How to use SAL

Skeleton assisted labeling (SAL) identifies trajectories using the segment markers in a skeleton. The unidentified trajectory part that is closest to a segment marker and fulfills the set distance criteria will be identified as the corresponding labeled trajectory. The options for SAL can be set at the SAL settings page.

Use the Claim threshold option to set the required closeness between a marker and a segment marker for claiming the associated trajectory label. The default value is 20 mm. Use a lower value when markers can be close to each other for example when solving fingers.

Use the Disqualification threshold option to set the maximum tolerated distance for a claimed trajectory part from a segment marker at any frame. This option can be used to prevent that the wrong markers that happened to be close to a missing segment marker at some instance are accepted as a solution. It is recommended to start with a rather high value (e.g. 500 mm) since the solved skeleton may be offset due to the missing marker. Decrease the value when too many wrong markers are labeled through SAL.

SAL can be used both in real-time and in post-processing. Activate the corresponding Apply SAL processing step on the Processing page in the Project options dialog.

  • Real-time
    To use SAL in real-time it is required to have a solved skeleton, which means that the AIM and Solve Skeletons processing step must be activated as Real time actions. The AIM algorithm has priority over the SAL algorithm, but SAL can label trajectories which were missed by AIM. These labeled trajectories are then used for the next frame of AIM and skeleton solver processing steps.

  • Post-processing
    To use SAL as a post-processing step it is required that the file has solved skeletons. Apply SAL either via the Reprocessing dialog or with the Identify trajectories using skeleton (SAL) on the Skeleton menu. When changing the SAL settings, the file should be reprocessed with the new values for them to take effect. Check that the labeled trajectories are correct and then run the Solve skeletons processing step again in reprocessing to update the skeleton data. Repeat the steps of SAL and skeleton solving as many times as needed to get the skeleton data.

    The process can be combined with manual labeling for example by drag and drop of a unidentified trajectory on a segment marker.