Activity settings
If you selected Activity analysis in the Experiment Settings, you must create settings for this analysis.
To make it easier to judge whether the settings are correct, make sure the detected Body fill of your subject is not shown in the Video window. Click the Show/Hide button in the top-right corner of your window, select Detection Features and deselect Body fill and Noise. Then select Activity. Close the Detection Features window and play the video. The detected pixel change between samples is shown in purple.
Open the Activity section in the Detection Settings pane.
This value gives the threshold for the difference in gray scale values, between a sample and the previous sample.
Use this filter to remove noise in the video, or camera image. With the background noise filter, a pixel change is only counted as a change, if the surrounding pixels also have changed. The pixels that are not fully surrounded with changed pixels are removed and around the remaining pixels a layer of changed pixels is added. The higher the setting for the background noise filter, the more surrounding pixels are used.
Below: Activity is based on the change in the pixels’ gray scale value with time. Left: The black squares represent pixels that have changed between two consecutive samples. First, all pixels that are not completely surrounded by one layer of changed pixels are removed (gray squares). Then, one layer of changed pixels is added around the remaining pixels. The resulting blob of changed pixels looks smoothed (right).
Use the compression artifacts filter to compensate for video artifacts that are regularly recurring. With the compression artifacts filter, only the changes that are occurring in a number of consecutive frames are taken into account.
▪If you track live, we recommend to leave this setting on the default value Off.
▪If you track from video, or if you select Redo tracking from an existing video file, select On.
▪However, if you are interested in very brief or fast occurring changes, leave the setting for the Compression artifacts filter on Off.
Create settings in such a way that all activity of your animal is detected and some noise is left. Also try whether lowering the sample rate and using Video Pixel Smoothing improves Activity detection. Then, click the Show/Hide button once more and select Detection Features. De-select Activity and select Body fill. Then create detection settings for your subject. Or, if you need different sample rates for activity analysis and tracking, create separate detection settings for tracking.
It is also possibly to only carry out activity analysis and not create detection settings for tracking. However, if you do so, it may happen that EthoVision XT has so much difficulties to detect the animal, that this decreases the performance of acquisition. This may result in many missed samples. Therefore, while creating activity settings, check that the proportion missed samples does not become too high. See Missed samples