Q Is the design of PutMovieIntoDataFork/NewMovieFrom DataFork with
offsets such that the offset can't change and the movie can't be moved around
in the file after creation?
A Yes, this is the case. If you want to purge and re-arrange the movies in a file
after they have been initially stored in the file, you should create a
temporary file, do the changes, and then remove the original file and rename
the temporary file to the same name as the original file.
