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Alex293591989qhl
Participant
June 24, 2023
Question

Advice on a pretty extreme case of mixed frame rates?

  • June 24, 2023
  • 1 reply
  • 2989 views

I'm creating a sequence that consists of hundreds of clips of various frame rates.  These are sports clips, many of them rare and from different countries, that were gathered from various online sources.  So unfortunately there isn't a great option for getting all this footage in the same frame rate.

 

Below, I've included a breakdown of the clips by frame rate.  I'd be grateful for any advice on how best to proceed, e.g. with regards to sequence settings and everything else.

 

In case it's helpful, the end product will be a YouTube video.  In an ideal world, I'd love to be able to show the higher frame rate content as is, as it looks much better since this is sports footage, but I realize that might not result in the best overall end product.

 

 

***

 

 

23.98 fps: 11 clips (4%)

 

25 fps: 82 clips (27%)

 

30 fps: 120 clips
29.71 fps: 2 clips
29.94 fps: 2 clips
29.97 fps: 21 clips
30.12 fps: 1 clips
SUBTOTAL: 146 clips (48%)

 

50 fps: 29 clips
49.92 fps: 2 clips
SUBTOTAL: 31 clips (10%)

 

60 fps: 29 clips
59.94 fps: 8 clips
SUBTOTAL: 37 clips (12%)

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    1 reply

    Remote Index
    Remote Index
    June 24, 2023

    Hello Alex etc.,

     

    I suggest the first step is to clarify the issues you are facing.

     

    1. Scaling and Cropping (Resolution & Aspect Ratio)

    You haven't said what the various resolutions here are, but some sort of upscaling and/or cropping may be necessary.

     

    2. Converting Interlaced or Progressive Frames

    You haven't said if all the footage is progressive, but I suspect it may be mixed (some interlaced). So you may have to do some conversion or deal with interlacing issues.

     

    3. Standardizing Frame Rates

    The 5 categories of footage you've outlined is a good start - the next step being to standardize the frame rates.

     

    4. Frame Rate Conversions

    ... 5 different frame rates is still a lot!

     

    I'll ignore 1 and 2 above for the moment (since you did not ask about them).

     

    STANDARDIZING FRAME RATES

    Arguably, this step is not necessary (and arguably you won't see any tangible results on short clips), but I'd recommend standardizing - it will produce more consistent results on long clips and will also help you organize options if things get complicated down the line.

    I suggest using the Interpret Footage command for this in Premiere Pro. Unfortunately, using this command is not compatible with using the proxy workflow in Premiere Pro, but if you are not using that it shouldn't be an issue.

    In the project window, select each clip and right click Modify > Interpret Footage and use the "Assume This Frame Rate" option. You will then change each clip to one of the 5 categories you have grouped in your list above. But this is where you have a decision to make.

    I suggest using one of two sets of frame rates:

    - 24fps, 25fps, 30fps, 50fps, 60fps ("whole" frame rates)

    - 23.98fps, 25fps 29.97fps, 50fps, 59.94fps ("fractional" frame rates)

    There's an argument that the "whole" frame rates are a better choice (because there are no standard "fractional" frame rates near 25fps and 50fps to match the rest), but either option will work.

     

    "MASTER" SEQUENCE FRAME RATE

    In general, you will get better results from converting lower frame rates to higher frame rates. That's not universally true, but it's a good genearalization to start with. (I'd be interested if anyone has advice otherwise).

    Therefore, depending on your decision above, you will either choose 60fps or 59.94fps as your "master" framerate (ie. this is the highest frame rate of your clips which you have standardized). This will be the framerate of the sequence you will be editing / finalizing in. Everything will be converted to this frame rate.

    The next question you will face is how to do your frame rate conversions

     

    PREMIERE PRO FRAME RATE CONVERSIONS - 3 OPTIONS

    A. "QUICK AND DIRTY"

    If you simply drag your clips (which have had their frame rates standardized to 1 of 5 fps rates) into the timeline, Premiere Pro does what I call a fast and dirty frame rate conversion. It will simply duplicate (or drop) frames to acheive the necessary frame rate. (You may need to render). This may produce satisfactory results for you needs.

