Using External timebase for synchronization to a time code signal

The Qualisys system can be synchronized to an external time code. The following standards are supported:

  • SMPTE at frame rates of 24 Hz, 25 Hz, and 30 Hz, without dropped frames.
  • IRIG A and B, Direct Current Level Shift (DCLS)

SMPTE

SMPTE time code is a set of cooperating standards to label individual frames of video or film with a time code defined by the Society of Motion Picture and Television Engineers. SMPTE time code signals can be generated by time code generators or external audio interfaces. SMPTE is commonly used for synchronization in audio/video applications. Qualisys supports SMPTE standards at frame rates of 24 Hz, 25 Hz and 30 Hz, without dropped frames. For more specific information about how to use SMPTE for synchronization of captures with audio recordings, see chapter Using SMPTE for synchronization with audio recordings.

The use of SMPTE time code requires a Camera Sync Unit. Alternatively, for Oqus systems an Oqus Sync Unit can be used. The SMPTE time code signal should be connected to the SMPTE input port. The capture frequency can be set to a multiple or a divisor of the SMPTE frame rate in the External timebase settings on the Synchronization page.

Do not use External timebase settings that result in a camera frequency higher than 0.975*maximum frequency at the full image size.

When using SMPTE as an external timebase source the shutter delay (Delay from signal to shutter opening on the External timebase page) should be at least 100 microseconds for a consistent number of cameras frame per SMPTE frame. The shutter delay value is automatically set to 100 μs when selecting SMPTE.

IRIG

Inter-Range Instrumentation Group time codes, commonly known as IRIG time codes, are standard formats for transferring timing information. Atomic frequency standards and GPS receivers designed for precision timing are often equipped with an IRIG output. IRIG is commonly used in communication systems, data handling systems, military systems, telemetry systems, high speed cameras and in machine vision. Qualisys supports the IRIG A and the IRIG B standards of DCLS type (Direct Current Level Shift).

The use of IRIG time code requires a Camera Sync Unit. The IRIG time code signal should be connect to the Event input port on the Camera Sync Unit. The capture frequency can be set to a multiple or a divisor of time code frequency in the External timebase settings on the Synchronization page.

Do not use External timebase settings that result in a camera frequency higher than 0.975*maximum frequency at the full image size.

IRIG cannot be used when there are any Oqus cameras included in the system.

Timestamps

When using time code as external timebase source, time stamps are recorded by default, so that each camera frame includes a time stamp. When the capture rate is set to a multiple or divisor of the time code frequency, the first camera frame of a capture may not correspond to the start of a time code period or frame. For synchronization to an external signal you will need to look up a camera frame at which the time code increased and take the offset into account.