Single-chip composite/S-video
NTSC/PAL/SECAM to YCrCb digitizer
On-chip UltralockTM
Square pixel and CCIR601 resolution
for NTSC, PAL (B, D, G, H, I , M, N,
N combination, OO) and SECAM
2H adaptive comb filtering (NTSC)
Single crystal for all video formats
d i g i t a l i n f o t a i n m e n t p r o d u c t s
Digital Video Decoder
B t 8 3 5
D i s t i n g u i s h i n g F e a t u r e s
Integrated VideoStream III
Video Capture Processor for TV/VCR
Analog Input and VBI Data Decoding
Conexant's Bt835 video capture processor is a single-chip decoding
and filtered scaling solution for analog NTSC/PAL/SECAM baseband
signals from TV tuners, VCRs, cameras, and other sources of
composite or Y/C video. The Bt835 is the first video capture solution
for low-cost PC video/graphics systems to deliver total integration
of the video digitization, synchronization, 2H adaptive Y/C separation,
scaling and VBI data passthrough functions. Using mixed signal
and DSP circuitry, the Bt835 converts an analog composite video
waveform into a scaled digital video stream while supporting a
variety of video formats, resolutions and frame rates.
Optimized for PC Video Capture
The Bt835 provides the most cost-effective, high-quality video
input solution for low-cost PC multimedia subsystems, which
integrate both graphics acceleration and video capabilities on
one add-in card or the PC motherboard itself.
The Bt835 minimizes the cost of the video capture function
integration in a number of ways. First, recognizing that YCrCb
to RGB color space conversion is now a standard feature of
multimedia controllers for acceleration of digital video playback,
the Bt835 avoids redundant functionality and allows the
downstream controller to perform this task
.
d i g i t a l i n f o t a i n m e n t p r o d u c t s
Digital Video Decoder
B t 8 3 5
Secondly, the Bt835 integrates a multi-tap filtered
video downscaler, which enables the video controller
to accept a high-quality user-scaled image with no
further video processing. Finally, the Bt835 minimizes
the number of interface pins required by a downstream
multimedia controller -- keeping package costs to
a minimum.
Analog Video Input Interface
The Bt835 supports composite and S-video
sources in NTSC, PAL and SECAM video formats.
Four composite, or three composite and one
S-video sources are selected through an on-chip
4:1 analog multiplexor. The Bt835 integrates two
flash Analog-to-Digital Converters (ADCs) which
provide high-performance 8x oversampling of the
NTSC/PAL color subcarrier. Oversampling of the
analog signal enables simple external anti-aliasing
filters to be implemented (if required) and enhances
digital filtering performance on-chip.
Clock generation is provided by a low-cost crystal.
The Bt835 needs only one 14.318 MHz crystal for
NTSC, PAL and SECAM operation. The onboard PLL
multiplies this frequency to 28.64 MHz for NTSC and
35.48 MHz for PAL/SECAM, for 8x Fsc sampling of the
baseband video signal. The fixed, integral relationship
between the subcarrier frequency (Fsc) and the
sample rate optimizes the performance of the
downstream Y/C separation and minimizes the cost
of implementation. The Bt835 also incorporates
auto-format detect capability through which it can
sense the presence of an NTSC or PAL video source
on the input after power up and configure itself
accordingly for correct decoding of the video.
UltralockTM
Employing a Conexant patented Ultralock technique,
the Bt835 achieves both horizontal and subcarrier
synchronization to the incoming analog video signal.
It will always generate the required number of pixels
per line from an analog source in which the line
length can vary by as much as a few microseconds.
MUX0
Analog
Mux
AGC
40 MHz
ADC
XTO
I2C
JTAG
Video
Timing Unit
Horizontal,
Vertical, and
Temporal
Scaling
Digital
Video Input
Video
Timing
Video
Timing
Output
Control
Output
Data
16
Decimation
LPF
Output F
ormat
ting
MUX1
MUX2
MUX3
SYNCDET
REFOUT
CREF+
CIN
CREF-
UltralockTM
and Clock
Generation
Luma-Chroma
Separation
and
Chroma
Demodulation
Bt835 block diagram
Ultralock`s digital locking circuitry enables the Bt835
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 non-linear
techniques that are difficult, if not impossible, to
implement in genlock systems. Unlike linear techniques,
it adapts the locking mechanism automatically. This
removes the requirement to reset the locking range
of the genlock circuit, which other video decoding
technologies impose to accommodate the type of
source being used in a particular system setup.
Digital Video Output Interface
The output pixel port of the Bt835 can be configured
in a variety of flexible formats to support many
different system implementations. The video pixels
are delivered as a continuous video stream running
at a 4x Fsc rate which is synchronous to the ADC
sample clock. Both YCrCb and YUV 4:2:2 pixels can
be provided over an 8- or 16-bit data bus. Three clock
signals are provided for the system interface: CLK x 1
and CLK x 2, which operate at 4x Fsc and 8x Fsc
respectively; and QCLK, which can be configured
to be a pixel load clock for a downstream video
controller. Both data and clock operate at 2x the
video pixel rate when the pixel port is configured in
an 8-bit-wide mode. The Bt835 also has the capability
of embedding the video control signals in the digital
pixel stream in either ViP mode or ByteStream mode.
