SD card can only save alarm recording, no alarm snapshot.
that playing back mean local snapshot which you click snapshot button on panel to take, not alarm snapshots
alarm snapshot can only be sent by email or NAS. you can check amount of alarm picture in email or NAS.
Camera is is very sensitive and not intelligent as we think. Small movement even like light change will trigger alarm because the alarm theory is that two different pictures appear in front of lens. Hope you can forgive that weakness. Our technician team is working to reduce false alarm.
If you want to know the meaning of I-Frame parameter and power frequency, I will ask our top technician first and then give you answer.