mixer/software: new mixer which controls filter/volume

This mixer plugin may be used instead of the traditional global
software mixer.  It integrates with the "volume" filter plugin, and
can control the software volume of an audio output which has no
hardware mixer.

2 files changed, 157 insertions, 0 deletions

diff --git a/src/mixer/software_mixer_plugin.c b/src/mixer/software_mixer_plugin.c
new file mode 100644
index 00000000..661334e1
--- /dev/null
+++ b/src/mixer/software_mixer_plugin.c
@@ -0,0 +1,124 @@
+/*
+ * Copyright (C) 2003-2009 The Music Player Daemon Project
+ * http://www.musicpd.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 "software_mixer_plugin.h"
+#include "mixer_api.h"
+#include "filter_plugin.h"
+#include "filter_registry.h"
+#include "filter/volume_filter_plugin.h"
+#include "pcm_volume.h"
+
+#include <assert.h>
+#include <math.h>
+
+struct software_mixer {
+	/** the base mixer class */
+	struct mixer base;
+
+	struct filter *filter;
+
+	unsigned volume;
+};
+
+static struct mixer *
+software_mixer_init(G_GNUC_UNUSED const struct config_param *param)
+{
+	struct software_mixer *sm = g_new(struct software_mixer, 1);
+
+	mixer_init(&sm->base, &software_mixer_plugin);
+
+	sm->filter = filter_new(&volume_filter_plugin, NULL, NULL);
+	assert(sm->filter != NULL);
+
+	sm->volume = 100;
+
+	return &sm->base;
+}
+
+static void
+software_mixer_finish(struct mixer *data)
+{
+	struct software_mixer *sm = (struct software_mixer *)data;
+
+	g_free(sm);
+}
+
+static bool
+software_mixer_open(struct mixer *data)
+{
+	struct software_mixer *sm = (struct software_mixer *)data;
+
+	(void)sm;
+	return true;
+}
+
+static void
+software_mixer_close(struct mixer *data)
+{
+	struct software_mixer *sm = (struct software_mixer *)data;
+
+	(void)sm;
+}
+
+static int
+software_mixer_get_volume(struct mixer *mixer)
+{
+	struct software_mixer *sm = (struct software_mixer *)mixer;
+
+	return sm->volume;
+}
+
+static bool
+software_mixer_set_volume(struct mixer *mixer, unsigned volume)
+{
+	struct software_mixer *sm = (struct software_mixer *)mixer;
+
+	assert(volume <= 100);
+
+	sm->volume = volume;
+
+	if (volume >= 100)
+		volume = PCM_VOLUME_1;
+	else if (volume > 0)
+		volume = pcm_float_to_volume((exp(volume / 25.0) - 1) /
+					     (54.5981500331F - 1));
+
+	volume_filter_set(sm->filter, volume);
+	return true;
+}
+
+const struct mixer_plugin software_mixer_plugin = {
+	.init = software_mixer_init,
+	.finish = software_mixer_finish,
+	.open = software_mixer_open,
+	.close = software_mixer_close,
+	.get_volume = software_mixer_get_volume,
+	.set_volume = software_mixer_set_volume,
+	.global = true,
+};
+
+struct filter *
+software_mixer_get_filter(struct mixer *mixer)
+{
+	struct software_mixer *sm = (struct software_mixer *)mixer;
+
+	assert(sm->base.plugin == &software_mixer_plugin);
+
+	return sm->filter;
+}
diff --git a/src/mixer/software_mixer_plugin.h b/src/mixer/software_mixer_plugin.h
new file mode 100644
index 00000000..a59f7ede
--- /dev/null
+++ b/src/mixer/software_mixer_plugin.h
@@ -0,0 +1,33 @@
+/*
+ * Copyright (C) 2003-2009 The Music Player Daemon Project
+ * http://www.musicpd.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 SOFTWARE_MIXER_PLUGIN_H
+#define SOFTWARE_MIXER_PLUGIN_H
+
+struct mixer;
+struct filter;
+
+/**
+ * Returns the (volume) filter associated with this mixer.  All users
+ * of this mixer plugin should install this filter.
+ */
+struct filter *
+software_mixer_get_filter(struct mixer *mixer);
+
+#endif