Drop in frames with Femto Mega

Hi,
I am using Pyorbbecsdk (branch: main) for my Femto Mega camera on Windows 10. I am trying to test the frame success rate for color stream.

I did 2 experiments:

  1. How much time does it take to capture 150 frames at 3840 x 2160 @ 15 fps? Ans: 13.260 secs
  2. How many frames are captured in 10 seconds at 3840 x 2160 @ 15 fps? Ans: 137 frames

I am having trouble getting frames accurately at the specified FPS.

Can someone help? I am not sure if I am missing something here.

Firmware version 1.2.7
Connecting through USB 3.2