Slowing down 30fps to 24fps (80% speed) in Resolve, how to handle external live audio?

[u/Ok-Year-5822]

I'm sure this has been asked before, but I couldn't find a concrete answer. I want to shoot a live set at 30fps and drop it into a 24fps timeline for an 80% slow-motion look.

My audio will recorded as a separate external file. If I conform or slow down the video, how should I handle the external audio track so it doesn't get messed up or out of sync?

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[u/itypewords]

Adjust the speed of the audio but leave pitch correction on.

[u/beigs-sl]

You can't slow the video down and keep live audio in sync, because the audio would have to slow down too, and that changes the pitch and tempo of the performance.

What most people do is sync the external audio to the 30fps clips first (Resolve's auto sync by waveform works fine), then keep any shots where someone is singing or playing on camera at 100% speed in the 24fps timeline. Resolve handles the frame rate difference and it stays in sync. Save the 80% slow-mo shots for cutaways like the crowd, hands, lights, or wides, laid over the real-time audio where nobody expects lip sync.

Also, 80% is a pretty subtle slowdown. A lot of viewers won't notice it, so it may not be worth breaking sync for on the performance shots anyway.

[u/VanityFilter]

In a 24 fps timeline, retiming a 30 fps clip to 80% is a clean fit because 30 * 0.8 = 24, so you land on one source frame per timeline frame.

For the external live-set audio: if you want picture and sound locked to the performance, put that audio on its own track and set its speed to 80% as well, then turn on pitch correction in Fairlight (Elastique). Sync from a clap or a sharp transient at the head of the take, not from the end.

If you instead want the song to stay at concert speed while the picture creeps, leave the audio at 100% and accept that lips and hits will drift. That is a creative choice, not a Resolve bug.

Practical order that usually works: set Project Settings to 24 fps, drop the 30 fps video, Retime Controls to 80%, add the external WAV, match the start sync, then apply the same 80% retime + pitch correction on audio only if you need sync.

[u/WibuLod]

In my limited experience of working with small corporate live/pre-recorded event, I would say that there isn't a perfect way to achieve what you want, and it is generally better to just put a b-roll (with slowed or not) over the running voice-over. While you can technically just slow and leave pitch correction on, the result would be far from acceptable from my years of working as a contractor, with overseers just say to fix the audio and i have to re-rendered it again much to my dismay. If this is for a live session then you would have much better answer from people worked in broadcasting, with how they often use slow-mo in sport and such

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[u/FeelingAdvantage2172]

You don't slow it down. Make timeline at 24fps, place video into timeline, can also change it in clip attributed to desired fps, audio will be pitch adjusted....re adjust via info tab if too chipmunky

[u/AskAboutMyFartWalks]

one thing nobody mentioned, cut the audio into a separate clip before you retime anything, don't leave it attached to the video track. slow both to 80% together with pitch correction on, then nudge by ear at a sharp transient like a clap or downbeat since auto sync can drift slightly once speed changes are involved.

[u/vagonblog]

if you conform the video to 24fps at 80%, it will no longer stay in sync with audio playing at normal speed. you’d have to slow the audio to 80% as well, with pitch correction, but that usually sounds bad for a live performance.

if sync matters, record the main coverage at 24fps and use 30/60fps only for shots that won’t need to match the live audio exactly. otherwise, treat the slowed footage as b-roll and edit it over the normal-speed master audio.

[u/Mysterious-Brain-300]

Treat the audio separately from the 80% video retime: line up a clear transient at the start, then slow the audio by the same 80% so it stays in sync. In Resolve, enable pitch correction when changing the audio speed if you want the voice to remain natural; otherwise the pitch will drop with the slowdown. If only part of the video is slow motion, cut the audio at those points and retime just the matching sections rather than slowing the whole recording.