BT848 ETC, BT848 Datasheet - Page 75

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

Bt848/848A/849A
Single-Chip Video Capture for PCI
Figure 27. Luma and Chroma 2x Oversampling Filter
Brooktree
2X Oversampling and
®
Input Filtering
NTSC
Digitized video needs to be bandlimited in order to avoid aliasing artifacts. Be-
cause the Bt848 samples the video data at 8xFsc (over twice the normal rate), no
filtering is required at the input to the A/Ds. The analog video needs to be band lim-
ited to 14.32 MHz in NTSC and 17.73 MHz in PAL/SECAM mode. Normal video
signals do not require additional external filtering. However, if noise or other sig-
nal content is expected above these frequencies, the optional anti-aliasing filter
shown in Figure 25 may be included in the input signal path. After digitization, the
samples are digitally low pass filtered and then decimated to 4xFsc. The response
of the digital low pass filter is shown in Figure 27. The digital low pass filter pro-
vides the digital bandwidth reduction to limit the video to 6 MHz.
PAL/SECAM
L848A_A
NTSC
E
LECTRICAL
PAL/SECAM
Input Interface
I
NTERFACES
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