cx23881 Conexant Systems, Inc., cx23881 Datasheet - Page 4

• Manufacturer Part Number: cx23881
• Description: Pcl Audio/video Broadcast Decoder
• Manufacturer: Conexant Systems, Inc.

Reduced Instruction Set Computing (RISC) Engine
The CX23880/CX23881 enables separate destinations for
the odd and even video fields, each controlled by a pixel
RISC instruction list. This instruction list is created by the
CX23880/CX23881 device driver and may be run in the
on-chip memory or host memory. The instructions control
the transfer of pixels to target memory locations on a byte
resolution basis. Complex clipping can be accomplished by
the instruction list, blocking the generation of PCI bus cycles
for pixels that are not to be seen on the display.
The DMA channels can be programmed on a field basis to
deliver the video data in packed or planar format. In packed
mode, YCrCb data is stored in a single continuous block of
memory. In planar mode, the YCrCb data is separated into
three streams which are burst to different target memory
blocks. Having the video data in planar format is useful for
applications where data compression is accomplished via
software and the CPU.
UltraLock™
The CX23880/CX23881 employs a proprietary technique
known as UltraLock to lock on to the incoming analog video
signal. It consistently generates the required number of
pixels per line from an analog source in which line length
can vary by as much as a few microseconds. UltraLock’s
digital locking circuitry enables the CX23880/CX23881 to
lock onto video signals quickly and accurately, regardless
of their source. The technique is completely digital, so
UltraLock can recognize unstable signals caused by
VCR head switches or any other deviation and can adapt
the locking mechanism to accommodate the source.
UltraLock uses nonlinear techniques that are difficult,
if not impossible, to implement in genlock systems.
Unlike linear techniques, it adapts the locking mechanism
automatically.
Vertical Blanking Interval (VBI) Data Capture
The CX23880/CX23881 provides a flexible solution for
capturing and decoding disparate VBI data types such as
closed-caption data, teletext, vertical internal time and
control (VITC) codes, HTML data, or multicast data. The
CX23880/CX23881 can operate in a VBI line output mode,
in which the VBI data is only captured from selected lines.
This mode of operation enables concurrent capture of VBI
lines containing ancillary data and normal video image
data. In addition, the CX23880/CX23881 supports a VBI
frame output mode in which every line in the video frame
is treated as if it were a VBI line. This mode of operation is
designed for use with still-frame capture and processing
applications, where sophisticated image decoding can be
performed in the software domain.
Macrovision
With the advent of more powerful CPUs that enable
software-based video compression, low-cost hardware
MPEG encoders, cheap and rewritable storage media, and
pervasive broadband communications, original content
protection is paramount. To this end, the CX23880/CX23881
fully implements Macrovision 7.01 detection. When an end-
user attempts to connect a digital video disk (DVD) player,
a digital satellite/cable decoder’s composite, or s-video out-
puts to the input of a CX23880/ CX23881-based PCI card,
Macrovision pulses and signals are detected, and appropriate
flag bits are set. It is up to the board vendor to read the flag
bits and determine what action will be taken.
Analog Audio Capture
The CX23880/CX23881 captures and decodes all major
terrestrial broadcast audio standards. The CX23880/CX23881
digitizes and oversamples the low intermediate frequency
(IF) signal from a TV tuner, and extracts and decodes the
broadcast audio signal. The decoded audio is sample rate
converted to a 48 KHz pulse code modulation (PCM) stereo
signal to simplify processing and interfacing. This 48 KHz
stream can be routed to the built-in (90 dB Signal-to-Noise
Ratio (SNR) stereo audio Digital-to-Analog Converters
(DACs) for connection to the PC’s sound card or headphones,
to an external Digital-Audio Interface, or to the PCI bus and
host for direct capture by a software audio codec. The
CX23881 only supports NICAM, A2 and FM broadcast audio
standards primarily for the European marketplace.
If capture of line-level stereo audio signals is required, an
inexpensive audio analog-to-digital converter A/D may
be directly connected to the CX23880/CX23881’s I
port and controlled via the serial bus master.
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