synchronizationClock

Declaration

var synchronizationClock: CMClock? { get }

Discussion

All capture output sample buffer timestamps are on the synchronization clock’s timebase. Use this clock in conjunction with the clock from an AVCaptureInput.Port object to synchronize capture output with external data sources such as Core Motion samples.

The example below shows how to reverse synchronize the output timestamps to the original timestamps in the captureOutput(_:didOutput:from:) method:

func captureOutput(_ output: AVCaptureOutput, didOutput sampleBuffer: CMSampleBuffer, from connection: AVCaptureConnection) {
    // Get the original and capture session clocks.
    guard let port = connection.inputPorts.first,
          let originalClock = port.clock,
          let sessionClock = captureSession?.synchronizationClock else { return }
        
    // Get the presentation timestamp of the current sample buffer.
    let syncedPTS = sampleBuffer.presentationTimeStamp
        
    // Convert the timestamp to the original timebase.
    let originalPTS = sessionClock.convertTime(syncedPTS, to: originalClock)
}

This property is key-value observable.

See Also

Synchronizing output

• masterClock