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• OpenCV videowriter H264 codec (ffmpeg)

  18 juin 2019, par alcon

  I want to save a video with opencv with lossless compresion so I don’t lose any details of the frames. Everything works with the xvid codec but offcourse this is not a lossless compression so I found that the x264 codec is suitable. However it doesn’t work, I tried the following sample code but while running I get the following error : "could not find encoder for codec id 28 : encoder not found."

  cv::VideoWriter makeVideo;
  
  makeVideo.open("makevideo//newVideo.mp4", CV_FOURCC('X','2','6','4'), 30, cv::Size(1600,1200), true);
  
  cv::Mat image = imread("makevideo//frames//111.png");
  
  
  
  for(int i = 0; i < 200; i++)
  
      makeVideo << image;
  
  
  
  makeVideo.release();

  I found that for this to work, I need to have ffmpeg support. I’m currently using opencv2.4.6 and in this discussion (how can I use the openCV FFMPEG video I/O rather than the DirectShow one in Windows ?) someone mentioned that in opencv2.4 ffmpeg is automatically included. But its not working....

  Here (How to compile OpenCV 2.3 with ffmpeg support with Visual Studio 2010) I found how to compile opencv and ffmpeg yourself on windows. I followed all the steps sucessfully but still I get the same error....

• Playing MP4 file in Powerpoint

  14 mai 2019, par BrewGold

  I have a huge MP4 file (4GB) an hour long video. I want to extract port of the file. So I used the following command to extract 70 seconds(00:01:10) of video starting from 11 minutes

  ffmpeg -i INPUT.mp4 -ss 00:11:00 -t 00:01:10 -c:v copy -c:a copy OUTPUT.mp4

  Now I got a small file extracted from Input.MP4
  The output.mp4 file size is still big(90 MB). So I used the following command

  ffmpeg -i OUTPUT.mp4 -c:v libx264 -crf 30 SmallSizeVideo.avi

  I got SmallSizeVideo.avi file which is approximately 6MB.

  I am using Powerpoint 2010. I want to insert the video in Powerpoint and play.

  Unfortunately when I embed SmallSizeVideo.avi Powerpoint is unable to play

  1) Is my approach correct ?
  2) What is the best way to situation like me to play small portion of clips in powerpoint

  Thank you

• Statically linking FFmpeg libraries into native C++ node addon

  11 juin 2019, par Suhail Doshi

  I trying to run a node addon that links to libraries without having to include their dynamic .dll library :

  When I try to include their static archive : .dll.a extension on Windows, the node addon returns an error :

  $ node index.js --client 
  
  internal/modules/cjs/loader.js:840 
  
    return process.dlopen(module, path.toNamespacedPath(filename));
  
                   ^
  
  
  
  Error: The specified procedure could not be found.

  This generally means that it was expecting to load some other function from a library but failed to find it. If there’s a way to debug this error message more specifically, I’d also love to know how !

  I’ve tried re-ordering the libraries, using different extensions, etc.

  I originally used just the .lib extension instead of the .dll.a extensions and the program works fine if I include the .dll’s.

  The code works fine if I use .lib files and place their corresponding .dlls in the same directory as the application I am executing.

  I’ve used these resources :

  • .lib’s are stubs for compile time & don’t solve the problem : Program statically linked to a library but still needs dll to run
  • Literature about .dll.a files : MinGW creating dll.a files ? What type of library files are those ?
  • Statically link ffmpeg : https://fritzone.wordpress.com/2010/05/11/link-with-static-ffmpeg/ but it ffmpeg-dev doesn’t have .a files, it has .dll.a files and I am already trying that route.

  I am using N-API and here’s what I am doing in binding.gyp :

  'libraries': [
  
              "ws2_32.lib",
  
  
  
              "C:\\Users\\$(username)\\Desktop\\workspace\\ffmpeg-win64-dev\\lib\\libavcodec.dll.a",
  
              "C:\\Users\\$(username)\\Desktop\\workspace\\ffmpeg-win64-dev\\lib\\libavutil.dll.a",
  
              "C:\\Users\\$(username)\\Desktop\\workspace\\ffmpeg-win64-dev\\lib\\libswresample.dll.a",

  I am expecting my application (node index.js --client) to run correctly without the need the .dlls I’ve had to include in the past.

  EDIT

  It’s possible this problem is as simple as : How do you statically link these FFmpeg libraries on Windows vs having anything to do with node specifically.