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261
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1 /*
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2 * SDL_sound -- An abstract sound format decoding API.
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3 * Copyright (C) 2001 Ryan C. Gordon.
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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 Lesser General Public
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7 * License as published by the Free Software Foundation; either
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8 * version 2.1 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 * Lesser 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 Lesser General Public
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16 * License along with this library; if not, write to the Free Software
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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
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20 /*
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21 * MPGLIB decoder for SDL_sound. This is a very lightweight MP3 decoder,
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22 * which is included with the SDL_sound source, so that it doesn't rely on
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23 * unnecessary external libraries.
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24 *
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25 * The SMPEG decoder plays back more forms of MPEGs, and may behave better or
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26 * worse under various conditions. mpglib is (apparently) more efficient than
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27 * SMPEG, and, again, doesn't need an external library. You should test both
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28 * decoders and use what you find works best for you.
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29 *
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30 * mpglib is part of mpg123, which can be found in its original form at:
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31 * http://www.mpg123.de/
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32 *
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33 * Please see the file COPYING in the source's root directory. The included
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34 * source code for mpglib falls under the LGPL, which is the same license as
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35 * SDL_sound (so you can consider it a single work).
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36 *
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37 * This file written by Ryan C. Gordon. (icculus@clutteredmind.org)
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38 */
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39
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40 #if HAVE_CONFIG_H
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41 # include <config.h>
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42 #endif
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43
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44 #ifdef SOUND_SUPPORTS_MPGLIB
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45
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46 #include <stdio.h>
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47 #include <stdlib.h>
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48 #include <string.h>
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49 #include <assert.h>
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50 #include "mpglib/mpg123_sdlsound.h"
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51 #include "mpglib/mpglib_sdlsound.h"
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52
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53 #include "SDL_sound.h"
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54
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55 #define __SDL_SOUND_INTERNAL__
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56 #include "SDL_sound_internal.h"
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57
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58 static int MPGLIB_init(void);
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59 static void MPGLIB_quit(void);
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60 static int MPGLIB_open(Sound_Sample *sample, const char *ext);
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61 static void MPGLIB_close(Sound_Sample *sample);
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62 static Uint32 MPGLIB_read(Sound_Sample *sample);
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63 static int MPGLIB_rewind(Sound_Sample *sample);
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64
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65 static const char *extensions_mpglib[] = { "MP3", NULL };
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66 const Sound_DecoderFunctions __Sound_DecoderFunctions_MPGLIB =
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67 {
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68 {
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69 extensions_mpglib,
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70 "MP3 decoding via internal mpglib",
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71 "Ryan C. Gordon <icculus@clutteredmind.org>",
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72 "http://www.icculus.org/SDL_sound/"
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73 },
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74
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75 MPGLIB_init, /* init() method */
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76 MPGLIB_quit, /* quit() method */
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77 MPGLIB_open, /* open() method */
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78 MPGLIB_close, /* close() method */
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79 MPGLIB_read, /* read() method */
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80 MPGLIB_rewind /* rewind() method */
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81 };
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82
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83
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84 /* this is what we store in our internal->decoder_private field... */
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85 typedef struct
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86 {
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87 struct mpstr mp;
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88 Uint8 inbuf[16384];
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89 Uint8 outbuf[8192];
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90 int outleft;
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91 int outpos;
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92 } mpglib_t;
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93
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94
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95
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96 static int MPGLIB_init(void)
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97 {
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98 return(1); /* always succeeds. */
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99 } /* MPGLIB_init */
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100
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101
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102 static void MPGLIB_quit(void)
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103 {
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104 /* it's a no-op. */
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105 } /* MPGLIB_quit */
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106
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107
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108 static int MPGLIB_open(Sound_Sample *sample, const char *ext)
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109 {
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110 Sound_SampleInternal *internal = (Sound_SampleInternal *) sample->opaque;
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111 mpglib_t *mpg = NULL;
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112
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113 /*
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114 * If I understand things correctly, MP3 files don't really have any
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115 * magic header we can check for. The MP3 player is expected to just
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116 * pick the first thing that looks like a valid frame and start
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117 * playing from there.
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118 *
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119 * So here's what we do: If the caller insists that this is really
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120 * MP3 we'll take his word for it. Otherwise, use the same test as
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121 * SDL_mixer does and check if the stream starts with something that
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122 * looks like a frame.
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123 *
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124 * A frame begins with 11 bits of frame sync (all bits must be set),
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125 * followed by a two-bit MPEG Audio version ID:
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126 *
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127 * 00 - MPEG Version 2.5 (later extension of MPEG 2)
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128 * 01 - reserved
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129 * 10 - MPEG Version 2 (ISO/IEC 13818-3)
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130 * 11 - MPEG Version 1 (ISO/IEC 11172-3)
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131 *
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132 * Apparently we don't handle MPEG Version 2.5.
