
Philips Semiconductors
Image Co-Processor
File: icp.fm5, modified 7/26/99
PRELIMINARY INFORMATION
13-27
The Integer increment and Fraction increment values are
the scaling parameters. there is a separate scaling pa-
rameter for each of the Y, U and V input components.
The Integer value is a 16-bit integer, and the Fraction val-
ue is a positive binary fraction between 0 and 0.99999+.
For up scaling (output image bigger), the increment val-
ue is the inverse of the scaling value. If you are upscaling
by a factor of 2.5, the increment value will be the inverse
of 2.50 = 0.40. The Integer increment value will be 0 and
the Fraction increment value will be 0.40. For down scal-
ing, the increment value is equal to the scaling value. If
you are down scaling by 2.5 (output image smaller), the
Integer increment value will be 2, and the Fraction incre-
ment value will be 0.500.
To perform scaling, the Integer and Fractional increment
values must be generated and placed in the parameter
table. The simplest way to generate these values in com-
mon computer languages such as C is as follows:
1. Generate the Increment Value as a oating point
number = Input Width / Output Width
2. Multiply the Increment Value by 65536
3. Convert the result to a Long Integer (32 bits). The up-
per 16 bits of the Long integer will be the Integer in-
crement value, and the lower 16 bits will be the Frac-
tional value.
4. Store the 32-bit Long integer in the parameter table as
the combined Integer and Fractional increment val-
ues.
For YUV 4:2:2 or YUV 4:2:0 input data and RGB output
data, the scaling factor for U and V must be twice the
scaling factor for Y, unless YUV4:2:2 sequencing is used
for speed. In YUV 4:2:2 or YUV 4:2:0 data, the horizontal
components of U and V are half those of Y. The U and V
must be upscaled by 2 to generate a YUV 4:4:4 format
internally for YUV to RGB conversion. For YUV 4:1:1 in-
put data, the U and V components must be upscaled by
a factor of 4 to generate the required internal YUV 4:4:4
format.
The Start Fraction defines the starting value in the scal-
ing counter for each line. It is a 16-bit, two’s complement
fractional value between -0.500 and 0.49999+. The Start
Fraction allows the input data to be offset by up to half a
pixel, referred to the input pixel grid. It is zero for Y and
for UV co-sited data, and is set to minus 0.25 (C000) for
interspersed to co-sited conversion of U and V data. The
minus 0.25 value effectively shifts the U and V data to-
ward the start of the line by 1/4 pixel, the amount required
for conversion.
The Alpha 1 and Alpha 0 values are 8-bit fields within the
16-bit Alpha field. These values are loaded into the Alpha
1 and Alpha 0 registers, respectively, for use by RGB
15+
α and YUV 4:2:2+α overlay formats in alpha blend-
ing.
The Overlay start and end pixels and lines define the
start and end pixels and lines within the output image for
the overlay. The first pixel of the overlay image will be
blended with the pixel at the Overlay Start Pixel and
Overlay Start Line in the output image.
13.6.10.3 Control Word Format
The Control word provides bit fields which affect the hor-
izontal filtering operation. The format of the Control word
is as follows.
Bits Name
Function
15
Bypass
Normally set to 0 to enable ltering.
Can be set to 1 to accomplish data
move without ltering.
14
422SEQ
4:2:2 Sequence bit. Used with YUV
4:2:2 output
13
YUV420
YUV 4:2:0 input format
12
OEN
Overlay enable. Valid only for PCI out-
put
11
PCI
PCI output enable. Otherwise SDRAM
output
10
BEN
Bit mask enable. Valid only for PCI
output
9
GETB
Large down scaling bit. Picks ve
input pixels nearest 5 output pixels
and passes to lter.
Equivalent to lter bypass + 5-tap lter
of output pixels. LSB value = 0 for l-
tering.
8
OLLE
Overlay little endian enable
7-6 OFRM
Overlay format
0 = RGB 24+
α
1 = RGB 15+
α
2 = YUV 4:2:2+
α
5
CHK
Chroma keying enable
4
LE
RGB output little endian enable
3-0 RGB
RGB Output Code
0 = YUV 4:2:2+
α
1 = YUV 4:2:2
2 = RGB 24+
α
Alpha 1 & Alpha 0
Overlay
Line Offset
Alpha 1 & Alpha 0 blend code for RGB15+
α, etc.;
Line offset from X0Y0 to X0Y1
Overlay End pixel
Overlay Start Pixel
Start and end pixels along line
Overlay End Line
Overlay Start Line
Start and end lines in frame
Table 13-14. Horizontal Filter to RGB Output Parameter Table
Parameter Word
Description
Upper 2 bytes
Lower 2 bytes