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1 <HTML
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2 ><HEAD
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3 ><TITLE
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4 >SDL_ConvertAudio</TITLE
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5 ><META
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6 NAME="GENERATOR"
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7 CONTENT="Modular DocBook HTML Stylesheet Version 1.61
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8 "><LINK
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9 REL="HOME"
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10 TITLE="SDL Library Documentation"
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11 HREF="index.html"><LINK
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12 REL="UP"
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13 TITLE="Audio"
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14 HREF="audio.html"><LINK
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15 REL="PREVIOUS"
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16 TITLE="SDL_BuildAudioCVT"
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17 HREF="sdlbuildaudiocvt.html"><LINK
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18 REL="NEXT"
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19 TITLE="SDL_MixAudio"
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20 HREF="sdlmixaudio.html"></HEAD
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21 ><BODY
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22 CLASS="REFENTRY"
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23 BGCOLOR="#FFF8DC"
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24 TEXT="#000000"
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25 LINK="#0000ee"
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26 VLINK="#551a8b"
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27 ALINK="#ff0000"
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28 ><DIV
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29 CLASS="NAVHEADER"
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30 ><TABLE
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31 WIDTH="100%"
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32 BORDER="0"
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33 CELLPADDING="0"
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34 CELLSPACING="0"
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35 ><TR
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36 ><TH
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37 COLSPAN="3"
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38 ALIGN="center"
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39 >SDL Library Documentation</TH
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40 ></TR
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41 ><TR
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42 ><TD
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43 WIDTH="10%"
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44 ALIGN="left"
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45 VALIGN="bottom"
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46 ><A
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47 HREF="sdlbuildaudiocvt.html"
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48 >Prev</A
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49 ></TD
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50 ><TD
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51 WIDTH="80%"
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52 ALIGN="center"
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53 VALIGN="bottom"
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54 ></TD
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55 ><TD
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56 WIDTH="10%"
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57 ALIGN="right"
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58 VALIGN="bottom"
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59 ><A
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60 HREF="sdlmixaudio.html"
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61 >Next</A
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62 ></TD
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63 ></TR
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64 ></TABLE
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65 ><HR
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66 ALIGN="LEFT"
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67 WIDTH="100%"></DIV
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68 ><H1
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69 ><A
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70 NAME="SDLCONVERTAUDIO"
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71 >SDL_ConvertAudio</A
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72 ></H1
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73 ><DIV
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74 CLASS="REFNAMEDIV"
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75 ><A
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76 NAME="AEN6426"
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77 ></A
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78 ><H2
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79 >Name</H2
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80 >SDL_ConvertAudio -- Convert audio data to a desired audio format.</DIV
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81 ><DIV
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82 CLASS="REFSYNOPSISDIV"
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83 ><A
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84 NAME="AEN6429"
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85 ></A
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86 ><H2
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87 >Synopsis</H2
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88 ><DIV
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89 CLASS="FUNCSYNOPSIS"
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90 ><A
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91 NAME="AEN6430"
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92 ></A
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93 ><P
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94 ></P
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95 ><PRE
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96 CLASS="FUNCSYNOPSISINFO"
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97 >#include "SDL.h"</PRE
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98 ><P
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99 ><CODE
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100 ><CODE
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101 CLASS="FUNCDEF"
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102 >int <B
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103 CLASS="FSFUNC"
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104 >SDL_ConvertAudio</B
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105 ></CODE
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106 >(SDL_AudioCVT *cvt);</CODE
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107 ></P
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108 ><P
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109 ></P
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110 ></DIV
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111 ></DIV
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112 ><DIV
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113 CLASS="REFSECT1"
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114 ><A
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115 NAME="AEN6436"
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116 ></A
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117 ><H2
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118 >Description</H2
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119 ><P
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120 ><TT
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121 CLASS="FUNCTION"
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122 >SDL_ConvertAudio</TT
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123 > takes one parameter, <TT
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124 CLASS="PARAMETER"
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125 ><I
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126 >cvt</I
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127 ></TT
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128 >, which was previously initilized. Initilizing a <A
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129 HREF="sdlaudiocvt.html"
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130 ><SPAN
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131 CLASS="STRUCTNAME"
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132 >SDL_AudioCVT</SPAN
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133 ></A
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134 > is a two step process. First of all, the structure must be passed to <A
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135 HREF="sdlbuildaudiocvt.html"
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136 ><TT
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137 CLASS="FUNCTION"
