SlightlyOT: Only every other "stripe" records

earthrisers wrote on 5/27/2005, 5:01 AM
Here's one I'd never experienced before: At a shoot last night of a local children's production, for the first 13 minutes of my tape (in my Sony TRV11 camcorder), only every other stripe of the video recorded.
What I mean is: picture the video field divided into 10 horizontal rows. Only the 1st, 3rd, 5th, 7th, and 9th rows recorded. In the even-numbered rows, what USED TO BE on the tape, is still there. And the sound is totally unusable--a garbled hybrid, I'm guessing, of the old and the new.

After 13 minutes and a few seconds, it suddenly becomes all fine. During the shoot, everything seemed to be working right - the picture in the LCD screen looked perfect. So I didn't see the problem until I got home and began my editing session.

My first wild guess was the "interleaving" isn't working properly -- but interleaving doesn't divide the field only into 10 stripes, does it?

Fortunately this was a 2-camera shoot, so we're not dead. (The other camera was a relatively new, professional-model Sony.) But the other camera was mainly doing wide shots, while I was doing the close-ups. So the first 13 minutes of the show are going to be a bit static, visually. But at least not totally lost.

Anybody have a clue as to the nature of the Alternate Stripes Problem?

Comments

farss wrote on 5/27/2005, 6:28 AM
Seeing as how it came good my best guess is either condensation or a head clog or a mixture of both.
Bob.
tailgait wrote on 5/27/2005, 6:57 AM
Farss--

This happens a lot with any digital tape. The problem may not be on the tape at all, but only when you enter it into the video capture program. It can be caused by the tape having been re-wound at an angle near the beginning, so when it unwinds in capture (or viewing) mode, it does not go over the heads in the same manner that it was recorded. If you look at the tape through the window, you will see some ridges sticking out near the beginning. This means it's not feeding properly upon viewing. This produces alternate lines (usually green) in the output. This may or many not be your problem, but I have come across this a number of times. It pays to use only one type of tape (I use Sony Pro Minis).
Burt
johnmeyer wrote on 5/27/2005, 7:32 AM
I have exactly the same camera, and have had exactly the same problem on and off for the past three years. So far, I've never lost any video as a result of the problem. It only seems to affect playback. Head cleaning tape was suggested, and I used that. Sometimes it seemed to help, and sometimes it didn't. However, I really never believed it was the problem because the onset was so sudden, and then it would sometimes disappear all on its own. Heads don't just clog and unclog like that (if you've ever looked at heads under a magnifier, while you clean them, the oxide buildup is quite noticeable and can sometimes be fairly stubborn to remove.

I believe the actual cause is a corroded switch. Fortunately, at least on my camera, you can often get that switch to work again simply by recording a short section of video on a blank area of tape, or on another tape. Thus, my suggestion is to put the camera into the camera record mode, record five seconds of video, and then switch back to playback. Sometimes you have to do the 2-3 times. I've had this problem for two years, and this cures it every time. Interestingly, I haven't had the problem for almost four months, and I've used the camera a lot in that time.

Now, have you had the "creeping zoom" problem yet? That's where the zoom turns itself on, to the slowest setting, and all your shots now have this slow zoom effect. The solution to that is to hit the camera with one sharp slap of the open hand. I've had this problem for almost the same length of time, and this has worked every time. Not very professional when people see you abusing your camera, but you do what you've got to do.
earthrisers wrote on 5/27/2005, 9:29 AM
Thanks, all -- John, most directly relevantly. But John, you say you never lost any video, but only had a problem in playback. I don't follow that part...

The problem on my tape definitely isn't only a playback problem -- because the show that USED to be on that tape, still IS there, in alternating horizontal strips only, in between the alternating horizontal strips of the NEW show. Fortunately, it's only for those 13 minutes, after which everything got good. Clearly, whatever the problem is/was, must have happened during "record" as opposed to playback.

Our videotaping partners had a problem recently with a broken microphone connection, during a single-camera shoot. Outside of the technical specifics, one obvious lesson for both our partner and us is to avoid single-camera shoots when shooting for a client. (My problem happened during a 2-camera shoot, luckily for me.)

-Ernie

PS: No "creeping" zoom so far. I'd keep my fingers crossed, but then I couldn't operate those tiny buttons...
johnmeyer wrote on 5/27/2005, 9:39 AM
Clearly, whatever the problem is/was, must have happened during "record" as opposed to playback.

I'm not sure I follow your logic. My contention is -- at least based on my own experience with the identical problem on my own TRV-11 -- is that the video on your 13 minute segment is still there, without stripes. I was able, dozens of times, to get video that was playing back with the stripes to playback normally after I had gone to another section of tape, where I could overwrite video I didn't care about, put the camera into camera mode, press the record button, let it record for about five seconds, and then stop it. I then rewound to the "bad" section, and the stripes were gone.

Of course, your problem may be different, and no video actually got recorded on the striped portion. Have you tried my "fix?" Also, have you tried playing the bad portion of the tape in another camera?
earthrisers wrote on 5/27/2005, 9:42 AM
John: The tape I used last night was one that I had also used last week, in recording a chorale concert.

In the tape that resulted last night, in the first 13 minutes, it's like this:
Picture an American flag, with 10 stripes instead of 13. In stripe number 1,3,5,7,9 there is video from last night's concert. In stripe number 2,4,6,8,10 there is video from last week's chorale concert.
riredale wrote on 5/27/2005, 6:24 PM
Sounds like a tape head issue (or the supporting electronics).

Regarding the zoom creep: my little TRV8 began doing this a couple of years ago. Service guy replaced the zoom rocker switch, which had a crack in it. $200.
Quryous wrote on 5/27/2005, 6:36 PM
In the RARE event that I reuse a tape, I black stripe it first in an effort to eleminate exactly this sort of problem. Black striping and THEN recording seems to guarantee better, i.e., full erasure of prior data. I don't usually black stripe otherwise, but this seems good insurance.
JohnnyRoy wrote on 5/27/2005, 6:41 PM
Wow this just happened to me with my Panasonic GS-200. It’s brand new so I doubt dirty heads are the issue (I’ve hardly used it). The problem is identical to yours only it happened 23 minutes into a 44 minute recording and only lasted for 30 seconds. If I stop and start the tape while its happening, I get solid blue horizontal bands because the LCD turns blue when the tape stops. So it is definitely not playing back these bands. Do you think it could be a bad tape? I use Fujifilm miniDV tape (always have).

~jr
Steve Mann wrote on 5/27/2005, 11:44 PM
The head drum actually contains two "heads", 180-degrees apart from each other so that a head will be in contact with the tape all the time.. One reads/writes the even stripes, the other handles the odd stripes. Ten stripes make one frame.

Steve Mann
johnmeyer wrote on 5/28/2005, 7:30 AM
As I said in an earlier post, I tried head cleaning tapes, and even cleaned the heads myself using a chamosis swap, using the same techniques I use to clean larger heads on VCRs. This made absolutely no difference. The problem sometimes would go away after cleaning, but sometimes not.

I can't remember at what point I realized that it was the fact that I was putting the camera into RECORD mode (which I did during cleaning), not the cleaning tape itself. I haven't used the cleaning tape in over a year, and I've been able to "cure" the problem every time simply by switching into record mode.

Since other brands and model probably don't have the same mechanical defect as this TRV11, you still might want to try the cleaning tape. However, tapes don't suddenly go from a perfectly clear picture in one frame to having all the video picked up by one head completely gone. I realize that the information is digital, but even digital degrades more subtly than that, as anyone who has seen digital "dropouts" on their playback knows (noise blocks on the picture).