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• Emulate YUV420 stream for OpenCV

  11 avril 2024, par Ivan

  I'm working on a project that will treat the images coming from a camera in YUV420 format connected by ethernet.

  


  During the development, we can't have constant access to the camera so I wanted to emulate the behaviour.

  


  My idea is to take video, convert it from mp4 to yuv using ffmpeg :

  


  ffmpeg -i input.mp4 -pix_fmt yuv420p output.yuv


  


  Then, stream the video in an infinite loop.
This works :

  


  ffmpeg -stream_loop -1 -f rawvideo -s 960x540 -r 30 -pix_fmt yuv420p -i output.yuv -f mpegts udp://127.0.0.1:23000


  


  I managed to read (and show) the images with :

  


  #In python
import cv2
cap = cv2.VideoCapture('udp://127.0.0.1:23000', cv2.CAP_FFMPEG)
...


  


  However, the shape of the images I get is (540, 960, 3), but I expected YUV420 format, I wanted (540*3/2, 960) or 3 channel 540x960, 540/2x960/2, 540/2x960/2.

  


  How can I get the "raw" format ?, I'm not sure if it is ffmpeg or opencv adding treatment to the stream.

  


• Fluent-ffmpeg : merging video and audio = wrong frames

  5 juin 2015, par rhanb

  I’m trying to merge a video (mp4) without audio stream with an audio file (mp3). I’m developing under nodewebkit a video software which means that I have to use ogg files, so when the user upload a video or a audio file it converts it in ogg whatever its format. Then when the user want to export its video I’m exporting frames from a canvas to PNG images. Once this is done I’m creating a video from the frames with a 30 fps with this following code :

  var videoMaker = function () {
  
  
  
      console.log('videoMaker');
  
  
  
      var deffered = Q.defer();
  
      if (!FS.existsSync($rootScope.project.path + '/video')) {
  
          filestorageService.createFolder($rootScope.project.path + '/video');
  
      }
  
      audioMaker().then(function () {
  
          var commandVideo = new Ffmpeg({
  
              source: $rootScope.project.path + '/frames/%d.png'
  
          });
  
          commandVideo.setFfmpegPath(ffmpegPath);
  
          commandVideo.addOptions(['-c:v libx264', '-r 30']).withFpsInput(30).format('mp4').on('error', function (err) {
  
              console.log('video', err);
  
          }).on('end', function () {
  
              console.log('video win');
  
              deffered.resolve();
  
          }).save($rootScope.project.path + '/video/rendu.mp4');
  
      });
  
      return deffered.promise;
  
  };

  Then i’m reconverting the audio wich has been uploaded by the user to mp3 :

  var audioMaker = function () {
  
  
  
      console.log('audioMaker');
  
      var deffered = Q.defer();
  
      if ($rootScope.project.settings.music.path !== '') {
  
          FS.writeFileSync($rootScope.project.path + '/music/finalMusic.mp3', null);
  
          var commandAudio = new Ffmpeg({
  
              source: $rootScope.project.settings.music.path
  
          });
  
          commandAudio.setFfmpegPath(ffmpegPath);
  
          if ($rootScope.project.settings.music.fadeIn) {
  
              commandAudio.audioFilters('afade=t=in:ss=0:d=0.5');
  
          }
  
          console.log($rootScope.project.settings.music.fadeOut, $rootScope.project.settings.music.fadeIn);
  
          if ($rootScope.project.settings.music.fadeOut) {
  
              var time = sceneService.getTotalDuration() - 0.5;
  
              commandAudio.audioFilters('afade=t=out:st=' + time + ':d=0.5');
  
          }
  
          commandAudio.toFormat('mp3').on('end', function () {
  
              console.log('audio win');
  
              deffered.resolve();
  
          }).on('error', function (err) {
  
              console.log('audio', err);
  
          }).save($rootScope.project.path + '/music/finalMusic.mp3');
  
      } else {
  
          deffered.resolve();
  
      }
  
      return deffered.promise;
  
  };

  Until there everything is alright those files work well but when i do this :

  var command = new Ffmpeg({
  
      source: $rootScope.project.path + '/video/rendu.mp4'
  
  });
  
  command.setFfmpegPath(ffmpegPath);
  
  console.log($rootScope.project.settings.music.path !== '');
  
  if ($rootScope.project.settings.music.path !== '') {
  
      command.addInput($rootScope.project.path + '/music/finalMusic.mp3');
  
      command.addOptions(['-c:v copy', '-c:a copy']);
  
      if ($rootScope.project.settings.music.duration > sceneService.getTotalDuration()) {
  
          command.addOptions(['-shortest']);
  
      }
  
      command.on('error', function (err) {
  
          console.log(err);
  
      }).on('end', function () {
  
          console.log("win");
  
          //filestorageService.rmFolder($rootScope.project.path + '/frames');
  
      }).save($rootScope.project.path + '/video/rendu.mp4');
  
  } else {
  
      filestorageService.rmFolder($rootScope.project.path + '/frames');
  
  }

  And my final file has the music and the right duration but the frames aren’t right, any ideas ?

• RTSP streaming to video file using FFMPEG library

  17 août 2017, par Gona

  I want to save video taken with a network camera(IP camera) as a video file like .avi.

  At first I tried OpenCV but I have a codec problem and try to use FFMPEG.
  This is the first time to use FFMPEG so I am looking for some sample code.

  The overall project structure is C# with a C++ DLL, so I want to save(or write or record) the camera stream as a video file in C++.

  Camera stream is received using RTSP, and the RTSP URL is also known.
  How to save RTSP stream as video file using FFMPEG library ? The codec is H264.

  I would appreciate it if you could show me some sample code.

  My development environment is 64-bit Windows 10 and Visual Studio 2015.
  I downloaded FFMPEG library version 20170817-92da230, 64-bit architecture and linking both Shared and Dev from here https://ffmpeg.zeranoe.com/builds/