pnx1500 NXP Semiconductors, pnx1500 Datasheet - Page 588

• Manufacturer Part Number: pnx1500
• Description: Pnx15xx Series Connected Media Processor
• Manufacturer: NXP Semiconductors

Philips Semiconductors
Volume 1 of 1
PNX15XX_SER_3
Product data sheet
Decimation Filter
After horizontal processing, chrominance may be down sampled to reduce memory
bandwidth or allow for higher quality vertical processing that is not available
otherwise. Mirroring of samples at the field boundaries compensate for run in and run
out conditions of the filter.
Normal Polyphase Filter Mode
The normal polyphase filter can be used to zoom out or downscale a video image.
Depending on the number of components, the filter uses 6 taps (three-component
mode) or 3 taps (four-component mode). For the normal polyphase filter, run-in and
run-out behavior are compensated by appropriate mirroring of samples at the field
boundaries. In order to align the first output pixel with the geometric location of the
first input pixel, the start phase has to be chosen as:
Transposed Polyphase Filter Mode
The transposed polyphase filter can only be used to downscale. By reversing the flow
through the normal polyphase filter, the transposed filter takes the output pixels as
reference and accumulates input pixels. The advantage of the transposed polyphase
filter is the longer effective filter length which allows for filtering out high frequencies
that interfere with downscaling. A drawback of this approach is that the filter
coefficients have to get optimized for the scaling ratio in order to avoid visible DC
ripples. Compensation for run-in and run-out behavior of the filter is not available. Use
of the transposed filter is limited to three components only.
The scaling ratio for the transposed polyphase HSP_ZOOM_0 = 0x1 0000h *
zoom_x , with zoom_x = pixel_out / pixel_in
Linear Phase Interpolation Mode (LPI)
In the linear phase interpolation mode, samples between two pixels are interpolated
by using the linear equation px = (1-phase) * x
interpolation creates adequate results especially when used with computer
generated graphics which, unlike motion video, is usually not bandwidth limited.
The LPI mode is enabled by setting HSP_PHASE_MODE = 7. Horizontal processing
mode has to be set to normal polyphase (HSP_MODE = 2) and four-component
mode has to be enabled (HSP_FIR_COMP = 1)
Color Space Matrix Mode
In addition to the normal and transposed polyphase filtering (scaling), the FIR filter
structure can instead be programed to perform color-space-conversion functions. A
dedicated set of registers holds the coefficients for the color space matrix.
dto_offset
=
0x200 filter_length
Rev. 3 — 17 March 2006
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Chapter 19: Memory Based Scaler
+ phase * x
© Koninklijke Philips Electronics N.V. 2006. All rights reserved.
PNX15xx Series
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. Linear phase
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