Sometimes pcap_sendpacket takes longer in some situations

I have noticed that pcap_sendpacket sometimes takes a long time while playing a video in Windows Media Player or any other video player.
Usually, this function finishes in about 20us, but it frequently takes up to 1000us while playing video.
The same problem occurs when opening sites such as YouTube with Chrome, while normal browsing does not cause the problem.
I just executed the "Examples-pcap/sendpack" example included in the Npcap SDK.

Interestingly, this problem occurs with "Realtek PCIe GBE Family Controller" and "Intel(R) Gigabit CT Desktop Adapter," but not with "ASIX AX88179 USB 3.0 to Gigabit Ethernet Adapter".

Does anyone have any idea what might be causing this problem?

Diagnostic information

• Windows version: Windows 11 Version 21H2, OS Build 22000.832)
  • I have confirmed that the same problems occur on other Windows 10 and Windows 11 machines.
• npcap version: 1.70
• npcap SDK version: 1.13

Start by reproducing the delay with the Examples-pcap/sendpack example on the listed Windows versions and adapters, comparing video playback with normal browsing. Trace the pcap_sendpacket path to determine where the extra time is introduced. Done means the cause is isolated and a corrective change or clearly documented limitation is established.