Reducing false positives
Tune your object filters to adjust false positives: min_area
, max_area
, min_score
, threshold
.
For object filters in your configuration, any single detection below min_score
will be ignored as a false positive. threshold
is based on the median of the history of scores (padded to 3 values) for a tracked object. Consider the following frames when min_score
is set to 0.6 and threshold is set to 0.85:
Frame | Current Score | Score History | Computed Score | Detected Object |
---|---|---|---|---|
1 | 0.7 | 0.0, 0, 0.7 | 0.0 | No |
2 | 0.55 | 0.0, 0.7, 0.0 | 0.0 | No |
3 | 0.85 | 0.7, 0.0, 0.85 | 0.7 | No |
4 | 0.90 | 0.7, 0.85, 0.95, 0.90 | 0.875 | Yes |
5 | 0.88 | 0.7, 0.85, 0.95, 0.90, 0.88 | 0.88 | Yes |
6 | 0.95 | 0.7, 0.85, 0.95, 0.90, 0.88, 0.95 | 0.89 | Yes |
In frame 2, the score is below the min_score
value, so frigate ignores it and it becomes a 0.0. The computed score is the median of the score history (padding to at least 3 values), and only when that computed score crosses the threshold
is the object marked as a true positive. That happens in frame 4 in the example.