src/pcm_volume.c

   1 /*
   2  * Copyright (C) 2003-2010 The Music Player Daemon Project
   3  * http://www.musicpd.org
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  18  */
  19
  20 #include "config.h"
  21 #include "pcm_volume.h"
  22 #include "pcm_utils.h"
  23 #include "audio_format.h"
  24
  25 #include <glib.h>
  26
  27 #include <stdint.h>
  28 #include <string.h>
  29
  30 #undef G_LOG_DOMAIN
  31 #define G_LOG_DOMAIN "pcm_volume"
  32
  33 static void
  34 pcm_volume_change_8(int8_t *buffer, unsigned num_samples, int volume)
  35 {
  36         while (num_samples > 0) {
  37                 int32_t sample = *buffer;
  38
  39                 sample = (sample * volume + pcm_volume_dither() +
  40                           PCM_VOLUME_1 / 2)
  41                         / PCM_VOLUME_1;
  42
  43                 *buffer++ = pcm_range(sample, 8);
  44                 --num_samples;
  45         }
  46 }
  47
  48 static void
  49 pcm_volume_change_16(int16_t *buffer, unsigned num_samples, int volume)
  50 {
  51         while (num_samples > 0) {
  52                 int32_t sample = *buffer;
  53
  54                 sample = (sample * volume + pcm_volume_dither() +
  55                           PCM_VOLUME_1 / 2)
  56                         / PCM_VOLUME_1;
  57
  58                 *buffer++ = pcm_range(sample, 16);
  59                 --num_samples;
  60         }
  61 }
  62
  63 #ifdef __i386__
  64 /**
  65  * Optimized volume function for i386.  Use the EDX:EAX 2*32 bit
  66  * multiplication result instead of emulating 64 bit multiplication.
  67  */
  68 static inline int32_t
  69 pcm_volume_sample_24(int32_t sample, int32_t volume, G_GNUC_UNUSED int32_t dither)
  70 {
  71         int32_t result;
  72
  73         asm(/* edx:eax = sample * volume */
  74             "imul %2\n"
  75
  76             /* "add %3, %1\n"  dithering disabled for now, because we
  77                have no overflow check - is dithering really important
  78                here? */
  79
  80             /* eax = edx:eax / PCM_VOLUME_1 */
  81             "sal $22, %%edx\n"
  82             "shr $10, %1\n"
  83             "or %%edx, %1\n"
  84
  85             : "=a"(result)
  86             : "0"(sample), "r"(volume) /* , "r"(dither) */
  87             : "edx"
  88             );
  89
  90         return result;
  91 }
  92 #endif
  93
  94 static void
  95 pcm_volume_change_24(int32_t *buffer, unsigned num_samples, int volume)
  96 {
  97         while (num_samples > 0) {
  98 #ifdef __i386__
  99                 /* assembly version for i386 */
 100                 int32_t sample = *buffer;
 101
 102                 sample = pcm_volume_sample_24(sample, volume,
 103                                               pcm_volume_dither());
 104 #else
 105                 /* portable version */
 106                 int64_t sample = *buffer;
 107
 108                 sample = (sample * volume + pcm_volume_dither() +
 109                           PCM_VOLUME_1 / 2)
 110                         / PCM_VOLUME_1;
 111 #endif
 112                 *buffer++ = pcm_range(sample, 24);
 113                 --num_samples;
 114         }
 115 }
 116
 117 static void
 118 pcm_volume_change_32(int32_t *buffer, unsigned num_samples, int volume)
 119 {
 120         while (num_samples > 0) {
 121 #ifdef __i386__
 122                 /* assembly version for i386 */
 123                 int32_t sample = *buffer;
 124
 125                 *buffer++ = pcm_volume_sample_24(sample, volume, 0);
 126 #else
 127                 /* portable version */
 128                 int64_t sample = *buffer;
 129
 130                 sample = (sample * volume + pcm_volume_dither() +
 131                           PCM_VOLUME_1 / 2)
 132                         / PCM_VOLUME_1;
 133                 *buffer++ = pcm_range_64(sample, 32);
 134 #endif
 135
 136                 --num_samples;
 137         }
 138 }
 139
 140 bool
 141 pcm_volume(void *buffer, int length,
 142            const struct audio_format *format,
 143            int volume)
 144 {
 145         if (volume == PCM_VOLUME_1)
 146                 return true;
 147
 148         if (volume <= 0) {
 149                 memset(buffer, 0, length);
 150                 return true;
 151         }
 152
 153         switch (format->format) {
 154         case SAMPLE_FORMAT_S8:
 155                 pcm_volume_change_8((int8_t *)buffer, length, volume);
 156                 return true;
 157
 158         case SAMPLE_FORMAT_S16:
 159                 pcm_volume_change_16((int16_t *)buffer, length / 2,
 160                                      volume);
 161                 return true;
 162
 163         case SAMPLE_FORMAT_S24_P32:
 164                 pcm_volume_change_24((int32_t*)buffer, length / 4,
 165                                      volume);
 166                 return true;
 167
 168         case SAMPLE_FORMAT_S32:
 169                 pcm_volume_change_32((int32_t*)buffer, length / 4,
 170                                      volume);
 171                 return true;
 172
 173         default:
 174                 return false;
 175         }
 176 }