Grass Valley 8990ARC v.3.0 - Manual (Page 51)

8990ARC Instruction Manual 51
Functional Description
required for vertical magnification, where the starting position of the
output will be at last 3/4 position in the input picture. The worst case is 4:3
input and mode 3 (full-width) with the vertical position set at the bottom
of the field. In all modes, the overall delay will be fixed at this worst case
for each line rate.
H & V Re-sizing Algorithm
Scaling up (magnify) creates more pixels or lines in a selected region than
is available in the input and therefore requires a horizontal or vertical posi-
tion adjustment. It is accomplished by periodically holding off the reading
of data from the input FIFO, while re-computing a new pixel/line in its cor-
responding poly-phase filter.
Scaling down (shrink) decimates pixels or lines from the entire source
image and results in a blanked region in the output, which is adjusted
using the horizontal or vertical position adjustment. It is accomplished by
periodically holding off the writing of data to the output FIFO, while
re-computing a new pixel/line in its corresponding poly-phase filter.
In modes 2 and 3 only one operation is performed, H or V scale up or down.
In mode 4, the 14:9 sub-image both scaling up and scaling down are done
independently and simultaneously.
Vertical Resize Filtering
All the poly-phase filters used for vertical magnification or shrink have
maximum bandwidth. Video sources with high contrast or chroma satu-
rated horizontal edges will produce some filter ringing within a few lines
above and below the edge. One example of such an edge is contained in the
SMPTE color bar test pattern. If this effect needs to be eliminated, then
linear-interpolators can be used in these vertical processing modes in the V
Process BW configuration selection. The consequence of this selection is
having a reduced vertical bandwidth.
Video Index Information Coding Support
Video source data can be inserted on lines 11 and 324 in 625 line rate or lines
14 and 277 in 525 line rate systems per SMPTE RP-186 specification. The
very first section of this coding region, Class 1.1, data octet 1, encodes
options on the source of being 525/625 line and 4x3 or 16x9 format. If the
input to the 8990ARC contains this section of coding and the Video Index
Control function is enabled, the mode will automatically change to 1 (no
processing) if the input format and selected output format are the same. It
will revert to the previous, 2 through 4 selection when either the input
format changes or the user changes the desired output format.