Latest post Sun, Oct 30 2022 12:11 PM by Cutyes. 1 replies.
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  • Thu, Oct 27 2022 3:46 PM

    • GaetanM
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    • Joined on Tue, Apr 20 2021
    • Posts 4
    • Points 50

    Managing and synching slow-mo shots (72fps) in 24fps project

    Hi all,


    I am currently in the process of synching media for a feature. Everything was shot in 24fps except for a few slow-mo action shots that were filmed in 72fps, which have externally recorded sound. I am currently looking for the best way to sync the audio for these clips. The high framerate shots were initially provided to me by the lab interpreted as 24 fps in DnxHD 115 MXF (so 3x times slower than normal in playback).

    Of course if I simply do an autosync the audio and video don't actually match since the video is playing 3x slower than the audio.

    I've tried converting the media file back to 72fps but then I can't import it into the project unless I consolidate it to 24fps and loose two thirds of the frame, which means that the slow-mo will be a choppy mess in editing all the way until it is conformed outside of avid with the original 72fps file.

    So what's the best way to go about this? I understand that avid doesn't manage mixed frame rates but I imagine that there must be a solution to this, given how common high framerates and slow-mo is nowadays. Or is it impossible to get synchronized audio on a high fps shot like this ?


    Thanks !


    Working on Avid on Mac Studio M1 Max in Media Composer 2022.7.0

  • Sun, Oct 30 2022 12:11 PM In reply to

    • Cutyes
    • Top 500 Contributor
    • Joined on Sat, Jan 14 2012
    • Berlin
    • Posts 218
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    Re: Managing and synching slow-mo shots (72fps) in 24fps project

    The way I know:

    1) Make subclips of the slow-motion masterclips. Name them as you usually name them but add something to the name that identifies them as slow motion, e. g. „72 fps“

    2) Edit those subclips into a timeline and batch-throw an appropriate timewarp preset - in your case 300% - on them. Make sure the preset’s algorithm is set to „Both Fields“. The default „Duplicated Fields“ will most likely give you jaggy lines.

    3) Sync your audio to the sped-up video.

    4) Make sub-sequences of the parts that have video AND audio. You might want to adjust your out-points so that the clips don’t contain any freeze frames at the end.

    5) Auto sync those sub-sequences into subclips. The timewarp is now seemingly baked in and the subclips behave like regular 24 fps subclips.

    6) Again, name them as you usually name them, but this time add something to the name that identifies them as sped-up clips, e. g. „24 fps“.


    Now you have two clips for each take. One MOS@slow-motion, one with synced audio@24 fps.


    Step #1 as well as the additional naming might seem cumbersome but there are reasons:

    - The „24 fps“ in the name signals that this is a sped-up clip and tells the editor that an according slow-motion clip exists.

    - That slow motion clip can be easily accessed by hitting „match frame“ from within the 24 fps clip.

    - „Match frame“ will take you to the properly named 72 fps subclip which, I think, is to be much preferred over being match framed to the masterclip.

    But what is MOST IMPORTANT about this: Most (all?) conforming tools don’t recognize the baked-in timewarp as a timewarp effect. They only read start TC and duration and then fill the gap with the original slow-motion clip. So, at the end of editing, before it comes to conforming, the clips with baked-in timewarp should be replaced by slow-motion clips with actual timewarp effects on them. That is where adding a suffix like „24 fps“ to the clip’s name comes in helpful, because the suffix can easily be searched for (reference clips, sift, search etc.) in the timeline. Assigning a specific colour to the sped-up clips can also help identifying them visually.

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