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• Failed to capture a avi file using opencv

  30 avril 2017, par Wei

  I am quite new to c++ compilation. I am trying to work on a simple problem using opencv where I read a video file and display it.

  My code looks like :

  #include <opencv></opencv>cv.h>
  
  #include <opencv></opencv>highgui.h>
  
  #include "opencv2/opencv.hpp"
  
  #include <opencv2></opencv2>core/core.hpp>
  
  #include <opencv2></opencv2>highgui/highgui.hpp>
  
  
  
  
  
  #include 
  
  #include 
  
  
  
  #include <algorithm>
  
  #include 
  
  #include 
  
  #include 
  
  #include <fstream>
  
  #include <iostream>
  
  #include <vector>
  
  #include <list>
  
  #include <string>
  
  
  
  
  
  using namespace cv;
  
  
  
  IplImage* image = 0; 
  
  IplImage* prev_image = 0;
  
  
  
  int show = 1; 
  
  
  
  int main( int argc, char** argv )
  
  {
  
      int frameNum = 0;
  
  
  
      char* video = argv[1];
  
      VideoCapture capture(video);
  
  
  
      if( !capture.isOpened() ) { 
  
          printf( "Could not initialize capturing..\n" );
  
          return -1;
  
      }
  
  
  
      if( show == 1 )
  
          cvNamedWindow( "Video", 0 );
  
  
  
      while( true ) {
  
          IplImage* frame = 0;
  
          int i, j, c;
  
  
  
          // get a new frame
  
          //frame = cvQueryFrame( capture );
  
          Mat mat_img;
  
          capture >> mat_img;
  
          IplImage frame1 = mat_img.operator IplImage();
  
          frame = &amp;frame1;
  
          if( !frame )
  
              break;
  
  
  
          if( !image ) {
  
              image =  cvCreateImage( cvSize(frame->width,frame->height), 8, 3 );
  
              image->origin = frame->origin;
  
          }
  
  
  
          cvCopy( frame, image, 0 );
  
  
  
          if( show == 1 ) {
  
              cvShowImage( "Video", image);
  
              c = cvWaitKey(3);
  
              if((char)c == 27) break;
  
          }
  
  
  
          std::cerr &lt;&lt; "The " &lt;&lt; frameNum &lt;&lt; "-th frame" &lt;&lt; std::endl;
  
          frameNum++;
  
      }
  
  
  
      if( show == 1 )
  
          cvDestroyWindow("Video");
  
  
  
      return 0;
  
  }
  
  </string></list></vector></iostream></fstream></algorithm>

  Then I compile it like :

  g++ test.cpp -o Video -pipe -D __STDC_CONSTANT_MACROS -D STD=std -Wall -I. -I/usr/local/ -O3 -DNDEBUG -ggdb -L/usr/local/ -lopencv_core -lopencv_highgui -lopencv_video -lopencv_imgproc -lavformat -lavdevice -lavutil -lavcodec -lswscale

  Compilation works fine and no errors returned.

  However, when I was running it, I got :

  (Video:5651): GLib-GObject-CRITICAL **: g_object_set: assertion 'G_IS_OBJECT (object)' failed
  
  Could not initialize capturing..

  Some other information :
  1. I test my opencv and ffmpeg by running simple examples, which work well.
  2. I can stream frames from my camera and display it using opencv.

  Anyone has idea of what causes this ?

  Any idea is appreciated.

• FFMPEG : extracting jpegs at 1 fps rate with "-r 1" or "vf fps=fps=1" causes first three frames to be wrong [closed]

  11 avril 2013, par Stefan

  I need to use ffmpeg to extract video stills from a video, one picture per second, starting with second 0. I created a 4min test video with a running timecode (25fps, starting with 00:00:00 running to 03:59:24) If I use either

  ffmpeg -i input.mp4 -f image2 -r 1 still-%d.jpeg

  or

  ffmpeg -i input.mp4 -f image2 -vf fps="fps=1" still-%d.jpeg

  I fail because the first three images do not display expected time codes 00:00:00, 00:01:00, 00:02:00, but 00:00:00, 00:00:01, 00:00:13, and all subsequent images show having frame 13 in their timecode (and not :00). This causes my video preview to be off by 1-2 seconds.

  I had to resort to invoke ffmpeg for each frame, using -ss 0..240 and -vframes 1 to extract exactly one frame at the exact time. This works perfectly, all output files show the timecode of the first frame of that second.

  This method is considerably slower, however, and I'd rather not use it.

  Is there something I missed with the -r option or fps filter ? I tried specifying fps=fps=1:round=zero, but I got an error saying that the key "round" was not found.

  Thank you in advance !

• Unable to find a suitable output format for "ffmpeg" [duplicate]

  25 mars 2020, par deva

  I’m trying to convert video to mp3 using ffmpeg library. when i execute the commands its fail and logs says :
  Unable to find a suitable output format for "ffmpeg".

  There is my code :

      try {
  
  
  
   String[] cmd = new String[]{"ffmpeg", "-i", selectedVideo.get(i),"-y", dstto};
  
  
  
          if (cmd.length!=0){
  
              fFmpeg.execute(cmd, new ExecuteBinaryResponseHandler(){
  
  
  
                  @Override
  
  
  
                  public  void onSuccess(String s){
  
  
  
                      Toast.makeText(getApplicationContext(),"success"+ s, Toast.LENGTH_SHORT).show();
  
  
  
                  }
  
  
  
  
  
  
  
                  @Override
  
  
  
                  public  void onFailure(String s){
  
  
  
                      Toast.makeText(getApplicationContext(),"fail"+ s, Toast.LENGTH_SHORT).show();
  
  
  
                      log.setText(s);
  
  
  
                  }
  
  
  
              });
  
  
  
          }
  
  
  
      } catch (FFmpegCommandAlreadyRunningException e) {
  
  
  
          e.printStackTrace();
  
  
  
      } ```