Nevion ARC-SD-XMUX4 - Manual (Page 10)

ARC-SD-XMUX4 Rev. B
nevion.com | 10
However, the fill factor descriptor may contain a code to indicate that the fill factor of the
picture is unknown. In that case, the code for the input aspect ratio is used.
SMPTE352M is a data packet that can be used to identify the aspect ratio of the picture.
Wide Screen Signaling present in the input video (WSS) can also be used to identify the
aspect ratio of the incoming picture. The trouble is that WSS codes are by themselves
indistinguishable from WSS Extended codes, but have a completely different meaning. This
means that the user must select if WSS should be interpreted as WSS or WSS-Ext, and if
this selection does not match the choice made in the equipment that inserted the WSS
information, the resulting scalings will seem unpredictable.
Mode 1: Full automatic mode
The aspect ratio control block will start by looking for AFD presence in the input signal to
select the aspect conversion. If that is not present it will look for VI, then WSS and finally
SMPTE S352M information. If no aspect ratio information is present in the video, the default
scaling setting will be used.
When a valid format descriptor is present, either from AFD or VI, all the conversions in the
AFD code drawing are possible for the given output environment.
In the case where only input environment information is available, a subset of the
conversions is used. The desired filling method must be set. This may be one of the
following:

Protect input frame : No cropping. Full curtains.

Zoom to fill frame : The image will be cropped and zoomed to fit. No curtains.

14:9 : The image will be zoomed and cropped. Narrow curtains (pillar or letter box).
If the input environment is the same as the output environment, no conversion will be
performed.
Mode 2: AFD or default
This mode will only use the AFD information if present. The default scaling will be used if
there is no AFD packet, no video index and no WSS, or if the active format descriptor is set
to ‘Unknown’.
Mode 3: Fill mode or default
This mode will only use the input aspect information from the AFD information if present.
The S352M packet will be used if it is present and neither AFD packets, VI, nor WSS are
present. The default setting will be used if there is no AFD packet, no video index, no WSS
and no S352M packet.