PNX1301EH NXP Semiconductors, PNX1301EH Datasheet - Page 216

• Manufacturer Part Number: PNX1301EH
• Manufacturer: NXP Semiconductors

Specifications of PNX1301EH

• Lead Free Status / RoHS Status: Not Compliant

PNX1300/01/02/11 Data Book
14.5
14.5.1
The ICP provides filtering, resizing (scaling) and YUV to
RGB conversion of the source image. Filtering provides
image enhancement. Scaling generates a new image
that is larger or smaller than the current image. YUV to
RGB conversion is used to generate an RGB version of
the image for output to an RGB format frame buffer
through the PCI interface or to SDRAM.
The filtering, scaling, and YUV to RGB conversion algo-
rithms are discussed separately. The ICP uses these al-
gorithms in two ways.
1. It provides one pass horizontal scaling with horizontal
2. It provides one pass vertical scaling with vertical 5-tap
14.5.2
The ICP provides high quality, 5-tap polyphase filtering,
both horizontal and vertical, of Y, U, or V data. Each filter
type is performed as a separate one dimensional filter
pass. Two dimensional filtering of the image requires two
passes of the one dimensional filters.
Multi-tap FIR filtering
In multi-tap FIR filtering of an image, the new filter output
(pixel) value is a weighted sum of adjacent pixels. The
weighting coefficients determine the type of filtering
used. A 5-tap filter generates the new pixel value as a
weighted sum of the current value and the two pixels on
either side (2 left and 2 right for horizontal filtering, 2
above and 2 below for vertical).
A multi-tap FIR filter can be used to generate values for
new pixels that are displaced from the original (‘center’)
pixel in the same way as linear interpolation. For exam-
ple, assume the new pixel location is shifted slightly to
the right of the center pixel of the input image. A horizon-
tal filter can be used to estimate the new pixel value by
weighting the right pixel filter coefficients more heavily
than the left, proportional to the relative position offset of
the new pixel. (In this sense, interpolation is a 2-tap fil-
ter.) This is shown in
vertical filter operations use this method to combine scal-
ing with filtering.
14-6
Figure 14-7. Pixel generation by interpolation and filtering
5-tap filtering of Y, U, or V.
filtering of Y, U, or V.
ALGORITHMS
Output Pixels
Input Pixels
Filtering
Introduction
Figure
PRELIMINARY SPECIFICATION
14-7. The ICP horizontal and
Mirroring pixels at the start and end of a line or window
A line may start and/or end at the edge of the input im-
age. In this case, the two start and/or end pixels needed
for the first and last pixels of the line, respectively, are
missing. The ICP uses pixel mirroring to solve this prob-
lem. In pixel mirroring, the two available pixels are used
to substitute the two missing pixels. The first pixel, uses
copies of the two pixels to the right as though they were
the two pixels to the left. Specifically, P+2 substitutes for
P-2, and P+1 substitutes for P-1. The last pixel uses cop-
ies of the two pixels to the left as though they were the
two pixels to the right. Since the left and right pixels are
now the same, this is called pixel mirroring.
There are five states of pixel mirroring: first output pixel,
second output pixel, middle pixels, next to last output pix-
el and last output pixel. The first output pixel uses pixels
numbered (2,1,0,1,2). The second pixel uses (1,0,1,2,3).
The middle pixels use (P-2, P-1, P, P+1, P+2). The next
to last pixel uses (N-3, N-2, N-1,N, N-1), where N is the
number of the last input pixel. The last pixel uses (N-2,
N-1, N, N-1, N-2).
In some cases of upscaling, one more input pixel may be
needed at the end of the line. In these cases, the pixel
value(s) are not generated by the mirror logic. Instead,
the ICP uses a copy of the last output pixel as the best
estimate of the required output pixel.
14.5.3
Scaling overview
Resizing, or scaling, the image means generating a new
image that is larger or smaller than the original. The new
image will have a larger or smaller number of pixels in the
horizontal and/or vertical directions than the original im-
age. A larger image is scaling up (more new pixels); a
smaller image is scaling down (fewer newer pixels). A
simple case is a 2:1 increase or decrease in size. A 2:1
decrease could be done by throwing away every other
pixel (although this simple method results in poor image
quality). A 2:1 increase is more interesting. The new pix-
els can be generated in between the old ones by:
1. Duplicating the original pixels
2. Linear interpolation, where the new in-between pixels
are the weighted average of the adjacent input pixels
Filter (uses 5 input pixels)
Interpolation (uses 2 input pixels)
Scaling
Philips Semiconductors