2004 Mar 03
41
Philips Semiconductors
Product specification
PAL/NTSC/SECAM video decoder with adaptive PAL/NTSC
comb filter, VBI data slicer and high performance scaler
SAA7114
8.3
Scaler
The High Performance video Scaler (HPS) is based on the
system as implemented in previous products (e.g.
SAA7140), but with some aspects enhanced. Vertical
upsampling is supported and the processing pipeline
buffer capacity is enhanced, to allow more flexible video
stream timing at the image port, discontinuous transfers,
and handshake. The internal data flow from block to block
is discontinuous dynamically, due to the scaling process.
The flow is controlled by internal data valid and data
request flags (internal handshake signalling) between the
sub-blocks; 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. The access/bandwidth requirements to the VGA
frame buffer are reduced significantly.
The high performance video scaler in the SAA7114 has
the following major blocks:
Acquisition control (horizontal and vertical timer) and
task handling (the region/field/frame based processing)
Prescaler, for horizontal downscaling by an integer
factor, combined with appropriate band limiting filters,
especially anti-aliasing for CIF format
Brightness, saturation, contrast control for scaled output
data
Line buffer, with asynchronous read and write, to
support vertical upscaling (e.g. for videophone
application, converting 240 into 288 lines, Y-C
B
-C
R
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-C
B
-C
R
4 : 2 : 2,
Y-C
B
-C
R
4 : 1 : 1 and Yonly (format also used for raw
data)
FIFO, 32-bit wide, with 64 pixel capacity in Y-C
B
-C
R
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:
in_lines
×
out_cycle_per_pix
×
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 equal to:
20 ms
24
64
μ
×
288
×
2
×
37 ns
×
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 equal to:
22
64
μ
s
×
–
720
240
×
1
×
37 ns
×
The video scaler receives its input signal from the video
decoder or from the expansion port (X port). It gets 16-bit
Y-C
B
-C
R
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 such as Y-C
B
-C
R
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 C
B
and C
R
samples. An Y-C
B
-C
R
4 : 1 : 1
input format is converted to 4 : 2 : 2 for the horizontal
prescaling and vertical filter scaling operation.
Thescaleroperationisdefinedbytwoprogrammingpages
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:
For signal source selection and formats
For task handling and trigger conditions
For input and output acquisition window definition
For H-prescaler, V-scaler and H-phase scaling.
Raw VBI data is handled as a specific input format and
needs its own programming page (equals own task).
0.98
T_v_blanking
–
T_out_clk
×
in_pixel
×
0.98
720
1.18
=
×
0.98
16.666 ms
2.34
=
×