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Correcting audio drift (VFR to CFR)
My audio falls out of sync with my video and I’ve just learned about Variable Frame Rate issues. The ONLY solution I’ve found online is using software that is only available on the Mac, Linux and PC, “Handbrake” to convert VFR to Constant Frame Rate. I only have iDevices and a work laptop that I cannot use for this.
Any suggestions?
Comments
Where are you playing audio and video that is getting out of sync? Can yo7 give more details about the situation?
Have you tried this technique using a speed editor feature?
Not sure what apps on iOS have this feature, if any, but thought it was worth suggesting since it doesn’t specifically require Handbrake.
Here’s what I recorded today as a test. It’s three short clips spliced together in iMovie (I also tried VM Editor). It starts off in sync, but it’s way off by the end. The audio is in syn in each clip, but any editing app will result in this mess.
See my vid. What I play only gets more syncopated and complicated. The solution in your vid isn’t practical and I doubt it would be effective.
I’m wondering if Lumafusion has some effective feature but I’d have to spend $30 and am doubting they would have solved this issue and not specifically advertised it in their description.
Also, the guy in the vid says newer iPhones can shoot at Constant Frame Rate. I can find no evidence of that being true.
You are using only idevices???
Are you editing on an iPad?
Are you using an external audio interface?
Yes, yes and yes. New iPad Air and Motu M2
I am still unclear. How were the videos shot, created and spliced.
If you play the originals are they in sync?
Sorry. The vids were shot with the front facing ipad camera in the native camera app. The audio was through the Motu, also captured in the camera app. The three raw clips are each in sync with no issues. It’s the video editors that can’t handle files with variable frame rate. In the above case, iMovie (on the iPad) was used to splice the three clips together.
So, it’s all good if I don’t want to do any editing....but I plan on making multi-tracked split screen vids.
You say “the video editors”, did you try anything besides iMovie?
It might be the case that LumaFusion can handle it.
First, I would correct the total audio offset. Audio is early right from the start.
Then, you might add one or two splits at low level sections in the audio track to lengthen it a bit (should suffice for the short clip) and fill the gaps with repeated, crossfaded snippets from around the splicing position. In your case, import the 3 videos first, then add the respective audio tracks separately.
Another option is to time-stretch (lossy) or even re-pitch (lossless) the whole track. Who cares if the audio is in tune?
I tried all kinds of audio adjustments and offsets to try to manually sync up the audio. The audio is not consistently late or early making this pretty much impossible as a remedy.
Ok, I figured it out. I set all the camera settings to the maximum 4K 60 FPS. I disabled the setting that allows it to drop the frame rate if is experiencing low lighting. However, I think the screenshot below is what solved it.
It’s weird that no one mentions what I’ve done above as a fix. Just listen to this guy’s explanation of how to fix it. He said he’s tried everything for iPhone videos and his cumbersome way is the only solution.
Nevermind. I was wrong. I thought it was fixed because I spliced a few test videos together without knocking it out of sync. However, I went back in and trimmed around the transition points and tested again. Out of sync.
You may check Lumafusion‘s specs if it can handle variable framerate.
If it does not, the the guy from the video above is stating the obvious:
convert the clips to constant framerate and cut/edit the converted copies.
That‘s exactly what Handbreak does (as mentioned), but it‘s not restricted to that app.
That’s why I started this post. I need to find an alternative to Handbrake. I’m hoping there’s an equivalent on I0S but I’m striking out.
Did you contact the lumafusion folks to see if it handles vfr correctly? There is a good chance that it does. And it lets you select the project frame rate.
I wrote them yesterday. At this point, I’m not hopeful. It seems everyone solves this issue outside of IOS. If Lumafusion can do it, someone out there would be screaming it from the rooftops.
With more experimentation, I’ve learned more. If I trim each clip in the native camera roll, they’ll stay in sync. Too much filtering or fancy visual effects throws it off. I can then splice the pre-trimmed clips together in iMovie and it stays in sync. However, audio is in stereo with only left channel containing a signal because the native camera app assigns each channel of the moto left and right. I’d have to have two mics and record in stereo to not have a mono video (or use the built-in iPad mic).
Importing the clip into Auria (I have the video import IAP) to convert mono->stereo throws everything out of sync. This means adding eq, compression or reverb is also a no go.
After experimenting for an estimated 8 hours, this is the best I can do. A lightly filtered mono video with zero audio treatment and no signal in the right channel.
LumaFusion can convert the clips to a constant frame rate. And the audio can be detached and re-aligned. How large are your clips? I could do a test if they aren’t too huge.
Oh man, I would really appreciate you testing that out. I’ll PM you with a dropbox link.
This looks like it could be the ticket. Nothing at all about this feature in the Lumafusion documentation.
Cool find
(I‘m barely into video atm, but wouldn‘t have expected the degree of the problem you experienced at all... at such a basic feature of post-processing)
I know, right? Read the comments on that solution vid.
I did a quick test and think that I have got it working. It'll be a while before I can get the test clip uploaded for you to check.
I think Lumafusion converts the clips into constant framerate data (though I could be wrong). On first import, the audio was out of sync. I detached the audio and slipped it later till it started in sync. I think they stay in sync -- but I wasn't able to do a super careful check. I'll PM you a link. You can check it out and let me know if more tweaking is needed.
Your test should include trimming on all of the clips, at least a few seconds off each end. I was able to put them together with no sync issues. It’s trimming the transitions that revealed the worst sync issues, though heavy visual filtering affected it as well.
@espiegel123 Well, Lumafusion is the answer. It can be used to fine tune clips and does nothing to throw them out of sync on mixdown. Thanks for your generous assistance!