Recover overwritten CCTV footage from hard drive

I am trying to recover deleted footage from a DVR. I pulled the hdd(Toshiba DT01ABA100v) from the DVR to look at the data in the drive and run carving tools(foremost and scalpel). My problem is that I am unable to mount the hdd. The following are the outputs of some of the commands I tried file -s /dev/sdb /dev/sdb: DOS/MBR boot sector MS-MBR Windows 7 english at offset 0x163 "Invalid partition table" at offset 0x17b "Error loading operating system" at offset 0x19a "Missing operating system", disk signature 0x26a0a7cf mount /dev/sdb /mnt/recdrive mount: wrong fs type, bad option, bad superblock on /dev/sdb, missing codepage or helper program, or other error Is there something I can use to find the file system and be able to mount the hdd?