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133 */
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134 if (__Sound_strcasecmp(ext, "MP3") != 0)
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135 {
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136 Uint8 mp3_magic[2];
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137
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138 if (SDL_RWread(internal->rw, mp3_magic, sizeof (mp3_magic), 1) != 1)
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139 {
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140 Sound_SetError("MP3: Could not read MP3 magic.");
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141 return(0);
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142 } /*if */
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143
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144 if (mp3_magic[0] != 0xFF || (mp3_magic[1] & 0xF0) != 0xF0)
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145 {
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146 Sound_SetError("MP3: Not an MP3 stream.");
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147 return(0);
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148 } /* if */
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149
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150 /* !!! FIXME: If the seek fails, we'll probably miss a frame */
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151 SDL_RWseek(internal->rw, -sizeof (mp3_magic), SEEK_CUR);
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152 } /* if */
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153
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154 mpg = (mpglib_t *) malloc(sizeof (mpglib_t));
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155 BAIL_IF_MACRO(mpg == NULL, ERR_OUT_OF_MEMORY, 0);
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156 mpg->outpos = mpg->outleft = 0;
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157 InitMP3(&mpg->mp);
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158
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159 SNDDBG(("MPGLIB: Accepting data stream.\n"));
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160
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161 internal->decoder_private = mpg;
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162 sample->actual.rate = 44100;
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163 sample->actual.channels = 2;
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164 sample->actual.format = AUDIO_S16LSB;
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165 sample->flags = SOUND_SAMPLEFLAG_NONE;
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166
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167 return(1); /* we'll handle this data. */
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168 } /* MPGLIB_open */
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169
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170
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171 static void MPGLIB_close(Sound_Sample *sample)
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172 {
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173 Sound_SampleInternal *internal = (Sound_SampleInternal *) sample->opaque;
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174 mpglib_t *mpg = ((mpglib_t *) internal->decoder_private);
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175 ExitMP3(&mpg->mp);
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176 free(mpg);
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177 } /* MPGLIB_close */
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178
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179
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180 static Uint32 MPGLIB_read(Sound_Sample *sample)
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181 {
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182 Sound_SampleInternal *internal = (Sound_SampleInternal *) sample->opaque;
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183 mpglib_t *mpg = ((mpglib_t *) internal->decoder_private);
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184 Uint32 bw = 0;
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185 int rc;
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186
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187 while (bw < internal->buffer_size)
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188 {
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189 if (mpg->outleft > 0)
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190 {
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191 Uint16 cpysize = internal->buffer_size - bw;
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192 if (cpysize > mpg->outleft)
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193 cpysize = mpg->outleft;
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194 memcpy(((Uint8 *) internal->buffer) + bw,
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195 mpg->outbuf + mpg->outpos, cpysize);
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196 bw += cpysize;
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197 mpg->outpos += cpysize;
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198 mpg->outleft -= cpysize;
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199 continue;
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200 } /* if */
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201
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202 /* need to decode more from the MP3 stream... */
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203 mpg->outpos = 0;
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204 rc = decodeMP3(&mpg->mp, NULL, 0, mpg->outbuf,
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205 sizeof (mpg->outbuf), &mpg->outleft);
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206 if (rc == MP3_ERR)
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207 {
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208 sample->flags |= SOUND_SAMPLEFLAG_ERROR;
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209 return(bw);
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210 } /* if */
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211
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212 else if (rc == MP3_NEED_MORE)
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213 {
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214 rc = SDL_RWread(internal->rw, mpg->inbuf, 1, sizeof (mpg->inbuf));
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215 if (rc == -1)
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216 {
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217 sample->flags |= SOUND_SAMPLEFLAG_ERROR;
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218 return(bw);
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219 } /* if */
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220 else if (rc == 0)
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221 {
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222 sample->flags |= SOUND_SAMPLEFLAG_EOF;
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223 return(bw);
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224 } /* else if */
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225
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263
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226 rc = decodeMP3(&mpg->mp, mpg->inbuf, rc,
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261
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227 mpg->outbuf, sizeof (mpg->outbuf), &mpg->outleft);
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228 if (rc == MP3_ERR)
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229 {
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230 sample->flags |= SOUND_SAMPLEFLAG_ERROR;
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231 return(bw);
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232 } /* if */
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233 } /* else if */
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234 } /* while */
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235
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236 return(bw);
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237 } /* MPGLIB_read */
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238
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239
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240 static int MPGLIB_rewind(Sound_Sample *sample)
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241 {
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242 Sound_SampleInternal *internal = (Sound_SampleInternal *) sample->opaque;
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243 mpglib_t *mpg = ((mpglib_t *) internal->decoder_private);
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244 BAIL_IF_MACRO(SDL_RWseek(internal->rw, 0, SEEK_SET) != 0, ERR_IO_ERROR, 0);
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245
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246 /* this is just resetting some fields in a structure; it's very fast. */
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247 ExitMP3(&mpg->mp);
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248 InitMP3(&mpg->mp);
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249 mpg->outpos = mpg->outleft = 0;
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250 return(1);
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251 } /* MPGLIB_rewind */
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252
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253
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254 #endif /* SOUND_SUPPORTS_MPGLIB */
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255
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256
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257 /* end of mpglib.c ... */
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258
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