| 摘要 |
PURPOSE:To improve the S/N of a reproduced video even at a low average video level APL, comparing a white peak level of an input signal with a standard white peak level, expanding the amplitude for recording, detecting the black peak level of a reproducing signal and converting the reproducing level. CONSTITUTION:The white peak is detected from a luminance signal Y at a white peak detection circuit 4 and compared with the standard white peak level at a comparison circuit 5. As the APL is low, a signal Y and a chroma signal C of a gain control circuit are expanded. In a pre-emphasis circuit 6, the high frequency component of the luminance is emphasized, the amplitude limit is done at white/black clip circuit 8 for modulation. As mentioned above, a signal with low APL is expanded for recording, then since the average black level is boosted to white signals are a whole, the effect on tape modulation noise to th black signal is reduced. At recording, since the average black level is boosted to the white level, the true black level is reproduced at the reproducing system. Thus, the S/N of the picture with low APL is improved. |
