AJA UDC - Manual (Page 8)

UDC Mini-Converter v2.3r1 www.aja.com 8
Downconvert Mode
This mode determines the type of Downconversion performed on the selected HD
source input. See the following Downconvert Illustrations for Downconversion examples.
This mode is in effect only when the input is HD (720p, 1080i, or 1080p) and the selected
output format is SD (525i or 625i).
Figure 4. Downconvert Mode Example
Selection Description Letterbox – Image is reduced with black top and bottom added to image area, with the
aspect ratio preserved.
Crop (default) – Image is cropped to fit new screen size.
Anamorphic – HD image is converted to full-screen SD with a 16x9 aspect ratio
(anamorphic).
14:9 – Image is reduced slightly with aspect ratio preserved. Black is added top and
bottom, and the left and right sides are cropped.
Auto AFD – Automatically selects the best Downconvert mode based on the input
video's Active Format Description (AFD) code.
Active Format Description (AFD) codes are carried in the vertical ancillary (VANC)
portion of HD SDI video signals, specified in SMPTE 2016 as follows: “AFD information
is intended to guide DTV receivers and/or intermediate professional video
equipment regarding the display of video of one aspect ratio on a display of another
aspect ratio.”
In the UDC Downconverter, the AFD code on the video input can be used to guide
the Downconverter in choosing which mode to use to best display the important
1 6
9
Anamorphic
Letterbox
4
3
16:9 Downconverts To These displays on 4:3
Crop
14:9