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Field edits on 720p to 1080i on Kona output

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Jeff Krebs
Field edits on 720p to 1080i on Kona output
on Mar 2, 2010 at 4:46:32 pm

Hello,
I have received a timeline on FCP 7.x that is 720p 59.94. Opening it up it says it is a 59.94 timebase. So far so good. I am using the Kona card to output to another device for colour grading. I could not get the output to tape function working. It would just show me a still frame on output. When outputing live it was working fine. So I output live.
Now I have noticed that 90% of the outgoing shots before each edit have a field edit on it. That is field 1 is the previous frame of the outgoing shot, field 2 is the next frame of the incoming shot. When I inspect the timeline on the finalcut, edits are correct. It seems to be pulldown added as the conversion happens from 720p to 1080i. Even though the timebase of both are 59.94. (If this was a 23.976 timeline where pulldown is added to make NTSC I would understand) but this is baffling me.

Thanks for any info or explanation.
Jeff

Jeff Krebs
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Jeremy Garchow
Re: Field edits on 720p to 1080i on Kona output
on Mar 2, 2010 at 5:43:03 pm

you are taking 60p (60 full frames a second) and going to 60i (60 fields per second, or 30 frames per second). Each p frame is going to get segmented and mapped to a field. With 60p material, that will mean it will translate to true 60i material (or 1080i 29.97). What you are seeing is correct.

Even though both are running at 60Hz, the way the frames are made up is different, one is true p (one progressive frame at a time), and one is interlaced (one field at a time, 2 fields per frame). If you need to keep a progressive workflow, you would have to make a 1080 60p dual link master where each 720p frame would be mapped to a corresponding 1080p frame.

Use the Kona control panel to make a 1080i cross convert.

Jeremy


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Jeff Krebs
Re: Field edits on 720p to 1080i on Kona output
on Mar 2, 2010 at 6:15:16 pm

ahh,
okay, since I don't have dual link and I have to deliver a 59.94 1080i master, I had no choice but to output to an Avid uncompressed using the secondary output from the Kona and fix the field edits by adding a freeze where I saw the split field. (pain in the butt though) I then brought it into a Lustre for grading and all was fine.

Thanks
Jeff

Jeff Krebs
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Jeremy Garchow
Re: Field edits on 720p to 1080i on Kona output
on Mar 2, 2010 at 6:51:30 pm

Just curious, but why not just grade 720p and make a 1080i master from that if you need to stay progressive through the grading process?

Jeremy


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