This usually happens when the video has a variable rather than constant frame rate -- a compression system occasionally used to create very small video files.
What model of camcorder is this video from? What format and resolution is it?
It's happened with several videos of different formats, but I suppose they could all have the same problem. How would I check if they have a variable framerate, and how do I fix it if they do?
Download the free program MediaInfo and open each file in it.
If you set the program's View menu to Tree, it will display all of the info about the video file. If you can't make sense of this data, you can copy and paste it to this forum and we'll help you interpret it.
Hm, I downloaded the program and I think I'm seeing the framerate info, but there doesn't seem to be any difference between videos that work and videos that don't. They all seem to have consistent framerates (the standard ~23.9 or ~29.9) and variable bitrates. This is only the information I could get from a glance with the basic view, but I don't think the framerate is the problem.
You may be right -- but without your providing more information about these clips, we can't say for sure.
BTW, what operating system do you have? Which processor are you running and with how much RAM?
Is this out of sync issue in your output or only when you play back the timeline?
Well, the problem is that there's no consistency to the clips. It applies to videos I've taken myself, screen captures, and to videos downloaded from the internet. It applies to all formats I've tested, but only with specific videos. There's nothing consistent about the clips that causes the problem, which is why I'm so baffled.
One thing I have discovered in my experiments with the videos, if I convert a video to a different format, the problem persists, but it may get better or worse. For example, .mp4 videos usually do not have this problem. I converted a 45 minute .m2ts video to a .mp4 video, and the cumulative desync by the end of the video went from several seconds to less than one. I don't know why this would happen, although it is helpful. I probably need to test this method more, as it may just be completely random.
I am running Windows 8.1 Pro, and I have an AMD FX 6300 and 12 GB of RAM. The desync is in my output.
I'm sorry I just can't help troubleshoot your issues if you won't answer my questions.