Local transform on files before sending?

[Michael Gardner]

David Howe wrote:
> Matt McCutchen wrote:
>> On Sun, 2009-02-08 at 20:28 -0600, Michael Gardner wrote:
>>> 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.
>> This feature is provided by a maintained patch, which is not very
>> mature:
>>
>> http://rsync.samba.org/ftp/rsync/patches/source-filter_dest-filter.diff
>>
>> Like many others, this patch is perhaps worthy but no one has shown an
>> interest in working on it recently.  If you are willing to improve the
>> patch to the point that it meets your needs, that would be great.
> 
> I can see this particular example being excessively cpu intensive though
> - having to re-encode an entire directory of lossless files as a
> different format so you can compute the hash - plus of course its
> possible that some encoding processes could be non-deterministic.

Not if you use timestamps instead of hashes, which rsync does by
default. You'd have to disable the filesize check, though, which is why
the patch above also provides a new --times-only switch.

That patch is pretty raw, though, and I don't think I have the time or
inclination to work on it-- my use case is not very urgent, and I don't
enjoy coding in plain C.