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Interlaced or not?
Hi,
I have a couple of questions concerning fields, hoping to clear my mind.
1) Footage shot on 35mm then telecined for video on a digibetacam, i always digitize as PAL 10bit uncompressed, in compositing stage i do some tests in after effects and it always shows that the footage is progressive instead of upper fields. How is that possible?
2) When exporting a movie in after effects or final cut pro as PAL uncompressed 10 bit, and then re-import.. the software automatically interprets as interlaced footage even if the sequence/comp settings were set to progressive prior exporting.
3) After Effects interprets any PAL footage SD or DV as lower-field first, which is not correct. Is there a reason for that?
Finally, can a codec actually produce scanlines in footage, if it is originally progressive? or is it just outputting to a certain amount of tapes that does that?
Thank you.
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9 Replies
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[Mohamed Kamel] ”
1) Footage shot on 35mm then telecined for video on a digibetacam, i always digitize as PAL 10bit uncompressed, in compositing stage i do some tests in after effects and it always shows that the footage is progressive instead of upper fields. How is that possible”
Hi Mohamed,
You are right, there are two fields but they come from the same picture. Both fields have been shoot at the same time and there is not movement that difference them. In an interlaced (PAL) you have 50 fields and 50 different images per second. In your movie you have 50 fields, but only 25 images per second.
[Mohamed Kamel] “2) When exporting a movie in after effects or final cut pro as PAL uncompressed 10 bit, and then re-import.. the software automatically interprets as interlaced footage even if the sequence/comp settings were set to progressive prior exporting.3) After Effects interprets any PAL footage SD or DV as lower-field first, which is not correct. Is there a reason for that? “
These are bad habits. With certain codecs like Prores or any MPEG-2 based format, this shouldn’t happens. Most of the QT based applications interpret DVs as Lower and all the 8/10b flavors as Upper. Anyway, whatever is the application you use, I recommends you check by yourself how the media is interpreted.[Mohamed Kamel] “Finally, can a codec actually produce scanlines in footage, if it is originally progressive? or is it just outputting to a certain amount of tapes that does that? “
Yes. There are applications that from one Progressive Frame can create two fields as they would have been took in different moments. If you have AE, I recommend you to try it with the “Reelsmart FieldsKit”.
It have a “re-interlacing” option and probably is the best tool to do this task.
Cheers,
Rafael -
[Mohamed Kamel] “1) Footage shot on 35mm then telecined for video on a digibetacam, i always digitize as PAL 10bit uncompressed, in compositing stage i do some tests in after effects and it always shows that the footage is progressive instead of upper fields. How is that possible?”
It’s both interlaced and progressive. Confused? That’s ok, you probably should be.
Film cannot be interlaced, digiBeta cannot be progressive. The progressive film frames are laid down on tape with fields. We call that PsF or Progressive segmented Frames. As Raphael says, you won’t see any movement between the upper and lower fields within a singe frame.
[Mohamed Kamel] “2) When exporting a movie in after effects or final cut pro as PAL uncompressed 10 bit, and then re-import.. the software automatically interprets as interlaced footage even if the sequence/comp settings were set to progressive prior exporting.”
Check your render settings in AE. It sounds like you may be rendering interlaced. If so, turn field rendering off.
[Mohamed Kamel] “Finally, can a codec actually produce scanlines in footage, if it is originally progressive? or is it just outputting to a certain amount of tapes that does that?”
You can introduce fields by rendering them or by playing out through a capture card. Either way can be done right or wrong and can look perfect or disastrous.
Arnie
Post production is not an afterthought!
https://www.arniepix.com/ -
A most excellent explanation Arnie, and I’m giving you a big unofficial award for excellent clarity.
David Roth Weiss
Director/Editor
David Weiss Productions, Inc.
Los AngelesPOST-PRODUCTION WITHOUT THE USUAL INSANITY ™
A forum host of Creative COW’s Apple Final Cut Pro, Business & Marketing, Indie Film & Documentary, and Film History & Appreciations forums.
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Thanks for these fast and very informative replies. So how do i work with psf footage? in FCP’s timeline..do i set the sequence settings to no fields or upper? or is there a way or a codec to digitize as psf in the first place?
Arnie, i’m positive that when i output 10bit uncompressed as progressive and my original comp settings are 720/576 Pal progressive and then import back, it reads it as lower fields.
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SD PAL is upper field. If AE has produced a file with fields lower, then the settings are wrong.There is nothing wrong with having AE render with fields as long as they remain upper.
Because SD is interlaced it is best to do everything as interlaced upper field. Stay uncompressed. Avoid DV codec.
Sequence settings should be PAL SD Uncompressed upper field 720 x 576.(assuming you have anamorphic footage from the 35mm not letterbox, then tick the anamorphic box as well.
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Yes but if i interpret my footage (35mm telecined) as upper fields, it kinda of blurs it. Also if i set my render setting to output upper fields it still introduces some blurring or flickery artifacts to my renders. So after testing what works as expected is when i interpert my 720/576 10 bit 422 which was originally shot with 35 mm, as progressive scan as well as outputting it with no fields…unless any other suggestions are out there.
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[David Roth Weiss] “A most excellent explanation Arnie, and I’m giving you a big unofficial award for excellent clarity.”
Suitable for framing! Too bad it doesn’t have Auggie’s picture on it, though!
Arnie
Post production is not an afterthought!
https://www.arniepix.com/ -
Where does it appear blurry? If it is FCP then that is because the FCP monitoring is progressive and not high resolution.
Are you monitoring on an external monitor? If the final result is for broadcast from digi beta, then you need to maintain interlaced upper field and judge only on an external interlaced monitor via a card like Decklink, Kona or Matrox.
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[Mohamed Kamel] “So after testing what works as expected is when i interpert my 720/576 10 bit 422 which was originally shot with 35 mm, as progressive scan as well as outputting it with no fields…unless any other suggestions are out there.”
That’s correct. you should render from AE, Motion, etc. as progressive. In FCP make sure the field dominance is set to “None”. When you lay off to tape, your sequence’s field dominance should still be set to none, but your output settings on your Decklink or Kona card should be set to upper field first.
Welcome to the insane world of broadcast/film engineering. Do not try to understand the logic, for there is none. It’s a series of compromises, accommodations, quick fixes etched in stone and oddball legacies posing as a body of standards. God help us all!
Arnie
Post production is not an afterthought!
https://www.arniepix.com/
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