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[Question] FPS in Davinci Resolve not matching source

https://forum.blackmagicdesign.com/viewtopic.php?f=21&t=136691

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[Question] FPS in Davinci Resolve not matching source

PostPosted: Wed Mar 10, 2021 4:15 am
by 2017bqj
Hi, I am a new convert to Davinci Resolve (Version 17 Build 39), coming from Premiere Pro. This is my first project and I am loving it, but something does not make sense to me. I have a 2+ hour clip that is 23.976026 FPS (FFMPEG and VLC confirm this). When I import it, Davinci Resolve warns me that “The selected clips have a different frame rate to the project…”, my project is set to 23.976 FPS. If I select “Don’t Change”, the audio track wanders out of sync by a few seconds by the end of the clip. If I select “Change” my project is reconfigured as 24 FPS but the audio is in sync throughout.

I have tried the same h264 video stream with and without the audio stream by importing the audio separately. I have imported the audio as AAC and PCM. I have also tried .mov and .mp4 containers. All with the same result.

Why does Davinci Resolve seem to think this video clip is 24 FPS? I could continue on with a 24 FPS project but I would like to understand why this is happening. I would also prefer to retain the original FPS for the final output.

Thanks in advance,
Brandon

Re: [Question] FPS in Davinci Resolve not matching source

PostPosted: Wed Mar 10, 2021 4:39 am
by Peter Chamberlain
Where is the source clip from?
it could be a variable frame rate clip as 23.976026 seems odd

Re: [Question] FPS in Davinci Resolve not matching source

PostPosted: Wed Mar 10, 2021 5:17 am
by Igor Riđanović
It might work if you right click the clip in the bin and change the clip attributes to force 23.976 rate on the clip.

Re: [Question] FPS in Davinci Resolve not matching source

PostPosted: Wed Mar 10, 2021 10:01 am
by Uli Plank
I bet it's VFR since you wrote "stream". VFR means trouble.

Re: [Question] FPS in Davinci Resolve not matching source

PostPosted: Thu Mar 11, 2021 4:42 am
by 2017bqj
Thank you for your kind responses.

Unfortunately, I don’t have the original video straight out of the camera. It was delivered to me having been transcoded and I don’t know what settings were used in the process. Obviously not ideal.

Using FFMPEG vfrdet seems to indicate that it is VFR (I always thought that VFR was some exotic thing I would never deal with :? ) anyone know of any other way to confirm that it is VFR? As I said in my original post, if I let DaVinci Resolve handle the video like 24 FPS then my audio remained in sync until the end…am I just incredibly lucky or does it do its best to handle VFR? I don’t know if there could be any noticeable frame rate conversion artifacts in the final product if I take this route.

I could reencode it again to CFR as I have seen suggested elsewhere on the forum.

Any other suggestions for how to deal with VFR video in DaVinci Resolve?

Thanks again for helping a newbie out,
Brandon