If required, instead of having to manually start and stop capture (see Capture the required movement), you can trigger data capture using an external device or based on a specified period of time.

You can configure Vicon Nexus to automate data capture with the options described in the following topics.

Automatically record data before capture is triggered

The Capture before start option enables you to specify the number of seconds of data to record prior to capture being triggered either manually (with the Start button) or automatically (based on timecode or a remote control device).

To automatically record before capture is triggered:

1. Ensure you have prepared for capture as described in Capture the required movement, and completed steps 1–4.
2. In the Capture Tools pane, expand Auto Capture Setup, select Capture Before Start (secs) and specify the number of seconds to record data prior to capture being triggered.
3. Trigger the capture manually or using one of the remote capture methods described in this section.
   The Vicon cameras capture the subject moving in the capture volume.
4. Stop the capture manually or using one of the remote capture methods described in this section.
   Nexus automatically switches to Offline mode and displays the subject data in the 3D Perspective view.

Stop data capture after elapsed time

The Stop after duration (secs) option enables you to specify a time period after which Nexus is to automatically stop a capture.

To stop data capture after a specified time period:

1. Ensure you have prepared for capture as described in Capture the required movement, and completed steps 1–4.
2. In the Capture Tools pane, expand Auto Capture Setup, select Stop After Duration (secs) and specify the number of seconds after which to automatically stop motion capture.
3. Capture a trial manually or using one of the remote capture methods described in this section.
   The Vicon cameras capture the subject moving in the capture volume. Nexus automatically stops the capture after the specified number of seconds, automatically switches to Offline mode, and displays the subject data in the 3D Perspective view.

Trigger data capture on labeling percentage

With the Start on Labeling (%) option selected, captures automatically start when a subject first fully enters the volume. If the Stop on Labeling % option is also selected, captures automatically stop when the subject leaves the volume.

You can set the labeling percentage (ie, the percentage of markers expected from the total number of markers in your subject's labeling skeleton) that needs to be recognized by Nexus within the capture volume for the subject to be considered as fully in the volume or to have left the volume and therefore to trigger capture start/stop.

The following procedure describes how to set up data capture to automatically crop live trials, based on labeling percentages. For information on how to automatically crop trials that you have already saved based on labeling percentages, see Crop trials.

1. Ensure you have prepared for capture as described in Capture the required movement, and completed steps 1–4.
2. In the Capture Tools pane, expand Auto Capture Setup and select Start on Labeling (%) and/or Stop on Labeling (%).
3. The default values for this operation start capture when at least 90% of a subject's markers are recognized and stop when less than 65% remain (volume exit). You can adjust these percentages to suit your capture type.

   

4. Have a subject wearing the required marker set enter the volume.

   
   

   Tip
   To check data quality, you can display the labeling percentage by selecting the subject and in a Graph view choosing Labeling to show how many labels are present on each frame.

   

Trigger data capture using a remote control device

The Start/Stop on remote trigger option enables you to use an external remote control device to trigger data capture. The remote control device must be connected to a Vicon Lock unit in your Vicon system (for details, see either the Vicon Vantage Reference Guide orthe documentation for your Vicon Lock). Both start and stop ports require the signal to be grounded (ie, falling edge TTL) to trigger the desired action within Nexus.

To trigger data capture using a remote control device:

1. Ensure you have prepared for capture as described in steps 1–4 of Capture the required movement.
2. In the Capture Tools pane, expand Auto Capture Setup, ensure the Advanced options are displayed, and select Start/Stop On Remote Trigger.
3. To set the system to a state where it is ready to accept a trigger signal for automatic capture based on a remote control device, click the Arm button.
   If you want to enable the system to remain ready to receive subsequent remote capture signals after the capture is stopped, click the Lock button to the right of the Arm button.
4. Trigger the start of the capture from your remote control device.
   The Vicon cameras capture the markers on the subject moving in the capture volume and the Start button switches to its Stop setting.
5. After you have acquired the data you need, trigger the stop of the capture from your remote control device.
   If you clicked the Lock button, the Arm button is re-enabled and the Stop button switches to its Start again, ready for a subsequent remote capture.
6. When you have finished your capture session, to review your subject data, manually load the trial.

Trigger data capture using timecode

The Start On Timecode and Stop On Timecode options enable you to use an external timecode source to trigger data capture in your Vicon system. The timecode source must be connected to a Vicon Lock in your Vicon system (for details, see either the Vicon Vantage Reference Guide or the documentation for your Vicon Lock), and the corresponding timecode options must be configured under the Vicon Lock node in the System Resources pane.

1. Ensure you have prepared for capture as described in steps 1–4 of Capture the required movement.
2. In the Capture Tools pane, expand Auto Capture Setup, ensure the Advanced properties are displayed and select one or both of the following options and specify the required timecode:
   
   • Start On Timecode
   • Stop On Timecode
3. Specify the start and stop values in the standard timecode format:
   hh:mm:ss:ff
   where:
   hh = hours (0-23), mm = minutes (0-59), ss = seconds (0-59), ff = frames (0-24 for PAL/SECAM, 0-29 for NTSC)
   For NTSC, the separator character changes between a colon ( : ) for non-drop frames and a semicolon ( ; ) for drop frames.
   For details on the use of timecode functionality in Vicon systems, see the Vicon Vantage Reference Guide.
4. To set the system to a state where it is ready to accept a trigger signal for automatic capture based on a timecode, click the Arm button.
5. If you want to enable the system to remain ready to receive subsequent timecode signals after the capture is stopped, click the Lock button to the right of the Arm button.
6. If you selected the Start On Timecode check box, start the timecode source from which the data capture is to be triggered; otherwise, under the Capture section click the Start button.
   When the specified timecode is reached, the Vicon cameras capture the subject in the volume and the Start button changes to Stop.
7. If you selected the Stop On Timecode check box, when the specified timecode is reached capture stops; otherwise, after you have acquired the data you need, click the Stop button.
   Nexus automatically switches to Offline mode and displays the subject data in the 3D Perspective view.

Trigger data capture over a network

You can broadcast a UDP message over an intranet or direct network cable connection to or from another application (or instance of Nexus) to trigger capture start and stop. Note that Nexus can send or receive the messages, but it cannot send and receive them simultaneously.

To trigger data capture over a network:

1. Ensure you have prepared for capture as described in steps 1–4 of Capture the required movement.
2. In the Capture Tools pane, expand Auto Capture Setup, ensure the Advanced options are displayed, select Start/Stop Over Network and from the adjacent drop-down list, select Send or Receive.
3. In the Address field, either select the IP address of the network card that will be used to send or receive the start/stop trigger message, or select All. In the adjacent field, specify the UDP port which is to send or receive the message.
4. To set the system to a state where it is ready to accept a trigger signal for automatic capture based on a signal broadcast over the network, click the Arm button.
5. If you want to enable the system to remain ready to receive subsequent network signals after the capture is stopped, click the Lock button to the right of the Arm button.
6. Start the capture from the remote software. You can start the capture using a timecode or immediately.

For information on the format of the packet, see UDP capture broadcast/trigger.