readAsync method
Implementation
Future<(bool, Mat)> readAsync() async =>
cvRunAsync2((callback) => cvideo.VideoCapture_Read_Async(ref, callback), (completer, p, p1) {
final rval = p.cast<ffi.Bool>().value;
calloc.free(p);
completer.complete((rval, Mat.fromPointer(p1.cast<cvideo.Mat>())));
});