code.delx.au - pulseaudio/blob - src/pulse/volume.h

   1 #ifndef foovolumehfoo
   2 #define foovolumehfoo
   3
   4 /* $Id$ */
   5
   6 /***
   7   This file is part of PulseAudio.
   8
   9   Copyright 2004-2006 Lennart Poettering
  10   Copyright 2006 Pierre Ossman <ossman@cendio.se> for Cendio AB
  11
  12   PulseAudio is free software; you can redistribute it and/or modify
  13   it under the terms of the GNU Lesser General Public License as published
  14   by the Free Software Foundation; either version 2 of the License,
  15   or (at your option) any later version.
  16
  17   PulseAudio is distributed in the hope that it will be useful, but
  18   WITHOUT ANY WARRANTY; without even the implied warranty of
  19   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  20   General Public License for more details.
  21
  22   You should have received a copy of the GNU Lesser General Public License
  23   along with PulseAudio; if not, write to the Free Software
  24   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
  25   USA.
  26 ***/
  27
  28 #include <inttypes.h>
  29 #include <pulse/cdecl.h>
  30 #include <pulse/sample.h>
  31
  32 /** \page volume Volume Control
  33  *
  34  * \section overv_sec Overview
  35  *
  36  * Sinks, sources, sink inputs and samples can all have their own volumes.
  37  * To deal with these, The PulseAudio libray contains a number of functions
  38  * that ease handling.
  39  *
  40  * The basic volume type in PulseAudio is the \ref pa_volume_t type. Most of
  41  * the time, applications will use the aggregated pa_cvolume structure that
  42  * can store the volume of all channels at once.
  43  *
  44  * Volumes commonly span between muted (0%), and normal (100%). It is possible
  45  * to set volumes to higher than 100%, but clipping might occur.
  46  *
  47  * \section calc_sec Calculations
  48  *
  49  * The volumes in PulseAudio are logarithmic in nature and applications
  50  * shouldn't perform calculations with them directly. Instead, they should
  51  * be converted to and from either dB or a linear scale:
  52  *
  53  * \li dB - pa_sw_volume_from_dB() / pa_sw_volume_to_dB()
  54  * \li Linear - pa_sw_volume_from_linear() / pa_sw_volume_to_linear()
  55  *
  56  * For simple multiplication, pa_sw_volume_multiply() and
  57  * pa_sw_cvolume_multiply() can be used.
  58  *
  59  * Calculations can only be reliably performed on software volumes
  60  * as it is commonly unknown what scale hardware volumes relate to.
  61  *
  62  * The functions described above are only valid when used with
  63  * software volumes. Hence it is usually a better idea to treat all
  64  * volume values as opaque with a range from PA_VOLUME_MUTE (0%) to
  65  * PA_VOLUME_NORM (100%) and to refrain from any calculations with
  66  * them.
  67  *
  68  * \section conv_sec Convenience Functions
  69  *
  70  * To handle the pa_cvolume structure, the PulseAudio library provides a
  71  * number of convenienc functions:
  72  *
  73  * \li pa_cvolume_valid() - Tests if a pa_cvolume structure is valid.
  74  * \li pa_cvolume_equal() - Tests if two pa_cvolume structures are identical.
  75  * \li pa_cvolume_channels_equal_to() - Tests if all channels of a pa_cvolume
  76  *                             structure have a given volume.
  77  * \li pa_cvolume_is_muted() - Tests if all channels of a pa_cvolume
  78  *                             structure are muted.
  79  * \li pa_cvolume_is_norm() - Tests if all channels of a pa_cvolume structure
  80  *                            are at a normal volume.
  81  * \li pa_cvolume_set() - Set all channels of a pa_cvolume structure to a
  82  *                        certain volume.
  83  * \li pa_cvolume_reset() - Set all channels of a pa_cvolume structure to a
  84  *                          normal volume.
  85  * \li pa_cvolume_mute() - Set all channels of a pa_cvolume structure to a
  86  *                         muted volume.
  87  * \li pa_cvolume_avg() - Return the average volume of all channels.
  88  * \li pa_cvolume_snprint() - Pretty print a pa_cvolume structure.
