Without data encryption all digital data, including Blue Ray, can be retrieved no matter the format. Tapes offer no encryption.
While Mac and Windows are offering software utilities by default to encrypt entire hard disks and drives (FileVault and Bitlocker, respectively), there have been knownvulnerabilities in both. Generally, many security experts have found that these default hard disk encryption tools are not fool proof, and can be cracked.1
TrueCrypt can be used to encrypt your video files. Available for all platforms, you can carry TrueCrypt files on any device. Picture or video files can be camouflaged as different file types by using TrueCrypt, and stored on any device including data DVDs. For more information: http://www.truecrypt.org/docs/?s=tutorial.
Advanced use of TrueCrypt can also allow you to create ‘hidden’ volumes. If you wish your storage to be hidden as well as encrypted, you must store the container in a non-journaling file system, such as FAT32. For more information: http://www.truecrypt.org/docs/?s=hidden-volume-precautions.
The one thing to remember about encrypting data is that it increases the size of your files, which brings in further issues on the storage capacity that you will need to have available.
For more information see: https://securityinabox.org/en/chapter-4 (English) and https://securityinabox.org/ar/chapter_04 (Arabic)
1 See: http://reviews.cnet.com/8301-13727_7-57370628-263/security-concerns-on-apples-filevault-decryption-via-firewire/; and http://www.ghacks.net/2009/12/07/bitlocker-encryption-not-100-secure-after-all/