How can I fix this exporting bug?

FCRedux Posts: 11 Just Starting Out

I edited a montage I working on and I exported it when i viewed it in the editor the slow mo and everything was right on time but when i exported it the time was unequal i guess you could say basically the export and the preview screen were 10x different how can I fix this?

Best Answers

  • triforcefx
    triforcefx United StatesPosts: 1,641 Moderator
    Answer ✓

    @FCRedux Xbox Game Bar uses Variable Frame Rate, which causes problems with HitFilm (and most video editors). You will need to transcode your footage to Constant Frame Rate (CFR):

    To avoid this in the future, you should consider using another screen recorder such as OBS, which has the option to use CFR.

    Also, as @Stargazer54 mentioned, you are under spec for HitFilm 2021.3. You could try your luck with the latest version, but you may run into strange issues such as this (this could easily be the VFR issue though).

    You should be fine for any earlier version. I personally recommend 2021.1, as 2021.2 can be a bit problematic.

  • triforcefx
    triforcefx United StatesPosts: 1,641 Moderator
    Answer ✓

    @FCRedux The video I shared isn't just about audio/visual sync. The solution offered can help with ANY weirdness caused by VFR footage. After reviewing your video, I believe this is almost certainly the answer.

    HitFilm needs a Constant Frame Rate because it counts in Frames, not Time. If you have 30 FPS footage, HitFilm expects there to be EXACTLY 30 frames for every second.

    Variable Frame Rate means that the number of frames in a second are changing one second could be 30, the next could be 23, then 25, then 15, then 27.736, etc., etc. This is fine for a media player that does count in Time, but hopefully you can see how that might break HitFilm.

    To put it a different way, if you have a 5 second long clip at 30 FPS CFR, you will have exactly 150 frames. If it's at 30 FPS VFR, you could have any number of frames from 75 - 150. That will absolutely break a frame-based slow motion effect.

  • Triem23
    Triem23 Posts: 20,292 Power User
    Answer ✓

    To build on what @triforcefx wrote, last year we had a user with an extreme VFR clip. He thought it was "29.97 fps," but it varied between 33 fps (FASTER than 29.97) and 0.5 fps. That's a really extreme swing, but, the point is Hitfilm has to try to fit these varying frame rates to a constant clock in real time.

    VFR can cause audio drift, stuttering frames, black frames and other issues and should ALWAYS be transcoded to CFR first.

    Once you've transcoded your footage open your existing project, right click the original clips on the Media Bin and select "Relink," then find and choose the transcoded version. This will swap out the original for transcoded files on your Timeline and will preserve most of your edit. You'll need to step through your Timeline to make certain the transcode didn't cause any edit points to "drift," but the "Slip" editing tool will let you quickly nudge everything into place.

    For FUTURE projects you'll want to transcode first, but, at least you can preserve this edit without a complete rebuild.

    Note that all phones and tablets shoot VFR, so those sources will always need a transcode.

    Consider shifting screen recorders to OBS. OBS, by default, also records VFR, but, in the Advanced options you can tell OBS to record CFR so you can skip the transcode stage.