Export Issue: Different Source Framerates Leads to Stuttering

I am using Hitfilm to create cinema montages, each comprising of multiple films. When exporting to the YouTube 1080p HD preset, I found in the final mp4 that the footage from select films was consistently losing frames while others were being spared.  After some experimentation, it became clear that the source footage of 23.976 fps was processing appropriately while the other footage, running at 24 fps and above, were the only ones suffering from this frame drop effect. I performed a sort of bandage solution by converting all of the footage with the inappropriate frame rates into the proper 23.976, and it worked, but it causes audio sync issues, increases storage requirements, and therefore can lead to more problems down the line.

I'm wondering if there is a way to process films of different frame rates without resorting to any converting, or otherwise if there is a way to convert video to a different frame rate without causing audio de-sync issues. 

 

 

 

Comments

  • CleverTagline
    CleverTagline Moderator Las Vegas, NVModerator, Website User, Ambassador, HitFilm Beta Tester Posts: 3,238 Ambassador

    You're more likely to encounter audio sync issues when using variable frame rate (VFR) footage. Using a tool like MediaInfo will tell you if your footage is VFR or constant (CFR).

    As for conversion, not all conversion tools will create CFR files. What I recommend is not just converting, but properly transcoding your source footage into a format/codec combo that is optimized for editing, as well as addressing whatever frame rate conversion you want to apply before you edit. If you’re not familiar with transcoding, I strongly suggest watching this video by @Triem23 . It talks about why transcoding is important, and shows several ways to do it using various tools.

  • Triem23
    Triem23 Moderator Moderator, Website User, Ambassador, Imerge Beta Tester, HitFilm Beta Tester Posts: 19,362 Ambassador

    @jsbarrett beat me to the video link. 

    As far as "stutter" goes, this is almost impossible to eliminate for the simple reason that you ARE starting with different frame rates. 23.97/24 varies by 1 frame every 10 seconds, so almost imperceptible, but (assuming you're editing in 24), 30, 59.97 and 60 just don't divide cleanly into 24. The only way to get a 1:1 frame cadence is to slow down video to 80% (29.97, 30, 59.97/70 fps source) or 40% (59.97 or 60 fps source). This either slows your audio (lowering pitch) or desyncs audio unless using specialized tools Hitfilm doesn't have. 

  • MichaelUjwary
    MichaelUjwary Website User Posts: 3

    Jsbarret, thank you, I will look at the video later and decide upon a course of action.

     

    Triem23, I'm not certain that the issue is due to the discrepancy itself, at least not fully. As you said, 23.97 and 24 varies by 1 frame every 10 seconds, yet two movies --each using one of the frame rates--end up exporting to something more like 23.97 and what looks like below 15. 

    I'll use an example to illustrate. I'll denote different movies by A, B, and C and their frame rates as 23 and 24.

    I edit these movies onto the timeline: A23, then B24, then C23. They don't seem to be noticeably different when I watch them through the viewer. Thinking that everything is fine, I export the whole thing.

     

    Suddenly, in the exported video, A23 runs fine, B24 seems like it's running at almost half frames, and C23 is fine too. This is by no means a 1 frame every 10 seconds level of difference. 

  • CleverTagline
    CleverTagline Moderator Las Vegas, NVModerator, Website User, Ambassador, HitFilm Beta Tester Posts: 3,238 Ambassador

    @MichaelUjwary To me what you described sounds like an issue coming from variable frame rates in some files, and/or a general impression that some files might be more editing-friendly than others. Even if a file has a constant frame rate, the compression used might still make it less than ideal for editing, which is why transcoding is still highly recommended. Transcoding not only addresses frame rate issues, but also frame access issues, which the video above describes in more detail. Easier frame access means a smoother editing experience (i.e. less stuttering during playback and scrubbing in HitFilm), while having a constant frame rate means (among other things) that audio and video stay in sync.

  • Triem23
    Triem23 Moderator Moderator, Website User, Ambassador, Imerge Beta Tester, HitFilm Beta Tester Posts: 19,362 Ambassador

    That can be a VFR issue as jsbarret mentioned above. The linked video goes into detail (because I got tired of retyping it).

    Hitfilm tries to interpret VFR footage  but often gets it wrong (whereas many NLEs won't even try). Why? Sometimes the VFR footage is REALLY variable... Especially phone and screen capture footage.

    Last year I shot footage of fireworks on a phone. All clips were "29.97". Hitfilm interpreted some as being 29.97, some as 24, some as 23.97, some as 15(!). Why the variation? The MediaInfo report told me a lot. The clip Hitfilm interpreted as 15fps varied from 29.97 fps to 11 fps (the VFR dropping frame rate on black sky between fireworks). The clips Hitfilm interpreted at 23.97 and 24 fps varied in frame rate from 20 to 29.97 (again with dark skies between fireworks). The clips interpreted as 29.97? Fountains with constant action. The frame rates varied between 29.97 and 27...

  • MichaelUjwary
    MichaelUjwary Website User Posts: 3

     Update:

    I updated Hitfilm (I was using version 9 or 10 for my previous project) and now I see that the editor no longer accepts some of the films I used. These are mkv files and, as it turns out, that file type was the sole one implicated in all of the problematic films. I am modifying my thesis to suggest that the issue has not been with the frame rates themselves but rather using an unsuitable container. If that's the case, then easily solved; just do some transcoding. 

  • LeRoiLightning
    LeRoiLightning Website User Posts: 33

    Anyone got suggestions for a good all round format and settings for transcoding footage for use in HitFilm? I tried cineform (converted by HitFilm) but, although the resulting file sizes were large, the resulting quality was a bit subpar (kind of grainy and blocky). I ended up editing with the original files again. 

  • Triem23
    Triem23 Moderator Moderator, Website User, Ambassador, Imerge Beta Tester, HitFilm Beta Tester Posts: 19,362 Ambassador

    @LeRoiLightning what was your source footage from, and what Cineform quality settings did you use. Otherwise, watch the video @CleverTagline linked above. It discusses the pros and cons of various codecs, shows several programs for transcoding, and the description links to some other good threads on this forum covering other transcoding options not in the video.

    That said, on PC Cineform is generally the way to go. This is why I asked what your Cineform settings were. It should be basically visually lossless.

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