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| 5131 | clevermous | 1 | |
| 2 | > |
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| 3 | > |
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| 4 | >SDL_AudioCVT |
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| 5 | > |
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| 7 | CONTENT="Modular DocBook HTML Stylesheet Version 1.64 |
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| 13 | TITLE="Audio" |
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| 16 | TITLE="SDL_FreeWAV" |
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| 19 | TITLE="SDL_BuildAudioCVT" |
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| 20 | HREF="sdlbuildaudiocvt.html"> |
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| 21 | > |
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| 35 | > |
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| 36 | > |
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| 37 | COLSPAN="3" |
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| 38 | ALIGN="center" |
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| 39 | >SDL Library Documentation |
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| 43 | WIDTH="10%" |
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| 44 | ALIGN="left" |
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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 | > |
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| 60 | HREF="sdlbuildaudiocvt.html" |
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| 61 | >Next |
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| 62 | > |
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| 63 | > |
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| 64 | > |
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| 65 | > |
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| 66 | ALIGN="LEFT" |
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| 67 | WIDTH="100%"> |
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| 68 | > |
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| 69 | > |
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| 70 | NAME="SDLAUDIOCVT" |
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| 71 | >SDL_AudioCVT |
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| 72 | > |
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| 73 | > |
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| 74 | CLASS="REFNAMEDIV" |
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| 75 | > |
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| 76 | NAME="AEN6337" |
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| 77 | > |
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| 78 | > |
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| 79 | >Name |
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| 80 | >SDL_AudioCVT -- Audio Conversion Structure |
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| 81 | > |
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| 82 | CLASS="REFSECT1" |
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| 83 | > |
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| 84 | NAME="AEN6340" |
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| 85 | > |
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| 86 | > |
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| 87 | >Structure Definition |
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| 88 | > |
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| 89 | CLASS="PROGRAMLISTING" |
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| 90 | >typedef struct{ |
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| 91 | int needed; |
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| 92 | Uint16 src_format; |
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| 93 | Uint16 dest_format; |
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| 94 | double rate_incr; |
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| 95 | Uint8 *buf; |
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| 96 | int len; |
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| 97 | int len_cvt; |
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| 98 | int len_mult; |
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| 99 | double len_ratio; |
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| 100 | void (*filters[10])(struct SDL_AudioCVT *cvt, Uint16 format); |
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| 101 | int filter_index; |
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| 102 | } SDL_AudioCVT; |
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| 103 | > |
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| 104 | > |
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| 105 | CLASS="REFSECT1" |
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| 106 | > |
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| 107 | NAME="AEN6343" |
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| 108 | > |
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| 109 | > |
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| 110 | >Structure Data |
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| 111 | > |
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| 112 | CLASS="INFORMALTABLE" |
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| 113 | > |
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| 114 | NAME="AEN6345" |
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| 115 | > |
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| 116 | > |
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| 117 | > |
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| 118 | > |
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| 119 | BORDER="0" |
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| 120 | CLASS="CALSTABLE" |
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| 121 | > |
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| 122 | > |
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| 123 | > |
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| 124 | ALIGN="LEFT" |
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| 125 | VALIGN="TOP" |
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| 126 | > |
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| 127 | CLASS="STRUCTFIELD" |
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| 128 | > |
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| 129 | >needed |
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| 130 | > |
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| 131 | > |
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| 132 | > |
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| 133 | ALIGN="LEFT" |
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| 134 | VALIGN="TOP" |
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| 135 | >Set to one if the conversion is possible |
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| 136 | > |
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| 137 | > |
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| 138 | > |
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| 139 | ALIGN="LEFT" |
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| 140 | VALIGN="TOP" |
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| 141 | > |
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| 142 | CLASS="STRUCTFIELD" |
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| 143 | > |
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| 144 | >src_format |
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| 145 | > |
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| 146 | > |
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| 147 | > |
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| 148 | ALIGN="LEFT" |
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| 149 | VALIGN="TOP" |
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| 150 | >Audio format of the source |
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| 151 | > |
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| 152 | > |
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| 153 | > |
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| 154 | ALIGN="LEFT" |
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| 155 | VALIGN="TOP" |
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| 156 | > |
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| 157 | CLASS="STRUCTFIELD" |
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| 158 | > |
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| 159 | >dest_format |
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| 160 | > |
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| 161 | > |
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| 162 | > |
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| 163 | ALIGN="LEFT" |
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| 164 | VALIGN="TOP" |
