Local transform on files before sending?

[Michael Gardner]

Is it possible to have rsync do a transform on each file before sending
it? This would be useful for things like individually compressed or
encrypted backups, or in my case, syncing lossy copies of my FLAC music
to an mp3 player or laptop.

If not, is there demand for such a feature? It seems like it would be of
use to many people, and in principle it shouldn't interfere with
incremental file transfers or even checksum-based skipping, since you
could transform the file locally before comparing it with the
destination file.

-Michael