This is one of the only worthwhile things on TV tonight – but at four hours long, it should fill the bill. This expanded 1994 version of the classic Woodstock documentary, originally released in 1970 as a visual record of the seminal 1969 rock concert, makes room for additional performances, including more by Janis Joplin, Jefferson Airplane, and Canned Heat. Other performers include Richie Havens, Joan Baez, The Who, Arlo Guthrie, Country Joe McDonald, a seminal set by Joe Cocker, and, in one of their first gigs together in front of an audience, Crosby, Stills & Nash. As always when experiencing Woodstock in any form, and especially with Michael Wadleigh’s Director’s Cut, turn the volume up loud – and stay away from the brown acid.