ADV7181 AD [Analog Devices], ADV7181 Datasheet - Page 31

• Manufacturer Part Number: ADV7181
• Description: Multiformat SDTV Video Decoder
• Manufacturer: AD [Analog Devices]

For example, program the ADV7181B into manual fixed gain
mode with a desired gain of 0.89.
1.
2.
3.
4.
5.
BETACAM Enable Betacam Levels, Address 0x01 [5]
If YPrPb data is routed through the ADV7181B, the automatic
gain control modes can target different video input levels, as
outlined in Table 41. Note that the BETACAM bit is valid only if
the input mode is YPrPb (component). The BETACAM bit
basically sets the target value for AGC operation.
A review of the following sections is useful:
•
•
The automatic gain control (AGC) algorithms adjust the levels
based on the setting of the BETACAM bit (see Table 35.).
Table 35. BETACAM Function
BETACAM
0 (default)
1
Table 38. Betacam Levels
Name
Y Range
Pb and Pr Range
Sync Depth
Use Equation 1 to convert the gain:
0.89 × 2048 = 1822.72
Truncate to integer value:
1822.72 = 1822
Convert to hexadecimal:
1822d = 0x71E
Split into two registers and program:
Luma Gain Control 1 [3:0] = 0x7
Luma Gain Control 2 [7:0] = 0x1E
Enable Manual Fixed Gain Mode:
Set LAGC[2:0] to 000
SETADC_sw_man_en, Manual Input Muxing Enable,
Address C4 [7] to find how component video (YPrPb) can
be routed through the ADV7181B.
Video Standard Selection to select the various standards,
for example, with and without pedestal.
Description
Assuming YPrPb is selected as input format.
Selecting PAL with pedestal selects MII.
Selecting PAL without pedestal selects SMPTE.
Selecting NTSC with pedestal selects MII.
Selecting NTSC without pedestal selects SMPTE.
Assuming YPrPb is selected as input format.
Selecting PAL with pedestal selects BETACAM.
Selecting PAL without pedestal selects BETACAM
variant.
Selecting NTSC with pedestal selects BETACAM.
Selecting NTSC without pedestal selects BETACAM
variant.
Betacam (mV)
0 to 714 (incl. 7.5% pedestal)
–467 to +467
286
Betacam Variant (mV)
0 to 714
–505 to +505
286
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PW_UPD Peak White Update, Address 0x2B [0]
The peak white and average video algorithms determine the
gain based on measurements taken from the active video. The
PW_UPD bit determines the rate of gain change. LAGC[2:0]
must be set to the appropriate mode to enable the peak white or
average video mode in the first place. For more information,
refer to the LAGC[2:0] Luma Automatic Gain Control, Address
0x30 [7:0] section.
Setting PW_UPD to 0 updates the gain once per video line.
Setting PW_UPD to 1 (default) updates the gain once per field.
CAGC[1:0] Chroma Automatic Gain Control,
Address 0x2C [1:0]
The two bits of Color Automatic Gain Control mode select the
basic mode of operation for automatic gain control in the
chroma path.
Table 36. CAGC Function
CAGC[1:0]
00
01
10 (default)
11
CAGT[1:0] Chroma Automatic Gain Timing,
Address 0x2D [7:6]
The Chroma Automatic Gain Timing register allows the user to
influence the tracking speed of the chroma automatic gain
control. This register has an effect only if the CAGC[1:0]
register is set to 10 (automatic gain).
Table 37. CAGT Function
CAGT[1:0]
00
01
10
11 (default)
Chroma Gain
SMPTE (mV)
0 to 700
–350 to +350
300
Description
Manual fixed gain (use CMG[11:0]).
Use luma gain for chroma.
Automatic gain (based on color burst).
Freeze chroma gain.
Description
Slow (TC = 2 sec)
Medium (TC = 1 sec)
Fast (TC = 0.2 sec)
Adaptive
MII (mV)
0 to 700 (incl. 7.5% pedestal)
–324 to +324
300
ADV7181B