The video field/frame synchronization signals and
others are coded into the pixel data stream using
out-of-range luminance and chrominance data
values. This feature eliminates the requirement for
the downstream video controller to allocate pins to
receive video control signals from the Bt835.
The Bt835 features a digital video input interface
where any digital video stream from sources such
as a MPEG-II decoder or a digital camera with 8-bit
YCrCb outputs can take advantage of the Bt835's
sophisticated video scaler and color control circuitry.
CCIR656 inputs and 8-bit YCrCb data with external
syncs are supported.
I2C
Digital Video
Bt832
Digital
Video
Decoder
Bt835
Digital
Video
Encoder
Bt868/869
Analog Video
Frame Buffer
Serial Interface
Composite
S-Video
TV
VGA Monitor
Memory Controller
Zooming
9
24
Color Space
Conversion
GUI
Accelleration
RAMDAC
Video/graphics system
f e a t u r e s a n d s p e c i f i c a t i o n s
Single-chip composite/S-video
NTSC/PAL/SECAM to YCrCb digitizer
On-chip UltralockTM
Square pixel and CCIR601 resolution
for NTSC, PAL (B, D, G, H, I , M, N, N
combination, OO) and SECAM
2H adaptive comb filtering (NTSC)
Single crystal for all video formats
High quality horizontal and vertical
filtered scaling
Closed caption decoding
Vertical blanking interval data
passthrough
Programmable temporal
decimation for a reduced frame-rate
video sequence
Programmable hue, brightness,
saturation, and contrast
8x Fsc sampling to simplify external
analog filtering
Two-wire I2C bus interface
8- or 16-bit pixel interface
YCrCb (4:2:2) output format
Software selectable four-input
analog mux
8 fully programmable GPIO pins
Auto NTSC/PAL format detect
Automatic gain control
User programmable peaking filter
3.3V I/0 mode
IEEE 1149.1 (JTAG) interface
100-pin PQFP package
Multimedia
Image processing
Desktop video
Video phone
Personal video conferencing
Interactive video
VBI Data Capture
The Bt835 provides a complete solution for capturing and
decoding Vertical Blanking Interval (VBI) data by operating
in a VBI line output mode, in which the VBI data is only
captured during select lines. This mode of operation enables
the concurrent capturing of VBI lines which contain ancillary
data and the processing of normal video image data.
In addition, the Bt835 supports a VBI frame output mode, in
which every line in the video frame is treated as if it were
VBI line data. This mode of operation is designed for use
with still frame capture/processing applications.
Scaling
The Bt835 integrates a high-quality comprehensive scaler
for image downsizing. The scaling factor is selectable to
be arbitrary and independent in X and Y dimensions with
minimum scaling factors of 0.071 in X and Y. This enables
full-resolution video to be reduced to any size down to icon
resolution. The video can be optionally band-limited using
a digital low-pass filter prior to scaling to minimize aliasing
artifacts induced by the scaling process. Horizontal scaling
is implemented through a six-tap 32-phase interpolation
filter. Vertical scaling is performed with a multi-tap eight-
phase interpolation filter. In addition to scaling, the video
image may be cropped to an arbitrarily sized window.
Y/C Separation
Y/C separation involves extracting the luminance (Y)
and the chrominance (C) components from the composite
information. This is followed by quadrature demodulation
to generate the baseband components (I and Q for NTSC
or U and V for PAL) from the chrominance signal. The Bt835
implements an adaptive 2H comb filter to separate the
chrominance from the luminance while maintaining full
vertical resolution and eliminating"hanging dots" for the
best possible NTSC Y/C separation. For PAL/SECAM video,
the Bt835 uses a notch/chroma comb filter. The Bt835 also
provides hue, saturation, brightness and contrast controls
-- providing end users with the flexibility to adjust the
decoded image`s appearance.
Host Interface
Bt835 register access is implemented using I2C, which is
a serial two-wire interface (one data pin and one clock pin).
The Bt835 behaves as an I2C slave with a data transfer rate
of 100 Kbps.
www.conexant.com
General Information:
U.S. and Canada: (800) 854-8099
International: (949) 483-6996
Headquarters Newport Beach
4311 Jamboree Rd, P.O. Box C
Newport Beach, CA 92660-3095
Order# 101784A
01-0835
2001, Conexant Systems, Inc. All Rights Reserved.
Conexant and the Conexant logo are trademarks
of Conexant Systems, Inc. Other trademarks are
owned by their respective owners. Although Conexant
strives for accuracy in all its publications, this material
may contain errors or omissions and is subject to
change without notice.
THIS MATERIAL IS PROVIDED AS IS
AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES,
INCLUDING MERCHANTABILITY, FITNESS FOR A PARTICULAR
PURPOSE AND NON-INFRINGEMENT.
Conexant shall not be
liable for any special, indirect, incidental or consequential
damages as a result of its use.
Product Features
Applications
PDF 
ZIP