MY109111A - Managing letterbox displays - Google Patents

Abstract

A VIDEO DISPLAY CONTROL SYSTEM COMPRISES A VIDEO DISPLAY HAVING A FIRST FORMAT DISPLAY RATIO. A PICTURE HEIGHT CIRCUIT DETERMINES AN ACTIVE VIDEO PICTURE HEIGHT FROM AN INPUT VIDEO SIGNAL HAVING A SECOND FORMAT DISPLAY RATIO. A DETECTOR CIRCUIT IDENTIFIES LETTERBOX FORMATS RESPONSIVE TO THE ACTIVE VIDEO PICTURE HEIGHT IN THE VIDEO SIGNAL AND DETERMINES A FORMAT DISPLAY RATIO OF THE LETTERBOX PICTURE. A ZOOM CONTROL CIRCUIT IS OPERABLE IN A FIRST MODE OF OPERATION FOR ENLARGING THE PICTURE IN SIZE TO FILL THE DISPLAY SUBSTANTIALLY ENTIRELY, NOTWITHSTANDING CONSEQUENT CROPPING OF THE PICTURE, AND OPERABLE IN A SECOND MODE OF OPERATION FOR ENLARGING THE PICTURE IN SIZE TO SUBSTANTIALLY FILL THE DISPLAY VERTICALLY, NOTWITHSTANDING CONSEQUENT UNUSED PORTIONS OF THE DISPLAY. A VERTICAL PAN CONTROL CIRCUIT AUTOMATICALLY CENTERS THE PICTURE IN BOTH MODES OF OPERATION. THE DETECTOR CAN IDENTIFY THE FORMAT DISPLAY RATIO OF THE LETTERBOX FORMAT PICTURE A CIRCUIT RESPONSIVE TO THE IDENTIFIED FORMAT DISPLAY RATIO CONTROLS IMAGE ASPECT RATIO DISTORTION OF THE ENLARGED PICTURE. A DEFLECTION SYSTEM IS CONTROLLABLE IN VERTICAL SIZE BY A VARIABLE VERTICAL SCAN RATE, IN HORIZONTAL SIZE BY VARIABLE HORIZONTAL VIDEO EXPANSION AND COMPRESSION, AND IN PAN POSITION BY VARYING THE VERTICAL RESET IN PHASE. (FIG.2)