ADV7182 View Datasheet(PDF) - Analog Devices
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ADV7182 Datasheet PDF : 96 Pages
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Data Sheet
CG[11:0], Chroma Gain, Address 0x2D[3:0],
Address 0x2E[7:0]; CMG[11:0], Chroma Manual Gain,
Address 0x2D[3:0], Address 0x2E[7:0]
Chroma gain[11:0] is a dual-function register. If written to, a
desired manual chroma gain can be programmed. This gain
becomes active if the CAGC[1:0] function is switched to manual
fixed gain. See Equation 2 for calculating a desired gain.
If read back, this register returns the current gain value. Depending
on the setting in the CAGC[1:0] bits, this is either:
• The chroma manual gain value (CAGC[1:0] set to chroma
manual gain mode).
• The chroma automatic gain value (CAGC[1:0] set to either
of the automatic modes).
Table 47. CG/CMG Function
CG[11:0]/CMG[11:0] Read/Write
CMG[11:0]
Write
CG[11:0]
Read
Description
Manual gain for chroma path
Currently active gain
Chroma_Gain ≅
CMG[11 : 0]decimal
(2)
ChromaCalibrationFactor
where ChromaCalibrationFactor is a decimal value between 0
and 4095.
Calculation of Chroma Calibration Factor
Take the following steps to calculate the chroma calibration factor:
1. Apply a CVBS signal with the color bars/SMPTE bars test
pattern content directly to the measurement equipment.
2. Ensure correct termination of 75 Ω on the measurement
equipment. Measure chroma output levels.
3. Reconnect the source to the CVBS input of the ADV7182
system that has a back end gain of 1. Repeat the measurement
of chroma levels.
4. Turn off the chroma AGC and manually change the
chroma gain control register, CMG[11:0], until the chroma
level matches that measured directly from the source.
This value, in decimal, is the chroma calibration factor.
ADV7182
CKE, Color Kill Enable, Address 0x2B[6]
The color kill enable bit allows the optional color kill function
to be switched on or off.
For QAM-based video standards (PAL and NTSC), as well as
FM-based systems (SECAM), the threshold for the color kill
decision is selectable via the CKILLTHR[2:0] bits.
If color kill is enabled and the color carrier of the incoming
video signal is less than the threshold for 128 consecutive video
lines, color processing is switched off (black and white output).
To switch the color processing back on, another 128 consecutive
lines with a color burst greater than the threshold are required.
The color kill option works only for input signals with a modulated
chroma part. For component input (YPrPb), there is no color kill.
Set CKE to 0 to disable color kill.
Set CKE to 1 (default) to enable color kill.
CKILLTHR[2:0], Color Kill Threshold, Address 0x3D[6:4]
The CKILLTHR[2:0] bits allow the user to select a threshold for
the color kill function. The threshold applies only to QAM-based
(NTSC and PAL) or FM-modulated (SECAM) video standards.
To enable the color kill function, the CKE bit must be set. For the
000, 001, 010, and 011 settings, chroma demodulation inside
the ADV7182 may not work satisfactorily for poor input video
signals.
Table 48. CKILLTHR Function
Description
CKILLTHR[2:0] NTSC, PAL
SECAM
000
Kill at <0.5%
No color kill
001
Kill at <1.5%
Kill at <5%
010 (default) Kill at <2.5%
Kill at <7%
011
Kill at <4%
Kill at <8%
100
Kill at <8.5%
Kill at <9.5%
101
Kill at <16%
Kill at <15%
110
Kill at <32%
Kill at <32%
111
Reserved for Analog Devices internal use only;
do not select
Rev. A | Page 33 of 96
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