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| 165 | >Audio format of the destination |
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| 166 | > |
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| 167 | > |
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| 168 | > |
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| 169 | ALIGN="LEFT" |
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| 170 | VALIGN="TOP" |
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| 171 | > |
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| 172 | CLASS="STRUCTFIELD" |
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| 173 | > |
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| 174 | >rate_incr |
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| 175 | > |
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| 176 | > |
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| 177 | > |
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| 178 | ALIGN="LEFT" |
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| 179 | VALIGN="TOP" |
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| 180 | >Rate conversion increment |
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| 181 | > |
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| 182 | > |
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| 183 | > |
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| 184 | ALIGN="LEFT" |
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| 185 | VALIGN="TOP" |
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| 186 | > |
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| 187 | CLASS="STRUCTFIELD" |
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| 188 | > |
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| 189 | >buf |
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| 190 | > |
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| 191 | > |
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| 192 | > |
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| 193 | ALIGN="LEFT" |
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| 194 | VALIGN="TOP" |
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| 195 | >Audio buffer |
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| 196 | > |
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| 197 | > |
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| 198 | > |
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| 199 | ALIGN="LEFT" |
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| 200 | VALIGN="TOP" |
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| 201 | > |
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| 202 | CLASS="STRUCTFIELD" |
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| 203 | > |
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| 204 | >len |
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| 205 | > |
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| 206 | > |
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| 207 | > |
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| 208 | ALIGN="LEFT" |
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| 209 | VALIGN="TOP" |
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| 210 | >Length of the original audio buffer in bytes |
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| 211 | > |
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| 212 | > |
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| 213 | > |
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| 214 | ALIGN="LEFT" |
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| 215 | VALIGN="TOP" |
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| 216 | > |
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| 217 | CLASS="STRUCTFIELD" |
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| 218 | > |
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| 219 | >len_cvt |
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| 220 | > |
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| 221 | > |
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| 222 | > |
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| 223 | ALIGN="LEFT" |
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| 224 | VALIGN="TOP" |
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| 225 | >Length of converted audio buffer in bytes (calculated) |
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| 226 | > |
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| 227 | > |
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| 228 | > |
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| 229 | ALIGN="LEFT" |
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| 230 | VALIGN="TOP" |
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| 231 | > |
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| 232 | CLASS="STRUCTFIELD" |
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| 233 | > |
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| 234 | >len_mult |
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| 235 | > |
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| 236 | > |
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| 237 | > |
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| 238 | ALIGN="LEFT" |
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| 239 | VALIGN="TOP" |
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| 240 | > |
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| 241 | CLASS="STRUCTFIELD" |
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| 242 | > |
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| 243 | >buf |
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| 244 | > |
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| 245 | > must be |
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| 246 | CLASS="STRUCTFIELD" |
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| 247 | > |
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| 248 | >len |
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| 249 | > |
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| 250 | >* |
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| 251 | CLASS="STRUCTFIELD" |
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| 252 | > |
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| 253 | >len_mult |
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| 254 | > |
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| 255 | > bytes in size(calculated) |
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| 256 | > |
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| 257 | > |
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| 258 | > |
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| 259 | ALIGN="LEFT" |
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| 260 | VALIGN="TOP" |
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| 261 | > |
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| 262 | CLASS="STRUCTFIELD" |
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| 263 | > |
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| 264 | >len_ratio |
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| 265 | > |
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| 266 | > |
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| 267 | > |
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| 268 | ALIGN="LEFT" |
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| 269 | VALIGN="TOP" |
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| 270 | >Final audio size is |
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| 271 | CLASS="STRUCTFIELD" |
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| 272 | > |
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| 273 | >len |
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| 274 | > |
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| 275 | >* |
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| 276 | CLASS="STRUCTFIELD" |
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| 277 | > |
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| 278 | >len_ratio |
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| 279 | > |
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| 280 | > |
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| 281 | > |
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| 282 | > |
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| 283 | > |
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| 284 | ALIGN="LEFT" |
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| 285 | VALIGN="TOP" |
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| 286 | > |
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| 287 | CLASS="STRUCTFIELD" |
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| 288 | > |
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| 289 | >filters[10](..) |
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| 290 | > |
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| 291 | > |
