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NXP Semiconductors
PNX15xx/952x Series
Volume 1 of 1
Chapter 19: Memory Based Scaler
PNX15XX_PNX952X_SER_N_4
NXP B.V. 2007. All rights reserved.
Product data sheet
Rev. 4.0 — 03 December 2007
19-589
2.4.4
Vertical Video Filters
The polyphase lter used for vertical processing can only be operated in the normal
polyphase mode.This lter can be used as a two-component 6-tap lter, a three-
component 4-tap lter or a four-component 3-tap lter (optionally, linear phase
interpolation). In the two-component mode, each lter unit can be run independently,
to allow 4:2:0 to 4:2:2 conversion or vice versa.
2.4.5
De-Interlacing in MBS
The current de-interlacing algorithms, implemented inside the MBS, are as follows:
Simple Median Filtering (Vertical Temporal Median -- VTM)
Majority Selection Algorithm (MSA)
Field Insertion and Line Doubling
MBS supports both eld insertion and line doubling based simple de-interlacing in the
pixel-fetch unit.
If de-interlacing is enabled, the previous and current elds have to be fed into the
scaler as one interleaved frame. For the MSA, the rst line has to originate in the
previous eld, while in VTM, the rst line has to be fetched from the current eld.
Base Address Mode = 1 can be selected to assist in weaving the two elds together
into one frame.
Edge Dependent De-Interlacing (EDDI)
The purpose of EDDI is to improve the appearance of long diagonal edges, without
degrading other parts of the image. EDDI is used as a post-processing unit for the de-
interlacer.
2.4.6
Color-Key Processing
Color-key processing, to convert alpha values into color key values and/or vice versa,
are only available for the 4:4:4 video formats.
Color Key to Alpha Conversion
To avoid color key values getting altered during video processing, color-key
matching samples can be tagged as
transparent by generating an alpha value of
zero at the input of the MBS. Non-keyed samples get assigned a programmable
alpha value. After video processing is over, the alpha value can be stored in
memory together with the other components or can be used to re-key the keying
Color Key Replace
Scaling of video streams containing color keys can lead to artifacts at the corners
between keyed and non-keyed samples, due to the “smearing effect of the low
pass lter. The effect is heightened by the highly saturated colors normally used
for keying. To avoid these artifacts, color keyed samples are replaced with either
gray, black, or the previous sample (gray if at the start of the line),.
Alpha to Color Key Convert