rework AudioUnit variable input port count.

[ardour.git] / libs / ardour / audio_unit.cc

diff --git a/libs/ardour/audio_unit.cc b/libs/ardour/audio_unit.cc
index bcf4778b7dfe38ad1a87343a968ec71b51322d30..063055b5e63fc018b22bdee07aea3dda4aceeb98 100644 (file)
--- a/libs/ardour/audio_unit.cc
+++ b/libs/ardour/audio_unit.cc
@@ -423,7 +423,7 @@ AUPlugin::AUPlugin (AudioEngine& engine, Session& session, boost::shared_ptr<CAC
        , input_offset (0)
        , input_buffers (0)
        , frames_processed (0)
-       , _match_ioports (false)
+       , audio_input_cnt (0)
        , _parameter_listener (0)
        , _parameter_listener_arg (0)
        , last_transport_rolling (false)
@@ -1014,8 +1014,8 @@ AUPlugin::configure_io (ChanCount in, ChanCount out)
        AudioStreamBasicDescription streamFormat;
        bool was_initialized = initialized;
        int32_t audio_out = out.n_audio();
-       if (_match_ioports) {
-               in.set (DataType::AUDIO, audio_out);
+       if (audio_input_cnt > 0) {
+               in.set (DataType::AUDIO, audio_input_cnt);
        }
        int32_t audio_in = in.n_audio();
 
@@ -1143,6 +1143,32 @@ AUPlugin::can_support_io_configuration (const ChanCount& in, ChanCount& out)
                audio_out = audio_in;
        }
 
+       /* kAudioUnitProperty_SupportedNumChannels
+        * https://developer.apple.com/library/mac/documentation/MusicAudio/Conceptual/AudioUnitProgrammingGuide/TheAudioUnit/TheAudioUnit.html#//apple_ref/doc/uid/TP40003278-CH12-SW20
+        *
+        * - both fields are -1
+        *   e.g. inChannels = -1 outChannels = -1
+        *    This is the default case. Any number of input and output channels, as long as the numbers match
+        *
+        * - one field is -1, the other field is positive
+        *   e.g. inChannels = -1 outChannels = 2
+        *    Any number of input channels, exactly two output channels
+        *
+        * - one field is -1, the other field is -2
+        *   e.g. inChannels = -1 outChannels = -2
+        *    Any number of input channels, any number of output channels
+        *
+        * - both fields have non-negative values
+        *   e.g. inChannels = 2 outChannels = 6
+        *    Exactly two input channels, exactly six output channels
+        *   e.g. inChannels = 0 outChannels = 2
+        *    No input channels, exactly two output channels (such as for an instrument unit with stereo output)
+        *
+        * - both fields have negative values, neither of which is –1 or –2
+        *   e.g. inChannels = -4 outChannels = -8
+        *    Up to four input channels and up to eight output channels
+        */
+
        for (vector<pair<int,int> >::iterator i = io_configs.begin(); i != io_configs.end(); ++i) {
 
                int32_t possible_in = i->first;
@@ -1314,9 +1340,10 @@ AUPlugin::can_support_io_configuration (const ChanCount& in, ChanCount& out)
                }
 
                if (found) {
-                       if (possible_in < -2 && possible_in == possible_out) {
-                               // input-port count needs to match output-port
-                               _match_ioports = true;
+                       if (possible_in < -2 && audio_in == 0) {
+                               // input-port count cannot be zero, use as many ports
+                               // as outputs, but at most abs(possible_in)
+                               audio_input_cnt = max (1, min (audio_out, -possible_in));
                        }
                        break;
                }