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authorMichael Sevakis <jethead71@rockbox.org>2013-04-05 04:36:05 -0400
committerMichael Sevakis <jethead71@rockbox.org>2013-04-11 22:55:16 +0200
commitf5a5b946867677de76c405ee72e2ea47e36e4c83 (patch)
tree8fb97a35059a16681b726973b4a5e13d41f96a35 /firmware/export/pcm_sw_volume.h
parenta9049a79d706dba61837ad02c7d7e3475cb6c193 (diff)
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Implement universal in-PCM-driver software volume control.
Implements double-buffered volume, balance and prescaling control in the main PCM driver when HAVE_SW_VOLUME_CONTROL is defined ensuring that all PCM is volume controlled and level changes are low in latency. Supports -73 to +6 dB using a 15-bit factor so that no large-integer math is needed. Low-level hardware drivers do not have to implement it themselves but parameters can be changed (currently defined in pcm-internal.h) to work best with a particular SoC or to provide different volume ranges. Volume and prescale calls should be made in the codec driver. It should appear as a normal hardware interface. PCM volume calls expect .1 dB units. Change-Id: Idf6316a64ef4fb8abcede10707e1e6c6d01d57db Reviewed-on: http://gerrit.rockbox.org/423 Reviewed-by: Michael Sevakis <jethead71@rockbox.org> Tested-by: Michael Sevakis <jethead71@rockbox.org>
Diffstat (limited to 'firmware/export/pcm_sw_volume.h')
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1 files changed, 40 insertions, 0 deletions
diff --git a/firmware/export/pcm_sw_volume.h b/firmware/export/pcm_sw_volume.h
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+/***************************************************************************
+ * __________ __ ___.
+ * Open \______ \ ____ ____ | | _\_ |__ _______ ___
+ * Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ /
+ * Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < <
+ * Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \
+ * \/ \/ \/ \/ \/
+ * $Id$
+ *
+ * Copyright (C) 2013 by Michael Sevakis
+ *
+ * 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 software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ****************************************************************************/
+#ifndef PCM_SW_VOLUME_H
+#define PCM_SW_VOLUME_H
+
+#ifdef HAVE_SW_VOLUME_CONTROL
+
+#include <audiohw.h>
+
+#define PCM_MUTE_LEVEL INT_MIN
+
+#ifdef AUDIOHW_HAVE_PRESCALER
+/* Set the prescaler value for all PCM playback */
+void pcm_set_prescaler(int prescale);
+#endif /* AUDIOHW_HAVE_PRESCALER */
+
+/* Set the per-channel volume cut/gain for all PCM playback */
+void pcm_set_master_volume(int vol_l, int vol_r);
+
+#endif /* HAVE_SW_VOLUME_CONTROL */
+
+#endif /* PCM_SW_VOLUME_H */