With Hollywood's wholesale adoption of the talkies, the competition between the two fundamental approaches to sound-film production was soon resolved. Over the course of 1930–31, the only major players using sound-on-disc, Warner Bros. and First National, changed over to sound-on-film recording. Vitaphone's dominating presence in sound-equipped theaters, however, meant that for years to come all of the Hollywood studios pressed and distributed sound-on-disc versions of their films alongside the sound-on-film prints. Fox Movietone soon followed Vitaphone into disuse as a recording and reproduction method, leaving two major American systems: the variable-area RCA Photophone and Western Electric's own variable-density process, a substantial improvement on the cross-licensed Movietone. Under RCA's instigation, the two parent companies made their projection equipment compatible, meaning films shot with one system could be screened in theaters equipped for the other. This left one big issue—the Tobis-Klangfilm challenge. In May 1930, Western Electric won an Austrian lawsuit that voided protection for certain Tri-Ergon patents, helping bring Tobis-Klangfilm to the negotiating table. The following month an accord was reached on patent cross-licensing, full playback compatibility, and the division of the world into three parts for the provision of equipment. As a contemporary report describes: