Alexandre Lision | 7c6f4a6 | 2013-09-05 13:27:01 -0400 | [diff] [blame] | 1 | <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> |
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| 4 | <HEAD> |
| 5 | <TITLE> |
| 6 | libsndfile : the sf_command function. |
| 7 | </TITLE> |
| 8 | <META NAME="Author" CONTENT="Erik de Castro Lopo (erikd AT mega-nerd DOT com)"> |
| 9 | <!-- Another version at the bottom of the page. --> |
| 10 | <META NAME="Description" CONTENT="The libsndfile API."> |
| 11 | <META NAME="Keywords" CONTENT="WAV AIFF AU libsndfile sound audio dsp Linux"> |
| 12 | <LINK REL="stylesheet" HREF="libsndfile.css" TYPE="text/css" MEDIA="all"> |
| 13 | <LINK REL="stylesheet" HREF="print.css" TYPE="text/css" MEDIA="print"> |
| 14 | </HEAD> |
| 15 | |
| 16 | <BODY> |
| 17 | |
| 18 | <H1><B>sf_command</B></H1> |
| 19 | <PRE> |
| 20 | |
| 21 | int sf_command (SNDFILE *sndfile, int cmd, void *data, int datasize) ; |
| 22 | </PRE> |
| 23 | <P> |
| 24 | This function allows the caller to retrieve information from or change aspects of the |
| 25 | library behaviour. |
| 26 | Examples include retrieving a string containing the library version or changing the |
| 27 | scaling applied to floating point sample data during read and write. |
| 28 | Most of these operations are performed on a per-file basis. |
| 29 | </P> |
| 30 | <P> |
| 31 | The cmd parameter is a integer identifier which is defined in <sndfile.h>. |
| 32 | All of the valid command identifiers have names begining with "SFC_". |
| 33 | Data is passed to and returned from the library by use of a void pointer. |
| 34 | The library will not read or write more than datasize bytes from the void pointer. |
| 35 | For some calls no data is required in which case data should be NULL and datasize |
| 36 | may be used for some other purpose. |
| 37 | </P> |
| 38 | <P> |
| 39 | The available commands are as follows: |
| 40 | </P> |
| 41 | |
| 42 | <CENTER> |
| 43 | <TABLE BORDER="0" WIDTH="90%" CELLPADDING="4"> |
| 44 | <TR> |
| 45 | <TD><A HREF="#SFC_GET_LIB_VERSION">SFC_GET_LIB_VERSION</A></TD> |
| 46 | <TD>Retrieve the version of the library.</TD> |
| 47 | </TR> |
| 48 | <TR> |
| 49 | <TD><A HREF="#SFC_GET_LOG_INFO">SFC_GET_LOG_INFO</A></TD> |
| 50 | <TD>Retrieve the internal per-file operation log.</TD> |
| 51 | </TR> |
| 52 | <TR> |
| 53 | <TD><A HREF="#SFC_CALC_SIGNAL_MAX">SFC_CALC_SIGNAL_MAX</A></TD> |
| 54 | <TD>Retrieve the measured maximum signal value.</TD> |
| 55 | </TR> |
| 56 | <TR> |
| 57 | <TD><A HREF="#SFC_CALC_NORM_SIGNAL_MAX">SFC_CALC_NORM_SIGNAL_MAX</A></TD> |
| 58 | <TD>Retrieve the measured normalised maximum signal value.</TD> |
| 59 | </TR> |
| 60 | <TR> |
| 61 | <TD><A HREF="#SFC_CALC_MAX_ALL_CHANNELS">SFC_CALC_MAX_ALL_CHANNELS</A></TD> |
| 62 | <TD>Calculate peaks for all channels.</TD> |
| 63 | </TR> |
| 64 | <TR> |
