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Top Tip For Those Who Record Videos

posted on #1
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This has been a problem every time I record videos where I need to sync separate audio to a video. In my case, the mixed multi-track recording from Reaper of my drums against the video I've shot. Every time I import the video and audio into iMovie and line them up, the audio drifts out of sync with the video. I ended up time-stretching the audio to line it back up with the video. With drumming having lots of movement, audio being out of sync really, really shows and also really annoys me!

I messed with sample rates (44.1khz and 48khz, etc.) to no avail. Because it turns out the video is at fault. I shoot my videos on my iPhone 6S - usually 1080p at 60fps - because, frankly, the video quality is vastly superior to anything else I own!

All smartphones, including iPhones, actually record video at a Variable Frame Rate (VFR). Just because you set it to 60fps, it doesn't mean you're actually recording consistently 60fps. I guess it does it based on movement in the video or something in order to save storage space.

Video editors, like iMovie, can play VFR videos no problem so you don't notice the issue - until you need to sync separately-recorded audio to it which is most likely rendered at a consistent frame rate!

In short, you need to use another video editing app, such as Handbrake or OBS, to transcode the video to a genuine fixed frame rate (in my case 60fps). It doesn't affect quality as long as you set everything to the highest setting.

Now import the new video into iMovie and its job done! It's a pain to have to re-process the video but its taken me a lot of searching and research to find the answer to this problem which has been driving me mad!
Edited by mpointon on October 19 2018 13:54
If you make a mistake, do it again and make it look like you meant to do it!
posted on #2
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Great tip Martin, have been struggling with this as well, to the extent that I'd pretty much given up on matching music to videos. I'll give it a try.

-- Joe
posted on #3
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I should mention this problem is largely exclusive to video shot on smartphones. Most dedicated cameras (SLRs, etc.) always shoot at a fixed frame rate and never try to optimise their file size.
If you make a mistake, do it again and make it look like you meant to do it!
posted on #4
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Tried this out this evening on the previous video I did. Passed the raw file from my iPhone into Handbrake and told it to export the file at full quality but at a constant frame rate.

Put the video into iMovie, lined up my mixed WAV file and it worked first time. Audio and video now sync up and stay that way for the full length of the video!

Yay!
If you make a mistake, do it again and make it look like you meant to do it!
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