Grass Valley 8990ARC v.1.0 - Manual (Page 27)

8990ARC Instruction Manual 21
Functional Description
Active Picture Processing
The active picture portion is routed through the H & V re-sizing portion
shown. Depending on the mode and input format selected, H and V will be
scaled up or down. The maximum delay for this processing is required for
vertical magnification, where the starting position of the output will be at
last 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 or 324 in 625 line or 14 and 277
in 525 line 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