Quicktime loses audio sync then saving

Now that's very interesting (the keyframe idea) and one I never heard mentioned elsewhere! I sometimes do a LOT of cuts. Like taking a video over 3 hours and cut it down to 20 minutes where the clips may only last 5-15 seconds each!

I'm not familiar with all this terminology so let me present scenarios for better clarity:

1. After converting the file to ProRez, you were able to edit in QT and after saving, the audio still works? If so, it may depend on how many cuts before a problem becomes obvious, but if it worked for you, then I can test for more extreme cases.
2. As for Avidemux, I did look that up too and the editing seems fairly user friendly, but I'm not clear on whether I can just use that on a .mov file or would I first have to convert to ProRes? Would it properly handle a file without previously converting to prores, or would that still be a necessary step?

Related, I have sometimes thought about just switching from iMovie to Shotcut. I think there is a free version. Are you familiar with that and, if so, is there a better chance the audio would stay synced even without converting to ProRes first?

This morning the "error" was still there though last night I did another copy with a new name. It doesn't give an error, but the cloud symbol (without the exclamation point) is on that one. Don't know what to make of that. But normally I don't need to have the file in the cloud. I'd only need it while I'm editing it to avoid that audio sync issue.

As for editing in QT, I can make cuts anyplace I want and remove sections from start, end, or middle. I don't know if I do it the best way, but I only use one method:

1. Play the video in QT till I find the place I want to start.
2. Select "Split Clip" and then click the area before the split and hit the delete key. Then press return or click "done" to get back to the normal player view.
3. Play more until I hit a section I will be cutting out.
4. Split the clip again but then just press return to get back to normal player view.
5. Play more until I get to the next part I want to keep.
6. Split the clip and select the area right before the the last split (iow, the whole section I don't want) and press delete again, then return to player mode.

At this point I've removed the intro as well as one section in the middle. I just continue this process until I've gone through the whole video, removing all the parts I don't want.

I think it is important to be pretty methodical about it - that is, don't go backwards to delete something you changed your mind about. If you are making lots of cuts like I do, when in editing the places you "split the clip", you'll have a lot of these separate clips and easy to lose track of what each one is! So I'm always working from start to end. I might do some minor cuts when in iMovie creating my reaction to the video.

There may be things I don't know. Mostly I just figure out a way to do something but may not be the best way.

Maybe I'm missing something, but I don't see anything about a ProRes option in QuickTime. Can you clarify?

I use Downie 4 to get videos from YouTube and that app then uses Permute 3 (from the same company) to create a .mov file. I have found that minimizes some other problems I had when I was using Downie 4 to use it's own conversion method to create a mp4 file (.264). Before switching to Permute to convert, I'd often get a LOT of spinning wheels when even making tiny changes in iMovie, like just adding a title text to a video!).

Don't have FCP (I'm totally an amateur). Don't have ffmpeg either, but I'll look into it next time I'm doing a lot of this editing. Much of what you describe in Greek to me, but let's see if I can simplify it.

Since there is no problem until I start editing the file AND save it, I assume I can still download from YouTube using Downie 4, ending up with a .mov file.

So do I then load it into ffmpeg to edit out the stuff I don't want and then save from there? QT is the only app I've ever used for actual editing so I don't know about other options. Oh, I also edit within iMovie.

I just did some quick searching for info on ffmpeg. Seems to be more awkward to use than that I do with QT and iMovie though. I need something that lets me split clips as I go and delete sections I don't want but, of course, without the sync problems I'm running into!

Found this from 2017:

> You can convert to ProRes using the Finder. Select the files, right-click and use use Services>Encode Video Files.

I'm presently trying this conversion process. It took just a few minutes to convert a 713 MB .mov file to a 22.4 GB .mov file as a ProRes 422 version.

So IF the key is to use QT on a ProRes version, this may be a simple solution - unless I see a problem with it.

Of course, I'll still need to do it with a file that I then do heavy editing in QT to see if the sync still works!

One step at a time! :)

First big test and perhaps solves my problem!

I did use the Apple option to convert to ProRes on a video that is 140 minutes long. Then done and looking at it on my desktop, instead of showing the time length of the video, it said "Error". However, using the space bar to open it, it played just fine as I skipped around. Looking closer at the file, it has a cloud icon next to it with an exclamation point. So maybe the "error" means it wouldn't upload to iCloud. It's 138 GB. If it shows the error tomorrow, I may try copying it and pasting it on the desktop again and see if it uploads. Fortunately, I really don't need it to for my purposes.

So I went ahead and loaded it into QT and just started making lots of cuts, getting it down to about 32 minutes. I then Exported it twice. Once as H.264 and once as HEVC. Tried each after pressing the space bar and spot checked from beginning to end. Both seemed to work just fine. I had a total of 32 segments that were saved. Seems to me that should be enough.

I'll certainly be checking more when doing future videos, but this is the most helpful sign I've had and may have completely solved my problem!

Thanks a lot for all the help. I sure never would have thought ProRes might solve the problem!

Yes, iMovie can detach the audio and I've spend many hours doing that because of the sync issue!

I'm considering Avidemux as well as Shotcut. Just kinda leery about trying brand new things, but another problem I've had with iMovie is then I look back at some old projects, some images and clips I've added in will be missing! Even when actively working on a project, I have sometimes saved an image to the desktop, then drag it into iMovie. Since I don't want my desktop cluttered up, I periodically would either move those images to a folder or just delete them.

But sometimes they would also disappear from the project! But not always. Makes no sense to me. It seems that, once dragged into a project, it should always be there. So that's one reason I'm considering Shotcut, but presently have no idea if it does the things I can do on iMovie. Someone just recommended it to me.