O P E R A T I O N. . Options Window ..
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•Threshold - When edge differences between blocks in successive frames exceeds the threshold value, a change is registered. The threshold value may be set to a number between 0 and 255 with a default of 16. A low threshold number requires small edge differences between blocks to be considered a change; a high threshold number allows greater differences before a change is indicated.
S Example: A black foreground airplane against a blue and white sky can use a high threshold of 240. This threshold allows the DGy to locate only edges associated with the airplane while ignoring edges between sky and clouds. The threshold parameter would have to be lowered, possibly to 50, if edges of a light gray airplane needed to be located against a medium gray cloud background.
•Interframe Length - The interframe length establishes a minimum rate for the transmission of a new anchor frame regardless of the threshold or sensitivity setting. This insures that even slow, incremental changes are captured. Interframe length may be set to a value between 0 and 4095 with a default of 30. Interframe length should be adjusted after threshold and sensitivity parameters have been set.
To calculate the refresh rate:
Signal frame rate | = Refresh rate in Hz | |
Interframe length | ||
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SExample 1: For a frame rate of 15 fps and an interframe length of 5, the minimum frame update rate would be:
15 | = 3 Hz or 3 frames per second. | |
5 | ||
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SExample 2: For a frame rate of 30 fps and an interframe length of 59 the minimum update rate would be:
30 | = | 1 | Hz or once every 2 seconds. | |
60 | 2 | |||
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The optimal interframe compression settings for an input depend on the nature of the image; some experimentation may be required. Set interframe compression values low for an image with a high degree of motion; this will keep the motion smooth. Higher settings may be used for an image with little motion. The higher the interframe length, the greater the reduction of network bandwidth used.
| DGy Model 201x User’s Guide | 47 |
