Can what's on a tape cause dropped frames?

farss wrote on 9/22/2004, 1:20 AM
Yesterday I captured around 9 hours without a single dropped frame.
Today different tapes from a different camera at a different venue and I seem to be getting bursts of dropped frames. All the material is from 184 min DVCAM tapes recorded in DVCAM. I haven't been over the material as yet to have a good look at it (yawn!!) as I'm still capturing more of it. What also makes me a bit suspicious is these tapes seem to have been used before which is right pain cause even if I only need the first 2 hours there's something all the way to the end. Might be a job for SCL.
I mentioned the camera and the venue becuase I've had some nasty head clogs show up at the start of the first tape on the day. This is football and the games start early in the morning when the air is very cold and humid.
So I'm wondering if having the digital data getting screwed up coming off the tape could cause VidCap problems. The capture system is pretty marginal for the task but after I got some firewire dramas sorted out seems to be holding up OK until today.

Bob.

Comments

Grazie wrote on 9/22/2004, 1:32 AM
Do you "normalise" the tension on/from others tapes? On your machines run them forwards, all the way thru' and then back again? Could be . . might be worth a try . . could be mechanical . ..

Grazie
farss wrote on 9/22/2004, 1:42 AM
I know I 'should' do that although this is mostly an issue if they've been subject to a big change in temperature, they've been in the same place for days.
I'm just recapturing one and getting almost identical results in terms of dropped frames, curious!
Also forgot to mention, I have DV Scene Detection ON, last try I got 99 clips, yipes, I think not. I've wound the minimum clip length up to 5 secs to see what difference that makes. What's a bit odd is it seems when these cameras go into record there's a minor head clog, you know, a few frames of little stars. Maybe at that point the TC is all over the place and VidCap is going nuts.

Bob.
apit34356 wrote on 9/22/2004, 6:41 AM
farss, you probably already know this, but being in a field with cold and humid controls, the players are kicking up dust, mold particles, pollen.etc. so the tapes are probably dirty, as well as the camera head.
farss wrote on 9/22/2004, 8:13 AM
Oh yes, I know that only too well. I wasn't the cameraman, just the dumb shmuck trying to fix up the mess.
BTW, one little trick I learned about Sony cameras. If the camera lights up the Condensation alarm the ONLY way to reset it is to remove the battery.

But in the case I was talking about, in the space of 3 matches the cameraman created 93 clips, the camera me thinks is abit marginal, I found at least one major dropout and I'm suspecting that each time the camera went in and out of record VidCap sees dropped frames for a brief period. If there are actual dropped frames within a clip they sure stick out and I haven't found one in a clip but at the end of the capture VidCap reported around 130 frames were dropped.

Bob.
johnmeyer wrote on 9/22/2004, 9:24 AM
I think you said that you have done a complete FF and Rew of the tape, and then recaptured. If not, that is the first thing to try.

Another trick on my old Sony is to go to a portion of the tape that has video you don't care about (like the very end of the tape), put the camera in record mode, and then record 1-2 seconds of video. I cannot explain what this does, but it often solves problems I have with tapes that won't capture properly (i.e., that have those annoying single pixel dropouts, or which have large horizontal bars). Head cleaning doesn't solve these problems most of the time, but doing this 1-2 second record does.

I assume you have tried capturing the tape from a different camera.
Erk wrote on 9/22/2004, 2:27 PM
Ditto johnmeyer's comments about putting my Sony TRV-720 in record for a few moments to clear up problems. Not infrequently, I get a "head cleaning" warning when recording in through the analog converter, which my head cleaner doesnt' help with. I'll pop in a spare "junk" tape for this purpose, and it almost always clear it right up.

Greg
farss wrote on 9/22/2004, 2:57 PM
Interesting ideas guys and thanks for the heads up.
None of this was recorded in my cameras, that I should be so wealthy as to afford such cameras. They just give me the camera tapes to make into DVDs and I'm capturing the footage on a DSR-11, one of the few decent bits of kit that I own (apart from Vegas!).
But from what the client said one of the cameras was a hired unit so that may explain a few things.
I went through the last tape I captured carefully and I cannot see any signs of true dropped frames so I'm suspecting it's when the camera goes in/out of record that the problem occurs. I must say I don't see this problem on consummer cameras but I've seen it before I think on pro cameras, curious issue. The other thing that I've seen bring it one is crashing into record, switch camera on and before it's laced the tape hit record.

Bob.
B.Verlik wrote on 9/23/2004, 5:21 PM
That's exactly the point where I lose frames when I capture old analog tapes through an A/D converter. Right where a new recording starts. Obviously mine doesn't have a TBC. In your case the camera probably wasn't setting the tape at the right location for the next recording and if it was a previously used tape, provided a source of digital artifacts and glitches. Of course, I'm only guessing, as I've come to respect your wealth of knowledge.
farss wrote on 9/23/2004, 5:26 PM
Since my original post I've captured anothe 20 hours or so of footage on exactly the same setup and not one dropped frame. But these tapes are from another camera.
I've also reviewed the footage and 99% of the dropped frames must have been during camera startup as there's none in the actual footage. Seems this cameraperson did did a lot of stop / start shooting, about 35 clips in a 30 minute game. In between they were running after the action so that wouldn't have helped either.
If you're capturing from old VHS without a TBC all I can say is Good Luck! Dropped frames will be only one of the problems.

Bob.

B.Verlik wrote on 9/23/2004, 5:47 PM
So far I've had pretty good luck, but maybe that's because most of my transfering has been from S-VHS tapes. It's usually only a problem where a new recording starts on the tape. The worst problem I had was when I transfered a Hi-8 tape and any time the camera was shaken a little, it would drop frames. It was concert footage and trying to patch it all together afterwards was a real joy. Also, I almost hate to admit it, but I've been using a 'datavideo DAC-100' A/D converter, which seems to work pretty well, but I never see anybody comment on this unit. (I had to take the cheap route.) It may not be a Canopus ADVC-100, but it seems pretty good at $185. US, including shipping. (I wish I could afford the ADVC-300, but that's down the road right now.)