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View Full Version : DV Guru's Please Help, I'm dropping frames.



bradl
02-16-2004, 01:28 PM
VT3 Patch2, Dual Xeon Supermicro, 160 4 drive Segate Raid, 2GB RDRam, DX 9.0b using Canon GL2

We have a DV tape with some seriously backlit scenes and some burn in or white clip. Our original capture into VT was from a BetaSP. The Beta was a dub of the DV tape using SVHS cable- long story, but essentially the entire tape was need for other purposes than VT.

Decided to try capturing the segments I needed directly into VT. The white clipping is better but I am having other problems and have a few quick questions:

I am getting a jump of a frame or two every 2 to 4 seconds. Mostly noticable with the audio as it tends to drop out or pop as it relocks. I have tried Capture with '... DV capture' (i.e. no codec but DV Stream capture) with Stop on dropped frames (which it does not do) and I have tried with Batch Capture. What could be causing the dropped or missing frames?

Proc Amp settings on the DV switcher input work and I can set them to not white clip so badly, but I read somewhere that the settings aren't really recorded on DV main in. Is that true?

Would the MainActor DV codec make any difference over the Microsoft Codec? I thought that no codec is involved with a straight DV capture.

bradl
02-16-2004, 01:55 PM
More details:

I have rebooted. I have plenty of RAID left. The frames are dropped even as the GL2 plays and VT does nothing but sits there with the signal passing through it. On the GL2 Video and Audio is fine but the output of VT is not.

It is almost like the problem you can have with VHS playing through a Frame Sync. The video runs at a slightly off speed and the FS drops or repeats a frame now and again to compensate.

ScorpioProd
02-17-2004, 12:11 AM
Correct me if I'm wrong, but isn't what you're describing a problem noted with Canon DV camcorders not using 29.97fps but 29.96fps? I remember reading about issues with Canon DV camcorders with some systems before due to non-standard timing. Can you try a non-Canon camcorder as your source and see if the tape still has the problem?

As for proc amping, if you are doing a transfer of the DV file as its native stream instead of uncompressing it, then no, the proc amp isn't actually affecting it at all.

If you mean the MainConcept DV codec, that IS the codec that Newtek has hardwired in VT[3], so you automatically have it.

Though yes, you are correct that transfering a DV file from the tape to the hard drive if you are keeping it DV, isn't actually using a "codec" really.

What if you feed this tape to the VT[3] via Y/C and audio instead of firewire?

Jim Capillo
02-17-2004, 03:48 AM
Originally posted by ScorpioProd

What if you feed this tape to the VT[3] via Y/C and audio instead of firewire?

And try the Y/C thru an external TBC, if you have one.

bradl
02-18-2004, 11:36 PM
Thanks guys for your help. I tried using a Sony DV to playback for DV capture and it was slightly better but still had the problem. It may be as Eugene suggested a Canon problem in the recording. That is really unbelievable that Canon would make that mistake. I did not see our specific model listed as having the 29.96 frame rate so it may be something else, who knows...

I didn't try Y/C in but may when I get time. The footage was shot very poorly and SVHS version we dubbed made it even worse. Going DV straight in was much sharper and I recovered about half the white clipped area so I didn't even try the analog route.

Please pop over to this thread and comment on dealing with high contrast footage while shooting:
Lots of Bad Digital Camera Footage (http://vbulletin.newtek.com/showthread.php?s=&threadid=18428)