Alkeria NECTA Series - Calculating the Required Bandwidth

8. Capturing Images 102
Warning
PacketSize property can be set only when camera is not acquiring.
Note
PacketSize property has unit as specied in PacketSizeUnitInfo unit
info.
8.9.4.1 Calculating the required bandwidth
Whenever an operating parameter of the camera is set, NECTA automatically calculates the upper and
lower (optimum) PacketSize limits, optimizing camera performance. Nevertheless, it is useful to be
aware of parameters affecting the acquisition speed and, consequently, determining bandwidth require-
ments (and vice versa).
The video stream bandwidth is inuenced by video mode, ROI size, binning value, pixel format, ADC
resolution, shutter oor, and chunk data. Refer to the relevant sections for information about these
controls.
The following explanationis simplied for better understanding: the actual calculations made by NECTA
to determine the required bandwidth and maximum frame rate are slightly more complex and take into
account some additional details that have been left out here for the sake of simplicity.
In general, the required bandwidth is calculated based on the number of bytes per micro-frame µ
B
gen-
erated by the sensor:
µ
B
= (I
B
+ CD
B
) · R ·
125µs
1s
(8.11)
The quantity between round brackets is the total size in bytes of the frame and is the sum of two com-
ponents:
• I
B
is the image size in bytes and is the product of image width ROI
W
, image height ROI
H
and
number of bytes per pixel P
B
(I
B
= ROI
W
· ROI
H
· P
B
).
• CD
B
depends on the number of enabled chunk data elds, i.e. the size (in bytes) of ancillary in-
formation related to each of the lines and the frame (see Section 7.2). CD
B
can be calculated as
ROI
H
· CD
line
B
+ CD
frame
B
.
R is the image rate and is calculated as follows:
R =
f
SEN SOR
W · ROI
H
(8.12)