Headcams with Mocap

Brian Genna -

Actual production differences

Most everything extra that FTI does in using the headcams can be done concurrently with preparation and downtime inherent to every mocap shoot. In practice, using the headcams slows down a mocap shoot approximately 5-10% the first few days, then after everyone is used to using it, there is no reason for headcam use to slow down a shoot. If there are more actors than headcams or wireless video units, both will need to be swapped out between actors during the course of the day. If a schedule is followed, this can be done in between scenes while the next stage is being set while causing no delay to the production schedule. If a director makes last minute changes to whom he wants the headcams on for a specific scene, a delay can happen. Changing the cameras from one helmet to another can take from 2-8 minutes per camera. For wireless video units the change time takes from 1-4 minutes per unit.

Recommended Headcam crew:

For 1-3 actors, one crewman. 3-6 actors, we recommend two crew. 7-12 actors, three crew

Extra steps in preproduction for Mocap team

  • setup table/workstation for FTI equipment on side of stage with access to AC power.
  • allow 2-4 hours for initial setup and testing before first day of shooting to prepare decks, monitors, computers, cameras, cables, timecode, etc. Also a dry run to test headcam picture, sync, naming conventions, roll calling, etc. is recommended.
  • Setup place for a monitor near dressing room so crew can frame and focus the cameras before actors get to stage. Not absolutely necessary, but can be helpful in saving time on busy shoot days.

Extra steps in production for Mocap team

Before shooting:

  • Allow headcam crew to find a proper fit for the actor with the various pads and helmet sizes for their first day.
  • Placing markers on the helmet and having the actors wear the helmet while they do their range of motion for mocap.
  • Framing and focusing the cameras. This is handled by headcam crew and can happen before or right after the range of motion. 1-5 min per camera per actor.

During shooting:

  • Make sure video is rolling when mocap is rolling.
  • Between takes, plan layout of cables behind actors if wireless units are not being used. This includes making sure actors will not trip on a cable or cables will not interfere with set pieces. If wireless units are being used, this is unnecessary.
  • If more actors are being captured than cameras are available, planning when and to whom camera bars and packs are transferred between helmets. This will be handled by headcam crew, and will occur between scenes, but mocap team must also be aware to plan time accordingly.
  • If stunts are being performed, chin straps are highly recommended.

Data differences

Depending on your system, the mocap data may identify the lights on the headcams as markers. They can be ignored.

Handling FTI video data can be identical or very similar to managing witness camera data. All that is needed is a pipeline that captures the video data in a high quality and synchronized way. We recommend the AJA Ki PRO digital video recorders. The shots can be named the same as mocap and can be timecode locked to each other.

Time code can be managed in three ways. Any choice is fine, it is only important to be consistent.

  1. Have a master clock. This is a device that generates what is known as “time of day” timecode. The time code roughly matches the actual time of day and is sent out from the master clock to the mocap and the video recorders. The mocap and video recorders then imbed this timecode into the data.
  2. Have the video “slave” to timecode generated by mocap. Here the video imbeds the timecode that is generated by the mocap.
  3. Have the mocap “slave” to the video. Here the mocap imbeds the timecode that is generated by the video.

Option #1 requires an extra piece of equipment, but usually is best because on any given day, using a “time of day” system, there is no possibility of duplicate time codes being recorded, and thus preventing problems in post-production.

Whatever method is chosen, keep in mind timecode is an arbitrary number. It only exists so between different videos and different motion data sets, all data sets can reference an exact instance in time for making “in/out” selections.

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