[BRLTTY] [PATCH] Very preliminary Darwin audio support

[Peter Lundblad]

Hi,

The below patch adds very preliminary support for using the software
synth shipped with Mac OS X as a MIDI device for audio feedback. It is
definitely not ready. For example, it lacks error handling and logging
completely. I am posting it for some initial feedback on the
approach. Also, I am wondering if we should give this software synth a
special device name such as "builtin" to allow for extending it for
real MID devices later.

Feel free to test, criticize or whatever. "It works on my machine".

Regards,
//Peter

[[[
Add support for software synth audio on Darwin.
]]]

Index: Programs/sys_darwin.c
===================================================================
--- Programs/sys_darwin.c	(revision 2540)
+++ Programs/sys_darwin.c	(working copy)
@@ -37,7 +37,7 @@
 #endif /* ENABLE_PCM_SUPPORT */
 
 #ifdef ENABLE_MIDI_SUPPORT
-#include "sys_midi_none.h"
+#include "sys_midi_darwin.h"
 #endif /* ENABLE_MIDI_SUPPORT */
 
 #include "sys_ports_none.h"
Index: Programs/sys_midi_darwin.h
===================================================================
--- Programs/sys_midi_darwin.h	(revision 0)
+++ Programs/sys_midi_darwin.h	(revision 0)
@@ -0,0 +1,118 @@
+/*
+ * BRLTTY - A background process providing access to the console screen (when in
+ *          text mode) for a blind person using a refreshable braille display.
+ *
+ * Copyright (C) 1995-2006 by The BRLTTY Developers.
+ *
+ * BRLTTY comes with ABSOLUTELY NO WARRANTY.
+ *
+ * This is free software, placed under the terms of the
+ * GNU General Public License, as published by the Free Software
+ * Foundation.  Please see the file COPYING for details.
+ *
+ * Web Page: http://mielke.cc/brltty/
+ *
+ * This software is maintained by Dave Mielke <dave at mielke.cc>.
+ */
+
+#include <CoreServices/CoreServices.h>
+#include <AudioUnit/AudioUnit.h>
+#include <AudioToolbox/AudioToolbox.h>
+
+struct MidiDeviceStruct {
+  AUGraph graph;
+  AudioUnit synth;
+  /* Note that is currently playing. */
+  int note;
+};
+  
+
+MidiDevice *
+openMidiDevice (int errorLevel, const char *device) {
+  MidiDevice *midi;
+
+  if ((midi = malloc(sizeof(*midi)))) {
+    /* Create a graph with a synth and a default output unit. */
+    AUNode synthNode, outNode;
+    ComponentDescription cd;
+
+    cd.componentManufacturer = kAudioUnitManufacturer_Apple;
+    cd.componentFlags = 0;
+    cd.componentFlagsMask = 0;
+
+    NewAUGraph(&midi->graph);
+
+    cd.componentType = kAudioUnitType_MusicDevice;
+    cd.componentSubType = kAudioUnitSubType_DLSSynth;
+    AUGraphNewNode(midi->graph, &cd, 0, NULL, &synthNode);
+
+    cd.componentType = kAudioUnitType_Output;
+    cd.componentSubType = kAudioUnitSubType_DefaultOutput;
+    AUGraphNewNode(midi->graph, &cd, 0, NULL, &outNode);
+
+    AUGraphOpen(midi->graph);
+    AUGraphConnectNodeInput(midi->graph, synthNode, 0, outNode, 0);
+
+    AUGraphGetNodeInfo(midi->graph, synthNode, 0, 0, 0, &midi->synth);
+
+    AUGraphInitialize(midi->graph);
+
+    /* Turn off the reverb.  The value range is -120 to 40 dB. */
+    AudioUnitSetParameter(midi->synth, kMusicDeviceParam_ReverbVolume,
+			  kAudioUnitScope_Global, 0, -120, 0);
+
+    /* TODO: Maybe just start the graph when we are going to use it? */
+    AUGraphStart(midi->graph);
+  }
+
+  return midi;
+}
+
+void
+closeMidiDevice (MidiDevice *midi) {
+  if (midi) {
+    DisposeAUGraph(midi->graph);
+    free(midi);
+  }
+}
+
+int
+flushMidiDevice (MidiDevice *midi) {
+  return 1;
+}
+
+int
+setMidiInstrument (MidiDevice *midi, unsigned char channel, unsigned char instrument) {
+  MusicDeviceMIDIEvent(midi->synth, 0xC0 | channel, instrument, 0, 0);
+
+  return 1;
+}
+
+int
+beginMidiBlock (MidiDevice *midi) {
+  return 1;
+}
+
+int
+endMidiBlock (MidiDevice *midi) {
+  return 1;
+}
+
+int
+startMidiNote (MidiDevice *midi, unsigned char channel, unsigned char note, unsigned char volume) {
+  MusicDeviceMIDIEvent(midi->synth, 0x90 | channel, note, volume, 0);
+  midi->note = note;
+
+  return 1;
+}
+
+int
+stopMidiNote (MidiDevice *midi, unsigned char channel) {
+  return startMidiNote(midi, channel, midi->note, 0);
+}
+
+int
+insertMidiWait (MidiDevice *midi, int duration) {
+  accurateDelay(duration);
+  return 1;
+}
Index: configure.ac
===================================================================
--- configure.ac	(revision 2540)
+++ configure.ac	(working copy)
@@ -857,7 +857,7 @@
       ;;
    darwin*)
       system_object="darwin"
-      LIBS="-lIOKit -framework CoreFoundation ${LIBS}"
+      LIBS="-lIOKit -framework CoreFoundation -framework AudioUnit -framework AudioToolbox ${LIBS}"
       ;;
    *)
       AC_MSG_ERROR([no system object available for ${host_os}])