I have .m2ts files that I converted to .mp4 using iSkysoft Video Converter, and the .mp4 files' audio are always slightly out of sync, it is constant throughout the video, but the amount it is off by differs each time. To fix this, I have simply been detaching the audio in iMovie and dragging it to where it should be. But recently when I have tried doing this, without even dragging the audio after detaching it, there is no sound although the audio track is still there.

Is there a way to fix this?