From 3dd3c332414bfbebd69bfd71a4a3198198525eb6 Mon Sep 17 00:00:00 2001
From: Volker Fischer <corrados@users.noreply.github.com>
Date: Tue, 9 Feb 2021 20:32:10 +0100
Subject: Add ALSA midi input support.
---
drumgizmo/input/alsamidi.cc | 196 ++++++++++++++++++++++++++++++++++++++++++++
drumgizmo/input/alsamidi.h | 57 +++++++++++++
2 files changed, 253 insertions(+)
create mode 100644 drumgizmo/input/alsamidi.cc
create mode 100644 drumgizmo/input/alsamidi.h
(limited to 'drumgizmo/input')
diff --git a/drumgizmo/input/alsamidi.cc b/drumgizmo/input/alsamidi.cc
new file mode 100644
index 0000000..068ea2b
--- /dev/null
+++ b/drumgizmo/input/alsamidi.cc
@@ -0,0 +1,196 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/***************************************************************************
+ * alsamidi.cc
+ *
+ * Copyright 2021 Volker Fischer (github.com/corrados)
+ ****************************************************************************/
+
+/*
+ * This file is part of DrumGizmo.
+ *
+ * DrumGizmo is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * DrumGizmo 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 Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with DrumGizmo; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
+ */
+#include <iostream>
+#include <cassert>
+
+#include "cpp11fix.h" // required for c++11
+#include "alsamidi.h"
+
+struct AlsaMidiInitError
+{
+ int const code;
+ const std::string msg;
+
+ AlsaMidiInitError(int op_code, const std::string& msg)
+ : code{op_code}
+ , msg{msg}
+ {
+ }
+
+ static inline void test(int code, const std::string& msg)
+ {
+ if(code < 0)
+ {
+ throw AlsaMidiInitError(code, msg);
+ }
+ }
+};
+
+AlsaMidiInputEngine::AlsaMidiInputEngine()
+ : AudioInputEngineMidi{}
+ , in_port(0)
+ , seq_handle{nullptr}
+ , pos{0u}
+ , events{}
+{
+}
+
+AlsaMidiInputEngine::~AlsaMidiInputEngine()
+{
+ if(seq_handle != nullptr)
+ {
+ snd_seq_close(seq_handle);
+ }
+}
+
+bool AlsaMidiInputEngine::init(const Instruments& instruments)
+{
+ if(!loadMidiMap(midimap_file, instruments))
+ {
+ std::cerr << "[AlsaMidiInputEngine] Failed to parse midimap '"
+ << midimap_file << "'\n";
+ return false;
+ }
+
+ // try to initialize alsa MIDI
+ try
+ {
+ // it is not allowed to block in the run() function, therefore we
+ // have to use a non-blocking mode
+ int value = snd_seq_open(&seq_handle, "default",
+ SND_SEQ_OPEN_INPUT, SND_SEQ_NONBLOCK);
+ AlsaMidiInitError::test(value, "snd_seq_open");
+
+ value = snd_seq_set_client_name(seq_handle, "drumgizmo");
+ AlsaMidiInitError::test(value, "snd_seq_set_client_name");
+
+ in_port =
+ snd_seq_create_simple_port(seq_handle, "listen:in",
+ SND_SEQ_PORT_CAP_WRITE |
+ SND_SEQ_PORT_CAP_SUBS_WRITE,
+ SND_SEQ_PORT_TYPE_APPLICATION);
+ AlsaMidiInitError::test(in_port, "snd_seq_create_simple_port");
+ }
+ catch(AlsaMidiInitError const& error)
+ {
+ std::cerr << "[AlsaMidiInputEngine] " << error.msg
+ << " failed: " << snd_strerror(error.code) << std::endl;
+ return false;
+ }
+
+ return true;
+}
+
+void AlsaMidiInputEngine::setParm(const std::string& parm,
+ const std::string& value)
+{
+ if(parm == "midimap")
+ {
+ // apply midimap filename
+ midimap_file = value;
+ }
+ else
+ {
+ std::cerr << "[AlsaMidiInputEngine] Unsupported parameter '" << parm
+ << "'\n";
+ }
+}
+
+bool AlsaMidiInputEngine::start()
+{
+ return true;
+}
+
+void AlsaMidiInputEngine::stop()
+{
+}
+
+void AlsaMidiInputEngine::pre()
+{
+}
+
+void AlsaMidiInputEngine::run(size_t pos, size_t len,
+ std::vector<event_t>& events)
+{
+ assert(events.empty());
+ snd_seq_event_t* ev = NULL;
+ if ( snd_seq_event_input(seq_handle, &ev) >= 0 )
+ {
+ // TODO Better solution needed: The ALSA MIDI event structure does
+ // not seem to contain the raw MIDI data, therefore we have to re-create
+ // the raw MIDI data based on the ALSA sequence event information.