  89  */
  90
  91 /** \file
  92  * Constants and routines for volume handling */
  93
  94 PA_C_DECL_BEGIN
  95
  96 /** Volume specification:
  97  *  PA_VOLUME_MUTED: silence;
  98  * < PA_VOLUME_NORM: decreased volume;
  99  *   PA_VOLUME_NORM: normal volume;
 100  * > PA_VOLUME_NORM: increased volume */
 101 typedef uint32_t pa_volume_t;
 102
 103 /** Normal volume (100%) */
 104 #define PA_VOLUME_NORM (0x10000)
 105
 106 /** Muted volume (0%) */
 107 #define PA_VOLUME_MUTED (0)
 108
 109 /** A structure encapsulating a per-channel volume */
 110 typedef struct pa_cvolume {
 111     uint8_t channels;                     /**< Number of channels */
 112     pa_volume_t values[PA_CHANNELS_MAX];  /**< Per-channel volume  */
 113 } pa_cvolume;
 114
 115 /** Return non-zero when *a == *b */
 116 int pa_cvolume_equal(const pa_cvolume *a, const pa_cvolume *b);
 117
 118 /** Set the volume of all channels to PA_VOLUME_NORM */
 119 #define pa_cvolume_reset(a, n) pa_cvolume_set((a), (n), PA_VOLUME_NORM)
 120
 121 /** Set the volume of all channels to PA_VOLUME_MUTED */
 122 #define pa_cvolume_mute(a, n) pa_cvolume_set((a), (n), PA_VOLUME_MUTED)
 123
 124 /** Set the volume of all channels to the specified parameter */
 125 pa_cvolume* pa_cvolume_set(pa_cvolume *a, unsigned channels, pa_volume_t v);
 126
 127 /** Maximum length of the strings returned by pa_cvolume_snprint() */
 128 #define PA_CVOLUME_SNPRINT_MAX 64
 129
 130 /** Pretty print a volume structure */
 131 char *pa_cvolume_snprint(char *s, size_t l, const pa_cvolume *c);
 132
 133 /** Return the average volume of all channels */
 134 pa_volume_t pa_cvolume_avg(const pa_cvolume *a);
 135
 136 /** Return TRUE when the passed cvolume structure is valid, FALSE otherwise */
 137 int pa_cvolume_valid(const pa_cvolume *v);
 138
 139 /** Return non-zero if the volume of all channels is equal to the specified value */
 140 int pa_cvolume_channels_equal_to(const pa_cvolume *a, pa_volume_t v);
 141
 142 /** Return 1 if the specified volume has all channels muted */
 143 #define pa_cvolume_is_muted(a) pa_cvolume_channels_equal_to((a), PA_VOLUME_MUTED)
 144
 145 /** Return 1 if the specified volume has all channels on normal level */
 146 #define pa_cvolume_is_norm(a) pa_cvolume_channels_equal_to((a), PA_VOLUME_NORM)
 147
 148 /** Multiply two volumes specifications, return the result. This uses PA_VOLUME_NORM as neutral element of multiplication. This is only valid for software volumes! */
 149 pa_volume_t pa_sw_volume_multiply(pa_volume_t a, pa_volume_t b);
 150
 151 /** Multiply to per-channel volumes and return the result in *dest. This is only valid for software volumes! */
 152 pa_cvolume *pa_sw_cvolume_multiply(pa_cvolume *dest, const pa_cvolume *a, const pa_cvolume *b);
 153
 154 /** Convert a decibel value to a volume. This is only valid for software volumes! \since 0.4 */
 155 pa_volume_t pa_sw_volume_from_dB(double f);
 156
 157 /** Convert a volume to a decibel value. This is only valid for software volumes! \since 0.4 */
 158 double pa_sw_volume_to_dB(pa_volume_t v);
 159
 160 /** Convert a linear factor to a volume. This is only valid for software volumes! \since 0.8 */
 161 pa_volume_t pa_sw_volume_from_linear(double v);
 162
 163 /** Convert a volume to a linear factor. This is only valid for software volumes! \since 0.8 */
 164 double pa_sw_volume_to_linear(pa_volume_t v);
 165
 166 #ifdef INFINITY
 167 #define PA_DECIBEL_MININFTY (-INFINITY)
 168 #else
 169 /** This value is used as minus infinity when using pa_volume_{to,from}_dB(). \since 0.4 */
 170 #define PA_DECIBEL_MININFTY (-200)
 171 #endif
 172
 173 PA_C_DECL_END
 174
 175 #endif