Most of the time most students attending live lectures are there to just listen. At least that was my experience when I was still studying. I found video recordings to be just as good as, or even better than, attending lectures. With recordings you can study things at your own pace, while doing exercises/experiments. You can also review the lectures later when preparing for an exam, or when you just want a refresher on some topic. And they obviously help when you have overlapping classes. You can always email/talk to the teacher if you have a question about something.