MiniDVs as a Backup Medium?

Matey-O asks: "Having purchased a MiniDV camcorder for the impending arrival of my twins (I suspect a majority of camcorder sales HAVE to be bought by new parents), I also purchased the firewire connection kit. Based on the software estimates on how much uncompressed video can be stored on the harddisk, it looks like a 60 minute MiniDV cassette holds about 15 Gb. Since the PC can control the camera, and the transfer is billed as lossless, has any work been done on using MiniDV as a backup medium? One Cassette looks like it'd store ALL of my important info, and at $5 per, it'd be pretty economical too." Reading this definition, it looks like the submitter may be mistaken about the 15GB size, and the Backfire pages at Sourceforge indicate a more realistic figure of 12GB. Backfire itself looks like it might be the project the Matey-O wants, but the last update is from April of 2000. Has anyone taken up this idea and tried this particular backup path, before? Is it a practical alternative to your standard computer tape drives?

Comments

tape backup

[TheSHAD0W]

Tape backups for PCs have been around for literally decades, and they've always been problematic. I'd really have to recommend against using a MiniDV backup solution, especially one where neither hardware nor tapes are meant for data back-up. The transfer may be "lossless", but the tape may not be; a drop out on the tape that would cause a slight blip on the video would ruin your data unless you used a sophisticated error correction scheme (which would also use up a lot of the data space), but even a great ECC might not avoid the many dips that might be present on a tape meant for video use.

Who's smoking? Frame drop != data loss

[FeatureBug]

A dropped frame is a visual symptom. It doesn't tell you how much data was lost. A dropped frame doesn't necessarily mean all of the data or even any of the data for that particular frame is actually unreadable on the tape. Dropped frames have many temporary causes like dust particles on the magnetic tape, faulty cables, cosmic rays or strong RF interference hitting the electronics, buggy software, drivers or slow CPU in the case of computer DV decoding, etc. Granted, it could be a patch of tape is really damaged, causing tens or even x hundreds of bits to be lost.

Whatever the cause, a camcorder's builtin error correction can usually recover from small amounts of bad data. That's good enough for making videos but not for making backups. By using an additional layer of Reed-Solomon error correction as used in Rsbep DV Backup bad data up to 12240 consecutive bytes can be recovered, not counting any additional lower-level bad data the camcorder's internal FEC may have seen and corrected. The Rsbep guy found he could make up to 0.5mm diameter pinholes in the tape without losing data! I've seen professional data-grade backup tapes lose data after damage to a much smaller spot of 0.2mm diameter. I would say backups on MiniDV with RS error correction are feasible and cost-effective at 4USD/10GB. At 3.6Mbps, DV backups are also fast.

IANAFS but I've used a lot of different MiniDV equipment and I've never had a problem like yours with dropped frames. Maybe your DV camcorder has dirty/misaligned/worn heads any of which could cause dropped frames.