[SOLVED] Different framerates composited together cause flickering and then blackscreen

cmddata
cmddata Posts: 10 Just Starting Out*
edited October 12 in HitFilm

This first happened only during exporting and not during viewerplayback, but I have a project that's at 1080p30 and I am combining two video clips, both at 1080p but one is at 60 and the other is at 30. Weirdly the 30fps clip starts to flicker on and off seemingly every other frame while the 60fps clip is just fine. Any idea what might cause this? I have both clips in a composite shot and I set the composite settings in both to 30fps


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Answers

  • littlehausbigcity
    littlehausbigcity Posts: 54 Just Starting Out*

    I'm going to go out on a limb and say, convert the 60fps footage to 30 frames and also make sure your timeline is also at 30 frames per second so all footage matches and see what you get.

    It may be a conflict between the different frame rates, and/or your timeline if it's not matched to both.

  • cmddata
    cmddata Posts: 10 Just Starting Out*

    That's the weird part I synced all of the framerates. All of the composite settings and project settings are set to 30fps

  • Stargazer54
    Stargazer54 Posts: 3,435 Ambassador

    Mixing different frame rates is problematic. As @littlehausbigcity suggested, converting everything to the same frame rate is best. That said, you can get away with editing at 30 fps with a single 60 fps video because there is more frame data available than needed and the software doesn't have to think extra hard. But as you can imagine, editing at 60 fps with a 30 fps clip forces the system to interperlate the missing frames. Mixing 60 fps and 30 fps only exacerbates the problem.

    Also listing system specs would be helpful. Please follow these guidelines when posting a tech question: https://community.fxhome.com/discussion/57390/support-posting-requirements-read-before-posting#latest

  • littlehausbigcity
    littlehausbigcity Posts: 54 Just Starting Out*

    What Stargazer54 said, also this, is your 60fps interlaced or progressive? I ask as HF does not like interlaced footage, needs to be progressive and may be causing your 30fps footage to go all wonky during export. Just a guess.

  • Triem23
    Triem23 Posts: 20,070 Ambassador
    edited October 11

    Another thought - if both videos are screen caps or web cams, they could be variable frame rate (VFR). Hitfilm (and other NLEs) want constant frame rate (CFR).

    In short, with VFR footage "60" fps might actually be "60, 55, 63, 40, 30, 47, 60, etc." This means Hitfilm is trying to duplicate/drop frames in real time to make a second with 47 frames fit into 60 frames. Combining exacerbates the issue.

    A "Tree" report from (free) MediaInfo can confirm if this is an issue. Post that here and we'll verify.

    In that case, a transcode to CFR before import would help. So, like @Stargazer54 and @littlehausbigcity suggest, a transcode is still likely your best bet.

    This video talks more about codecs and VFR, has a section on MediaInfo and sections on transcoding, including (in the Handbrake section) optimized encode settings for Hitfilm performance. Chapters in the description.

    Run the MediaInfo report for us first. If you have VFR, it might be better to transcode from VFR "60fps" to CFR 60fps. There's a way to relink transcoded media back into an existing project and preserve the edits, but, because of the way Hitfilm parses frames it won't work if you change the source video frame rate from 60 to 30. I'd like to try and solve this problem AND preserve your existing work so you don't have to re-edit.

    For FUTURE projects you'll want to conform all your footage to the desired output frame rate first (unless you need a high frame rate for slo-mo, but your current project is talking heads, so no slo-mo).

    So, I suggest downloading (free) Handbrake. It's a good and fast mp4 transcoder, and you'll probably end up needing it.

  • cmddata
    cmddata Posts: 10 Just Starting Out*

    Thank you so much for the detailed answers :)

    My specs are i5-11400f, 32gb RAM & Radeon 6600XT, temperatures are all well controlled, 50-60 degrees under high load.

    I'll try the transcode but I must reiterate that the clip that's flickering and eventually dies is the 30fps video, not the 60fps video (Which is on the left in the original gif) The whole project is 30fps which led me to check my OBS settings and it turns out I accidentally recorded at a bitrate of 40000kbps which made the file over 60gb. Could that be the cause of the flickering where hitfilm runs out of some sort of memory?

    I'll watch the video and try out transcoding the videos before importing them and will report back if it helps :)

  • Triem23
    Triem23 Posts: 20,070 Ambassador

    Hell, if nothing else, transcoding will shrink that file!

    Still wanna check for VBR. VBR can cause flickering, stuttering or dropouts on expirt.

  • cmddata
    cmddata Posts: 10 Just Starting Out*

    Ok I've checked with MediaInfo and both of my video clips are constant, with one obviously still being 30fps and the other 60fps. Would be worth it to try and transcode the 60fps into 30fps?

  • cmddata
    cmddata Posts: 10 Just Starting Out*

    UPDATE:

    Transcoding both videos and re-making the composite shots fixed the issue, the video exported no problem, I'll have a look if OBS has a setting for constant framerate. In any case everyone's comments helped out a lot, thank you very much :)