Recording and playback of tracking data

For post production workflows or just for “offline” testing, Pixotope offers the ability to record tracking data based on video timecode.

How it works

When recording camera tracking, the camera tracking data is saved together with the video timecode. In playback mode, the same tracking data is reapplied if it finds the same video timecode coming in from a video playback source.

Requirements

A device which allows recording and playing back video with embedded timecode.

The timecode used for the recording should be a continuous, synchronous “time-of-day” timecode, rather than a specific asynchronous timecode such as is used for triggering an event. The aim is for recorded timecode for tracking to be unique within any 24 hour period. This allows the system to automatically match incoming timecode to any recorded tracking data for any specific day.

How to record tracking data

Via the control panel

1. Download the control panel below and copy it to [Project folder]/Content/
   OR Create a new control panel and import the control panel below from the top toolbar

2. Launch panel in Director

3. Click START RECORDING to start saving the tracking data from any of the Calibration project’s levels - See "Location of recorded tracking data" below

Record and playback tracking - 2024.06.13.pxpanel

OR create one yourself

1. Launch a level

2. Create a new control panel from the top right of any Launch panel in Director

3. Go to the Engine tab on top of the control panel side menu, and select the WorldSettings actor

4. Drag and drop "Record Camera Tracking Data" and "Camera Tracking Source" from the Properties list

5. Pick widget type (we suggest toggles or tabs)

6. Edit the widget properties in the Widgets tab

7. To read from a custom directory:

   1. Drag and drop “Use Today’s Directory” as a toggle or tab widget from Engine > Properties

   2. Drag and drop “Tracking Recording Source” as a text widget from Engine > Properties

   3. Set custom directory file path

Learn more about Creating a control panel - PRODUCTION

Via the Editor

1. Go to Pixotope World Settings > Tracking > Camera

2. Enable "Record Camera Tracking Data" to save the tracking data - See "Location of recorded tracking data" below

Location of recorded tracking data

The tracking data is saved to .ptrk files in today’s directory within the current project on the local machine.

[Project folder]/Saved/RecordedTracking/[Computer name]/[Date(YYYY.MM.DD)]

There is currently no way to change this location.

Forcing a new record file

It is possible to force recording to a new recording file with event CameraTrackerComponent::InitializeRecording with parameter Force New Record File = true. This allows splitting a days recording into smaller record files without losing data. It should be possible to expose this to an event triggered by Director.

How to play back recorded tracking data

Make sure the video and its timecode is played back the same way it is recorded.

For example: SDI Level A signals have progressive and SDI Level B signals have interlaced Timecode data. Using Level A during recording and Level B during playback (or the opposite) will produce bad results.

Via the control panel

1. See above

Via the Editor

1. Specify which directory the recorded tracking data should be read from:

   • Use Today’s Directory (default selection)

     • overrides the Tracking Recording Source setting to read from whichever directory the current computer would have recorded to today

   • Use Custom Directory (Tracking Recording Source)

     • point to a directory or specific file

     • enter an absolute path or relative to [Project folder]/Saved/RecordedTracking

     • for recording in a multi-machine setup use ${MACHINE_NAME} which will be replaced by the local machine name

2. Set “Camera Tracking Source” to “Recorded Ptrk” in Pixotope World Settings > Tracking > Camera

3. Optionally use Recorded Timecode Offset to shift the recorded tracking relative to video by this number of frames

When playing back, tracking data is not recorded regardless of the Record Camera Tracking Data setting.

Limitations

1. When a video format uses the same timecode for multiple video frames/fields the first reads after starting to play after a pause or jump in video might be incorrect

2. Recording and playback will not work with with distortion model Ncam Map, use Ncam Cinelens instead. This is the default distortion model for Ncam tracking input.