Some sort of filter based filesystem

Lowell Gilbert freebsd-questions-local at
Tue Jul 19 16:18:48 GMT 2005

Svein Halvor Halvorsen <svein-freebsd-questions at> writes:

> What would be nice, is some kind of nullfs-like read only filesystem that 
> would send all files through a configurable filter when opened. That way I 
> could put all my music in FLAC format on hdd, and then, when I wanted to 
> transfer some tracks to my portable player, I could grab the files from 
> the ogg-directory. Or when I wanted to burn to CD-A, I could grab 'em from 
> the wav-dir. 
> Is something like this available somewhere? 

It's a clever idea, but not really very useful; usually a virtual
filesystem approach is good when you can generate the data as needed.
For something like this, you would need to pregenerate the various
forms anyway, so you wouldn't save disk space.

> Or how about some other solution, not file system based?

Scripting it would make sense; periodically scan the source directory
for new files and build the alternate formats.

I have a script that picks a random set of MP3 files out of a
directory and builds a regular audio CD with those songs, normalizing
the volume along the way.  [I use this to burn CD-RWs to listen to in
the gym.]  It might be a useful example: look in

Be well.
Lowell Gilbert, embedded/networking software engineer, Boston area

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