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NotSoSane
NotSoSane
Participant
August 2, 2019
Answered

24p 30i interlacing and strobing disaster

  • August 2, 2019
  • 3 replies
  • 1132 views

I have a very convoluted and complicated issue.  I will do my best to explain what is going on. I am aware that this is a decade old issue and software has changed a lot. I am also aware that this may not be fixable and I was naïve when I created the original project.

In 2007 I shot ten feature films on the Canon XL2.  I shot in 24p and edited on Final Cut Pro HD (7). Unfortunately, when I rendered out the final films, I rendered in 30i. I think, I'm still trying to verify, definitely 30 just don't know if 30i or 30p).  When that file was rendered and burned to DVD I receive horrible interlacing in between cuts and some fast motion. When I render the 30i into 24p mp4, I get horrible strobing on high action shots along with the interlacing.  I have decided to go back and re-edit the entire film saga but have lost some of the original tapes, so I'm forced to use some of the original render at 30fps, and mix with the raw 24p footage that I have been able to recapture.  I still received horrible strobing on a 24p timeline and have changed to a 30p timeline and it LOOKS like it may be working.  The final render this time around will be mp4 for streaming services, but can be rendered in any format that I choose.  Can anyone advise me on 1) what is going on, and 2) will there be an issue on my final render (the previews on the 30p timeline seem to be okay so far).  Below is my theory of what is happening, can anyone confirm?

Theory: When I originally rendered out the 24p footage onto a 30fps video, it created additional frames.  When I took the 30fps video and rendered it into 24p video, it would drop original unique frames while keeping the duplicated frames from the original rendering, which causes the stobing.  As for the interlacing in between cuts and fast motion, I don't know what's happening or how to solve the issue.

Thank you for the long drawn out explanation I just want to be as descriptive as possible.

    This topic has been closed for replies.
    Correct answer Warren Heaton

    It sounds like you didn't remove the 3:2 pulldown when you captured the DV footage in Final Cut Pro.  If you had, your FCP Sequence would have been p24 instead of i60.  Finishing on DVD, this would not be an issue as NTSC DVD-Video is also i60.  (Note: for the purposes of what I'm discussing here, 480i60, 480i30, 480i59.94 or 480i29.97 are all the same thing.)

    DV camcorders that shot p24 recorded i60 with 3:2 pulldown to tape.  If this isn't removed (that is, if you don't pull the footage up), then you have clips running at i60 that contain 3:2 pulldown and this can cause problems later in your workflow.  Fortunately it can be removed during capture or after capture.

    Side question: are you confident that none of the source footage was recorded at i60 instead of p24 by accident? 

    For the footage that you've recaptured, make sure it has been pulled up to p24 (it may show as 23.976).

    For the footage that you're extracting from the DVD, you should still be able to remove the 3:2 pulldown; however, it has to be done shot by shot.  Also, hopefully you've used something like DVDxDV to rip your DVD-Video VIDEO_TS data back to a movie file.  You'll want to go from VIDEO_TS to DV-NTSC or better yet Apple ProRes422.  You can make sub-clips in Premiere Pro or each shot.  Rather than have Premiere Pro remove the 3:2 pulldown, I'd send the sub-clips over to After Effects where it can guess at the cadence (the pattern used to get from whole frames to whole frames and split frames during 3:2 pulldown).  Render p24 out of AE and bring those back into Premiere Pro.

    Again, the 3:2 pulldown removal has to be shot by shot.

    -Warren

    3 replies

    NotSoSane
    NotSoSaneAuthor
    Participant
    August 8, 2019

    Thank you all for your help!  Both answers helped guide me down the right path.  The 30fps timeline seems to be working very well.  Whether I use the 24p footage or the 30i master render.  After a render out to mp4, I'm no longer getting the interlacing or strobing.  It looks like it was just happening on the export to DVD.  Trying to do anything on a 24p timeline does mess it up and give me the storbing, so I'm just going to stick with the 30 timeline now.  Thank you, this is an old project and it's really more of a personal crusade at this point, but it's a project that meant a lot to those of us who worked on it.  I'm glad we can get rid of that strobing.  Thanks again for all your help!

    Warren Heaton
    Community Expert
    Warren HeatonCommunity ExpertCorrect answer
    Community Expert
    August 2, 2019

    It sounds like you didn't remove the 3:2 pulldown when you captured the DV footage in Final Cut Pro.  If you had, your FCP Sequence would have been p24 instead of i60.  Finishing on DVD, this would not be an issue as NTSC DVD-Video is also i60.  (Note: for the purposes of what I'm discussing here, 480i60, 480i30, 480i59.94 or 480i29.97 are all the same thing.)

