AvatART App realtime video encoding with flutter ffmpeg

GenerateVideoFunc.dart

Future<String> generateVideo(String videoPath, List<StyleChangeRecord> videoChangeRecords, Function(data.Stack<ProgressItem> progress) callback) async {
  await _checkDirs();
  _cleanBasePathWithFilter(".aac");

  _pushProgress(ProgressItem("Transformation Step", 1, 4, "Clean folder.."), callback);
  List<Future> futures = <Future>[];
  new Directory('$basePath/$_framesFolder').listSync().forEach((frame) async {
    if (FileSystemEntity.typeSync(frame.path) == FileSystemEntityType.file) {
      futures.add((frame as File).delete());
    }
  });
  print ("Wait for delete files");
  Future.wait(futures);

  if (videoPath == "" || !File(videoPath).existsSync()) {
    videoPath = new Directory('$basePath')
        .listSync()
        .firstWhere((element) => element.path.endsWith("mp4"))
        .path;
  }

  print ("Original video path: $videoPath");
  DateTime now = DateTime.now();
  var currentTime = new DateTime(now.year, now.month, now.day, now.hour, now.minute, now.second);
  var destinPath = basePath +"/AvatART_${currentTime.toString().replaceAll(" ", "_")}.mp4";
  print ("Destination video path: $destinPath");

  _updateProgress("Creating frames..", callback);
  final FlutterFFmpeg _flutterFFmpeg = new FlutterFFmpeg();
  var _framesDir = await new Directory('$basePath/$_framesFolder').create();
  var rc = await _flutterFFmpeg.execute("-i $videoPath -vf fps=$fps ${_framesDir.path}/out%d.png");
  print ("FFMPEG 1 SAYS (0 = OK): " + rc.toString());

  _updateProgress("Extracting audio..", callback);
  rc = await _flutterFFmpeg.execute("-i $videoPath $basePath/audio.aac");
  print ("FFMPEG 2 SAYS (0 = OK): " + rc.toString());

  _updateProgress("Style transformations..", callback);
  await _processFileList(_framesDir.listSync(), videoChangeRecords, callback);

  _updateProgress("Merge results..", callback);
  final watermarkPath = await _checkWatermarkExist(videoPath);
  print ("WATERMARK APPLIED: $watermarkPath");
  rc = await _flutterFFmpeg.execute("-i ${_framesDir.path}/out%d.png -i $basePath/audio.aac -pix_fmt yuv420p -r $fps -shortest -y $basePath/preview.mp4");
  print ("FFMPEG 3 SAYS (0 = OK): " + rc.toString());

  _updateProgress("Finish processing..", callback);
  rc = await _flutterFFmpeg.execute("-i $basePath/preview.mp4 -i $watermarkPath -filter_complex \"overlay=0:0\" $destinPath");
  print ("FFMPEG 4 SAYS (0 = OK): " + rc.toString());
  return destinPath;
}