saa8115hl NXP Semiconductors, saa8115hl Datasheet - Page 10

• Manufacturer Part Number: saa8115hl
• Description: Saa8115hl-04 Digital Camera Usb Interface
• Manufacturer: NXP Semiconductors

1.
Philips Semiconductors
9397 750 07395
Product specification
Fig 3. The video formatter and compression engine.
Pentium — is a trademark of Intel Corp.
YUV7 to YUV0
8.4 Compression engine
From a full size QCIF picture a sub-QCIF (128
zoomed sub-QCIF format, the origin (upper left corner) is programmable via SNERT
in 13 steps (both horizontally and vertically), so that an electronic pan and tilt is
possible.
The incoming 4 : 2 : 2 data is vertically filtered to 4 : 2 : 0, in order to be sent over
USB, by throwing away colour samples. In the even lines the V-samples are
discarded, in the odd lines the U-samples.
The compression engine module (see
and QSIF but has optimal performance with CIF resolution (30 fps) and VGA
resolution (5 fps). The algorithm is Philips proprietary. The compression ratio is
continuously programmable by setting the maximum number of bits which can be
used for 4 compressed lines, a so-called band (see
the YUV input data by scaling down (divide by 2 or divide by 4 operations)
to 7 or 6 bits per sample. For compression with an output rate below 2 bpp (bits per
pixel) it leads to performance improvement.
For a number of compression ratios, performance is also improved thanks to different
quantization tables which are defined and stored in a ROM. The required table must
be selected via software.
Real time decoding can be done in software on any Pentium™
Table 4:
Format
CIF/SIF
QCIF/QSIF
VGA high quality
VGA
RAW VGA high quality
PREFILTER_A_ON_OFF
PREFILTER
A
Data rate performed by compression engine
PREFILTER B_COMB_ON_OFF
PREFILTER_B_ON_OFF
Rev. 04 — 10 August 2000
PREFILTER
B
VIDEO_OUTPUT_FORMAT
Advised data rate
2 bpp
6 bpp
3 bpp
1.5 bpp
4 bpp
UV_EXCHANGE
PAL_VGA
SCALER
DOWN
Figure
VP_C_ BITCOST_(MSB/LSB)
COMPRESSION_MODE
3) can process VGA, CIF, SIF, QCIF
COMPRESSION
96) cut can be made. For the
ENGINE
Table
Digital camera USB interface
FCE430
Maximum data rate
12 bpp (uncompressed)
uncompressed
4 bpp
3 bpp
4 bpp
4). It is possible to reduce
SAA8115HL
© Philips Electronics N.V. 2000. All rights reserved.
transfer
buffer
to
1
platform.
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