I was told that if I prerecorded timecode on a miniDV cassette with my Canon XL1s that I would be able to start and stop recording at any point on the tape and still be able to capture the video without confusing the heck out of my capturing software. In my experience that has been true. In fact, Ive been able to rerecord over the top of other sessions and still capture and log using the timecode that was originally recorded --- or at least it seems that way. If this is true, why doesn't the camera over-write the original time code with each new recording? Is there a seperate timecode track that is sensed by the camera and left untouched when rerecording over the same tape? Can someone tell me how this works?

Timecode is only unique (unless you can set it yourself) on the
tape. It isn't some form of date or time or anything. Timecode
layed down on the tape will not be re-recorded. Some decks
might perhaps have a feature to do this. Time and date information
as well as camera settings will always be recorded fresh.

Timecode is recorded from 00:00:00;00 unless the tape is paused and prerolls into existing TC. When you re-record over existing TC it is erased and regenerated by the camera.

The time code does record over, but by striping the tape, you essentially allow for insert editing, and since there's no break if you stop and start without rolling back into your previous shot, the time code will keep going on. If there is no video on the tape, the camera will reset to zero.

A much easier and simpler solution, which puts less wear and tear on the recorder and tape, is to shoot 5-10 seconds of rundown at the end of every shot. Then if you take the tape out and put it back in, just rewind into that rundown a few seconds, and the camera will pick up the time code and keep going instead of resetting to zero. Recording good head and tail on every shot is something all pros do anyway. You need the head for preroll, and you need the tail for the above reason, and so you can remove the tape without fear of damage to your shot. I never pull a tape out of a recorder unless it's in rundown. I grew up in the 16mm film days, so rundown was a way of life. Then I got into video in 3/4 days when tape damage from errant pinch rollers was a way of life, so I kept doing the rundown. Now with consumer and prosumer cameras that don't allow you to reset time code, it's still important, although damage from pinch rollers is, thankfully, rare.

You may want to take a look at this thread:

http://www.dvinfo.net/conf/showthread.php?threadid=18546

Jeff, what do you mean exactly by this "erased and regenerated"?

Ofcourse a new signal is being recorded to tape, so the everything
is being rewritten. But the camera will pick up the old TC and
move on from there (just tested that with my XL1S). Ofcourse if
you start on a blank spot he counter will reset to zero indeed.

Mini DV records the timecode multiplexed with the video signal. Pre-recorded video is erased (along with the timecode) when new video is recorded. New timecode is multiplexed with the new video. If before starting the recording of the new video, the tape was paused over pre-recorded video, the timecode will start numbering frames where the old timecode left off. However, if the new recording is paused over a blank spot, or pre-rolls over a blank spot, the timecode will start at zero again. The thread Edward linked to has a good discussion of timecode as well. During this type of recording (re-recording actually) you have two types of TC, preset and regenerated. Preset TC is where the user selects the exact point the TC will start by presetting the TC numbers. Regenerated TC uses the preexisting TC as the start point.

Okay, then we are all on the same line. Thanks for your clarification.

ok, I assume that DVcam tapes has the time code chip built in.

Some time ago (or perhaps still) you could by miniDV tapes with a memory chip or with out. Now someone told me that the mem chip was so that it tape could keep an linear unbroken timecode, to keep from the annoying resetting of the timecode right in the middle of your tape.

IS that in error?

The memory chip has nothing to do with time code.
The way to keep the time code continuous is to always make sure you shoot a few seconds of rundown at the tail of every shot. If you take the tape out or rewind to check a take, make sure when you start shooting again you do so in that rundown. The timecode will then pick up where it left off. If you go beyond where there is video on the tape, the timecode will, on consumer and prosumer cameras, reset itself to zero.

I can't even begin to tell you how frustrating it is when clients bring tapes that they shot and there is black at the front of the tape.

"Well I can see it in my camcorder when I play it back", yeah, because your camcorder tape path is shorter than the tape path in the professional video deck.

As Bill said, pre-roll and post-roll, at least 5-10 seconds. You'd be surprised how many times you'll use that footage. Sometimes it's an incredible help for filling in ambience sound when you're doing interviews because the person has stopped talking even though the camera is still rolling.

Still another good reason for shooting rundown is that when you eject the tape, you're doing it in a part of the tape that is not needed. I've never had a DVCAM tape damaged in this manner, but I have had that happen in Betacam, and it was a common thing back in the dreaded old 3/4 days. Having preroll time for editing, as Alessandro said, is also essential.