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Volition74au
Volition74au
Inspiring
March 12, 2020
Answered

mixed frame rate workflow

  • March 12, 2020
  • 4 replies
  • 12732 views

Hi Guys, Recently I've changed all my process to shooting at 25fps or multiples thereof as I'm in Australia and this helps with flickering in lights etc. I've only recently got into video creation and was using 24 fps up to a little while ago. I acquired a bunch of overlay's, some are at 23.976fp and this has got me wondering about how PremPro handles mixed frame rates.

I'm wondering a few things. 
- First what would you recommend for a workflow with , mixed frame rates? in PremPro, do all my sequences at 25 then export at 24/23.976, Do my sequences at 25fps and export at 25fps, or other? 
- second, Can someone explain what the program does when you have a 24fps footage in a 25fps sequence? Does it duplicate the last frame, blend the prev and after, ??
- third to help me understand. What happens to say a 25fps or 30fps in a 24 fps sequence. Does it drop, blend, other?

 

I'm intrigued especially when you are using layers. Say a 24fps overlaying a 25fps. Any PremPro wizards can help me gain some insight. I have searched but the details are not clear and people contradict each other too.

This topic has been closed for replies.
Correct answer John V Knowles

Premiere can handle mixing different frame rates. What happens is that depending on the timebase of your sequence (say it's 25fps), any off-rate footage you add will have pulldown added to compensate (and keep audio in sync, etc.) This usually involves a duplicate frame, but for the most part it's relatively seamless and not noticeable. What can be an issue is when you are cutting in footage from the source monitor to a sequence with a different frame rate; you'll likely see that your In and Out points from the Source are off by a frame.

 

My advice is to cut at the frame rate that covers the majority of your footage. Those overlays should be okay to layer on top, but if you have any issues then transcode them in advance and change the frame rate to 25fps. Note that transcoding is different than interpreting the footage, which will alter the speed to conform to the new frame rate.

 

As far as workflow, I would again cut as native as possible (matching the FPS of the bulk of your footage) and then make different outputs at the target framerate. That's where the frame blending setting in the Export window comes into play, and you may want to experiment with the different methods to see which one yields the best results. I personally recommend that editors nest a completed sequence in a blank sequence with the target frame rate and export that; in the past this has maintained all the edit points and sound sync, while providing the proper pulldown cadence on output. So in your example: cut 25fps, nest 25fps in a 23.976 sequence, export to 23.976.

 

HTH,

 

JVK

4 replies

Volition74au
Volition74auAuthor
Inspiring
March 13, 2020

Great stuff and prompt responses from everyone. For the ost part it would seem PremPro does the hard lifting from the sounds. 
I still like the idea of transcoding any of my overlays into say a PAL frequency if they are at NTSC rates.

Thanks. I still think I need to research exactly how NLE's deal with Bringing down say a 30fps into 23.976 or 25 etc. I like having a bit of understanding of how things work under the hood (bonnet for you NTSC people) so to speak.

Ann Bens
Community Expert
Ann BensCommunity Expert
Community Expert
March 13, 2020

If you are in Pal-land stick to Pal framerate.

S
Steve Griffiths
Inspiring
March 13, 2020

Also in Australia!

My 2 cents. Edit at 25fps

Where possible interpret your overlay footage that is at 23.976 to 25fps. Generally the 4% vision speed increase is unnoticable. Audio is slightly noticable.

For decades PAL countries ran 24fps movies at 25fps on TV. (hey 4% faster so they can run more ads!)

 

Of all the annoying issues with transcoded footage I believe the worst is the added frame when placing 24fps into a 25fps edit. To my eye - very noticable bump every second. 

 

If you have to drop any 24/23.976 material into your timeline 'as is' then apply 'speed/duration' set at 100% to that clip and change the 'Time Interpolation' to 'optical flow'. That will generally smooth out the bump without causing any artifacting - though not always.

 

    Warren Heaton
    Community Expert
    Warren HeatonCommunity Expert
    Community Expert
    March 12, 2020

    I'm going supply some additional information here:

     

    Since the live-action footage with sync sound is at 25 fps and the overlays without sync sound are at 23.976 fps, the overlays should assume a frame rate of 25 fps via the Interpret Footage settings (Clip > Modify > Interpret Footage > Frame Rate > Assume this frame rate).  Then, work at 25 fps.

     

    3:2 pulldown is the process of converting 24 or 23.976 to 29.97.  The other way around (29.97 with pulldown to 24 or 23.976) is "reverse telecine" or "pull-up".   In addition to only being 24p to 29.97i, pulldown is a form of format conversion that always goes from the lower progressive frame rate value of 24 to the higher interlaced frame rate value of 29.97 (sometimes reference by the field rate of 59.94).

     

    A 25 to 23.976 change is remastering the frame rate.  There is no pulldown in this type of format converison.  The frame controls for the retiming can involve removing the nearest frame, frame blending, or be motion compensated or just set so the source plays at the new frame rate (usually requiring a pitch adjustment).

     

     

     

    -Warren

     

     

      J
      Community Expert
      John V KnowlesCommunity ExpertCorrect answer
      Community Expert
      March 12, 2020

      Premiere can handle mixing different frame rates. What happens is that depending on the timebase of your sequence (say it's 25fps), any off-rate footage you add will have pulldown added to compensate (and keep audio in sync, etc.) This usually involves a duplicate frame, but for the most part it's relatively seamless and not noticeable. What can be an issue is when you are cutting in footage from the source monitor to a sequence with a different frame rate; you'll likely see that your In and Out points from the Source are off by a frame.

       

      My advice is to cut at the frame rate that covers the majority of your footage. Those overlays should be okay to layer on top, but if you have any issues then transcode them in advance and change the frame rate to 25fps. Note that transcoding is different than interpreting the footage, which will alter the speed to conform to the new frame rate.

       

      As far as workflow, I would again cut as native as possible (matching the FPS of the bulk of your footage) and then make different outputs at the target framerate. That's where the frame blending setting in the Export window comes into play, and you may want to experiment with the different methods to see which one yields the best results. I personally recommend that editors nest a completed sequence in a blank sequence with the target frame rate and export that; in the past this has maintained all the edit points and sound sync, while providing the proper pulldown cadence on output. So in your example: cut 25fps, nest 25fps in a 23.976 sequence, export to 23.976.

       

      HTH,

       

      JVK

      -------------------------------------------------------------------------JVK | Editor/Designer/Software Instructor. Pr, Ae, Ch, Ps, Ai, Id
        Ann Bens
        Community Expert
        Ann BensCommunity Expert
        Community Expert
        March 12, 2020

        I disagree; mixing socalled pal framerate with ntsc framerate is a pita.

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