Cropping - NEC µPD72257 Preliminary User's Manual

Video Input (Ravin-M only)

6.4.1 Cropping

Interlaced mode
Example
Two counters are used to identify the pixel in each line and the line in each field:
• The pixel counter PXCNT counts the pixels of each scanline. The
counter is reset to 0 at the beginning of each new scanline, i.e. with
each HSYNC.
• The line counter LNCNT counts the lines of each field. LNCNT is reset
to 0 at the beginning of each new field, i.e. with each VSYNC.
The size of the area to capture is defined by two registers:
• VInSTARTX.STARTX[9:0] defines the first pixel of each line to
capture. Thus if the pixel counter equals the VInSTARTX value, all
following pixels of the scanline are captured and passed on for
further processing.
Note that in case of YUV(4:2:2) data capturing
VInSTARTX.STARTX[9:0] must be even, i.e.
VInSTARTX.STARTX0 = 0.
• In case of interlaced capturing VInSTARTY.STARTY1[9:0] defines the
first line of the first field and VInSTARTY.STARTY2[9:0] the first line
of the second field to capture. Thus if the line counter equals the
VInSTARTY1 or VInSTARTY2 value, all following lines of the
respective field are captured and passed on for further processing.
In case of progressive capturing VInSTARTY.STARTY2[9:0] defines
the first line to capture, while VInSTARTY.STARTY1[9:0] is not of
concern.
Cropping of the image at the right and lower edge is done by the definition of the
scaled width and height (VInSCALEDWIDTH and VInSCALEDHEIGHT) in the
scaler unit.
In interlaced mode the first scanline to capture can be set independently for the
first and second field, whereas VInSTARTY.STARTY1[9:0] defines the first
scanline of the first field and VInSTARTY.STARTY2[9:0] the first scanline of the
second field.
In the above example the incoming video data has the format (600 x 480) pixels.
The first pixel to capture in each scanline shall be pixel 90, thus
VInSTARTX = 0000 005A
The first line to capture in each field shall be line 40, thus
VInSTARTY = 0028 0000
VInSTARTY.STARTY1[9:0] value doesn't matter.
This setting enables to capture a maximum of (550 x 440) pixels. Cropping at the
right and lower edge is performed in the scaler unit.
Preliminary User's Manual S19203EE1V3UM00
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H
. As progressive scan is assumed, the
H
Chapter 6
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