One video is creating an error but the other is not

Skip to first unread message

Sep 9, 2015, 3:32:35 PM9/9/15
to idTracker users
Both videos are in the same format and from the same device. One work fine while the other keeps producing an error (Reference to non-existent field 'solapanconcogidos').

Alfonso Pérez Escudero

Sep 9, 2015, 6:54:20 PM9/9/15
to idTracker users,

The error you are describing means that idTracker cannot learn the aspect of each individual in the video (sorry for the totally uninformative error message).

Possible causes are the following:

1) Video too short: in order to learn the aspect of each individual, idTracker needs a minimum amount of frames where all individuals are visible and moving separately. If the video is too short, it may not have enough of these frames. The adequate length of video depends on the number of individuals an how they move (you need longer videos if you have many individuals, if they cross very often, if they tend to be immobile for long periods or if they are not in view all the time). Usually we recor at least 30 minutes to be sure, but sometimes less can be enough (for example, for 5 zebrafish usually it is enough with 5 minutes of video).

2) Low quality video and/or wrong tracking parameters: idTracker needs to correctly distinguish between animals and background. And for this you need to adjust the tracking parameters until you see all animals in the displayed frame colored in green, and only the animals colored in green. Sometimes you may find that an animal is not detected, or an animal is detected as several different blobs, or that a background object is detected as an animal (is covered in green). But this should be the exception (it can happen in, say, up to 10% of the frames). Besides looking at the green pixels, you can check the correctness of the detection by looking at the "number of animals detected" in the bottom of idTracker's window. This number should match with the number of separate animals or group of animals you see in the frame. For example, if you have 5 animals and they are separated, the number should be 5. If you have 5 animals, 3 are separated and the other 2 are crossing, this number should be 4 (3 individuals + 1 pair).

3) Wrong number of individuals: There is a box where you need to enter the number of individuals. It is crucial that this number exactly matches the number of individuals in your video.

4) Animals not moving or together all the time: To learn the aspect of each individual, idTracker needs to find it in different postures. For this, the animal must move. So if some of the individuals in your video are immobile for long periods, identifications get complicated. Also, the animals must be moving separately for at least some portions of the video, the tracking will fail if they don't. For example, mice that are already familiar with the set-up tend to curl together in a corner and sleep. This is cute, but very bad news for idTracker.
Reply all
Reply to author
0 new messages