    B.  "FRAME BLENDING"

    If you right-click on a clip in your master timeline and choose "Clip Speed/Duration" you will see options for "Time Interpolation" at the bottom of the dialog. The above "quick and dirty" method is the default (known as "frame sampling" here). The second option is "frame blending" which does what it says ... combining or blending frames to create new ones. You probably have to render the clip after.

    C. "OPTICAL FLOW"

    This is the third option in the dialog. The above two options do no destroy or create new frames - this option uses software magic to analyze existing footage and create new frames as necessary. You will need to render the clip after. Depending on the footage, it will either be amazing or heavily artefacted (unusable) or somewhere in between.

     

    FRAME RATE CONVERSIONS OUTSIDE PREMIERE PRO

    The other option to consider is whether you want to use other software or hardware to effect the frame rate conversion. Every method has strengths and weaknesses.

     

    Testing and experimenting will help you make your decision.

     

     

     

    R.

     

     

     

     

     

      A
      Alex293591989qhlAuthor
      Participant
      June 25, 2023

      Thanks so much for this detailed response, @Remote Index.  A few follow-ups to what you wrote...

       

      1) The aspect ratio for all the clips should already be consistent.  With resolution, roughly two-thirds of the clips are 1080p and roughly one-third are 720p.  I'd of course like the sequence itself to be in 1080p.  I'd love to get your thoughts and recommendations on my options for approaching this.

       

      2) A few of the videos were originally interlaced, but they've already been converted to progressive.

       

      3) On standardizing frame rates, all of these clips are in the 5-20 seconds range.  Since you mentioned that standardizing is particularly helpful for longer clips, I'm wondering if this is worth the hassle in this case?

       

      4a) I will have to play around with the different frame rate conversion options and see how they look.  I should mention that these are figure skating clips, and thus have a lot of insanely fast motion, e.g. skaters rotating during jumps.  I'm curious if that influences your opinion at all on which approach might work best.

       

      4b) With 48% of the clips at 30fps, I've had some people say I should go with that.  Althought that of course means I'd be losing frames from the 10% of the videos that are at 50fps and the 12% of the videos that are at 60fps, so I'm a bit torn.  What are the downsides of using 30fps clips in a 60fps sequence?  Wouldn't it look more or less the same as in a 30fps sequence?  Or am I overlooking something?

       

      4c) One other thing I should mention is that I think a very small number of the videos might be variable rate.  Do these require special handling?

      Remote Index
      Remote Index
      June 25, 2023

      Hello Alex etc.,

       

      Some follow up:

       

      UPSCALING
      The built-in upscaling in Premiere Pro should be good for your purposes - there are several ways to scale up the 720p footage in a 1080p timeline. Others may have advice on better options (but I don't!).


      STANDARDIZING FRAME RATES
      The main advantage of standardizing the frame rates is that the frame rate conversions will be consistent. But it is true that with frame rates so close to the standards, you will likely not notice this on short clips.

      To give an extreme example - a clip of 10 frame duration in a 24fps timeline will be 10 frames long whether the clip is 23.976fps, 24fps, or 24.62fps; however if such a clip is over 1000 frames long (41 seconds or so) it’ll start to show a difference of 1 frame or so given those different frame rates - somewhere in the timeline, 1 frame will be doubled or dropped.

      My suggestion to standardize is simply to avoid such anomalies - to remove one confounding factor in assessing the results of the various methods.


      FRAME RATE CONVERSIONS
      a. Definitely you will have to test and assess the results - what looks good for one clip will not necessarily work for another. You may have to use different methods on different clips. On the other hand, you may find a combination of methods gives a distracting “feel” while watching, and you may settle on one consistent method (for a unified “feel”) even though the results on specific clips are sub optimal. I would say that very fast motion can yield very poor results with optical flow, but again you’ll have to test to see how it goes.

      b. A 30fps clip in a 60fps timeline should yield a very simple, consistent result with the first method I listed (“frame sampling” or “quick and dirty”). That is - every frame should simply be doubled. This should look and feel exactly like watching a 30fps timeline and technically it is - Premiere Pro is literally showing 30 different pictures per second.

      c. Variable frame rate clips are evil and should be attended to with extreme prejudice. I am not sure of the best tools to do frame rate conversions on these to get them to constant frame rates, but if you do a search in this forum I believe it has been discussed before (even recently).

       

      Test! Watch the results! Try something different and repeat!

       

      R.

       

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