BT848 ETC, BT848 Datasheet - Page 134

• Manufacturer Part Number: BT848
• Description: Single-Chip Video Capture for PCI
• Manufacturer: ETC

C
HDELAY/HSCALE
HDELAY/HSCALE
HDELAY = 128 * (#DesiredPixels/#Hactive Pixels)
HSCALE = 4096 * (#HactivePixels/#DesiredPixels –1)
This is the alternate usage for the HDELAY and HSCALE registers when using the Bt848A/849A.
er.Since overscan, underscan, or normal scan is a subjective requirement, the formula for horizontal scaling may need
to be adjusted for each video input format or standard being implemented.
empirically determined for video input formats where the normal 0x80 and scaled derivatives do not correctly com-
pensate for horizontal misalignment.
124
ONTROL
The HSCALE function has not changed, but there are more #HactivePixels standard input formats to consid-
HDELAY should be set to 128 (0x80) for most pixel formats when unscaled. However, HDELAY may need to be
R
EGISTER
D
IGITAL
V
IDEO
I
N
S
UPPORT
(B
T
848A/849A O
L848A_A
NLY
)
Single-Chip Video Capture for PCI
Bt848/848A/849A
Brooktree
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