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| 292 | > |
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| 293 | ALIGN="LEFT" |
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| 294 | VALIGN="TOP" |
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| 295 | >Pointers to functions needed for this conversion |
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| 296 | > |
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| 297 | > |
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| 298 | > |
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| 299 | ALIGN="LEFT" |
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| 300 | VALIGN="TOP" |
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| 301 | > |
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| 302 | CLASS="STRUCTFIELD" |
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| 303 | > |
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| 304 | >filter_index |
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| 305 | > |
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| 306 | > |
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| 307 | > |
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| 308 | ALIGN="LEFT" |
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| 309 | VALIGN="TOP" |
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| 310 | >Current conversion function |
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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 | > |
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| 316 | > |
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| 317 | > |
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| 318 | > |
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| 319 | CLASS="REFSECT1" |
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| 320 | > |
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| 321 | NAME="AEN6397" |
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| 322 | > |
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| 323 | > |
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| 324 | >Description |
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| 325 | > |
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| 326 | >The |
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| 327 | CLASS="STRUCTNAME" |
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| 328 | >SDL_AudioCVT |
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| 329 | > is used to convert audio data between different formats. A |
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| 330 | CLASS="STRUCTNAME" |
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| 331 | >SDL_AudioCVT |
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| 332 | > structure is created with the |
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| 333 | HREF="sdlbuildaudiocvt.html" |
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| 334 | > |
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| 335 | CLASS="FUNCTION" |
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| 336 | >SDL_BuildAudioCVT |
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| 337 | > |
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| 338 | > function, while the actual conversion is done by the |
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| 339 | HREF="sdlconvertaudio.html" |
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| 340 | > |
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| 341 | CLASS="FUNCTION" |
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| 342 | >SDL_ConvertAudio |
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| 343 | > |
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| 344 | > function. |
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| 345 | > |
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| 346 | >Many of the fields in the |
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| 347 | CLASS="STRUCTNAME" |
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| 348 | >SDL_AudioCVT |
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| 349 | > structure should be considered private and their function will not be discussed here. |
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| 350 | > |
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| 351 | > |
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| 352 | > |
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| 353 | CLASS="VARIABLELIST" |
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| 354 | > |
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| 355 | > |
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| 356 | > |
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| 357 | CLASS="TYPE" |
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| 358 | >Uint8 * |
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| 359 | > |
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| 360 | CLASS="STRUCTFIELD" |
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| 361 | > |
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| 362 | >buf |
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| 363 | > |
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| 364 | > |
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| 365 | > |
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| 366 | > |
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| 367 | >This points to the audio data that will be used in the conversion. It is both the source and the destination, which means the converted audio data overwrites the original data. It also means that the converted data may be larger than the original data (if you were converting from 8-bit to 16-bit, for instance), so you must ensure |
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| 368 | CLASS="STRUCTFIELD" |
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| 369 | > |
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| 370 | >buf |
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| 371 | > |
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| 372 | > is large enough. See below. |
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| 373 | > |
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| 374 | > |
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| 375 | > |
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| 376 | CLASS="TYPE" |
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| 377 | >int |
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| 378 | > |
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| 379 | CLASS="STRUCTFIELD" |
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| 380 | > |
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| 381 | >len |
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| 382 | > |
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| 383 | > |
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| 384 | > |
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| 385 | > |
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| 386 | >This is the length of the original audio data in bytes. |
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| 387 | > |
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| 388 | > |
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| 389 | > |
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| 390 | CLASS="TYPE" |
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| 391 | >int |
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| 392 | > |
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| 393 | CLASS="STRUCTFIELD" |
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| 394 | > |
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| 395 | >len_mult |
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| 396 | > |
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| 397 | > |
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| 398 | > |
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| 399 | > |
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| 400 | >As explained above, the audio buffer needs to be big enough to store the converted data, which may be bigger than the original audio data. The length of |
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| 401 | CLASS="STRUCTFIELD" |
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| 402 | > |
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| 403 | >buf |
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| 404 | > |
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| 405 | > should be |
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| 406 | CLASS="STRUCTFIELD" |
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| 407 | > |
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| 408 | >len |
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| 409 | > |
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| 410 | >* |
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| 411 | CLASS="STRUCTFIELD" |
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| 412 | > |
