Hello there.
I use an MacBook air and have audacity. My microphone is a blue yeti. When I do my YouTube videos I record and with my phone camera that has it’s own audio and at the same time through my microphone. Now the problem is that when I bring my audio and video to iMovie in the start the video is in sync but at the end around 55 minutes it’s completely out synced. Is there any way to fix that?
Change speed of the audio so the durations match.
Change tempo can also fix this type of sync problem but it adds artefact noises.
It’s not unusual to have sync problem with Separate Sound.
That’s why the movie people use the clapboard at the front of each take. Write down all the shoot and show info. Hold the board where the camera can see it and the sound system can hear it. Yell “Camera Mark” and bang the clapper. Start the performance immediately without stopping anything. You might get a chuckle or two when you do this, but you and I know the problems this is curing.
What’s not so well known in the case of completely wild shoots is the End Mark. Hold the board upside down when you get done and use that to resolve sampling errors or other timing issues. Yell “End Mark” (bang).
If you have no end mark you’ll have to guess where sync is. Guessing lip sync from live video is an art form. There’s no trick I know of.
Effect > Change Speed. Try a multiplier of 1.088.
That’s the difference between Audio sampling at 44100 and video sampling at 48000. If that fails, try the other direction at 0.918.
You may be able to resolve this issue down to almost zero by running the Audacity capture at 48000 instead of 44100. Experiment.
That was the good news—the predictable error. There is an unpredictable error where one recorder is running slightly off from the other. That’s the one which will give you really tiny but annoying errors. That one you either resolve by eye, or do a “fake” recording for an hour and use the beginning and end marks to get the correction number which will stay constant no matter what you shoot (as long as you never change recorders).
If you totally offended the sound angels, your Audacity capture may skip frames when it feels like it. One poster had that problem recently. The two ends were OK but the middle was off. Run away.
Good luck. We applaud your use of separate sound. I hate videos that use the microphone on the camera and I have to sit through room echoes and reverb. Nothing says “My First Video” better than bad sound.
One other oddity. Video editors typically will only let you change sound sync in even video frames. If you need sync changes finer than that, you’ll have to fine tune the correction in Audacity before you do the import to the video.
Do Not use MP3 anywhere in the production. Export your sound shoot as WAV (Microsoft) 16-bit and only edit and produce with a copy. The original works are Camera Masters. Don’t mess with them. Park them on their own archive storage. Edit copies.
Koz
Change tempo can also fix this type of sync problem but it adds artefact noises.
That’s not the only thing it does. It also changes voice pitch—or it fails to correct the voice pitch error you already have. If you did everything right, you should have a simple speed error which changes both duration and pitch.
Do post back how it came out and what you did to it.
Include, if possible, the address where we can view the work.
Koz