THOMSON VK231PS, Technical Manual

Page: 109 / 139

105
YNR AND DROPOUT DETECTION
The signal that arrives at IV001 Pin 26 is sent to a switch. The output of this switch is
connected to the input of a CCD delay circuit (IV100) and the noise reduction stage. This
circuit delays the luminance channel by one line. The delayed channel is reinjected at 40 of
IV001, and adjusted to the correct level by an AGC. The delayed channel is applied to the
second input of the switch and to the second input of the noise reducer.
When a dropout is detected on the input FM signal, the detection stage forces the delayed
channel to be taken into account, which compensates for the drop.
YNR (noise reduction) is performed by a digital low-pass filter that adds the direct and delayed
channels.
OUTPUT STAGE
After non-linear de-emphasis, HF noise reduction is performed.
The luminance signal is then sent to the Y/C mixer via a sharpness stage.
The MUTE stage inserts the artificial vertical pulses, PV, in Special Effects.
The video signal is available on IV001 Output 38.