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• Flutter (Dart) : Record two videos, merge them and then view new video in gallery

  14 juin 2020, par Ittai Barkai

  I am aware that there already exists a solution to a very similar question, which can be found on the following link : Flutter/Dart : Find two video segments and merge them into a single valid video file ? However, being relatively new to Flutter (and programming in general) I cannot seem to replicate the desired result.

  



  My app is very simple and currently looks like this :

  



  

  



  I click on the button "Record Video" to record two videos, which are both successfully stored into the device's gallery. Using the Flutter image_picker and gallery_saver packages and the following piece of code :

  



      void _recordVideo() async {
    ImagePicker.pickVideo(source: ImageSource.camera)
        .then((File recordedVideo) {
      if (recordedVideo != null && recordedVideo.path != null) {
        setState(() {
          _buttonText = 'Saving in Progress...';
        });
        GallerySaver.saveVideo(recordedVideo.path).then((_) {
          setState(() {
            _buttonText = 'Video Saved!\n\nClick to Record New Video';
            if (_storedVideoOne == null) {
              _storedVideoOne = recordedVideo;
              print('video 1 stored');
            } else {
              _storedVideoTwo = recordedVideo;
              print('video 2 stored');
              _videoMerger();
            }
          });
        });
      }
    });
  }


  



  I can view these videos when I click on the button at the bottom "View Video From Gallery".

  



  Next I try to merge these two stored video files, using the flutter_ffmpeg package, as well as following the solution provided in the stack overflow question mentioned above. I try and do this using the following function I wrote :

  



  void _videoMerger() async {


    final appDir = await syspaths.getApplicationDocumentsDirectory();
    String rawDocumentPath = appDir.path;
    final outputPath = '$rawDocumentPath/output.mp4';

    final FlutterFFmpeg _flutterFFmpeg = new FlutterFFmpeg();

        String commandToExecute = '-i ${_storedVideoOne.path} -i ${_storedVideoTwo.path} -filter_complex \'[0:0][1:0]concat=n=2:v=0:a=1[out]\' -map \'[out]\' outputPath';
        _flutterFFmpeg.execute(commandToExecute).then((rc) => print("FFmpeg process exited with rc $rc"));

  }


  



  But after running the function I do not seem to get a new combined video, which should be stored in outputPath and ideally also viewable in the gallery. Uploaded the Flutter project onto GitHub here :

  



  https://github.com/IttaiBarkai/Flutter-Video-Merger

  



  Any help would be greatly appreciated :)

  


• How to use FFmpeg to record multiple screens on MacOS？

  1er novembre 2018, par 郭德纲

  I wanted to record multiple screens simultaneously on MacOS and store them in a video file.Same as the screenshot below.
  

  I found a command to do this, but need to know the size of each screen.

  ffmpeg \
  
  -f avfoundation -pix_fmt uyvy422 -i 1 \
  
  -f avfoundation -pix_fmt uyvy422 -i 2 \
  
  -pix_fmt yuv420p -r 30 -preset ultrafast -b:v 5000k -t 15 \
  
    -filter_complex \
  
      "nullsrc=size=3286x1080 [background]; \
  
      [0:v] setpts=PTS-STARTPTS [left]; \
  
      [1:v] setpts=PTS-STARTPTS [right]; \
  
      [background][left] overlay=shortest=1 [background+left]; \
  
      [background+left][right] overlay=shortest=1:x=1366 [left+right]" \
  
    -map [left+right] out.mp4 -y

  Is there a way to record a screen without knowing the size of each screen ?

• Streaming video (C# using FFmpeg AutoGen) sends multiple data requests

  14 juillet 2016, par williamtroup

  I’ve written a video generator that rights a video in h264 format (mp4). When I stream the video from my azure service, i’m seeing the following network traffic :

  

  The AVCodecContext layout I’m using is as follows :

  AVCodec* videoCodec = ffmpeg.avcodec_find_encoder(AVCodecID.AV_CODEC_ID_H264)
  
  AVCodecContext* videoCodecContext = ffmpeg.avcodec_alloc_context3(videoCodec);
  
  videoCodecContext->bit_rate = 400000;
  
  videoCodecContext->width = 1280;
  
  videoCodecContext->height = 720;
  
  videoCodecContext->gop_size = 12;
  
  videoCodecContext->max_b_frames = 1;
  
  videoCodecContext->pix_fmt = videoCodec->pix_fmts[0];
  
  videoCodecContext->codec_id = videoCodec->id;
  
  videoCodecContext->codec_type = videoCodec->type;
  
  videoCodecContext->time_base = new AVRational
  
  {
  
      num = 1,
  
      den = 30
  
  };
  
  
  
  ffmpeg.av_opt_set(videoCodecContext->priv_data, "preset", "ultrafast");

  I’m also tried setting the "movflags" option for avformat_write_header() via an AVDictionary, but then av_write_trailer() returns -2, cause the file to not finish writing.

  I cannot figure out how to solve this problem. Videos generating using Windows Movie Maker stream perfectly.

  I know this has something to do with mdat and mov positions.

  Also, this appears to only happening in Google Chrome.