1 files changed, 81 insertions, 0 deletions
diff --git a/src/pcm/PcmVolume.hxx b/src/pcm/PcmVolume.hxx
new file mode 100644
index 000000000..8cd82acf7
--- /dev/null
+++ b/src/pcm/PcmVolume.hxx
@@ -0,0 +1,81 @@
+/*
+ * Copyright (C) 2003-2013 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 MPD_PCM_VOLUME_HXX
+#define MPD_PCM_VOLUME_HXX
+
+#include "PcmPrng.hxx"
+#include "AudioFormat.hxx"
+
+#include <stdint.h>
+#include <stddef.h>
+
+enum {
+	/** this value means "100% volume" */
+	PCM_VOLUME_1 = 1024,
+};
+
+struct AudioFormat;
+
+/**
+ * Converts a float value (0.0 = silence, 1.0 = 100% volume) to an
+ * integer volume value (1000 = 100%).
+ */
+static inline int
+pcm_float_to_volume(float volume)
+{
+	return volume * PCM_VOLUME_1 + 0.5;
+}
+
+static inline float
+pcm_volume_to_float(int volume)
+{
+	return (float)volume / (float)PCM_VOLUME_1;
+}
+
+/**
+ * Returns the next volume dithering number, between -511 and +511.
+ * This number is taken from a global PRNG, see pcm_prng().
+ */
+static inline int
+pcm_volume_dither(void)
+{
+	static unsigned long state;
+	uint32_t r;
+
+	r = state = pcm_prng(state);
+
+	return (r & 511) - ((r >> 9) & 511);
+}
+
+/**
+ * Adjust the volume of the specified PCM buffer.
+ *
+ * @param buffer the PCM buffer
+ * @param length the length of the PCM buffer
+ * @param format the sample format of the PCM buffer
+ * @param volume the volume between 0 and #PCM_VOLUME_1
+ * @return true on success, false if the audio format is not supported
+ */
+bool
+pcm_volume(void *buffer, size_t length,
+	   SampleFormat format,
+	   int volume);
+
+#endif