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138 >SDL_BuildAudioCVT</TT
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139 ></A
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140 > along with source and destination format parameters. Secondly, the <SPAN
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141 CLASS="STRUCTNAME"
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142 >cvt</SPAN
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143 >-><TT
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144 CLASS="STRUCTFIELD"
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145 ><I
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146 >buf</I
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147 ></TT
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148 > and <SPAN
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149 CLASS="STRUCTNAME"
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150 >cvt</SPAN
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151 >-><TT
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152 CLASS="STRUCTFIELD"
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153 ><I
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154 >len</I
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155 ></TT
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156 > fields must be setup. <SPAN
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157 CLASS="STRUCTNAME"
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158 >cvt</SPAN
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159 >-><TT
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160 CLASS="STRUCTFIELD"
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161 ><I
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162 >buf</I
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163 ></TT
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164 > should point to the audio data and <SPAN
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165 CLASS="STRUCTNAME"
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166 >cvt</SPAN
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167 >-><TT
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168 CLASS="STRUCTFIELD"
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169 ><I
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170 >len</I
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171 ></TT
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172 > should be set to the length of the audio data in bytes. Remember, the length of the buffer pointed to by <TT
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173 CLASS="STRUCTFIELD"
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174 ><I
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175 >buf</I
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176 ></TT
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177 > show be <TT
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178 CLASS="STRUCTFIELD"
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179 ><I
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180 >len</I
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181 ></TT
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182 >*<TT
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183 CLASS="STRUCTFIELD"
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184 ><I
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185 >len_mult</I
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186 ></TT
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187 > bytes in length.</P
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188 ><P
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189 >Once the <SPAN
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190 CLASS="STRUCTNAME"
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191 >SDL_AudioCVT</SPAN
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192 >structure is initilized then we can pass it to <TT
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193 CLASS="FUNCTION"
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194 >SDL_ConvertAudio</TT
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195 >, which will convert the audio data pointer to by <SPAN
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196 CLASS="STRUCTNAME"
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197 >cvt</SPAN
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198 >-><TT
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199 CLASS="STRUCTFIELD"
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200 ><I
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201 >buf</I
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202 ></TT
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203 >. If <TT
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204 CLASS="FUNCTION"
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205 >SDL_ConvertAudio</TT
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206 > returned <SPAN
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207 CLASS="RETURNVALUE"
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208 >0</SPAN
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209 > then the conversion was completed successfully, otherwise <SPAN
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210 CLASS="RETURNVALUE"
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211 >-1</SPAN
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212 > is returned.</P
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213 ><P
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214 >If the conversion completed successfully then the converted audio data can be read from <SPAN
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215 CLASS="STRUCTNAME"
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216 >cvt</SPAN
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217 >-><TT
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218 CLASS="STRUCTFIELD"
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219 ><I
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220 >buf</I
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221 ></TT
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222 >. The amount of valid, converted, audio data in the buffer is equal to <SPAN
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223 CLASS="STRUCTNAME"
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224 >cvt</SPAN
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225 >-><TT
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226 CLASS="STRUCTFIELD"
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227 ><I
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228 >len</I
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229 ></TT
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230 >*<TT
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231 CLASS="STRUCTFIELD"
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232 ><I
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233 >cvt</I
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234 ></TT
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235 >-><SPAN
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236 CLASS="STRUCTNAME"
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237 >len_ratio</SPAN
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238 >.</P
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239 ></DIV
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240 ><DIV
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241 CLASS="REFSECT1"
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242 ><A
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243 NAME="AEN6471"
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244 ></A
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245 ><H2
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246 >Examples</H2
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247 ><PRE
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248 CLASS="PROGRAMLISTING"
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249 >/* Converting some WAV data to hardware format */
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250 void my_audio_callback(void *userdata, Uint8 *stream, int len);
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251
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252 SDL_AudioSpec *desired, *obtained;
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253 SDL_AudioSpec wav_spec;
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254 SDL_AudioCVT wav_cvt;
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255 Uint32 wav_len;
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256 Uint8 *wav_buf;
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257 int ret;
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258
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259 /* Allocated audio specs */
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260 desired=(SDL_AudioSpec *)malloc(sizeof(SDL_AudioSpec));
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261 obtained=(SDL_AudioSpec *)malloc(sizeof(SDL_AudioSpec));
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262
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263 /* Set desired format */
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264 desired->freq=22050;
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265 desired->format=AUDIO_S16LSB;