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| 413 | >len_mult |
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| 414 | > |
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| 415 | >. |
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| 416 | > |
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| 417 | > |
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| 418 | > |
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| 419 | CLASS="TYPE" |
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| 420 | >double |
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| 421 | > |
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| 422 | CLASS="STRUCTFIELD" |
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| 423 | > |
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| 424 | >len_ratio |
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| 425 | > |
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| 426 | > |
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| 427 | > |
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| 428 | > |
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| 429 | >When you have finished converting your audio data, you need to know how much of your audio buffer is valid. |
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| 430 | CLASS="STRUCTFIELD" |
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| 431 | > |
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| 432 | >len |
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| 433 | > |
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| 434 | >* |
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| 435 | CLASS="STRUCTFIELD" |
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| 436 | > |
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| 437 | >len_ratio |
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| 438 | > |
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| 439 | > is the size of the converted audio data in bytes. This is very similar to |
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| 440 | CLASS="STRUCTFIELD" |
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| 441 | > |
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| 442 | >len_mult |
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| 443 | > |
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| 444 | >, however when the convert audio data is shorter than the original |
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| 445 | CLASS="STRUCTFIELD" |
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| 446 | > |
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| 447 | >len_mult |
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| 448 | > |
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| 449 | > would be 1. |
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| 450 | CLASS="STRUCTFIELD" |
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| 451 | > |
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| 452 | >len_ratio |
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| 453 | > |
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| 454 | >, on the other hand, would be a fractional number between 0 and 1. |
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| 455 | > |
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| 456 | > |
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| 457 | > |
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| 458 | > |
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| 459 | > |
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| 460 | CLASS="REFSECT1" |
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| 461 | > |
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| 462 | NAME="AEN6442" |
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| 463 | > |
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| 464 | > |
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| 465 | >See Also |
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| 466 | > |
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| 467 | > |
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| 468 | HREF="sdlbuildaudiocvt.html" |
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| 469 | > |
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| 470 | CLASS="FUNCTION" |
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| 471 | >SDL_BuildAudioCVT |
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| 472 | > |
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| 473 | >, |
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| 474 | |||
| 475 | HREF="sdlconvertaudio.html" |
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| 476 | > |
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| 477 | CLASS="FUNCTION" |
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| 478 | >SDL_ConvertAudio |
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| 479 | > |
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| 480 | >, |
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| 481 | |||
| 482 | HREF="sdlaudiospec.html" |
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| 483 | > |
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| 484 | CLASS="STRUCTNAME" |
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| 485 | >SDL_AudioSpec |
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| 486 | > |
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| 487 | > |
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| 488 | > |
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| 489 | > |
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| 490 | CLASS="NAVFOOTER" |
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| 491 | > |
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| 492 | ALIGN="LEFT" |
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| 493 | WIDTH="100%"> |
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| 494 | WIDTH="100%" |
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| 495 | BORDER="0" |
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| 496 | CELLPADDING="0" |
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| 497 | CELLSPACING="0" |
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| 498 | > |
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| 499 | > |
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| 500 | WIDTH="33%" |
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| 501 | ALIGN="left" |
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| 502 | VALIGN="top" |
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| 503 | > |
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| 504 | HREF="sdlfreewav.html" |
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| 505 | >Prev |
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| 509 | ALIGN="center" |
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| 510 | VALIGN="top" |
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| 511 | > |
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| 512 | HREF="index.html" |
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| 513 | >Home |
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| 514 | > |
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| 515 | > |
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| 517 | ALIGN="right" |
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| 518 | VALIGN="top" |
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| 519 | > |
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| 520 | HREF="sdlbuildaudiocvt.html" |
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| 521 | >Next |
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| 526 | WIDTH="33%" |
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| 528 | VALIGN="top" |
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| 529 | >SDL_FreeWAV |
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| 530 | > |
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| 531 | WIDTH="34%" |
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| 532 | ALIGN="center" |
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| 533 | VALIGN="top" |
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| 535 | HREF="audio.html" |
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| 536 | >Up |
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| 539 | WIDTH="33%" |
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| 540 | ALIGN="right" |
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| 541 | VALIGN="top" |
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| 542 | >SDL_BuildAudioCVT |
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| 543 | > |
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| 544 | > |
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| 545 | > |
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| 546 | > |
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| 547 | > |
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| 548 | > |