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annotate src/audio/alsa/SDL_alsa_audio.c @ 354:30935e76acb5

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Updated ALSA audio support for ALSA 0.9
author Sam Lantinga <slouken@libsdl.org>
date Mon, 15 Apr 2002 07:38:54 +0000
parents f6ffac90895c
children a1e54d1ba16f
rev   line source
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1 /*
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2 SDL - Simple DirectMedia Layer
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3 Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002 Sam Lantinga
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4
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5 This library is free software; you can redistribute it and/or
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6 modify it under the terms of the GNU Library General Public
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7 License as published by the Free Software Foundation; either
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8 version 2 of the License, or (at your option) any later version.
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9
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10 This library is distributed in the hope that it will be useful,
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11 but WITHOUT ANY WARRANTY; without even the implied warranty of
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12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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13 Library General Public License for more details.
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14
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15 You should have received a copy of the GNU Library General Public
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16 License along with this library; if not, write to the Free
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17 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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18
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19 Sam Lantinga
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20 slouken@libsdl.org
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21 */
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22
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23
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24
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25 /* Allow access to a raw mixing buffer */
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26
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27 #include <stdlib.h>
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28 #include <stdio.h>
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29 #include <string.h>
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30 #include <errno.h>
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31 #include <unistd.h>
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32 #include <fcntl.h>
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33 #include <signal.h>
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34 #include <sys/types.h>
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35 #include <sys/time.h>
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36
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37 #include "SDL_audio.h"
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38 #include "SDL_error.h"
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39 #include "SDL_audiomem.h"
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40 #include "SDL_audio_c.h"
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41 #include "SDL_timer.h"
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42 #include "SDL_alsa_audio.h"
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43
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44 /* The tag name used by ALSA audio */
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45 #define DRIVER_NAME "alsa"
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46
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47 /* The default ALSA audio driver */
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48 #define DEFAULT_DEVICE "plughw:0,0"
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49
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50 /* Audio driver functions */
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51 static int ALSA_OpenAudio(_THIS, SDL_AudioSpec *spec);
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52 static void ALSA_WaitAudio(_THIS);
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53 static void ALSA_PlayAudio(_THIS);
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54 static Uint8 *ALSA_GetAudioBuf(_THIS);
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55 static void ALSA_CloseAudio(_THIS);
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56
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57 static const char *get_audio_device()
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58 {
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59 const char *device;
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60
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61 device = getenv("AUDIODEV"); /* Is there a standard variable name? */
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62 if ( device == NULL ) {
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63 device = DEFAULT_DEVICE;
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64 }
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65 return device;
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66 }
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67
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68 /* Audio driver bootstrap functions */
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69
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70 static int Audio_Available(void)
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71 {
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72 int available;
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73 int status;
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74 snd_pcm_t *handle;
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75
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76 available = 0;
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77 status = snd_pcm_open(&handle, get_audio_device(), SND_PCM_STREAM_PLAYBACK, 0);
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78 if ( status >= 0 ) {
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79 available = 1;
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80 snd_pcm_close(handle);
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81 }
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82 return(available);
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83 }
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84
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85 static void Audio_DeleteDevice(SDL_AudioDevice *device)
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86 {
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87 free(device->hidden);
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88 free(device);
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89 }
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90
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91 static SDL_AudioDevice *Audio_CreateDevice(int devindex)
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92 {
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93 SDL_AudioDevice *this;
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94
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95 /* Initialize all variables that we clean on shutdown */
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96 this = (SDL_AudioDevice *)malloc(sizeof(SDL_AudioDevice));
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97 if ( this ) {
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98 memset(this, 0, (sizeof *this));
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99 this->hidden = (struct SDL_PrivateAudioData *)
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100 malloc((sizeof *this->hidden));
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101 }
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102 if ( (this == NULL) || (this->hidden == NULL) ) {
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103 SDL_OutOfMemory();
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104 if ( this ) {
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105 free(this);
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106 }
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107 return(0);
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108 }
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109 memset(this->hidden, 0, (sizeof *this->hidden));
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110
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111 /* Set the function pointers */
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112 this->OpenAudio = ALSA_OpenAudio;
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113 this->WaitAudio = ALSA_WaitAudio;
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114 this->PlayAudio = ALSA_PlayAudio;
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115 this->GetAudioBuf = ALSA_GetAudioBuf;
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116 this->CloseAudio = ALSA_CloseAudio;
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117
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118 this->free = Audio_DeleteDevice;
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119
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120 return this;
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121 }
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122
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123 AudioBootStrap ALSA_bootstrap = {
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124 DRIVER_NAME, "ALSA 0.9 PCM audio",
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125 Audio_Available, Audio_CreateDevice
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126 };
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127
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128 /* This function waits until it is possible to write a full sound buffer */
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129 static void ALSA_WaitAudio(_THIS)
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130 {
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131 /* Check to see if the thread-parent process is still alive */
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132 { static int cnt = 0;
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133 /* Note that this only works with thread implementations
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134 that use a different process id for each thread.