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266 desired->samples=8192;
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267 desired->callback=my_audio_callback;
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268 desired->userdata=NULL;
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269
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270 /* Open the audio device */
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271 if ( SDL_OpenAudio(desired, obtained) < 0 ){
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272 fprintf(stderr, "Couldn't open audio: %s\n", SDL_GetError());
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273 exit(-1);
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274 }
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275
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276 free(desired);
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277
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278 /* Load the test.wav */
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279 if( SDL_LoadWAV("test.wav", &wav_spec, &wav_buf, &wav_len) == NULL ){
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280 fprintf(stderr, "Could not open test.wav: %s\n", SDL_GetError());
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281 SDL_CloseAudio();
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282 free(obtained);
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283 exit(-1);
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284 }
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285
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286 /* Build AudioCVT */
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287 ret = SDL_BuildAudioCVT(&wav_cvt,
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288 wav_spec.format, wav_spec.channels, wav_spec.freq,
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289 obtained->format, obtained->channels, obtained->freq);
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290
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291 /* Check that the convert was built */
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292 if(ret==-1){
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293 fprintf(stderr, "Couldn't build converter!\n");
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294 SDL_CloseAudio();
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295 free(obtained);
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296 SDL_FreeWAV(wav_buf);
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297 }
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298
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299 /* Setup for conversion */
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300 wav_cvt.buf=(Uint8 *)malloc(wav_len*wav_cvt.len_mult);
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301 wav_cvt.len=wav_len;
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302 memcpy(wav_cvt.buf, wav_buf, wav_len);
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303
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304 /* We can delete to original WAV data now */
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305 SDL_FreeWAV(wav_buf);
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306
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307 /* And now we're ready to convert */
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308 SDL_ConvertAudio(&wav_cvt);
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309
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310 /* do whatever */
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311 .
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312 .
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313 .
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314 .
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315 </PRE
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316 ></DIV
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317 ><DIV
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318 CLASS="REFSECT1"
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319 ><A
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320 NAME="AEN6474"
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321 ></A
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322 ><H2
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323 >See Also</H2
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324 ><P
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325 ><A
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326 HREF="sdlbuildaudiocvt.html"
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327 ><TT
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328 CLASS="FUNCTION"
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329 >SDL_BuildAudioCVT</TT
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330 ></A
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331 >,
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332 <A
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333 HREF="sdlaudiocvt.html"
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334 ><TT
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335 CLASS="FUNCTION"
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336 >SDL_AudioCVT</TT
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337 ></A
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338 ></P
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339 ></DIV
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340 ><DIV
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341 CLASS="NAVFOOTER"
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342 ><HR
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343 ALIGN="LEFT"
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344 WIDTH="100%"><TABLE
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345 WIDTH="100%"
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346 BORDER="0"
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347 CELLPADDING="0"
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348 CELLSPACING="0"
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349 ><TR
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350 ><TD
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351 WIDTH="33%"
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352 ALIGN="left"
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353 VALIGN="top"
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354 ><A
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355 HREF="sdlbuildaudiocvt.html"
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356 >Prev</A
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357 ></TD
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358 ><TD
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359 WIDTH="34%"
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360 ALIGN="center"
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361 VALIGN="top"
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362 ><A
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363 HREF="index.html"
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364 >Home</A
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365 ></TD
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366 ><TD
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367 WIDTH="33%"
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368 ALIGN="right"
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369 VALIGN="top"
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370 ><A
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371 HREF="sdlmixaudio.html"
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372 >Next</A
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373 ></TD
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374 ></TR
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375 ><TR
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376 ><TD
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377 WIDTH="33%"
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378 ALIGN="left"
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379 VALIGN="top"
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380 >SDL_BuildAudioCVT</TD
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381 ><TD
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382 WIDTH="34%"
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383 ALIGN="center"
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384 VALIGN="top"
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385 ><A
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386 HREF="audio.html"
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387 >Up</A
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388 ></TD
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389 ><TD
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390 WIDTH="33%"
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391 ALIGN="right"
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392 VALIGN="top"
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393 >SDL_MixAudio</TD
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394 ></TR
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395 ></TABLE
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396 ></DIV
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397 ></BODY
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398 ></HTML
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399 > |
