Dahua DH-XVR5104HS-4KL-I3 User Manual page 246

To lock the files to make it unable to be overwritten, select the files, and then click Lock.
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To add a mark to the file, select the files and then click Add Mark.
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Search by Picture
Select Main Menu > AI > AI Search > Face Recognition > Search by Picture.
Upload face pictures from Face Database or Local Upload.
Maximum 30 pictures can be uploaded at one time, and the system support searching 8
pictures at one time.
Face Database
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Backup
Search by picture
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User's Manual