SAA8116 Datasheet, PDF (15/60 Pages) NXP Semiconductors – Digital PC-camera signal processor including microcontroller and USB interface

Philips Semiconductors
Digital PC-camera signal processor including
microcontroller and USB interface
Product specification
SAA8116
MEASUREMENT ENGINE
The ME extracts statistical information from the video
stream. These measurements are used for the
auto-control loops in the microcontroller (AWB, AE
and AGC). They can also be used for other purposes, such
as colour detection. The measurements are performed on
pre-formatted Y, U and V streams. It is possible to
measure the accumulated value of the Y, U or V samples
either in the full active video window or in a simple
programmable window.
Five parallel measurements of the luminance can be done
for the auto exposure, each based on a proper window.
Y, U and V can be measured independently for the auto
white balance, all based on the same window.
During each frame, the microcontroller has access to the
measured values of the previous frame.
Video formatter
This block is used to convert the YUV 4 : 2 : 2 format to
4 : 2 : 0 required by the compression engine. The
incoming 4 : 2 : 2 data is vertically filtered. In raw mode,
this block is bypassed to create a full resolution snapshot.
The formatter can also perform downscaling to SIF and
QSIF (see Table 2).
To avoid aliasing, this formatter also contains horizontal
and vertical low pass pre-filters before downscaling.
Table 2 Scaler modes
SENSOR
TYPE
OUTPUT
FORMAT
SCALER MODES
VGA
SIF 320 × 240 scaled half horizontally
and vertically
QSIF 160 × 120 scaled quarter
horizontally and vertically
Compression engine
The compression engine module (see Fig.9) can process
VGA, SIF and QSIF, based on a Philips proprietary
algorithm. The compression ratio is continuously
programmable by setting a maximum bit cost limit. Input
data can also be a raw RGB sensor data to perform
optimum snapshot processing in the host software.
The compression engine uses several strategies and
Q-tables for optimum performance at a wide range of
compression ratios (up to 8×). The required table must be
selected via software. One table is optimized for
compressing the raw VGA data.
Real time decoding can be done in software on any
Pentium™ or AMD-K6 platform.
handbook, full pagewidth
PREFILTER_SEL_UV
PREFILTER_SEL_Y
YUV7 to
YUV0
PREFILTER
HORIZONTAL
DOWNSCALING
DATA FORMATTER
+
VERTICAL
DOWN SAMPLING
COMPRESSION
ENGINE
to
transfer
buffer
VF_LIMITER
SCALE_DATA
TABLE_SELECT
LDC
C_BITCOST_MSB
C_BITCOST_LSB
C_THRESHOLD_MSB
C_THRESHOLD_LSB
FCE744
Fig.9 The video formatter and compression engine.
2001 May 04
15