static org.bytedeco.javacpp.opencv_imgcodecs.cvSaveImage;
  
  import org.bytedeco.javacv.FFmpegFrameGrabber;
  
  import org.bytedeco.javacv.Frame;
  
  import org.bytedeco.javacv.FrameGrabber;
  
  import org.bytedeco.javacv.OpenCVFrameConverter;
  
  
  
  class VideoThumbnailer {
  
  public void createThumbnails(String videoname) throws FrameGrabber.Exception {
  
  
  
      FFmpegFrameGrabber g = new FFmpegFrameGrabber("videos/" + videoname);
  
      g.start();
  
      OpenCVFrameConverter.ToIplImage converterToIplImage = new OpenCVFrameConverter.ToIplImage();
  
      int length = g.getLengthInFrames();
  
      int fifty = length / 2;
  
      int twentyfive = fifty / 2;
  
      int seventyfive = fifty + twentyfive;
  
      int hundred = length - 1;
  
  
  
      //each frame of video
  
      for (int j = 0; j < length; j++) {
  
  
  
          if (j == twentyfive || j == fifty || j == seventyfive || j == hundred) {
  
              String ss = "";
  
              if (j == twentyfive) {
  
                  ss = "25";
  
              } else if (j == fifty) {
  
                  ss = "50";
  
              } else if (j == seventyfive) {
  
                  ss = "75";
  
              } else if (j == hundred) {
  
                  ss = "100";
  
              }
  
  
  
              g.setFrameNumber(j);
  
  
  
              Frame f = g.grabImage();
  
  
  
              opencv_core.IplImage image = converterToIplImage.convert(f);
  
              String img_path = "thumbnails/" + videoname + "." + ss + ".png";
  
              cvSaveImage(img_path, image);
  
          }
  
  
  
      }
  
      g.stop();
  
  }
  
  }

  That works fine on environment : Ubuntu 15.10 x64, Java v.1.7.0_101 and Netbeans 8.0.2 with Maven. So I exported the project to a runnable jar-file(with all dependencies included) and tried to start it on Windows 10 x64 via :

  java -jar VideoReporter-1.0-SNAPSHOT-jar-with-dependencies.jar

  On Windows an exception will be thrown when executing the .jar-file :

  Error putting member offsets for class org/bytedeco/javacpp/avutil$Pool_free_Pointer.
  
  Exception in thread "main" java.lang.NoClassDefFoundError: Could not initialize class org.bytedeco.javacpp.avutil
  
      at java.lang.Class.forName0(Native Method)
  
      at java.lang.Class.forName(Unknown Source)
  
      at org.bytedeco.javacpp.Loader.load(Loader.java:472)
  
      at org.bytedeco.javacpp.Loader.load(Loader.java:417)
  
      at org.bytedeco.javacpp.avformat$AVFormatContext.<clinit>(avformat.java:2719)
  
      at org.bytedeco.javacv.FFmpegFrameGrabber.startUnsafe(FFmpegFrameGrabber.java:391)
  
      at org.bytedeco.javacv.FFmpegFrameGrabber.start(FFmpegFrameGrabber.java:385)
  
      at de.stal.videoreporter.VideoThumbnailer.createThumbnails(VideoThumbnailer.java:15)
  
      at de.stal.videoreporter.MetaReader.slurpMetadata(MetaReader.java:67)
  
      at de.stal.videoreporter.VideoReporter.main(VideoReporter.java:19)
  
  </clinit>

  My pom.xml is :

