saa8115hl NXP Semiconductors, saa8115hl Datasheet - Page 9

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

8. Functional description
Philips Semiconductors
9397 750 07395
Product specification
8.1 Video synchronization
8.2 Frame rate converter and SDRAM interface
8.3 Video formatter: downsampler and cutter
The video synchronization module is capable of locking to the video signal
implementing a horizontal gate signal HREF (HREF = HIGH when data is valid) and a
VS signal indicating the start of a new video frame.
An optional SDRAM (external) can be accessed using the SDRAM interface which is
integrated in the SAA8115HL. Pinning and functionality is based on the NEC
When used, the memory is placed at the video input of the SAA8115HL before
prefilter, scaler and compression engine. At this point only YUV 4 : 2 : 2 formatted
data is available.
The use of the SDRAM is twofold:
This block is used to achieve the required output format from the specified sensor
formats (see
by-passed to create a full resolution snapshot.
Horizontally a downsampling from 512 or 640 to either 384, 320, 192 or 160 or from
352 to 176 is necessary. The horizontal downsampling is performed with the use of a
Variable Phase Delay filter (VPD-4). This filter can realize the needed downsample
factors. To avoid aliasing, this module also contains a prefilter which has four modes:
Prefilter B-comb is similar to prefilter B but inserts extra taps with amplification 0.
The vertical downsampling in PAL mode is from CIF to QCIF only. This is done via a
vertical filter A (3 taps). In VGA mode a 4 taps polyphase filter is applied to scale from
640
•
•
•
•
•
•
PD4516161 (16 Mbits) and the NEC PD4564163 (64 Mbits).
Lowering the frame rate. The memory enables to store one frame of video
accumulated at a specific rate and to read it out at a lower frame rate. For interline
VGA sensors, the input frame rate is either 30 fps or 15 fps. It can be lowered with
a factor of 2, 3, 6, 16 or 32. For CIF or medium resolution PAL, the input frame rate
is only 30 fps
Enhanced snapshot mode. Storage of full size VGA pictures in 4 : 2 : 2 format
which can be retrieved upon dedicated software command.
No filter for medium resolution PAL (512
(320
Prefilter A (3 taps) for VGA (640
QSIF (160
Prefilter B (7 taps) for medium resolution PAL to QCIF or QSIF
Prefilter A combined with prefilter B-comb (13 taps) for VGA to QCIF or QSIF.
480 to CIF and QCIF.
240)
Figure
120)
Rev. 04 — 10 August 2000
3). It works for YUV 4 : 2 : 2 only. In RAW mode this block is
480) to CIF or SIF, CIF to QCIF (176
288) to CIF (352
Digital camera USB interface
SAA8115HL
© Philips Electronics N.V. 2000. All rights reserved.
288) or SIF
144) or
9 of 51