Computer Memories said it has withdrawn from a plan to merge with Hemdale Film Corp. as a result of a court battle over the videocassette distribution of Hemdale's movies, "Platoon" and "Hoosiers." Hemdale had planned to go public by merging with Computer Memories, a Chatsworth company that was once a leading computer component manufacturer. The $24.8-million deal was almost complete. But Computer Memories said litigation involving Hemdale, Vestron and Home Box Office meant that the merger was no longer in the interests of its shareholders. A federal appeals court in Los Angeles has banned the video distribution of the movies in a contract dispute over rights to distribute videocassettes of the films.