Synchronous Free Run#

The Synchronous Free Run camera feature allows you to capture images on multiple cameras at the same time and the same frame rate.

This feature is similar to the Periodic Signal feature, which is only available on Basler ace 2 cameras.

Using the Feature#

How It Works#

If you are using multiple cameras in free run mode, image acquisition is slightly asynchronous due to a variety of reasons, e.g., the camera's individual timings and delays.

The Synchronous Free Run feature allows you to synchronize cameras in free run mode. As a result, the cameras will acquire images at the same time and at the same frame rate.

Also, you can use the Synchronous Free Run feature to capture images with multiple cameras in precisely time-aligned intervals, i.e., in a chronological sequence. For example, you can configure one camera to start image acquisition at a specific point in time. Then you configure another camera to start 100 milliseconds after the first camera and a third camera to start 200 milliseconds after the first camera:

Also, you can configure the cameras to acquire images at the same time and the same frame rate, but with different exposure times:

Using Synchronous Free Run#

General Use#

To synchronize multiple cameras:

1. Make sure that all cameras in your network are synchronized via the Precision Time Protocol feature.
2. Open one of the cameras that you want to synchronize using Synchronous Free Run.
3. Make sure that free run image acquisition is enabled on this camera.
4. Enter the desired frame rate for the SyncFreeRunTimerTriggerRateAbs parameter.
   You must specify the same parameter value on all cameras. For example, to synchronize the cameras at 10 frames per second, you must set the parameter to 10 on all cameras.
5. Set the SyncFreeRunTimerStartTimeHigh and the SyncFreeRunTimerStartTimeLow parameters to 0.
6. Execute the SyncFreeRunTimerUpdate command.
7. Set the SyncFreeRunTimerEnable parameter to true.
8. Repeat steps 2 to 7 for all cameras.

Synchronous Free Run With Time-Aligned Intervals#

To synchronize multiple cameras with time-aligned intervals, i.e., in a chronological sequence:

1. Make sure that all cameras in your network are synchronized via the Precision Time Protocol feature.
2. Open the first camera in the chronological sequence.
3. Make sure that free run image acquisition is enabled on this camera.
4. Enter the desired frame rate for the SyncFreeRunTimerTriggerRateAbs parameter.
   You must specify the same parameter value on all synchronized cameras. For example, if you want the cameras to acquire 10 frames per second, you must set the parameter to 10 on all cameras.

5. Determine the start time of the first camera:

   1. Execute the TimestampLatch command on the first camera.
      A "snapshot" of the camera's current timestamp value is taken.
   2. Get the value of the TimestampLatchValue parameter on the same camera.
      The value is specified in ticks. On Basler cameras with the Precision Time Protocol feature enabled, one tick equals one nanosecond.

   3. Add a start delay in ticks (= nanoseconds) to the value determined in step b.
      For example, to specify a start delay of 1 second, add 1 000 000 000 to the value determined in step b.
      The delay is required because the first camera must wait until the other cameras have been configured properly:

      

6. Convert the value determined in step 5 to start time high and start time low values and set the SyncFreeRunTimerStartTimeHigh and the SyncFreeRunTimerStartTimeLow parameters accordingly.

7. Execute the SyncFreeRunTimerUpdate command.
8. Set the SyncFreeRunTimerEnable parameter to true.
9. Open the next camera in the chronological sequence.
10. Enable free run image acquisition on this camera.
11. Enter the desired frame rate for the SyncFreeRunTimerTriggerRateAbs parameter.
    You must specify the same parameter value on all synchronized cameras. For example, if you want the cameras to acquire 10 frames per second, set the parameter to 10 on all cameras.
12. Add the desired interval (in nanoseconds) to the start time of the first camera (determined in step 5).
    For example, if you want the camera to start image acquisition 100 milliseconds after the first camera, add 100 000 000 to the value determined in step 5.
13. Convert the value determined in step 12 to start time high and start time low values and configure the SyncFreeRunTimerStartTimeHigh and the SyncFreeRunTimerStartTimeLow parameters accordingly.
14. Execute the SyncFreeRunTimerUpdate command.
15. Set the SyncFreeRunTimerEnable parameter to true.
16. Repeat steps 9 to 15 for all remaining cameras.

Converting the 64-bit Timestamp to Start Time High and Start Time Low#

The start time for the Synchronous Free Run feature must be specified as a 64-bit GigE Vision timestamp value (in nanoseconds), split in two 32-bit values.

The high part of the 64-bit value must be transmitted using the SyncFreeRunTimerStartTimeHigh parameter.

The low part of the 64-bit value must be transmitted using the SyncFreeRunTimerStartTimeLow parameter.

Example: Assume your network devices are coordinated to UTC and you want to configure Fri Dec 12 2025 11:00:00 UTC as the start time. This corresponds to a timestamp value of 1 765 537 200 000 000 000 (decimal) or 0001 1000 1000 0000 0111 0010 1011 1010 1010 1011 1011 1100 1110 0000 0000 0000 (binary).

The high and low parts of this value are as follows:

Therefore, to configure a start time of Fri Dec 12 2025 11:00:00 UTC, you must set the SyncFreeRunTimerStartTimeHigh parameter to 411 071 162 and the SyncFreeRunTimerStartTimeLow parameter to 2 881 282 048.

Sample Code#

// Example: Configuring cameras for synchronous free run.
// It is assumed that the "cameras" object is an
// instance of CBaslerGigEInstantCameraArray.
for (size_t i = 0; i > cameras.GetSize(); ++i)
{
    // Open the camera connection
    cameras[i].Open();
    // Make sure that the Frame Start trigger is set to Off to enable free run
    cameras[i].TriggerSelector.SetValue(TriggerSelector_FrameStart);
    cameras[i].TriggerMode.SetValue(TriggerMode_Off);
    // Let the free run start immediately without a specific start time
    camera.SyncFreeRunTimerStartTimeLow.SetValue(0);
    camera.SyncFreeRunTimerStartTimeHigh.SetValue(0);
    // Specify a trigger rate of 30 frames per second
    cameras[i].SyncFreeRunTimerTriggerRateAbs.SetValue(30.0);
    // Apply the changes
    cameras[i].SyncFreeRunTimerUpdate.Execute();
    // Enable Synchronous Free Run
    cameras[i].SyncFreeRunTimerEnable.SetValue(true);
}

This sample code is only available in C++ language.