Acquire the time to notify the application of one frame photographed with a terminal camera

I am producing the following applications.

- Data measured by Bluetooth device received by iPad terminal

- When receiving the above data, iPad terminal records how the device is measuring


By synchronizing / playing back "data measured with Bluetooth device" and "movie recorded with iPad"

I want to be able to confirm the state of moving subject of motion picture and the change of the value measured by the instrument.


However, depending on the terminal used for measurement, the time to shift the playback start position of the movie will differ.

 → 300 msec to 500 msec if it is a good terminal, 1000 msec if it is a bad terminal, etc.


If it is possible to measure the time from the moment when the terminal's camera shoots until the data (#1) arrives in the application,

If only the difference in time is shifted and played back, will motion and sensor movements match? I believe.


#1

captureOutput: didOutputSampleBuffer: fromConnection:



Is there a way to acquire the time from the moment when the terminal's camera shoots, until the data arrives in the application?