[LAD] RFC: Default discovery paths for LADSPA, LRDF, LV2 and DSSI (and more?)

[Chris Cannam]

On Wed, Jun 24, 2009 at 8:22 PM, David Robillard<dave at drobilla.net> wrote:
> On Wed, 2009-06-24 at 17:55 +0200, Stefano D'Angelo wrote:
>> Hereby I propose some default paths which could be used, in the hope
>> that API authors lurking around here might want to recommend them and
>> host authors might want to use them:
>> [...]
>
> Note the order matters for PATH-like variables such as these.
>
> The LV2 discovery paths are documented here, FWIW:
>
> http://lv2plug.in/docs/index.php?title=Filesystem_Locations

The DSSI documentation doesn't specify the path at all (sorry, Steve).

For what it's worth:

Rosegarden looks in ~/.dssi, /usr/local/lib/dssi and /usr/lib/dssi in
that order.  Its default path for LADSPA is identical except with
ladspa instead of dssi.

The simple host in the DSSI distribution looks in /usr/local/lib/dssi,
/usr/lib/dssi and ~/.dssi, in that order.  Yes, this is different from
Rosegarden!  I could probably argue for either ordering, but I can't
easily justify the discrepancy.  I suspect Rosegarden reflects my true
preference here.

(I've never really got on with the idea of using ~/.ladspa instead of
~/ladspa -- these are perhaps substantial binary files, why hide them
in a configuration directory? -- but it seemed to be widespread for
LADSPA hosts at the time DSSI was thought up, so we copied it for the
first DSSI hosts.)

For Vamp analysis plugins (http://vamp-plugins.org) I did include a
path recommendation, which is implemented by the plugin loader
included in the SDK.  On Linux it is ~/vamp first, then
/usr/local/lib/vamp and /usr/lib/vamp, in that order.  The provided
plugin loader actually looks in ~/.vamp as well -- a hangover from
LADSPA/DSSI and something I really ought to treat as a bug since all
the documentation differs.  On OS/X the paths are
~/Library/Audio/Plug-Ins/Vamp and /Library/Audio/Plug-Ins/Vamp in that
order.  On Windows the only location searched is "%ProgramFiles%\\Vamp
Plugins".  Note that Vamp isn't a proper acronym, which is why the
paths say Vamp rather than VAMP.

Sonic Visualiser, my only cross-platform LADSPA host so far, uses the
same paths as Rosegarden on Linux.  On OS/X its LADSPA and DSSI paths
are the same as those for Vamp above, but with LADSPA/DSSI (all caps)
instead of Vamp.  On Windows, for LADSPA it looks in
"%ProgramFiles%\\LADSPA Plugins" followed by
"%ProgramFiles%\\Audacity\\Plug-Ins" (because many users will have
effects originally installed for Audacity which IIRC loads them only
from there) and for DSSI it looks in "%ProgramFiles%\\DSSI Plugins"
only.

In every case above, the default path is completely overridden by any
value found in the relevant one of the LADSPA_PATH, DSSI_PATH or
VAMP_PATH environment variables (colon-separated everywhere except on
Windows where it is semicolon-separated).


Chris