| 65 | <TD><A HREF="#SFC_CALC_NORM_MAX_ALL_CHANNELS">SFC_CALC_NORM_MAX_ALL_CHANNELS</A></TD> |
| 66 | <TD>Calculate normalised peaks for all channels.</TD> |
| 67 | </TR> |
| 68 | |
| 69 | <TR> |
| 70 | <TD><A HREF="#SFC_SET_NORM_FLOAT">SFC_SET_NORM_FLOAT</A></TD> |
| 71 | <TD>Modify the normalisation behaviour of the floating point reading and writing functions.</TD> |
| 72 | </TR> |
| 73 | <TR> |
| 74 | <TD><A HREF="#SFC_SET_NORM_DOUBLE">SFC_SET_NORM_DOUBLE</A></TD> |
| 75 | <TD>Modify the normalisation behaviour of the double precision floating point reading and writing functions.</TD> |
| 76 | </TR> |
| 77 | <TR> |
| 78 | <TD><A HREF="#SFC_GET_NORM_FLOAT">SFC_GET_NORM_FLOAT</A></TD> |
| 79 | <TD>Retrieve the current normalisation behaviour of the floating point reading and writing functions.</TD> |
| 80 | </TR> |
| 81 | <TR> |
| 82 | <TD><A HREF="#SFC_GET_NORM_DOUBLE">SFC_GET_NORM_DOUBLE</A></TD> |
| 83 | <TD>Retrieve the current normalisation behaviour of the double precision floating point reading and writing functions.</TD> |
| 84 | </TR> |
| 85 | <TR> |
| 86 | <TD><A HREF="#SFC_GET_SIMPLE_FORMAT_COUNT">SFC_GET_SIMPLE_FORMAT_COUNT</A></TD> |
| 87 | <TD>Retrieve the number of simple formats supported by libsndfile.</TD> |
| 88 | </TR> |
| 89 | <TR> |
| 90 | <TD><A HREF="#SFC_GET_SIMPLE_FORMAT">SFC_GET_SIMPLE_FORMAT</A></TD> |
| 91 | <TD>Retrieve information about a simple format.</TD> |
| 92 | </TR> |
| 93 | |
| 94 | <TR> |
| 95 | <TD><A HREF="#SFC_GET_FORMAT_INFO">SFC_GET_FORMAT_INFO</A></TD> |
| 96 | <TD>Retrieve information about a major or subtype format.</TD> |
| 97 | </TR> |
| 98 | |
| 99 | <TR> |
| 100 | <TD><A HREF="#SFC_GET_FORMAT_MAJOR_COUNT">SFC_GET_FORMAT_MAJOR_COUNT</A></TD> |
| 101 | <TD>Retrieve the number of major formats.</TD> |
| 102 | </TR> |
| 103 | <TR> |
| 104 | <TD><A HREF="#SFC_GET_FORMAT_MAJOR">SFC_GET_FORMAT_MAJOR</A></TD> |
| 105 | <TD>Retrieve information about a major format type.</TD> |
| 106 | </TR> |
| 107 | <TR> |
| 108 | <TD><A HREF="#SFC_GET_FORMAT_SUBTYPE_COUNT">SFC_GET_FORMAT_SUBTYPE_COUNT</A></TD> |
| 109 | <TD>Retrieve the number of subformats.</TD> |
| 110 | </TR> |
| 111 | <TR> |
| 112 | <TD><A HREF="#SFC_GET_FORMAT_SUBTYPE">SFC_GET_FORMAT_SUBTYPE</A></TD> |
| 113 | <TD>Retrieve information about a subformat.</TD> |
| 114 | </TR> |
| 115 | |
| 116 | <TR> |
| 117 | <TD><A HREF="#SFC_SET_ADD_PEAK_CHUNK">SFC_SET_ADD_PEAK_CHUNK</A></TD> |
| 118 | <TD>Switch the code for adding the PEAK chunk to WAV and AIFF files on or off.</TD> |
| 119 | </TR> |
| 120 | |
| 121 | <TR> |
| 122 | <TD><A HREF="#SFC_UPDATE_HEADER_NOW">SFC_UPDATE_HEADER_NOW</A></TD> |
| 123 | <TD>Used when a file is open for write, this command will update the file |
| 124 | header to reflect the data written so far.</TD> |
| 125 | </TR> |
| 126 | <TR> |
| 127 | <TD><A HREF="#SFC_SET_UPDATE_HEADER_AUTO">SFC_SET_UPDATE_HEADER_AUTO</A></TD> |
