I agree with the opinions above. The biggest disadvantage is that not all students can complete the tasks before the class, which will decrease the effiency of the class if teachers design the whole class by assuming all students have got enough input before the class.
However, advantages are more obvious, including saving time and giving more autonomy to students. And what these tools appeal the most is that they allow teachers or students to create their own questions and annotations anywhere on a video. In this way, students can also raise their questions or point out their difficulties anywhere, so teachers can know better about their students’ learning problems. What’s more, by responding to others’ comments or questions, students can interact with others durign the listening process, which can’t be achived in the traditional class.