Letter-box screen detection apparatus

摘要

The DC level of the low-frequency component of a horizontal frequency is detected from a video signal by a horizontal low pass filter (LPF) 16d and a DC value detection circuit. In addition, the high-frequency component of the horizontal frequency is detected from the video signal by a horizontal band pass filter (BPF) and a nonlinear circuit. Furthermore, a high-frequency component in the vertical direction is detected from the video signal by a vertical BPF 16i and a nonlinear circuit 16i. On the basis of three detection results, the presence/absence of a non-image portion of the video signal is determined by a determination circuit.