Screenshot take a black image from video

Hi there. Im trying to develop an ionic 2 app which take screenshot from video. I added cordova-screenshot plugin which telling in ionic website. The plugin take screenshot and save it but there is a problem. The problem is: in saving image there is only black screen instead of video. In fact, video playing successfuly, im taking screenshot with an ionbutton while the video is playing but doesnt work. When i take screenshot with device buttons technically, it can take screenshot same as device screen. But plugin isnt like that. Whats the problem? how can i solve? image