PEDL87V21071-01
OKI Semiconductor
ML87V21071
[Notes on Using Noise State Detection and Auto Mode Noise Reduction]
Using the noise state detection and auto mode noise reduction functions of this IC can degrade picture quality
because of the possibility of wrong detection of noise state due to persistence of vision . Therefore, check the
following points beforehand and then use these functions:
1. Noise state detection is performed once in vertical blanking in one frame. Since it is not possible to
correctly determine the noise detection position by factors such as TV system, area, input source (VTR,
DVD), pre-stage tuner and video decoder, accurate detection of the noise state is disabled. Therefore,
confirm the operation prior to using these functions.
2. Where the input source has been recorded by a home VTR, the data of the blanking period in particular is
uncertain. Do not use noise reduction in the noise follow-up status (YDTO2 = 1, CDTO2 = 1) unless you
have determined that there is no problem.
(There are some cases where the VTR is input as RF input, so take appropriate measures such as
preventing the noise follow-up status from operating on the RF channel for external input.)
3. In composite video input signal, if only that position is selectable in which data can be in the position of
noise state detection, enable the luminance link mode for chrominance by setting ACY=1 considering that
luminance data can enter the chrominance data or do not use the chrominance auto mode.
4. There are cases of no noise in the vertical blanking period, or a part of the vertical blanking period, by a
pre-stage tuner or video decoder. Perform NRDTP[3:0] setting and make sure to select a position at which
noise level is the same as the valid data.
If noise is not detectable within the settable vertical blanking period at NRDTP[3:0] setting, then it is not
possible to use the noise state detection and the auto mode noise reduction.
5. Regarding the video signals added later of devices such as DVD, cameras, and digital recording, the noise
level of the added Sync. signals is detected as the noise state because the noise state detection is performed
in the vertical blanking period.
6. Noise state detection is not performed at all times if the hysteresis characteristic of noise state detection is
not valid (frequent occurrence of state switching). The noise detection is performed by NRDTON = 1 (8
frames or more) at the time of RF channels or input source switching only. Thereafter, settings to hold the
noise state etc., at NRDTON = 0 up to the next switching become necessary.
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