4 files changed, 88 insertions, 15 deletions
diff --git a/src/mixer/MixerList.hxx b/src/mixer/MixerList.hxx
index e75b2e6ff..8be74adf2 100644
--- a/src/mixer/MixerList.hxx
+++ b/src/mixer/MixerList.hxx
@@ -27,6 +27,7 @@
 
 struct MixerPlugin;
 
+extern const MixerPlugin null_mixer_plugin;
 extern const MixerPlugin software_mixer_plugin;
 extern const MixerPlugin alsa_mixer_plugin;
 extern const MixerPlugin oss_mixer_plugin;
diff --git a/src/mixer/MixerType.cxx b/src/mixer/MixerType.cxx
index cd45db0d9..8972118e5 100644
--- a/src/mixer/MixerType.cxx
+++ b/src/mixer/MixerType.cxx
@@ -23,17 +23,19 @@
 #include <assert.h>
 #include <string.h>
 
-enum mixer_type
+MixerType
 mixer_type_parse(const char *input)
 {
 	assert(input != NULL);
 
 	if (strcmp(input, "none") == 0 || strcmp(input, "disabled") == 0)
-		return MIXER_TYPE_NONE;
+		return MixerType::NONE;
 	else if (strcmp(input, "hardware") == 0)
-		return MIXER_TYPE_HARDWARE;
+		return MixerType::HARDWARE;
 	else if (strcmp(input, "software") == 0)
-		return MIXER_TYPE_SOFTWARE;
+		return MixerType::SOFTWARE;
+	else if (strcmp(input, "null") == 0)
+		return MixerType::NULL_;
 	else
-		return MIXER_TYPE_UNKNOWN;
+		return MixerType::UNKNOWN;
 }
diff --git a/src/mixer/MixerType.hxx b/src/mixer/MixerType.hxx
index bfa2637b7..40f60203d 100644
--- a/src/mixer/MixerType.hxx
+++ b/src/mixer/MixerType.hxx
@@ -20,28 +20,31 @@
 #ifndef MPD_MIXER_TYPE_HXX
 #define MPD_MIXER_TYPE_HXX
 
-enum mixer_type {
+enum class MixerType {
 	/** parser error */
-	MIXER_TYPE_UNKNOWN,
+	UNKNOWN,
 
 	/** mixer disabled */
-	MIXER_TYPE_NONE,
+	NONE,
+
+	/** "null" mixer (virtual fake) */
+	NULL_,
 
 	/** software mixer with pcm_volume() */
-	MIXER_TYPE_SOFTWARE,
+	SOFTWARE,
 
 	/** hardware mixer (output's plugin) */
-	MIXER_TYPE_HARDWARE,
+	HARDWARE,
 };
 
 /**
- * Parses a "mixer_type" setting from the configuration file.
+ * Parses a #MixerType setting from the configuration file.
  *
- * @param input the configured string value; must not be NULL
- * @return a #mixer_type value; MIXER_TYPE_UNKNOWN means #input could
- * not be parsed
+ * @param input the configured string value; must not be NULL @return
+ * a #MixerType value; #MixerType::UNKNOWN means #input could not be
+ * parsed
  */
-enum mixer_type
+MixerType
 mixer_type_parse(const char *input);
 
 #endif
diff --git a/src/mixer/plugins/NullMixerPlugin.cxx b/src/mixer/plugins/NullMixerPlugin.cxx
new file mode 100644
index 000000000..b8894d443
--- /dev/null
+++ b/src/mixer/plugins/NullMixerPlugin.cxx
@@ -0,0 +1,67 @@
+/*
+ * Copyright (C) 2003-2014 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 "config.h"
+#include "mixer/MixerInternal.hxx"
+
+class NullMixer final : public Mixer {
+	/**
+	 * The current volume in percent (0..100).
+	 */
+	unsigned volume;
+
+public:
+	NullMixer(MixerListener &_listener)
+		:Mixer(null_mixer_plugin, _listener),
+		 volume(100)
+	{
+	}
+
+	/* virtual methods from class Mixer */
+	bool Open(gcc_unused Error &error) override {
+		return true;
+	}
+
+	void Close() override {
+	}
+
+	int GetVolume(gcc_unused Error &error) override {
+		return volume;
+	}
+
+	bool SetVolume(unsigned _volume, gcc_unused Error &error) override {
+		volume = _volume;
+		return true;
+	}
+};
+
+static Mixer *
+null_mixer_init(gcc_unused EventLoop &event_loop,
+		gcc_unused AudioOutput &ao,
+		MixerListener &listener,
+		gcc_unused const config_param &param,
+		gcc_unused Error &error)
+{
+	return new NullMixer(listener);
+}
+
+const MixerPlugin null_mixer_plugin = {
+	null_mixer_init,
+	true,
+};