bt848kpf ETC-unknow, bt848kpf Datasheet - Page 15

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

Bt848/848A/849A
Single-Chip Video Capture for PCI
Brooktree
Scaling and Cropping
®
Input Interface
UltraLock
GPIO
The Bt848/848A/849A employs a proprietary technique known as UltraLock to
lock to the incoming analog video signal. It will always generate the required num-
ber of pixels per line from an analog source in which the line length can vary by as
much as a few microseconds. UltraLock’s digital locking circuitry enables the Vid-
eoStream decoders to quickly and accurately lock on to video signals, regardless of
their source. Since the technique is completely digital, UltraLock can recognize
unstable signals caused by VCR headswitches or any other deviation, and adapt the
locking mechanism to accommodate the source. UltraLock uses nonlinear tech-
niques which are difficult, if not impossible, to implement in genlock systems. And
unlike linear techniques, it adapts the locking mechanism automatically.
The Bt848/848A/849A can reduce the video image size in both horizontal and ver-
tical directions independently using arbitrarily selected scaling ratios. The X and Y
dimensions can be scaled down to one-sixteenth of the full resolution. Horizontal
scaling is implemented with a six-tap interpolation filter while up to 5-tap interpo-
lation is used for vertical scaling with a line store.
scan lines and active horizontal pixels per line.
video bandwidth by allowing frames or fields to be dropped from a video sequence
at fixed but arbitrarily selected intervals.
Analog video signals are input to the Bt848/848A/849A via a three-input multi-
plexer that can select between three composite source inputs or between two com-
posite and a single S-video input source. When an S-video source is input to the
Bt848/848A/849A, the luma component is fed through the input analog multiplex-
er, and the chroma component is fed directly into the C input pin. An automatic
gain control circuit enables the Bt848 to compensate for non-standard amplitudes
in the analog signal input. On the Bt848A and Bt849A there is an additional mux
input (providing a four-input multiplexer).
and two clock output pins. One pair of crystal pins is for connection to a 28.64
MHz (8*NTSC Fsc) crystal which is selected for NTSC operation. The other is for
PAL operation with a 35.47 MHz (8*PAL Fsc) crystal. Either fundamental or third
harmonic crystals may be used. Alternatively, CMOS oscillators may be used.
The Bt848/848A/849A provides a 24-bit general purpose I/O bus. This interface
can be used to input or output up to 24 general purpose I/O signals. Alternatively,
the GPIO port can be used as a means to input or output video decoder data. For ex-
ample, the Bt848/848A/849A can input the video data from an external video de-
coder and bypass the Bt848/848A/849A’s internal video decoder block. Another
application is to output the video decoder data from the Bt848/848A/849A over the
GPIO bus for use by external circuitry.
The video image can be arbitrarily cropped by reducing the number of active
The Bt848/848A/849A supports a temporal decimation feature that reduces
The clock signal interface consists of two pairs of pins for crystal connection
L848A_A
F
UNCTIONAL
Functional Overview
D
ESCRIPTION
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