    DV camcorders that shot p24 recorded i60 with 3:2 pulldown to tape.  If this isn't removed (that is, if you don't pull the footage up), then you have clips running at i60 that contain 3:2 pulldown and this can cause problems later in your workflow.  Fortunately it can be removed during capture or after capture.

    Side question: are you confident that none of the source footage was recorded at i60 instead of p24 by accident? 

    For the footage that you've recaptured, make sure it has been pulled up to p24 (it may show as 23.976).

    For the footage that you're extracting from the DVD, you should still be able to remove the 3:2 pulldown; however, it has to be done shot by shot.  Also, hopefully you've used something like DVDxDV to rip your DVD-Video VIDEO_TS data back to a movie file.  You'll want to go from VIDEO_TS to DV-NTSC or better yet Apple ProRes422.  You can make sub-clips in Premiere Pro or each shot.  Rather than have Premiere Pro remove the 3:2 pulldown, I'd send the sub-clips over to After Effects where it can guess at the cadence (the pattern used to get from whole frames to whole frames and split frames during 3:2 pulldown).  Render p24 out of AE and bring those back into Premiere Pro.

    Again, the 3:2 pulldown removal has to be shot by shot.

    -Warren

    NotSoSane
    NotSoSaneAuthor
    Participant
    August 2, 2019

    Thank you.

    First, the render of the old original file I'm working with is a Quicktime MOV, not the DVD rip.  Haven't touched that.  I rendered out the entire movie into an MOV file 9with separate dialogue, music and SFX tracks).  Still trying to find out if it was p or i.

    Second, it's very likely I got the pulldown wrong back in the day.  I had so many options and there wasn't the slew of information back then on internet as there is today and had like 4 different pulldown options.  I'm sure I selected the wrong one. There was like 2:3:3:2, 2:3:2 and a few others. I had no idea which one was the right one. 

    Third, it's very likely that at least SOME of the original footage was recorded on 30i as sometimes I'd have to shoot something else and I'd forget to switch back to 24p when we started shooting again.

    Fourth, The footage that I have RE-captured is showing as 23.976 on the premiere project media window.  The original movie MOV file is showing as 29.97.  I did send a clip for some visual effects over to After Effects from the timeline and the interlacing was absolutely horrible at first, but when I rendered out the preview it looked perfect. I will render out into an mp4 the file this weekend and see how it looks and if I get the interlacing.  Hopefully I won't have to split each and every clip. they are 10 features so I'd have to replace the razor in the blade tool a few dozen times, haha.

    Warren Heaton
    Community Expert
    Warren HeatonCommunity Expert
    Community Expert
    August 2, 2019

    ***** Still trying to find out if it was p or i.

    The easiest way to do this is to drop the file into After Effects.   Look at the Poster Preview at the top of the Project Tab for the frame rate.  AE will show the frame rate and if AE detects 3:2 pulldown, it will indicate it.  Or if it detects fields, it will indicate it as well (you'll see the message "Separating Fields").  You'll also be able to open the clip in the Footage pane and advance though it frame by fame (or field by field).

    ***** There was like 2:3:3:2, 2:3:2 and a few others. I had no idea which one was the right one. 

    This was important.  One allows you to pull it down and pull it back up and maintain all of the picture information.  The other one is meant for finishing and is a one way trip.  (I forget off-hand which is which.)

    ***** it's very likely that at least SOME of the original footage was recorded on 30i as sometimes I'd have to shoot something else and I'd forget to switch back to 24p when we started shooting again.

    This is... bad.

    ***** Hopefully I won't have to split each and every clip. they are 10 features so I'd have to replace the razor in the blade tool a few dozen times, haha.

    There's the right way and the wrong way.  The right way usually take more time.  You should have to segment the footage that you could not recapture and the focus on getting that to 23.976 as best as possible.

    bucksommerkamp
    Community Expert
    bucksommerkampCommunity Expert
    Community Expert
    August 2, 2019

    It sounds like this might a great chance to do some experimentation to see how fixable some of it might be. I’d start here:

    Learn interlacing and field order in Premiere Pro

    Take a short bit of one of the clips, apply different settings from these (de-interlace, change field order, etc.) and export for comparison. You might need to switch around for different things (action shots might need different treatment than slow dissolves, etc.). I think you have the tools to fix this already built-in, but will take some trial and error to see which ones work best with different scenarios.

    Please keep us posted!

    Buck

    NotSoSane
    NotSoSaneAuthor
    Participant
    August 2, 2019

    I will try and experiment this weekend.  So far the preview files seem to render without the issue with a 30p timeline, but I have yet to render a completed file.

    Warren Heaton
    Community Expert
    Warren HeatonCommunity Expert
    Community Expert
    August 2, 2019

    You should avoid a 30p Timeline.  There's no good path to 30p from 24p nor from 30i with 3:2 pulldown.

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