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SAA7115 View Datasheet(PDF) - Philips Electronics

Part NameDescriptionManufacturer
SAA7115 PAL/NTSC/SECAM Video Decoder with Adaptive PAL/NTSC Comb Filter, High Performance Scaler, I2C Sliced Data Readback and SQ Pixel Output Philips
Philips Electronics Philips
SAA7115 Datasheet PDF : 214 Pages
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Philips Semiconductors
CS-PD Hamburg
8.3 Scaler
The high performance video scaler in the SAA7115 has the following major blocks:
Acquisition control (horizontal and vertical timer) and task handling (the region/field/frame based processing)
Prescaler, for horizontal down-scaling by an integer factor, combined with appropriate band limiting filters, especially
anti-aliasing for CIF format
Brightness, saturation, contrast control to adjust scale dependent amplification
Line buffer, with asynchronous read and write, to support vertical up-scaling (e.g. for videophone application,
converting 240 into 288 lines, Y-CB-CR 4 : 2 : 2)
Vertical scaling, with phase accurate Linear Phase Interpolation (LPI) for zoom and downscale, or phase accurate
Accumulation Mode (ACM) for large downscaling ratios and better alias suppression
Variable Phase Delay (VPD), operates as horizontal phase accurate interpolation for arbitrary non-integer scaling
ratios, supporting conversion between square and rectangular pixel sampling
Output formatter for scaled Y-CB-CR 4 : 2 : 2, Y-CB-CR 4 : 1 : 1 and Y only (format also for raw data)
FIFO, 32-bit wide, with 64 pixel capacity in Y-CB-CR formats
Output interface, 8 or 16-bit (only if extended by H-port) data pins wide, synchronous or asynchronous operation, with
stream events on discrete pins, or coded in the data stream.
The overall H and V zooming (HV_zoom) is restricted by the input/output data rate relationships. With a safety margin of
2% for running in and running out,
the maximum HV_zoom is equal to: 0.98 × i--n---_----p---i-x---e----l--×-----i--n-T--_-_--l--ii-nn---pe----us---t-×-_---f-o-i-e-u--l--td-_----c---y-T--c--_-l-e-v--_-_---pb---e-l-a-r--_n----pk---ii-n-x---g-×-----T----_---o---u----t-_---c---l--k-
For example:
1. Input from decoder: 50 Hz, 720 pixel, 288 lines, 16-bit data at 13.5 MHz data rate, 1 cycle per pixel; output: 8-bit data
at 27 MHz, 2 cycles per pixel;
the maximum HV_zoom is about: 0.98 × -7--2-2---00-----m×-----s2---8----8--2--×-4----2-×----×-6---4-3---7--µ---n-s---s- = 1.18
2. Input from X-port: 60 Hz, 720 pixel, 240 lines, 8-bit data at 27 MHz data rate (ITU 656), 2 cycles per pixel; output via
I + H-port: 16-bit data at 27 MHz clock, 1 cycle per pixel;
the maximum HV_zoom is about: 0.98 × -1--7-6---2.--6-0--6---×-6----2-m--4---s0-----×----2-1--2---×--×---3--6-7--4---n---µ-s--s-- = 2.34
The data flow in the scaler is controlled by internal data valid and data request flags (internal handshake signalling)
between the sub-blocks, as the scaling process itself is discontinuous and dynamical. Therefore the entire scaler acts as
a pipeline buffer. Depending on the actually programmed scaling parameters the effective buffer can exceed to an entire
line. This allows vertical upscaling, more flexible video stream timing at the image port, discontinuous transfers and
handshake. The access/bandwidth requirements to the VGA frame buffer are reduced significantly.
The video scaler receives its input signal from the video decoder or from the expansion port (X-port). It gets 16-bit
Y-CB-CR 4 : 2 : 2 input data at a continuous rate of 13.5 MHz from the decoder. Discontinuous data stream can be
accepted from the expansion port (X-port), normally 8-bit wide ITU 656 like Y-CB-CR data, accompanied by a pixel
qualifier on XDQ.
The input data stream is sorted into two data paths, one for luminance (or raw samples) and one for time multiplexed
chrominance CB and CR samples. An Y-CB-CR 4 : 1 : 1 input format from the X-port is converted to 4 : 2 : 2 for the
horizontal prescaling and vertical filter scaling operation.
The scaler operation is defined by two programming pages A and B, representing two different tasks, that can be applied
field alternating or to define two regions in a field (e.g. with different scaling range, factors and signal source during odd
and even fields).
Each programming page contains control:
Confidential - NDA required
page 49
Last edited by H. Lambers
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