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• I build opencv 3.4 with Gstreamer MSVC 1.16.1, and now imread and VideoCapture not working

  9 mars 2020, par A.k.

  I build OpenCV 3.4 with Gstreamer MSVC 1.16.1, using Cmake and Visual Studio 10.
  I have include bin directory to the system path variable, added all additional include and library to Visual Studio.
  Now when I am trying to read an Image to test if OpenCV is correctly installed it throws an error as :
  OpenCV Error: Assertion failed (size.width>0 && size.height>0) in imshow, file .../opencv/modules/highgui/src/window.cpp
  The code was :

  Mat image1;
  
  image1 = imread("‪D:\\Capture2.JPG");
  
  if(! image1.data )                              // Check for invalid input
  
      {
  
          cout <<  "Could not open or find the image" << std::endl ;
  
      }
  
  imshow("Image",image1);
  
  cvWaitKey(0);
  
  return 0;

  Now I tried to play a video using demo code from openCV site :

  // opencv_3.4_test.cpp : Defines the entry point for the console application.
  
  //
  
  
  
  #include "stdafx.h"
  
  
  
  #include "opencv2/opencv.hpp"
  
  #include <iostream>
  
  
  
  using namespace std;
  
  using namespace cv;
  
  
  
  int _tmain(int argc, _TCHAR* argv[])
  
  {
  
       // Create a VideoCapture object and open the input file
  
    // If the input is the web camera, pass 0 instead of the video file name
  
    VideoCapture cap("‪Wildlife.mp4"); 
  
  
  
    // Check if camera opened successfully
  
    if(!cap.isOpened()){
  
      cout &lt;&lt; "Error opening video stream or file" &lt;&lt; endl;
  
      return -1;
  
    }
  
  
  
    while(1){
  
  
  
      Mat frame;
  
      // Capture frame-by-frame
  
      cap >> frame;
  
  
  
      // If the frame is empty, break immediately
  
      if (frame.empty())
  
        break;
  
  
  
      // Display the resulting frame
  
      imshow( "Frame", frame );
  
  
  
      // Press  ESC on keyboard to exit
  
      char c=(char)waitKey(25);
  
      if(c==27)
  
        break;
  
    }
  
  
  
    // When everything done, release the video capture object
  
    cap.release();
  
  
  
    // Closes all the frames
  
    destroyAllWindows();
  
  
  
    return 0;
  
  }
  
  </iostream>

  The program is building correctly but I am getting following error while running it :

  warning: Error opening file (/build/opencv/modules/videoio/src/cap_ffmpeg_impl.hpp:808)
  
  warning: ?Wildlife.mp4 (/build/opencv/modules/videoio/src/cap_ffmpeg_impl.hpp:809)
  
  GStreamer: error opening bin syntax error

  Where can be the error as they both are simplest OpenCV program.

• How to build FFmpeg.NET .dll ?

  1er mars 2014, par user2656632

  I need to use some FFmpeg functions in C# (to be precise, in GTK#). So I downloaded wrapper FFmpeg.NET. After that I try to build FFMpeg.NET.2008.sln(reference : I will build dll in Visual Studio 2008, but will use in GTK#), then get the following errors :

  Error 1 error PRJ0019 : A tool returned an error code from "Performing
  Makefile project actions" FFMpeg.NET
  Error 2 The referenced assembly
  "C :\Users\Zhenya\Documents\ffmpegdotnet-94877(CLEAR)\bin
  (debug shared)\ffmpeg.net.dll" was not found. If this assembly is
  produced by another one of your projects, please make sure to build
  that project before building this one.

  How to fix these issues ?

  Or how to correctly build this wrapper to get .dll ?

  Thanks !

• How can I improve the frame rate of my Raspberry Pi to YouTube stream ?

  2 août 2021, par RDowns

  I am using a Raspberry Pi 4 2GB to live stream to YouTube.

  


  The performance is pretty poor at the moment as I am trying to go through terminal and I feel the setting's are not correct. Performance is OK however if I go directly through YouTube studio and use the 'Webcam' option instead of 'Stream'.

  


  These are the settings that I am currently using :

  


  raspivid -o - -t 0 -vf -hf -fps 30 -b 6000000 | ffmpeg -threads 0 -f v4l2 -i /dev/video0 -ar 44100 -ac 2 -acodec pcm_s16le -f s16le -ac 2 -i /dev/zero -acodec aac -ab 128k -strict experimental -s 640x480 -b 6000000 -aspect 16:9 -vcodec h264_omx -vb 820k -pix_fmt yuv420p -g 60 -r 30 -f

  


  What options can I change in this command to improve the frame rate and give better performance ?