On erasing DV tapes (this is weird!)

[absinthe]

I've searched the forum a bit for advice on whether or not DV tapes should be/can be erased prior to reuse, but opinions seem split. I'd just like to point out what happened to me with a tape that was almost new (this was the first time it had been recorded over).

My wife took the camcorder on a little trip to a museum with one of the kids and taped over an old tape from Christmas (I had already captured and processed the Xmas video and didn't need it anymore). What resulted was for the most part just fine, but there are two extended sections in the middle of what she taped (she taped about an hour) that have both the old (taped over) and the new footage in a pattern of large stripes. See the attached pic.

Needless to say, a lot of this footage was useless.

I can't imagine what she might have done that could've caused this. It's a JVC NTSC camera and Sony 60 min. tape. I've taped over others of these same tapes and have never seen this.

Ideas? And how about a quick-n-easy erasing method? Or, hey, even a long, drawn-out, complex one would do :).

-abs

[Mug Funky]

IIRC, DV's error concealment is just a matter of repeating the last good decoded block. i think something similar extends to recording, as i've seen something similar before (though not as extreme) when i was recording and my actor gave the camera a bit of a knock. if the camera gets a bad block, it simply doesn't write it to the tape, hence whatever was there last will stay there. if you were to erase the tape, the same thing will probably happen, except instead of the previous recording you'll have black blocks showing through.

perhaps the heads are dirty (doesn't seem likely) or there's some mechanical problem with the camera that hopefully will sort itself out.

are you getting occasional "splats" in the rest of the video where you see a bit of the last recording coming through?

[edit] excuse the lack of readability - i really should get some sleep

[theReal]

Has the tape been in the camera since christmas?

What you have here are serious drop-outs, they usually appear when the camera heads are dirty, the tape is bad or when the camera is damaged.
One way to damage a tape is to leave it in the camera for a long time when it's not used - that's why I was asking if the tape had been in there since christmas...

What you can do is clean the camera heads with a head cleaner tape. Also don't re-use the damaged tape anymore.

[FredThompson]

No question about it, that's a dirty tape.

My experience has been the best option is to treat DV tapes as if they were film with the exception that I record the entire tape with the lens cap on then rewind before actual use. This re-tensions the tape (you'll notice there are no hub-locking piece in miniDV plastic boxes) and puts a timecode on the entire tape.

It is frequently impossible to re-record so the cost of the tape itself is minimal compared to the loss. eCost and many other places online typically have packs of 10 miniDV tapes for $15 or so. I've got about 30 virgin tapes on hand right now.

The desire to re-use the tape does not compare to the impact of a bad recording.

It's a lesson learned the hard way.

[absinthe]

Wow, I'd almost forgotten about this thread. DV forum doesn't seem too popular here :).

There is in fact a good chance that the tape stayed in the camera a long while. I'm sure I traveled with that tape in at Christmas, then came home and just put the camera away. I guess that's a lesson learned.

I just took a trip out to Kansas and made a point to record the lens cap for an hour before I left.

Anyway, camera's pretty new so I doubt there's anything wrong with it. I wouldn't think the heads would be dirty as it was just purchased at Christmas, hasn't been used much, and stays in a nice camera bag. But I suppose it couldn't hurt to run a head cleaner through it. I'll have to make a point to discard that particular tape.

Thanks,

-abs

[theReal]

Don't use head cleaner tapes too often, though (and never more than a few seconds) because they gradually wear of the camera heads!

[captain_video]

I second that opinion. Head cleaning tapes can often be too abrasive and continual use can damage the heads on a VCR (remember those?) or camcorder. I like to use a bulk eraser for any tapes that I want to use over. I think Rat Shack has them for about $30 or so.

[FredThompson]

A bulk eraser won't do a thing to prevent loose oxide or foreign matter from getting on the tape. If anything, it will encourage loose oxide to become more loose by exposing the tape to such a strong directional magnetic pull.

--

Something which hasn't been discussed is to avoid opening the tape compartment in a dusty or humid environment. It's also a wise practice to ensure the tapes are at the same temp as the recording environment to prevent condensation on the tape. Moisture + dust = dirt.

[Gunner]

Yup, that's from a dirty tape or a dirty head.

I also suggest you use the same brand and type of tape for the life of your video camera. Most brands will have various productions methods (Metal evaporated, Cobalt evaporated, Super Advanced Metal Evaporation, Multipuretron vapor-deposited film, etc) and most have different types of lubricant on the tape. If you use one type of tape and then switch to another type, you can get a buildup of junk on the camera head and have problems like dropouts.

Personally, I always use new tapes for anything important that I film. I only reuse old tapes on things that I can afford to lose if it doesn't turn out correct. I also suggest using a high quality tape if you own a high quality camera, like a Sony PD170.