| 摘要 |
PURPOSE:To prevent the deterioration of a main video image at the superimposing display by driving a switching circuit based on a control signal in a multiplex signal representing a character and a graph in a receiver recording the character and graph. CONSTITUTION:The way of superimposition on a video signal is switched for the display on a CRT15 and the RF modulation. In displaying the character and graph without superimposition, chrominance signals (r), (g), (b) of a base frequency band based on a data signal are encoded as they are and an output of an encoder 16B is subject to RF modulation without any modification. In displaying superimposingly a pattern of a character and a graph on a received video image, only a part where the level of a luminance Ys signal in the encoded character and graph signal is at a high level is inserted to a video detection output signal to form a composite video signal. |
