AJA FS2 Manual - Manual (Page 66)

FS2 v2.1r1 www.aja.com 66
selections do not precisely describe the resulting picture. For example, 14x9 is not
precisely 14x9. However, picture scaling is such that the visual effect closely resembles an
HD-to-SD downconvert.
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 FS2 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 content of
the input 16:9 HD video on the 4:3 SD output. For example, if the input AFD code is 10
(Full Frame), it means that the input video has important picture information throughout
the full 16:9 frame, so the Downconverter should use Letterbox mode to be sure none of
the content is cropped off. An AFD code of 9 (Pillarbox) says that the input video only has
content within the center 4:3 area of the picture (usually because it originally came from
an Upconverted SD signal) so the Downconverter Crop mode would be the best choice.
There are 16 possible HD AFD codes, of which 8 are in common use. The FS2 does not
process or use SD AFD codes.
FS2 AFD processing (passing, removing, and re-inserting) occurs based on the setting of
parameters 7, 5.4, 16.1, and 16.2.
Auto AFD mode fully defines the size, position, and aspect ratio of the output raster. Thus,
when in Auto AFD mode (Output Format set to an SD format, with an HD video input, and
Downconvert Mode set to Auto AFD), any Custom Size/Pos settings are ignored, and those
menus (13.0 - 13.8) are hidden. Likewise, when in Auto AFD mode, any Region Of Interest
settings are ignored, and those menus (14.0 - 14.4) are hidden.
Crop (default)
Anamorphic
14:9
Auto AFD
Letterbox
Image is cropped to fit new screen size.
HD image is converted to full-screen SD with a 16x9 aspect ratio
(anamorphic).
Image is reduced slightly with aspect ratio preserved. Black is
added top and bottom, and the left and right sides are cropped.
Automatically selects the best Downconvert mode based on the
input video's Active Format Description (AFD) code. If the input
video is not carrying an AFD VANC code, the Downconverter
defaults to the mode specified in parameter menu 16.3
Downconvert AFD Default.
Image is reduced with black top and bottom added to image area,
with the aspect ratio preserved.