speed vs. resolution - RC Groups
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Aug 29, 2012, 12:50 AM
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speed vs. resolution

As suspected, downsampling with maximum instead of lowpass filtering made the LED stand out more. The problem was resolution. 88x96 wasn't going to give useful distance data. A solidly lit LED with multiple frames blended might improve the accuracy.

Analyzing the data on the microcontroller without compressing it can get it up to 320x240 70fps. 640x480 still only goes at 20fps. That definitely made you wonder what the point was of not using a webcam. Only the simplest algorithm can go at 70fps & it still takes a lot of optimization.

Accessing heap variables has emerged as a real bottleneck for GCC. Temporaries on the stack greatly speed up processing but create spagetti code.

The microcontroller thresholds the luminance & compresses the 0's. Works fine, as long as only the aircraft light crosses the threshold. A large bright area would make it explode. Compressing the 1's would take too many clockcycles.

The leading flashing LED algorithm begins with blob detection. Blobs which come within a certain distance of another blob in a certain number of sequential frames are considered always on & discarded. The largest of the blobs which don't have anything appear within a certain area in every frame is considered the target.
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