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Output Aspect Ratio Control
There are four controls for Output Aspect Ratio (OAR):
•
display aspect ratio
•
screen aspect ratio
•
image shift
•
underscan
The Display Aspect Ratio is the full aspect ratio of the display, normally specified in the display manual.
Common display aspect ratios are 4:3 and 16:9. Less common ones are 5:4, 2.35:1 and others.
The example below shows a 4:3 projector with a 16:9 screen.
The region outside the Active Output area (called the mask) is inactive, and only important for creat-
ing video timing signals for the display. input video data is never mapped to this region.
When the Display Aspect Ratio is not the same as Active Output Aspect Ratio, the mask is set to
blanking levels and always centers the position of the active area over the display area.
Image shift allows you to adjust the location of the image on your screen both horizontally and vertically
when the ‘Screen’ aspect ratio is not equal to the ‘Display’ aspect ratio. The example below shows 16:9
projector (1.78:1) and a 2.35:1 screen, you can shift the image to match the exact location of your screen.
In this situation, the image is shifted down putting all of the mask at the top of the projected image.
Underscan represents the visible display area, a sub-set of the Active Output Area. Underscan is like
a negative zoom which preserves the aspect ratio of the active area. The default for this setting is 0.
As you increase underscan, the smaller portion of the active display area appears while preserving
the aspect ratio of the active display area.
Mask
Active Output
Area
16
9
Mask
Screen Aspect Ratio
(2.35:1)
Screen Aspect Ratio
(2.35:1)
Visible Area
Active
Output
Page 37, R2
page 38
Image
4
3
Mask
Active Output
Area
16
9
Mask
Screen Aspect Ratio
(2.35:1)
Screen Aspect Ratio
(2.35:1)
Visible Area
Active
Output
Page 37, R2
page 38
Image
4
3
Mask
Active Output
Area
16
9
Mask
Screen Aspect Ratio
(2.35:1)
Screen Aspect Ratio
(2.35:1)
Visible Area
Active
Output
Page 37, R2
page 38
Image
4
3