AJA FS2 - Manual (Page 156)

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Downconvert
Mode Downconvert Mode selects the type of Downconversion performed by the Video
Processor on the selected HD source input. See the following Downconvert
Illustrations for Downconversion examples. This parameter is in effect only when
the input is HD (720p, 1080i, or 1080p) and the selected output format is SD (525i or
625i), or when the input is 2K (2048 x 1080)and the output is HD (720p, 1080i, or
1080p). When downconverting from 2K, the 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.
Notes:
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 AFD
settings on these screens (Video 1 & 2).
(7) Downconvert Mode Selections Selection Descriptions
Crop
Anamorphic
14:9
Auto AFD
Letterbox (default)
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.