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• Merge commit ’ff7adead0a667e606f5a41dca591f074f9ff2f32’

  29 mars 2015, par Michael Niedermayer

  Merge commit ’ff7adead0a667e606f5a41dca591f074f9ff2f32’
  * commit ’ff7adead0a667e606f5a41dca591f074f9ff2f32’ :
  
    udp : Fix pkt_size management
  Merged-by : Michael Niedermayer <michaelni@gmx.at>
  

  • [DH] libavformat/udp.c

• C++/OpenCV - VideoCapture doesn't work but it worked before with exactly the same code

  5 mars 2015, par Damià Obrador

  I’m trying to write a shot boundary detection algorithm in C++ using OpenCV. After all, I have to say that I have no experience working with OpenCV.

  I have been improving the following code (and I am still in it) during the last two weeks and everything seems the works correctly, not in terms of perfect shot detection, but every line of code did what was expected from it.

  #include <cstdlib>
  
  #include <opencv2></opencv2>opencv.hpp>
  
  #include <opencv2></opencv2>core/core.hpp>
  
  #include <opencv2></opencv2>video/background_segm.hpp>
  
  #include <opencv2></opencv2>highgui/highgui.hpp>
  
  #include <iostream>
  
  #include <opencv2></opencv2>imgproc/imgproc.hpp>
  
  #include 
  
  #include <istream>
  
  #include <fstream>
  
  using namespace cv;
  
  
  
  
  
  
  
  int main(){
  
  
  
      VideoCapture capture("vdevendetta.mp4");
  
      if ( !capture.isOpened() )
  
       {
  
           std::cout &lt;&lt; "Cannot open the video file";
  
           return -1;
  
       }
  
      int numFrames=capture.get(CV_CAP_PROP_FRAME_COUNT);
  
      bool SB_counter=false;
  
      Mat currentFrame;
  
      Mat frame;
  
      Mat fore;
  
      Mat back;
  
      vector<mat> frames;
  
      FileStorage file;
  
      FileStorage file2;
  
      Mat prev_Y;
  
      Mat channels[3];
  
      for(int i=0;i>currentFrame;
  
              frame=currentFrame.clone();
  
              cvtColor(frame,frame,CV_BGR2YUV);
  
              split( frame, channels );
  
              prev_Y=channels[0];
  
              SB_counter=false;
  
          }
  
          else
  
          {
  
              capture>>currentFrame;
  
              frame=currentFrame.clone();
  
              Mat channels[3];
  
              cvtColor(frame,frame,CV_BGR2YUV);
  
              split( frame, channels );
  
              Mat curr_Y=channels[0];
  
              channels[0]=prev_Y;
  
              prev_Y=curr_Y;
  
              merge(channels,3,frame);
  
              cvtColor(frame,frame,CV_Luv2BGR);
  
              cvtColor(frame,frame,CV_BGR2GRAY);
  
              frames.push_back(frame);
  
          }
  
  
  
      }
  
  
  
      vector<double> MAFDs;
  
      vector<double> MAFD;
  
      vector<double> aux;
  
      double min;
  
      double min2;
  
  
  
      for(int j=1;j14)
  
          {
  
              std::cout&lt;&lt;"De"&lt;*
  
      std::ofstream fout("MAFD.txt");
  
      if(fout.is_open()==true)
  
      {
  
        //file opened successfully so we are here
  
        std::cout &lt;&lt; "File Opened successfully!!!. Writing data from array to file" &lt;&lt; std::endl;
  
  
  
          for(int i = 0; MAFD[i] != '\0'; i++)
  
          {
  
          fout &lt;&lt; MAFD[i]; //writing ith character of array in the file
  
          }
  
        std::cout &lt;&lt; "Array data successfully saved into the file test.txt" &lt;&lt; std::endl;
  
      }
  
      else //file could not be opened
  
      {
  
          std::cout &lt;&lt; "File could not be opened." &lt;&lt; std::endl;
  
      }*/
  
      return 0;
  
  }
  
  </double></double></double></mat></fstream></istream></iostream></cstdlib>

  Three days ago I had an strange problem. The line :

  VideoCapture capture("vdevendetta.mp4");

  stopped working. I spent many hours looking for the solution but nothing seems to repair it. After reading everything related with OpenCV, VideoCapture and ffmpeg that I found on internet I decided to reinstall everything taking care of each detail, but it still didn’t work. Finally I solved it changing the line with this other one :

  VideoCapture capture("/home/damia/Documentos/Universitat/ARA/PAEAV/workspace_cpp/SBD/src/vdevendetta.mp4");

  I did not know why this solved it because the video is in the same directory than the program, but I continued working because everything seemed correct.
  Today I had the same problem again on the new line.
  The terminal doesn’t show any error comment (exceptuating "Cannot open the video file", obviously) but the code doesn’t work again.

  I’m using Ubuntu 14.04 LTS, OpenCV 2.4.9 and Eclipse.

  I think if someone test the code it will run correctly, but I would like to know if there is something I have no taking into account.

  Thank you very match.

• understand what is the GOP size (i-frame/p-frame ratio) in a video

  29 avril 2012, par nkint

  i am doing stuffs with a video in action script and i need to seek a video to acertain frame. according to the reference, using NetStream.seek i can seek only to the nearest k-frame :

  Seeks the keyframe (also called an I-frame in the video industry) closest to the specified location. The keyframe is placed at an offset, in seconds, from the beginning of the stream.
  
  
  
  Video streams are usually encoded with two types of frames, keyframes (or I-frames) and P-frames. A keyframe contains an entire image, while a P-frame is an interim frame that provides additional video information between keyframes. A video stream typically has a keyframe every 10-50 frames.

  and so i need to understand how many p-frame and i-frame there are in a video encoded in .f4v format.

  i am on mac and on ubuntu, i don't care about the tool to use (mayebe some ffmpeg/mencoder call should be perfect), any advice ?