Alexander Street Press provides 332 videos relating to the Vietnam War, much of which are of talking heads, but there are still many more visual documentaries in the collection.
Besides the link below, you can access these videos by going to the library main page, and under Streaming Videos, click American History in Video, and then in the search box, type in Vietnam War.
A forty-five minute British documentary on United States entrance into the Vietnam War.
This thirty minute video created by the United States government dates from 1962 and is about the early North Vietnamese subversion in the South Vietnam.
This forty minute video on the Tet Offensive was produced by A&E Television Networks in 1975.
This 1975 video from the Army Pictorial Service covers the whole Vietnam War involvement.
This is an independently made documentary from 1990, produced and directed by Pamela Sporn.