5 –Camera Controller
A6700sc/A6750sc User’s Manual
32
Analog Video Setup Options
AGC Mode
Plateau: Uses a plateau equalization (PE) algorithm to scale the image
data for video display
DDE: Digital Detail Enhancement.
Manual Linear: Scales the image data to a windowed section of data range
as set by the user
Auto Linear: Same as Manual Linear except camera analyzes image and
sets limits at ~1% and 98% of the histogram.
Plateau P
Bounds
Scaling factor for the Plateau Equalization function
Note: Plateau P is only visible when AGC Mode>>Plateau is selected
Sets the lower and upper data range to be scaled to on the video data.
Note: Bounds is only visible when AGC Mode>>Manual Linear is selected
DDE Sharpness
Only visible when AGC is set to DDE. Selects the amount of enhancement
processing.
Palette
Allows user to select the color scheme to use on the analog video channel.
Brightness and
Contrast
Allows user to set brightness and contrast on the video encoder. As shown
in Figure 4-16, this occurs after the digital data has been scaled and
converted to analog. These controls don’t tend to have as much effect as
the controls that are applied to the digital side (before the video encoder).
Corrected Data
Uncorrected Data
Mux
Plateau
Scalar
Linear
Scalar
GUI: Plateau P
GUI: Bounds
Mux
GUI: AGC Mode
Video
Encoder
GUI: Format
GUI: Position
GUI: Brightness
GUI: Contrast
Overlay
GUI: Overlay
GUI: NUC’d
Analog Video
Pallete
Scalar
GUI: Palette
Figure 4-5: Analog Video Flow
The Manual Linear algorithm evenly distributes the grayscale values over the digital values. This
works fairly well if the image dynamic range is fairly evenly distributed but in general does not produce
high contrast imagery, but it also does not saturate or clip the hot and cold regions either. The
Plateau Equalization algorithm (also called PE) is a nonlinear AGC algorithm that uses the image
histogram to optimally map the 256 gray scales. This algorithm works well for most scenes but it
works best when the scene has a “bi-modal” distribution (two clumps). It usually the most popular
because algorithm because it produces high contrast (but more saturated) video. The following
pictures illustrate the differences in AGC algorithms. (The data was captured from the digital output
but the effect is similar for the analog side.)