+ std::vector<uint8_t> midi_buffer(3, 0);
+ bool message_type_handled = true;
+
+ switch(ev->type)
+ {
+ case SND_SEQ_EVENT_NOTEON:
+ midi_buffer[0] = ev->data.note.channel + 0x90; // NoteOn
+ midi_buffer[1] = ev->data.note.note;
+ midi_buffer[2] = ev->data.note.velocity;
+ break;
+
+ case SND_SEQ_EVENT_NOTEOFF:
+ midi_buffer[0] = ev->data.note.channel + 0x80; // NoteOff
+ midi_buffer[1] = ev->data.note.note;
+ midi_buffer[2] = ev->data.note.off_velocity;
+ break;
+
+ case SND_SEQ_EVENT_KEYPRESS:
+ midi_buffer[0] = ev->data.note.channel + 0xA0; // NoteAftertouch
+ midi_buffer[1] = ev->data.note.note;
+ midi_buffer[2] = ev->data.note.velocity;
+ break;
+
+ case SND_SEQ_EVENT_CONTROLLER:
+ midi_buffer[0] = ev->data.control.channel + 0xB0; // ControlChange
+ midi_buffer[1] = ev->data.control.param;
+ midi_buffer[2] = ev->data.control.value;
+ break;
+
+ default:
+ // unkown message type, ignore the message
+ message_type_handled = false;
+ break;
+ }
+
+ if(message_type_handled)
+ {
+ // since we do not want to introduce any additional delay for the
+ // MIDI processing, we set the offset to zero
+ processNote(midi_buffer.data(), midi_buffer.size(), 0, events);
+ }
+ }
+ snd_seq_free_event(ev);
+}
+
+void AlsaMidiInputEngine::post()
+{
+}
+
+bool AlsaMidiInputEngine::isFreewheeling() const
+{
+ return true;
+}
diff --git a/drumgizmo/input/alsamidi.h b/drumgizmo/input/alsamidi.h
new file mode 100644
index 0000000..73e0fc8
--- /dev/null
+++ b/drumgizmo/input/alsamidi.h
@@ -0,0 +1,57 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/***************************************************************************
+ * alsamidi.h
+ *
+ * Copyright 2021 Volker Fischer (github.com/corrados)
+ ****************************************************************************/
+
+/*
+ * This file is part of DrumGizmo.
+ *
+ * DrumGizmo is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * DrumGizmo 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 Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with DrumGizmo; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
+ */
+#pragma once
+#include <memory>
+#include <alsa/asoundlib.h>
+
+#include "audioinputenginemidi.h"
+#include "midimapper.h"
+#include "midimapparser.h"
+
+class AlsaMidiInputEngine
+ : public AudioInputEngineMidi
+{
+public:
+ AlsaMidiInputEngine();
+ ~AlsaMidiInputEngine();
+
+ // based on AudioInputEngineMidi
+ bool init(const Instruments& instruments) override;
+ void setParm(const std::string& parm, const std::string& value) override;
+ bool start() override;
+ void stop() override;
+ void pre() override;
+ void run(size_t pos, size_t len, std::vector<event_t>& events) override;
+ void post() override;
+ bool isFreewheeling() const override;
+
+private:
+ int in_port;
+ snd_seq_t* seq_handle;
+
+ std::string midimap_file;
+ std::size_t pos;
+ std::vector<event_t> events;
+};
--
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