Edited Audio Won't Realign

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*Please link to previous thread if you believe this has been sufficiently covered already.

Suppose I record a video on my iPhone of me playing guitar and signing.
Then I upload to iMovie (on Macbook, not mobile), detach audio, paste into Garageband (Macbook, not mobile), and then paste edited audio back into iMovie.
Should all be fine and seamless?
Why or why not?
 
Well as long as the frame rates and bit rate are the same, the theory is that it will be in sync. The snag however is these are apps meant to be for basic, not advanced work. Im assuming in your case what you really mean is you have done this and it does not work as you want? How so? Is the sync out but solid, or does it drift? If its a bit random it is probably lost frames in random places. A good test is to shoot with your camera a video screen that has timecode running on it with a 1k audio tone. Stick that into movie maker and then check there are no spikes in the audio where something glitched. Then split the audio and put it into garage band, fiddle then put it back. Garage band just isnt a full featured DAW. Then you can compare the original audio with the edited audio and see where things go wrong. If sync is very bad do it with a drum pattern with clear clicks. This will make, viewed with the original, finding where the errors easier. A common snag is the phone frame rate. 29.97 is not 30. My current phone shoots 30fps but an older one kept doing the 29.97. I cured that with an app called from memory, mavis. It took control of the phones frame rate properly.
 
29.97 fps is the standard frame rate for US video, has been since color was added to the standard. 30 fps is a rounded up approximation. Very often (but not always), if something says 30 it's actually 29.97.
 
that's the trouble - back in the day, we had of course 25fps here in the UK and quite expensive gizmos required to convert to and from US tapes - at 29.97. To be fair, most US kits now tends to use 30fps - while of course some carry on with the old, and a few shoot 245, because film did!
Now its digital, the technical reason for the US doing 29,97 has gone away. worst bit though is when you need to run timecode. 30 works fine, hours, minutes, seconds and frames - rolling over at 24,25, 30 or 50 - whatever. 29.97 buggers it up, so they started a system where frames would be dropped and not counted. in an hour about a hundred get dumped so at the end of the hour we have all zeros!

I think this is where many errors come from. are we counting every frame or not? Oner thing I used to do in my early twenties was show people how to use multi-standard TV equipment. A U-matic tape from the US was never simple to make play here.
 
Many times when it says 30, it's actually 29.97.

But if the OP is just doing audio and not doing anything that changes the play speed (like stretching and resampling), it should line up. I've noticed with mp3 files, the audio can be offset a few milliseconds, enough for me to notice.
 
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