saa6712e NXP Semiconductors, saa6712e Datasheet - Page 18

• Manufacturer Part Number: saa6712e
• Description: Xga Rgb To Tft Graphics Engine
• Manufacturer: NXP Semiconductors

Philips Semiconductors
7.7
The SAA6712E features different scaling engines for up
and downscaling, for both horizontal and vertical
processing. The horizontal scaling engines are
independent from each other. The vertical scaling engines
share the line buffer, so they cannot operate in parallel.
7.7.1
The upscaling engine is used for enlarging the incoming
video frames. The magnification can be programmed
individually for horizontal and vertical scaling.
The maximum scaling factor for both directions is 64.
The implemented filter algorithm (see Fig.7) uses
interpolation with pixel enhancement, based on a free
programmable transition function. It is therefore possible
to define the transition between two calculated pixels to
obtain different sharpness characteristics. This transition
function must be defined in the 7 bits
with a number ranging from 0 to 64. Different functions can
be programmed for horizontal and vertical scaling.
1999 Aug 25
handbook, full pagewidth
XGA RGB to TFT graphics engine
(1) The linear interpolation results in smoothing the sharp edges of the original picture if a pixel must be calculated.
(2) Some kind of
(3) Phase correct pixel repetition can be done with this function.
Scaling algorithm
U
PSCALING
1
x
function results in sharper edges, because of the smaller transition interval.
A
O
B
64 look-up table,
Fig.7 Interpolation function definition.
intensity of
output pixel O
100% A,
100% B
0% B
0% A,
100% A,
0% B
18
7.7.2
The downscaling engine is used for reducing the incoming
RGB data stream, i.e. for displaying high resolution input
frames on panels with a smaller resolution.
The scaling ratio can be programmed independently for
both horizontal and vertical downscaling units.
The algorithm uses pixel accumulation, achieving a
minimum scaling factor of
D
OWNSCALING
(3)
(2)
100% B
0% A,
(1)
1
64
ratio between
input pixels A, B
.
Preliminary specification
MHB250
SAA6712E