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Pull down added during digitize

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thebishop
Pull down added during digitize
on Nov 12, 2007 at 8:34:19 pm

I'm digitizing 23.98 footage from HDCAM into Final Cut. The signal out of the deck is 1080sp23.98.

I am trying to capture it as 23.98fps DV yet when i play back the captured clip, a pulldown is clearly added. The timecode readout in Final Cut shows me PD timecode. The burn in on the screen shows me native.

What could be causing this?



Powermac G5 Quad 2.5
3 GB RAM
Quaddro 512MB Video Card
Kona LHe


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JeremyG
Re: Pull down added during digitize
on Nov 13, 2007 at 1:02:24 am

Because a Kona cannot play out to 23.98 dv to any sort of monitor so it's adding the pulldown on the fly when you play back out.

Make sense?


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thebishop
Re: Pull down added during digitize
on Nov 13, 2007 at 1:22:26 am

I understand that. But the image itself is interlaced in quicktime or FCP. It has nothing to do with output.

Powermac G5 Quad 2.5
3 GB RAM
Quaddro 512MB Video Card
Kona LHe


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JeremyG
Re: Pull down added during digitize
on Nov 13, 2007 at 1:52:10 am

A ha, I got ya.

Have you set the frame rate as 23.98 and not 29.97? If you have setup to strictly down-convert the material to dv, the Kona is going to add pulldown. You have to setup your preset to capture dv @ 23.98. I am actually not sure if this will work. I DO know for a fact that you can go 1080 23.98 to 720p23.98. Why don't you do that? That data rate will be low (around 6 or so MB/sec) if capturing @ DVCpro HD 720p23.98. I know the Kona does support 23.98 SD as an intermediate frame rate, but not sure if it will let you capture it. You should modify a preset, setup your control panel to test it.

Jeremy





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thebishop
Re: Pull down added during digitize
on Nov 13, 2007 at 2:01:35 am

The deck won't let me down convert with center crop out of the SDI or HDSDI plugs at 23.98. SDI downconversion only supports 29.97 for some reason. And, it seems that the Kona LHe doesn't support real-time downconversion. I could be wrong about that, but I don't see the setting in the control panel. I only see downconversion to an SDI stream.

Here's what I ended up doing:

HDSDI 1080Psf 23.98 into FCP at DVCPRO HD.

I then created a preset in Compressor that gave me 720x486, 23.98fps, Photo JPEG with a 4x3 Center crop.

All the timecode remains and it plays back identical to the higher res version. Whew!

That only took 6 hours to figure out.

Thanks for your help.


Powermac G5 Quad 2.5
3 GB RAM
Quaddro 512MB Video Card
Kona LHe


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JeremyG
Re: Pull down added during digitize
on Nov 13, 2007 at 2:05:24 am

[thebishop] "And, it seems that the Kona LHe doesn't support real-time downconversion."

It most definitely does. Simply select an SD easy setup within FCP and the Control panel should do the rest.

Jeremy


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cmlundy
Re: Pull down added during digitize
on Nov 13, 2007 at 5:09:06 pm

Assuming that card does the downconversion, as Jeremy says it does, the capture is simple. I use a Kona 3 and do all the time. You will need to duplicate and modify one of the Kona 525 23.98 capture presets. If you look in the setting for it you will see the Input Digitizer is most likely set to 525 29.97. You will want to change that to 525 23.98. Now 1080p 23.98 signal coming in to the card will be downconverted to 525 23.98. Make sure the Kona Control panel has Primary as 525 23.98 and Secondary as 1080p 23.98 and viola, you'll see the downconvert. One gotcha I have found with this conversion is that the card captures a frame prior to the In point you set for capture. Doesn't matter if you futz with capture offsets in Device Control, it won't help. If timecode accuracy is important for your project you will need to Modify > Timecode of clips after capture by 1 frame (easily down in FCP).

Chris Lundy
PostWorks, NY

I have informed AJA of this frame accuracy issue and have not seen any movement on it.


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JeremyG
Re: Pull down added during digitize
on Nov 13, 2007 at 5:21:20 pm

Thanks for confirming that, Chris. I thought it was capable.

Jeremy



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thebishop
Re: Pull down added during digitize
on Nov 13, 2007 at 5:24:16 pm

Thanks so much!

Powermac G5 Quad 2.5
3 GB RAM
Quaddro 512MB Video Card
Kona LHe


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