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135 */
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136 if (parent && (((++cnt)%10) == 0)) { /* Check every 10 loops */
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137 if ( kill(parent, 0) < 0 ) {
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138 this->enabled = 0;
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139 }
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140 }
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141 }
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142 }
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143
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144 static void ALSA_PlayAudio(_THIS)
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145 {
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146 int status;
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147 int sample_len;
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148 signed short *sample_buf;
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149
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150 sample_len = this->spec.samples;
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151 sample_buf = (signed short *)mixbuf;
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152 while ( sample_len > 0 ) {
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153 status = snd_pcm_writei(pcm_handle, sample_buf, sample_len);
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154 if ( status < 0 ) {
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155 if ( status == -EAGAIN ) {
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156 continue;
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157 }
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158 if ( status == -ESTRPIPE ) {
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159 do {
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160 status = snd_pcm_resume(pcm_handle);
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161 } while ( status == -EAGAIN );
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162 }
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163 if ( status < 0 ) {
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164 status = snd_pcm_prepare(pcm_handle);
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165 }
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166 if ( status < 0 ) {
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167 /* Hmm, not much we can do - abort */
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diff changeset
168 this->enabled = 0;
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diff changeset
169 return;
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170 }
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171 }
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diff changeset
172 sample_buf += status * this->spec.channels;
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diff changeset
173 sample_len -= status;
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174 }
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175 }
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176
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177 static Uint8 *ALSA_GetAudioBuf(_THIS)
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178 {
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179 return(mixbuf);
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180 }
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181
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182 static void ALSA_CloseAudio(_THIS)
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183 {
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184 if ( mixbuf != NULL ) {
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185 SDL_FreeAudioMem(mixbuf);
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186 mixbuf = NULL;
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187 }
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188 if ( pcm_handle ) {
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189 snd_pcm_close(pcm_handle);
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190 pcm_handle = NULL;
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191 }
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192 }
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193
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194 static int ALSA_OpenAudio(_THIS, SDL_AudioSpec *spec)
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195 {
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196 int status;
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197 snd_pcm_hw_params_t *params;
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198 snd_pcm_format_t format;
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199 snd_pcm_uframes_t frames;
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200 Uint16 test_format;
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201
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202 /* Open the audio device */
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203 status = snd_pcm_open(&pcm_handle, get_audio_device(), SND_PCM_STREAM_PLAYBACK, 0);
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204 if ( status < 0 ) {
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205 SDL_SetError("Couldn't open audio device: %s", snd_strerror(status));
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206 return(-1);
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207 }
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208
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209 /* Figure out what the hardware is capable of */
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210 snd_pcm_hw_params_alloca(&params);
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211 status = snd_pcm_hw_params_any(pcm_handle, params);
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212 if ( status < 0 ) {
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213 SDL_SetError("Couldn't get hardware config: %s", snd_strerror(status));
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214 ALSA_CloseAudio(this);
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215 return(-1);
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216 }
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217
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218 /* SDL only uses interleaved sample output */
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219 status = snd_pcm_hw_params_set_access(pcm_handle, params, SND_PCM_ACCESS_RW_INTERLEAVED);
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220 if ( status < 0 ) {
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221 SDL_SetError("Couldn't set interleaved access: %s", snd_strerror(status));
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222 ALSA_CloseAudio(this);
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223 return(-1);
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224 }
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225
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226 /* Try for a closest match on audio format */
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227 status = -1;
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228 for ( test_format = SDL_FirstAudioFormat(spec->format);
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229 test_format && (status < 0); ) {
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230 switch ( test_format ) {
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231 case AUDIO_U8:
354
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232 format = SND_PCM_FORMAT_U8;
