Add Monitor Return

This is a special case of an Internal Return processor
dedicated to the monitor-section. The main use-case will
be to collect signals from physical ports in a realtime-safe
manner (no connections or Port creation)

libs/ardour/ardour/monitor_return.h

@@ -0,0 +1,45 @@
+/*
+ * Copyright (C) 2021 Robin Gareus <robin@gareus.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef __ardour_monitor_return_h__
+#define __ardour_monitor_return_h__
+
+#include "ardour/internal_return.h"
+
+namespace ARDOUR {
+
+class AudioPort;
+
+class LIBARDOUR_API MonitorReturn : public InternalReturn
+{
+public:
+	MonitorReturn (Session&);
+	~MonitorReturn ();
+
+	void run (BufferSet& bufs, samplepos_t start_sample, samplepos_t end_sample, double speed, pframes_t nframes, bool);
+
+protected:
+	XMLNode& state ();
+
+	uint32_t _nch;
+	gain_t   _gain;
+};
+
+} // namespace ARDOUR
+
+#endif

libs/ardour/monitor_return.cc

@@ -0,0 +1,76 @@
+/*
+ * Copyright (C) 2021 Robin Gareus <robin@gareus.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include <algorithm>
+#include <glibmm/threads.h>
+
+#include "ardour/audio_port.h"
+#include "ardour/audioengine.h"
+#include "ardour/monitor_return.h"
+#include "ardour/session.h"
+
+using namespace ARDOUR;
+
+MonitorReturn::MonitorReturn (Session& s)
+	: InternalReturn (s, "Monitor Return")
+	, _nch (0)
+	, _gain (1.f)
+{
+#if 0
+	MonitorPort& mp (AudioEngine::instance()->monitor_port ());
+	mp->enable ();
+#endif
+}
+
+MonitorReturn::~MonitorReturn ()
+{
+	MonitorPort& mp (AudioEngine::instance()->monitor_port ());
+	mp.clear_ports (true);
+}
+
+void
+MonitorReturn::run (BufferSet& bufs, samplepos_t start_sample, samplepos_t end_sample, double speed, pframes_t nframes, bool result_required)
+{
+	InternalReturn::run (bufs, start_sample, end_sample, speed, nframes, result_required);
+
+	MonitorPort& mp (AudioEngine::instance()->monitor_port ());
+
+	if (mp.silent ()) {
+		return;
+	}
+
+	uint32_t nch = bufs.count().n_audio ();
+	if (_nch != nch) {
+		_nch = _nch;
+		_gain = nch > 0 ? (1.f / sqrtf (nch)) : 1.f;
+	}
+
+	const AudioBuffer& bb (mp.get_audio_buffer (nframes));
+	for (BufferSet::iterator b = bufs.begin (DataType::AUDIO); b != bufs.end (DataType::AUDIO); ++b) {
+		AudioBuffer* ab = dynamic_cast<AudioBuffer*> (&(*b));
+		ab->accumulate_with_gain_from (bb, nframes, _gain);
+	}
+}
+
+XMLNode&
+MonitorReturn::state ()
+{
+	XMLNode& node (InternalReturn::state ());
+	node.set_property ("type", "monreturn");
+	return node;
+}

libs/ardour/wscript

@@ -151,6 +151,7 @@ libardour_sources = [
         'monitor_control.cc',
         'monitor_port.cc',
         'monitor_processor.cc',
+        'monitor_return.cc',
         'mp3fileimportable.cc',
         'mp3filesource.cc',
         'mtc_slave.cc',