To detect a motion picture film source in a television signal.

A television scan line doubler (interlaced to progressive scan converter) incorporates the following aspects of: an improved field motion detector that does not treat low-frequency vertical transitions as motion; a frame motion detector having an improved ability to differentiate motion from subcarrier signal components; a sawtooth artifact detector; a sawtooth artifact detector in combination with a film pattern detector so that the artifact detector can take the film pattern detector out of a film mode earlier than it would if it only were responsive to a break in the film pattern; a tandem field motion detector; an improved field-based film detector; a film pattern detector and a motion detector used therewith that operates by performing end-of-field calculations of a film.