pnx1700 NXP Semiconductors, pnx1700 Datasheet - Page 443

• Manufacturer Part Number: pnx1700
• Description: Connected Media Processor
• Manufacturer: NXP Semiconductors

Philips Semiconductors
Volume 1 of 1
PNX17XX_SER_1
Preliminary data sheet
2.5.5 Horizontal Video Filters (Sampling, Scaling, Color Space Conversion)
Enabling the Dither Units
Immediately after the Dither unit is enabled or after a reset, the unit waits for the
beginning of a newly-captured image. Only then the unit starts dithering.
Once the Dither unit is operational (enabled), it keeps track of the order in which the
images arrive: we refer to the very first image at the unit dither as the even image, the
second image as the odd image, and so on. A frame here is defined as two images:
an even image followed by an odd image. This maintained state does not depend on
the selected alternation options, it is maintained as long as the Dither unit is enabled.
Any alternative activity corresponds to the internally-maintained state of a frame and
field (even or odd) and has nothing to do if the signal is coming from the top or the
bottom field.
Dithering operation also distinguishes between even and odd pixel-components of
the same type (either Y, U or V) in a line.
The first occurrence of a Y or U or V component in the first line in the first received
image is considered to be an even occurrence (or set ).
Interpolation Filter (Upsampling)
All horizontal video processing is based on equidistant sampled components. All
4:2:2 video streams, therefore, have to be upsampled before being scaled
horizontally. The interpolation FIR filter used can interpolate interspersed or co-sited
chroma samples. Mirroring of samples at the field boundaries compensate for run-in
and run-out conditions of the filter.
The following coefficients are used:
Decimation Filter (Downsampling)
After horizontal processing, the chrominance may be down-sampled to reduce
memory bandwidth or allow a higher-quality vertical processing not available
otherwise. Mirroring of samples at the field boundaries compensate for run in and run
out conditions of the filter.
The following coefficients are used:
Normal Polyphase Filter (Horizontal Scaling)
The normal polyphase filter can be used to zoom up (upscale) or downscale a video
image. Depending on the number of components, the filter is used with 6 taps (three-
component mode) or 3 taps (four-component mode).
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co-sited: A=(1) and B=(-3,19,19,-3)/32
interspersed: C=(-1,5,13,-1)/16 and D=(-1,13,5,-1)/16
co-sited: low pass A=(1,2,1)/4 or sub-sample A=(0,1,0)
interspersed: B=(-3,19,19,-3)/32
Rev. 1 — 17 March 2006
Chapter 12: Video Input Processor
© Koninklijke Philips Electronics N.V. 2006. All rights reserved.
PNX17xx Series
12-12