The California Film Institute’s inaugural documentary film festival opens this week in Marin County. The noncompetitive festival called Doclands features about 20 films from a number of countries and includes world, California, and Bay Area premiers. One highlight will be the screening of a four-hour documentary on the Grateful Dead, titled “Long Strange Trip,” which premiered at the Sundance Film Festival in January. Doclands runs from Wednesday through Sunday at the San Rafael Film Center and the Sequoia Theater in Mill Valley.