You don't need to stop video every one second like for duolingo, you just record video with monosnap and then later you replay this video and take notes. Taking notes while doing duolingo lesson will increase the time of learning. For youtube videos there is similar process you convert video to gif using freeconvert then you convert gif to pdf using pdf24. Then you read video and take notes. You could burn subtitles using VLC. Duolingo lessons or italki are same process because stopping video every one second seems boring process. Small example of pdf before writing notes