Q-See QSNDVR16M User Manual page 42

WATER MARK: If you choose "ON", this function is active. Water mark can protect recording files from being modified, as the modification
can be technically traced by checking watermark. The system will add the invisible code to the record when the "WATER MARK" is on;
this is covered in Chapter 3.3.3 Backup.
records continuously. If an alarm record occurred, the DVR records continuously and you can find
the alarm event through "event search" or "file search".
PLAY DEINTERLACE: Interlace scan and play. If you choose "ON", the DVR will play back after an
internal of line. If you choose the "OFF", this function is disabled.
Attention: This function is more useful in VGA output mode.
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