Redo a trial in EthoVision XT
EthoVision XT can be used to track in real-time but sometimes after the trial it will be apparent that the animal was not tracked well, the arena was miscalibrated, or for other reasons the track is not correct. If you recorded a video during the trial, you can retrack that video in the same experiment.
Note that retracking is not needed if you simply want to add or change zones for analysis. You can make those changes in the arena settings originally used to acquire the trial. What cannot be changed in the arena settings are the outline of the arena itself (since EthoVision ignored everything outside the arena), the calibration, and any zones used for trial control or hidden zones.
1. Clear and redo a trial
If you were tracking live and recorded a video, to redo a trial, in the Acquisition on the right side under Redo Trial click the Select button:
2. Select the trial(s) to redo
Pick the trial you want to redo, and pick the option “Clear tracks but re-use the video.” That will clear the track but keep the trial in the trial list with the video that was recorded.
You can repeat this for as many trials as required.
Note that if your experiment originally used video files rather than a camera, the option here will be "Clear tracks but re-use the video reference." This works the same way, allowing the video to be retracked. Alternatively for experiments working for video, you can simply delete the trial and track the video in a new trial.
3. Track saved video trials
You’ll now be able to pick the “Track the next saved video trial” option in the Acquisition and retrack. But before doing so, go to the Trial List and make sure to select the correct detection settings and/or arena settings for that trial. When you do retrack, by default it uses the “DDS” or Detection Determines Speed setting which means that it will track as fast as it is able, which in many cases will be faster than real time.
If you have many trials to redo, you can go through and select all of them to redo, then update the trial list to specify the correct detection settings to use for each trial, and then in the acquisition pick the option “Track all saved video trials” and it will run through the entire set one after the other without requiring your attention.
Trials which have been cleared but not yet retracked will be marked with a status of "Postponed" in the trial list. This indicates that the trial exists but the track data has not been acquired yet (tracking has been postponed).
Create a new experiment
Alternatively, sometimes it is easier to simply make a new experiment and use the videos from the original experiment. In that case you can set up the arena settings and detection settings based on those existing videos.
To easily create a new experiment with the same settings as the original, create a New Template Experiment, pick the Custom Template option, and select your original experiment as the template. This will copy all the settings but none of the data into the new experiment. Note that this will take a while if you have a lot of data in the original, as the original experiment is copied first and then the data is removed from the new copy.
The videos will be available in the Media Files folder of the original experiment.
The advantage of creating a new experiment is that you can use those videos when setting up your arena settings and detection settings.