experimental support for AU sidechain busses

some plugins include a sidechain bus which is not explicitly
listed under "Reported Channel Capabilities" list,
nor the "Input/Output Channel Handling"

diff --git a/libs/ardour/audio_unit.cc b/libs/ardour/audio_unit.cc
index c31d77256eda6f2fc826f51ca21f522f08f32b05..a520fbb00e981d4477ee4ae77f6f92a622590536 100644 (file)
--- a/libs/ardour/audio_unit.cc
+++ b/libs/ardour/audio_unit.cc
@@ -1256,7 +1256,22 @@ AUPlugin::can_support_io_configuration (const ChanCount& in, ChanCount& out, Cha
                return false;
        }
 
-       vector<pair<int,int> >& io_configs = pinfo->cache.io_configs;
+       vector<pair<int,int> > io_configs = pinfo->cache.io_configs;
+
+       if (input_elements > 1) {
+               const vector<pair<int,int> >& ioc (pinfo->cache.io_configs);
+               for (vector<pair<int,int> >::const_iterator i = ioc.begin(); i != ioc.end(); ++i) {
+                       int32_t possible_in = i->first;
+                       int32_t possible_out = i->second;
+                       if (possible_in <= 1 || possible_out <= 1) {
+                               continue;
+                       }
+                       for (uint32_t i = 1; i < input_elements; ++i) {
+                               // TODO: consider up-to bus_inputs[i]
+                               io_configs.push_back (pair<int,int> (possible_in + bus_inputs[i], possible_out));
+                       }
+               }
+       }
 
        DEBUG_TRACE (DEBUG::AudioUnits, string_compose ("%1 has %2 IO configurations, looking for %3 in, %4 out\n",
                                                        name(), io_configs.size(), in, out));