Audio and Video sync issues with both Constant and Variable Frame Rate

[atomicBRblaster]

Hi there guys,

Firstly I would like to thank you all in advance for your time and attention.

I am a drummer and I record some videos playing and I use my iPhone SE2 and an EKEN H9R 4k to shot my videos from different angles then I sync them with audio during the editing process and until now I did without any issues, but recently I got those videos and audio getting out of sync along the playback...Commonly I use the "Synchronize Clips" from Final Cut Pro X to get them correctly aligned and also it always worked but not this time, so I did manually using the first drum hits to align them as always.

After some research I found out that iPhone recorded it in VFR mode but after convert it to a 30fps CFR using Handbrake I still getting them out of sync IN BOTH CAMERAS footage like NEVER happened before.

Maybe you can see something I could not until I give up and try to re-shoot them all...

So in details I got:

A footage from my iPhone recorded in "Most Efficient" mode aiming a 1080p60fps, resulting in a VFR video that goes from 54 to 66 frames per second
A footage from my EKEN recorded in 1080p60fps
A audio file recorded in 24 bits and 48000Hz sample rate.

Once again, thanks a lot!

[Cornucopia]

pretty sure it is the iPhone at fault. prior to any conversion, extract the audio from your iphone video file and compare that audio with the audio from the eken or from the direct audio file. I am betting they will be in sync (or very, very close, once you get start times lined up).

While iPhone can NEVER shoot video in true CFR, you should use modes that won't make it worse (modes such as "Most Efficient" mode are very likely to use VFR even more strongly).
Much of what phones can shoot is very dependent on available light, so the more light you can throw on the scene, the more close to CFR target rate your phone cams can get.

Scott

[atomicBRblaster]

pretty sure it is the iPhone at fault. prior to any conversion, extract the audio from your iphone video file and compare that audio with the audio from the eken or from the direct audio file. I am betting they will be in sync (or very, very close, once you get start times lined up).

While iPhone can NEVER shoot video in true CFR, you should use modes that won't make it worse (modes such as "Most Efficient" mode are very likely to use VFR even more strongly).
Much of what phones can shoot is very dependent on available light, so the more light you can throw on the scene, the more close to CFR target rate your phone cams can get.

Scott

Sadly it did not work. I imported one of the videos directly from Photos into iMovie just to extract the audio and try to sync it with the audio, but it didn't succeeded...

I'm quite intrigued with this behavior because it is the SAME setup I used for a lot of videos that I did before...

[davexnet]

Can you shoot a small video and upload an untouched sample to the forum

[jagabo]

As you've discovered, most editors can't deal properly with variable frame rate video. You have to convert to constant frame rate first. Something like ffmpeg can do that.

ffmpeg -i vfr.mov -filter:v fps=29.97 -c:v prores -profile:v 3 -c:a copy cfr.mov

Use a frame rate that matches the main frame rate of your source. For example, if you shot a 30 fps video but it drops to 15 fps at time, use 30 fps.

And yes, a sample would help us help you.

[JN-]

If its a long duration video clip then sometimes it can be synced say at the start, but can be still out of sync later on, using vfr.

[Cornucopia]

pretty sure it is the iPhone at fault. prior to any conversion, extract the audio from your iphone video file and compare that audio with the audio from the eken or from the direct audio file. I am betting they will be in sync (or very, very close, once you get start times lined up).

While iPhone can NEVER shoot video in true CFR, you should use modes that won't make it worse (modes such as "Most Efficient" mode are very likely to use VFR even more strongly).
Much of what phones can shoot is very dependent on available light, so the more light you can throw on the scene, the more close to CFR target rate your phone cams can get.

Scott

Sadly it did not work. I imported one of the videos directly from Photos into iMovie just to extract the audio and try to sync it with the audio, but it didn't succeeded...

I'm quite intrigued with this behavior because it is the SAME setup I used for a lot of videos that I did before...

I'm not surprised that a standard NLE wouldn't import it properly. I suggest doing the audio extraction(s) via ffmpeg command line (or with a GUI helper) FIRST before checking in an NLE/DAW, because once it is audio-only you aren't hindered by framerate (since audio doesn't have a framerate, just its own constant samplerate - 48kHz).

Scott