This is the first time I have seen a video like this one. Usually videos of demonstrations are taken from inside the crowd. This one is taken from the Ministry of Interior in Tehran and you really get to see the size of the crowd. It seems that the people taking the video are trying to zoom in on faces, possibly for later identification.
This demonstration commemorates the student protests of 1999 . Maybe someone with better ears than ours can understand what is being said by the video makers and the students.