Vinten Radamec Free-d - Manual (Page 34)

Vinten Broadcast Ltd free - d ™ Installation Manual V1.4.4
Page 34 of 46
The ‘half box width’ determines the size of the outer box used in target
detection. The maximum value is 41 pixels: if a larger value is set the unit will
not operate correctly; the box height is calculated to ensure the box is square.
A value of zero signifies ‘automatic’: the
free-d™ unit sets the box size according
to the apparent size of the targets in the image.
The ‘black video clip level’ and ‘white video clip level’ determine the clipping,
which is applied before the target's position is measured. Too little clipping can
make the position measurement over-sensitive to level variation, such as
might be caused by uneven illumination. Too much clipping, however, can
cause excessive aliasing, which can impair the measurement accuracy.
The ‘maximum number of black pixels’ and ‘minimum number of white pixels’
values are used in conjunction with the ‘black video threshold’ and ‘white video
threshold’ to control the target detection process. A target is recognised if
there are at least the specified minimum number f pixels above the ‘white’
threshold within the inner box, and at most the specified maximum number of
pixels above the ‘black’ threshold between the inner and outer boxes.
The free-d™ unit acknowledges receipt of a D3 message by replying with a D3
message containing the new data.
A.3.5 Type D4 & D5 - target data
The D4 and D5 messages are used for transferring target data from the free-d™
unit. Each message contains data about a single target: requesting message
D4 causes data for target zero to be transmitted and requesting message D5
causes data for the next target in sequence to be transmitted. After data for
the last target has been sent, the next message will contain data for the first
target, with a message type of D4 (whether the request was for D4 or D5).
The messages contain 18 bytes as follows:
<D4> or <D5> Message type
<CA> Camera ID
<SN> Studio ID
<MH><ML> Target Number
<XH><XM><XL> Target X-Position
<YH><YM><YL> Target Y-Position
<HH><HM><HL> Target Height (Z-Position)
<FH><FM><FL> Target Flags
<CK> Checksum
The X-Position, Y-Position and Height are sent in the same format as the
camera position in message D1 (see Appendix B).