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720p 29.97 field dominance
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Oliver’s explanation is very good. I think that the use of 30 fps based tc has to be with dragging around the NTSC legacy for broadcast. If all of a sudden 60fps tc was unleashed on current broadcast infrastructures a lot of devices that would be totally confused so sending 30fps tc was probably a no brainer. I’m not even sure if there’s a SMPTE standard for 60fps based tc. My guess is probably not, and if there is, it’s probably not used too much today.
In FCP, you can change the tc from base 30 to base 60 fps. That way you can see exactly which frames get removed when working with 60fps tape base captures and removing VFR data when doing so.
If you have an ioHD you will notice that when playing out 60fps material and you have the front panel set to time code, the ioHD will display a frame number, then the next frame will have an asterisk indicating that it’s a different frame (but same tc number). So if you start on frame 01, the next frame according to the ioHD will be :01*. Basically, every frame number has two frames assigned to it.
The beauty of 60fps workflows is that it fits exactly in to 30fps based material. So if you’re shooting 30pN material, this gets translated to 30psf in 60i formats (being 1080i or SD). Shooting 24pN results in 24p material with 3:2 pulldown once going to a 60i based format. Shooting 60fps will turn in to plain old 60i material in 1080 and Sd formats. I wrote something a while ago that explains that concept in more detail.
https://forums.creativecow.net/readpost/98/869490
Hope this helps further your understanding of 720p.
In Oliver’s case it seems that there SHOULD be a way to change the field dom, but perhaps there’s not. Oliver, have you tried a firewire layoff to the 1400 yet as a test? What happens if you shot your 30pN timeline in a 60p timeline, render in the pulldown and layoff (FCP actually handles the proper pulldown in a 720p60 timeline). Does it happen then? What happens if you delay your in point by one frame?
Jeremy
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[Jeremy Garchow] “have you tried a firewire layoff to the 1400 yet as a test? What happens if you shot your 30pN timeline in a 60p timeline, render in the pulldown and layoff (FCP actually handles the proper pulldown in a 720p60 timeline). Does it happen then? What happens if you delay your in point by one frame? “
Jeremy,
It will be next week before I get back to that shop. The director/DP is going to shoot some 59.94 footage with his P2 camera for me to run a few tests. I am going to test 59.94 behavior with 59.94 media as well as 29.97PN media if rendered in a 59.94 timeline. AFAIK, the 1200A that I have access to only has SDI/HD-SDI, not FW. After I run those tests, I’ll be back and post the results. Thanks.
– Oliver
Oliver Peters Post Production Services, LLC
Orlando, FL
http://www.oliverpeters.com -
[Oliver Peters] “It will be next week before I get back to that shop.”
Me too. I would like to check it out for myself as well.
[Oliver Peters] “AFAIK, the 1200A that I have access to only has SDI/HD-SDI, not FW. “
Got ya. I thought you said 1400 by accident. It’s been a while, but I thought the 1200 came with firewire only and you had to outfit it with all the other ports (HD SDI, etc), but maybe I have that backwards and the firewire was an add-on. I forget. At any rate, if it does have firewire, I’d be curious to see if that will fix your problem.
[Oliver Peters] “After I run those tests, I’ll be back and post the results.”
Please do. I am curious as to what you’ll find.
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An update… Drivers were updated and I ran a series of tests before and after this update, as well as on two different machines. I ran tests with 29.97pn media in a 29.97p timeline (FCP adds 2:2 cadence for a 59.94p signal), as well as 29.97pn media rendered in a 59.94p timeline. These various tests were output to Digibeta. All results have been the same.
Field dominance of cuts recorded onto tape appears to be random. You can insert the same sequence multiple times and get different results. It appears that FCP “buffers” the first clip of video by between 0 and 2 additional interlaced fields, so the timeline on tape can be either accurate (F1 dominant), F2 dominant or 1 full frame delayed. This appears to be a result of the additional “length” on the first video clip. All subsequent clips are the proper length, so if the first clip is right, all cuts will fall on Field 1. If the first clip is 1 field longer, all subsequent cuts will fall on Field 2.
AJA support is aware of the issue and looking into it, but I’d bet the problem is with FCP or QT.
– Oliver
Oliver Peters Post Production Services, LLC
Orlando, FL
http://www.oliverpeters.com -
So, when I lay off a 720p 29.97 sequence (which goes to tape at 59.94) to the 1400 deck, then re-capture that tape back in FCP with an NTSC easy Setup, this is the same thing I was seeing. (The randomness made me think I was doing something wrong in my tests.)
If I do this and I determine the cuts are on the wrong field, is there a way to switch that in FCP so the cuts are on Field 1?
2 x3Ghz Quad MacPro
9 GB RAM
Mac OS X 10.5.5
QT 7.5.5
FCP 6.0.5
AJA Kona 3 (6.0.1 drivers)
G-Speed XL 12 RAID -
[Matt Larson] “If I do this and I determine the cuts are on the wrong field, is there a way to switch that in FCP so the cuts are on Field 1?”
No.
– Oliver
Oliver Peters Post Production Services, LLC
Orlando, FL
http://www.oliverpeters.com
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