Note that θS is responsible to filter bad matches. In fact, setting it to a low value yields a high precision, but achieves very low recall and thus low accuracy, discarding most of the correct matches. On the other hand, if its value is too high, it cannot filter bad matches and therefore the overall accuracy decreases (see Fig. 6.a). Similarly, θD controls the detection performance: increasing its value the precision improves but, at some point, recall sharply drops (θD>0.1). This is due to the fact that the method starts discarding too many frames. Based on these considerations we fixed these thresholds θS and θD to 270 and 0.06, respectively. It can be seen how the chosen values represent the best compromise in terms of overall performance.