OK, it may be that most of my videos are in sync to begin with (that is, there's nothing wrong with the mux), but my audio/video sync definitely gets messed up somewhere along the way. It would be easier to correct sync if I had a shorter video clip showing something where it's easy to read the sync. For me it's hard to try to adjust it watching dialogue. It's easier with something repetitive and snappy (like the knocking on a door) but it's hard to find such a segment in a full length movie.
Sweden