AJA UDC - Manuale (Pagina 21)

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21 AJA Up/Down/Cross Mini-Converter
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).
Note: 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 content
of the16:9 HD input 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 UDC does not process or use SD AFD codes.
Downconvert Mode
Selection Descriptions
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.