How to pause script until

Question

i have a script that is used to convert avchd files to qt formats.
it's got a problem, though, in that it moves from the currently
converting file to the next file too quickly. i thought i'd solved
this behaviour by including a routine that caused the script to
wait until it saw the qt file appear before moving on. problem is
now that, in the case of large files, the qt appears before it's
really finished converting and made usable, as if the container is
placed in the folder but is still being filled with the file contents
when the script moves on to the next file. since only one file can
be processed at a time, the script crashes at that point.
can anyone suggest a method for testing that these large files are
really complete before the script moves on?
thanks,
BabaG

Answer 1

The first approach would be to see what AppleScript support is built into the application you're using to convert the AVCHD files.
You may find the app has support for this, either by invoking some kind of 'convert' command (which would typically return a reference to the converted movie), or by providing some kind of application status (e.g. 'idle', 'processing', etc.) which you could poll until it indicates it's completed.
If that fails and the app isn't scriptable then your next best bet is to look at more detail at the output file. For example it's likely that the file gets created and the data written to it, and it's this writing stage that's taking time. The easiest approach then is to get the size of the file, wait a second or two, then check the file size again. If the size is increasing you know it's still being created. If the size is static then you can assume it's completed and you can continue your script, e.g. assuming your output file is in the variable output_file:
set done to false
set previous_size to 0
repeat until done = true
  set file_size to size of (info for output_file)
  if file_size > previous_size then
    set previous_size to file_size
    delay 1 -- wait a second before checking again
  else
   set done to true
  end if
end repeat
-- rest of code here