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• ffmpeg - reading meta data value every 16ms to produce overlay

  18 avril 2022, par bcardarella

  I'd like to combine a few data sources for telemetry overlays over a video. The MP4s have some metadata embedded from my GoPro but I have a few other data sources I'd like to include. I already have a way to generate a PNG of the data visualizations. What I am wondering if is ffmpeg includes a way to, every 16ms to take the current video frame, get the corresponding metadata values for that frame embedded within the mp4, send them off to the image creator, take that output and overlay over the video frame.

  


  My assumption is that the mp4 metadata will correspond to the frame of the video. In that video frame's metadata the GPX values that I will need to generate the visualization.

  


• OpenCV-C++ VideoCapture fails to open video files

  2 novembre 2016, par Akihiko

  Recently I upgraded my OS from Ubuntu Precise Saucy (13.10) to Trusty (14.04). After this upgrade, cv::VideoCapture became not working properly. The program aborts when reading a video file. For example,

  int main(int argc, char**argv)
  
  {
  
    cv::VideoCapture vin("sample/vout2l.avi");
  
  ...

  Executing this program, it aborts with a message :

  *** Error in `./cv2-videoread.out': malloc(): memory corruption: 0x0000000000e3eff0 ***
  
  Abort (core dumped)

  The backtrace looks like :

  [New LWP 15586]
  
  [New LWP 15587]
  
  [Thread debugging using libthread_db enabled]
  
  Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
  
  Core was generated by `./cv2-videoread.out'.
  
  Program terminated with signal SIGABRT, Aborted.
  
  #0  0x00007ff953e61c37 in raise () from /lib/x86_64-linux-gnu/libc.so.6
  
  (gdb) bt
  
  #0  0x00007ff953e61c37 in raise () from /lib/x86_64-linux-gnu/libc.so.6
  
  #1  0x00007ff953e65028 in abort () from /lib/x86_64-linux-gnu/libc.so.6
  
  #2  0x00007ff953e9e2a4 in ?? () from /lib/x86_64-linux-gnu/libc.so.6
  
  #3  0x00007ff953eabe26 in ?? () from /lib/x86_64-linux-gnu/libc.so.6
  
  #4  0x00007ff953eac1ab in ?? () from /lib/x86_64-linux-gnu/libc.so.6
  
  #5  0x00007ff953eadba4 in ?? () from /lib/x86_64-linux-gnu/libc.so.6
  
  #6  0x00007ff953eaf7d2 in posix_memalign () from /lib/x86_64-linux-gnu/libc.so.6
  
  #7  0x00007ff94fa640fe in av_malloc () from /usr/lib/x86_64-linux-gnu/libavutil.so.52
  
  #8  0x00007ff94fa641b1 in av_strdup () from /usr/lib/x86_64-linux-gnu/libavutil.so.52
  
  #9  0x00007ff94fa5e5db in av_dict_set ()
  
    from /usr/lib/x86_64-linux-gnu/libavutil.so.52
  
  #10 0x00007ff954738574 in CvCapture_FFMPEG::open(char const*) ()
  
    from /usr/lib/libopencv_highgui.so.2.4
  
  #11 0x00007ff954738719 in cvCreateFileCapture_FFMPEG ()
  
    from /usr/lib/libopencv_highgui.so.2.4
  
  #12 0x00007ff95473aac9 in cvCreateFileCapture_FFMPEG_proxy(char const*) ()
  
    from /usr/lib/libopencv_highgui.so.2.4
  
  ---Type <return> to continue, or q <return> to quit---
  
  #13 0x00007ff954722d89 in cvCreateFileCapture ()
  
    from /usr/lib/libopencv_highgui.so.2.4
  
  #14 0x00007ff954723045 in cv::VideoCapture::open(std::string const&amp;) ()
  
    from /usr/lib/libopencv_highgui.so.2.4
  
  #15 0x00007ff95472315c in cv::VideoCapture::VideoCapture(std::string const&amp;) ()
  
    from /usr/lib/libopencv_highgui.so.2.4
  
  #16 0x0000000000401281 in main (argc=1, argv=0x7fff1f938388) at cv2-videoread.cpp:30
  
  (gdb)
  
  </return></return>

  NOTE : cv::VideoCapture vin(... is 30th line.

  Before upgrading the OS, this code was working with the same input file.

  From the backtrace, it seems that the trouble happens at CvCapture_FFMPEG and libavutil. I upgraded the packages ffmpeg libavutil-dev libavutil51 libavutil52 but they were already up-to-date.
  Also, OpenCV packages are up-to-date (I checked libopencv-core-dev libopencv-core2.4 libopencv-dev libopencv-highgui-dev libopencv-highgui2.4).

  I also tested OpenCV built from source, but got the same results.

  Do you have ideas to figure this out ?

• Reading YUV file in opencv

  5 décembre 2016, par user1816546

  I am encountering a particular problem while attempting to read a .yuv video file in opencv. My code is as follows :

  #include <opencv2></opencv2>core/core.hpp>
  
  #include <opencv2></opencv2>highgui/highgui.hpp>
  
  #include <opencv2></opencv2>opencv.hpp>
  
  
  
  using namespace cv;
  
  using namespace std;
  
  
  
  int main( void )
  
  {
  
  
  
      VideoCapture cap("video/balloons1.yuv"); // open the video file for reading
  
  
  
      if ( !cap.isOpened() ) // if not success, exit program
  
      {
  
          cout &lt;&lt; "Cannot open the video file" &lt;&lt; endl;
  
          return -1;
  
      }
  
  
  
  return 0;
  
  }

  However, I keep encountering the following error :
  

  I have installed FFMPEG following the instructions from this website : http://www.wikihow.com/Install-FFmpeg-on-Windows and the installation seems to be correct. Does anyone have any ideas of what the problem might be ?