bt848kpf ETC-unknow, bt848kpf Datasheet - Page 38

• Manufacturer Part Number: bt848kpf
• Description: Single-chip Video Capture For Pci
• Manufacturer: ETC-unknow

F
Video Scaling, Cropping, and Temporal Decimation
Table 6. Scaling Ratios for Popular Formats Using Frequency Values
28
UNCTIONAL
Scaling Ratio
Full Resolution
1:1
CIF
2:1
QCIF
4:1
ICON
8:1
Image Cropping
D
ESCRIPTION
Format
NTSC SQ Pixel
NTSC CCIR601
PAL CCIR601
PAL SQ Pixel
NTSC SQ Pixel
NTSC CCIR601
PAL CCIR601
PAL SQ Pixel
NTSC SQ Pixel
NTSC CCIR601
PAL CCIR601
PAL SQ Pixel
NTSC SQ Pixel
NTSC CCIR601
PAL CCIR601
PAL SQ Pixel
to use a single field as opposed to using both fields. Using a single field will ensure
there are no inter-field motion artifacts on the scaled output. When performing sin-
gle field scaling, the vertical scaling ratio will be twice as large as when scaling
with both fields. For example, CIF scaling from one field does not require any ver-
tical scaling, but when scaling from both fields, the scaling ratio is 50%. Also, the
non-interlaced bit should be reset when scaling from a single field (INT=0 in the
VSCALE_HI register). Table 6 lists scaling ratios for various video formats, and
the register values required.
Cropping enables the user to output any subsection of the video image. The AC-
TIVE flag can be programmed to start and stop at any position on the video frame
as shown in Figure 15. The start of the active area in the vertical direction is refer-
enced to VRESET (beginning of a new field). In the horizontal direction it is ref-
erenced to HRESET (beginning of a new line). The dimensions of the active video
region are defined by HDELAY, HACTIVE, VDELAY, and VACTIVE. All four
registers are 10-bit values. The two MSBs of each register are contained in the
CROP register, while the lower eight bits are in the respective HDELAY_LO,
HACTIVE_LO, VDELAY_LO and VACTIVE_LO registers. The vertical and hor-
izontal delay values determine the position of the cropped image within a frame
while the horizontal and vertical active values set the pixel dimensions of the
cropped image as illustrated in Figure 15.
Note on vertical scaling: When scaling below CIF resolution, it may be useful
Total
Resolution
(including
sync and
blanking
interval)
780x525
858x525
864x625
944x625
390x262
429x262
432x312
472x312
195x131
214x131
216x156
236x156
97x65
107x65
108x78
118x78
L848A_A
Output
Resolution
(Active Pixels)
640x480
720x480
720x576
768x576
320x240
360x240
360x288
384x288
160x120
180x120
180x144
192x144
80x60
90x60
90x72
96x72
HSCALE
Register
Values
0x02AA
0x00F8
0x0504
0x033C
0x1555
0x11F0
0x1A09
0x1679
0x3AAA
0x3409
0x4412
0x3CF2
0x861A
0x7813
0x9825
0x89E5
Single-Chip Video Capture for PCI
VSCALE Register Values
Use Both
Fields
0x0000
0x0000
0x0000
0x0000
0x1E00
0x1E00
0x1E00
0x1E00
0x1A00
0x1A00
0x1A00
0x1A00
0x1200
0x1200
0x1200
0x1200
Bt848/848A/849A
Single
Field
N/A
N/A
N/A
N/A
0x0000
0x0000
0x0000
0x0000
0x1E00
0x1E00
0x1E00
0x1E00
0x1A00
0x1A00
0x1A00
0x1A00
Brooktree
®