  <?xml version="1.0" encoding="UTF-8"?>
  
  <project xmlns="http://maven.apache.org/POM/4.0.0">
  
  <modelversion>4.0.0</modelversion>
  
  <groupid>de.stal</groupid>
  
  <artifactid>VideoReporter</artifactid>
  
  <version>1.0-SNAPSHOT</version>
  
  <packaging>jar</packaging>
  
  <properties>
  
      UTF-8
  
      1.7
  
      1.7
  
  </properties>
  
  <build>
  
      <plugins>
  
          <plugin>
  
              <artifactid>maven-assembly-plugin</artifactid>
  
              <configuration>
  
                  <archive>
  
                      <manifest>
  
                          <mainclass>de.stal.videoreporter.VideoReporter</mainclass>
  
                      </manifest>
  
                  </archive>
  
                  <descriptorrefs>
  
                      <descriptorref>jar-with-dependencies</descriptorref>
  
                  </descriptorrefs>
  
              </configuration>
  
              <executions>
  
                  <execution>
  
                      <id>make-assembly</id>
  
                      <phase>package</phase> 
  
                      <goals>
  
                          <goal>single</goal>
  
                      </goals>
  
                  </execution>
  
              </executions>
  
          </plugin>
  
      </plugins>
  
  </build>
  
  <dependencies>
  
      <dependency>
  
          <groupid>org.apache.commons</groupid>
  
          <artifactid>commons-csv</artifactid>
  
          <version>1.1</version>
  
      </dependency>
  
      <dependency>
  
          <groupid>org.bytedeco</groupid>
  
          <artifactid>javacpp</artifactid>
  
          <version>1.2.1</version>
  
      </dependency>
  
      <dependency>
  
          <groupid>org.bytedeco</groupid>
  
          <artifactid>javacv</artifactid>
  
          <version>1.2</version>
  
      </dependency>
  
      <dependency>
  
          <groupid>com.fasterxml.jackson.dataformat</groupid>
  
          <artifactid>jackson-dataformat-csv</artifactid>
  
          <version>2.8.0.rc2</version>
  
      </dependency>
  
      <dependency>
  
          <groupid>javassist</groupid>
  
          <artifactid>javassist</artifactid>
  
          <version>3.12.1.GA</version>
  
      </dependency>
  
      <dependency>
  
          <groupid>commons-collections</groupid>
  
          <artifactid>commons-collections</artifactid>
  
          <version>3.2.1</version>
  
      </dependency>
  
      <dependency>
  
          <groupid>com.opencsv</groupid>
  
          <artifactid>opencsv</artifactid>
  
          <version>3.3</version>
  
      </dependency>
  
  </dependencies>
  
  </project>

  What might be the problem on Windows ? In my opinion there shouldn’t be a problem with access to openCV/FFMPEG-classes because they all have been included the .jar-file ? Is this a problem with the classpath ?

  Thanks, Peter

• OpenCV conda installation (missing ffmpeg) - Windows

  12 février 2017, par FZNB

  I managed to install OpenCV 3.1 using conda and Python 3.5 and everything seems to work fine.

  However, when trying to import a video file via ffmpeg I get this :

  import numpy as np
  
  import cv2
  
  
  
  cap = cv2.VideoCapture('data\vtest.avi')
  
  cap.read()
  
  
  
  #(False, None)

  When using still images or my laptop webcam it works (notice that the VideCapture returns None). Obviously, something is wrong with ffmpeg.

  I have tried a couple of things :

  1. Install ffmpeg binaries in my environment/PATH (works fine separately
     but apparently OpenCV cannot call it since it looks for specific dlls).

  2. Move to the bin folder (which is in my path as well) the
     dlls from the compiled version in
     sourceforge :

     opencv_ffmpeg310_64.dll

     opencv_ffmpeg310.dll

  Neither of the two options worked. Any ideas ?

• OpenCV-Python installation (missing ffmpeg) - Windows

  8 mai 2017, par FZNB

  I managed to install OpenCV 3.1 using conda and Python 3.5 and everything seems to work fine.

  However, when trying to import a video file via ffmpeg I get this :

  import numpy as np
  
  import cv2
  
  
  
  cap = cv2.VideoCapture('data\vtest.avi')
  
  cap.read()
  
  
  
  #(False, None)

  When using still images or my laptop webcam it works (notice that the VideCapture returns None). Obviously, something is wrong with ffmpeg.

  I have tried a couple of things :

  1. Install ffmpeg binaries in my environment/PATH (works fine separately
     but apparently OpenCV cannot call it since it looks for specific dlls).

  2. Move to the bin folder (which is in my path as well) the
     dlls from the compiled version in
     sourceforge :

     opencv_ffmpeg310_64.dll

     opencv_ffmpeg310.dll

  Neither of the two options worked. Any ideas ?