recapturing problem

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rmack350 wrote on 1/2/2005, 11:20 AM
Don't follow the advice in my previous post. It won't work.

The problem:
Two media files (which constitute entire tapes) have the wrong timecode. We don't need to know why at this point.

The task:
All of the events on the timeline from those two clips need to be slip/slid just enough to make the events right.

Assumption:
All of the events need to be slip/slid by the same number of frames. You'll have to work with the recaptured media. You won't be able to fix the capture because the fixable problem is in the veg file.

Solution:
1. back up the original project.
2. in a scrap copy of the project, switch your ruller to absolute frames.
3. make edit details window visible
4. Choose an event that you believe you'll be able to find the "real" start and end points. Note the current "Take Start" number in the details window. Now either slip/slide the event until it's right or edit the "take start" number directly.
5. Once you've got the event right, note the difference in the take start number.
6. now comes the sad part. For every event from that media file, you'll need to add those frames to the "Take Start" field. You'll then need to repeat this for the events from the other media file.

It should be possible to automate this but unless someone here points you at a script that does the job, I wouldn't get too caught up in it. Look around a little and then if you don't find anything real quick just roll up your sleeves and get going.

Maybe someone here will have a good suggestion to make this less painful.

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Here's another idea. Recreate the problem. Start a new vidcap file, load the problem tape. Rewind it all the way to its stop. Capture the entire tape. I'm assuming that Vidcap wil capture the tape exactly as before, with the wrong timecode. You'll need to name things in exactly the same way.

Now if you open the project, and assuming all the media is offline, you'll be able to point the project to the new media files. The key here is to NOT recapture the media using any program tools. Just do it exactly the way you did it the very first tme.

Rob Mack
rmack350 wrote on 1/2/2005, 11:37 AM
I think that the very head of the tape had a tiny little bit previously recorded timecode. On the first capture, Vidcap read the code and just started incrementing the frame count. Evidently it didn't detect that there was a jump in the time code. Since the tape was captured as one file, Vidcap never had occasion to read the actual timecode again. Rather, it just kept incrementing frames all through the file.

That's my guess. Here are some best practices that ought to help avoid this:

-Set custom timecode on each tape. Normally, you set tape one to start at hour one, tape two to start at hour two, and so on.
-Roll bars before you shoot. This gets all the important stuff away from the head of the tape.
-Use scene detection or log the clips before capture. This will force Vidcap to actually read the timecode every time it starts a clip. It will also limit the extent of foul-ups like this since a problem is more likely to be limited to just one file.

For a wedding, you'll probably have to pre-record the bars and timecode so that the tapes will just be ready to go. I assume you'll also need to have the head parked on the bars when you start to actually record.

Rob Mack
Grazie wrote on 1/2/2005, 12:07 PM
Rob, what do you reckon to this idea? Supposing if one was to "edit" with quantize off? What this mean if I would be somewhere "other" than a "full" frame? Then if one was to recapture, would that mean the recapture wiould be slightly off? What do you think?

Grazie
rmack350 wrote on 1/2/2005, 4:52 PM
G-

I think I know what you're talking about but I don't think I was talking about the "full frames/partial frames" thing.

"Recapture" just goes back and captures the timecode ranges you tell it to capture. I'm making a big assumption about Jimingo's tapes-that they have at least a couple of frames of "other" timecode from a previous use sitting there at the start of the tape. In my imaginary world, he/she started recording the wedding footage a little past these few frames. Now, on recapture, Vidcap starts at the very beginning and for some reason uses the older timecode as a start point and then just starts counting frames rather than checking the actual timecode. I think there must be a jump in the timecode, probably right at the head of the tape. Maybe it's just one frame.

Since the captures are done as single files, I suppose Vidcap could just get the initial timecode and then just count frames as they tick by. If so, it would never have to read timecode again since there's only one clip.

This is all hypothesis. I haven't tested any of it so it doesn't rise to the high level of being a theory (Theory being something supported by facts and useful for making accurate predictions).

Personally, I've never had a problem like this. Probably because I don't capture entire tapes and always get tapes from the shooter with bars at the head. I get plenty of other problems, though.

Rob Mack


jimingo wrote on 1/2/2005, 10:55 PM
It worked! I recaptured the video as a full tape without batch capturing and then replaced the file as Rob suggested and it worked. The same wrong timecode appeared (which is a good thing). The only thing I don't understand now is why it is reading a different timecode when I capture the full tape. All the tapes are brand new. There can't be any other timecode on them. This was a wedding I edited for a different company and their shooters hardly ever put bars in the begining of their tapes. From now on, I'll just capture their tapes from a couple of seconds into the video, instead of from the begining since that's what's causing this timecode mix up somehow.

Thanks for the help
-Jim
Grazie wrote on 1/2/2005, 11:02 PM
"From now on, I'll just capture their tapes from a couple of seconds into the video" . . . .oh yes! Let them timecodes start appearing . . nice clean and even. Great thread! K.I.S.S. always . . well mostly, works for me!

Glad you gotta a result - G
rmack350 wrote on 1/2/2005, 11:20 PM
Capturing from a few seconds in should do it. I don't really know what's causing the problem (obviously) but I thinkyou'd be well served to turn scene detection on the next time you capture. Then, if a clip has a problem you won't have to recapture the entire tape. Now would this timecode problem have rippled through most of the events in the project.

It's good news! I've been on the edge of my seat!

Rob Mack
Grazie wrote on 1/2/2005, 11:56 PM
Ho! I didn't read the bit about not capturing with scene detection on? I must have slipped over that one. And yes, I keep scene detection on for "take-dependent" work.

Great stuff! - Grazie