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233 break;
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234 case AUDIO_S8:
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235 format = SND_PCM_FORMAT_S8;
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236 break;
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237 case AUDIO_S16LSB:
354
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diff changeset
238 format = SND_PCM_FORMAT_S16_LE;
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239 break;
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240 case AUDIO_S16MSB:
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241 format = SND_PCM_FORMAT_S16_BE;
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242 break;
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243 case AUDIO_U16LSB:
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diff changeset
244 format = SND_PCM_FORMAT_U16_LE;
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245 break;
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246 case AUDIO_U16MSB:
354
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diff changeset
247 format = SND_PCM_FORMAT_U16_BE;
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248 break;
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249 default:
354
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diff changeset
250 format = 0;
0
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251 break;
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252 }
354
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253 if ( format != 0 ) {
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254 status = snd_pcm_hw_params_set_format(pcm_handle, params, format);
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diff changeset
255 }
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256 if ( status < 0 ) {
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257 test_format = SDL_NextAudioFormat();
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258 }
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259 }
354
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diff changeset
260 if ( status < 0 ) {
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261 SDL_SetError("Couldn't find any hardware audio formats");
354
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diff changeset
262 ALSA_CloseAudio(this);
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263 return(-1);
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264 }
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265 spec->format = test_format;
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266
354
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diff changeset
267 /* Set the number of channels */
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diff changeset
268 status = snd_pcm_hw_params_set_channels(pcm_handle, params, spec->channels);
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diff changeset
269 if ( status < 0 ) {
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diff changeset
270 status = snd_pcm_hw_params_get_channels(params);
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diff changeset
271 if ( (status <= 0) || (status > 2) ) {
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diff changeset
272 SDL_SetError("Couldn't set audio channels");
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diff changeset
273 ALSA_CloseAudio(this);
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diff changeset
274 return(-1);
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diff changeset
275 }
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diff changeset
276 spec->channels = status;
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diff changeset
277 }
0
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278
354
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diff changeset
279 /* Set the audio rate */
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diff changeset
280 status = snd_pcm_hw_params_set_rate_near(pcm_handle, params, spec->freq, NULL);
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diff changeset
281 if ( status < 0 ) {
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diff changeset
282 SDL_SetError("Couldn't set audio frequency: %s", snd_strerror(status));
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diff changeset
283 ALSA_CloseAudio(this);
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diff changeset
284 return(-1);
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diff changeset
285 }
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diff changeset
286 spec->freq = status;
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287
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diff changeset
288 /* Set the buffer size, in samples */
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diff changeset
289 frames = spec->samples;
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diff changeset
290 frames = snd_pcm_hw_params_set_period_size_near(pcm_handle, params, frames, NULL);
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diff changeset
291 spec->samples = frames;
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diff changeset
292 snd_pcm_hw_params_set_periods_near(pcm_handle, params, 2, NULL);
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diff changeset
293
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diff changeset
294 /* "set" the hardware with the desired parameters */
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diff changeset
295 status = snd_pcm_hw_params(pcm_handle, params);
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diff changeset
296 if ( status < 0 ) {
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diff changeset
297 SDL_SetError("Couldn't set audio parameters: %s", snd_strerror(status));
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diff changeset
298 ALSA_CloseAudio(this);
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299 return(-1);
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300 }
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301
354
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diff changeset
302 /* Calculate the final parameters for this audio specification */
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diff changeset
303 SDL_CalculateAudioSpec(spec);
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304
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diff changeset
305 /* Allocate mixing buffer */
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diff changeset
306 mixlen = spec->size;
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diff changeset
307 mixbuf = (Uint8 *)SDL_AllocAudioMem(mixlen);
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diff changeset
308 if ( mixbuf == NULL ) {
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diff changeset
309 ALSA_CloseAudio(this);
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diff changeset
310 return(-1);
0
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311 }
354
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312 memset(mixbuf, spec->silence, spec->size);
0
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313
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314 /* Get the parent process id (we're the parent of the audio thread) */
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315 parent = getpid();
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316
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317 /* We're ready to rock and roll. :-) */
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318 return(0);
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319 }