| 128 | <TD>Used when a file is open for write, this command will cause the file header |
| 129 | to be updated after each write to the file.</TD> |
| 130 | </TR> |
| 131 | |
| 132 | <TR> |
| 133 | <TD><A HREF="#SFC_FILE_TRUNCATE">SFC_FILE_TRUNCATE</A></TD> |
| 134 | <TD>Truncate a file open for write or for read/write.</TD> |
| 135 | </TR> |
| 136 | |
| 137 | <TR> |
| 138 | <TD><A HREF="#SFC_SET_RAW_START_OFFSET">SFC_SET_RAW_START_OFFSET</A></TD> |
| 139 | <TD>Change the data start offset for files opened up as SF_FORMAT_RAW.</TD> |
| 140 | </TR> |
| 141 | |
| 142 | |
| 143 | |
| 144 | <!-- |
| 145 | <TR> |
| 146 | <TD><A HREF="#add-dither">add dither</A></TD> |
| 147 | <TD>Add dither to output on write.</TD> |
| 148 | </TR> |
| 149 | --> |
| 150 | </TABLE> |
| 151 | </CENTER> |
| 152 | |
| 153 | <BR><BR> |
| 154 | |
| 155 | <HR> |
| 156 | |
| 157 | <!-- ========================================================================= --> |
| 158 | <A NAME="SFC_GET_LIB_VERSION"></A> |
| 159 | <H2><BR><B>SFC_GET_LIB_VERSION</B></H2> |
| 160 | <P> |
| 161 | Retrieve the version of the library as a string. |
| 162 | </P> |
| 163 | <P> |
| 164 | Parameters: |
| 165 | <PRE> |
| 166 | sndfile : Not used |
| 167 | cmd : SFC_GET_LIB_VERSION |
| 168 | data : A pointer to a char buffer |
| 169 | datasize : The size of the the buffer |
| 170 | </PRE> |
| 171 | <P> |
| 172 | Example: |
| 173 | </P> |
| 174 | <PRE> |
| 175 | char buffer [128] ; |
| 176 | sf_command (NULL, SFC_GET_LIB_VERSION, buffer, sizeof (buffer)) ; |
| 177 | </PRE> |
| 178 | |
| 179 | <DL> |
| 180 | <DT>Return value:</DT> |
| 181 | <DD><DD>This call will return the length of the retrieved version string. |
| 182 | </DL> |
| 183 | <DL> |
| 184 | <DT>Notes:</DT> |
| 185 | <DD> |
| 186 | The string returned in the buffer passed to this function will not overflow |
| 187 | the buffer and will always be null terminated . |
| 188 | </DL> |
| 189 | |
| 190 | <!-- ========================================================================= --> |
| 191 | <A NAME="SFC_GET_LOG_INFO"></A> |
| 192 | <H2><BR><B>SFC_GET_LOG_INFO</B></H2> |
| 193 | <P> |
| 194 | Retrieve the log buffer generated when opening a file as a string. This log |
| 195 | buffer can often contain a good reason for why libsndfile failed to open a |
| 196 | particular file. |
| 197 | </P> |
| 198 | <P> |
| 199 | Parameters: |
| 200 | <PRE> |
| 201 | sndfile : A valid SNDFILE* pointer |
| 202 | cmd : SFC_GET_LOG_INFO |
| 203 | data : A pointer to a char buffer |
| 204 | datasize : The size of the the buffer |
| 205 | </PRE> |
| 206 | <P> |
| 207 | Example: |
| 208 | </P> |
| 209 | <PRE> |
| 210 | char buffer [2048] ; |
| 211 | sf_command (sndfile, SFC_GET_LOG_INFO, buffer, sizeof (buffer)) ; |
| 212 | </PRE> |
| 213 | |
| 214 | <DL> |
| 215 | <DT>Return value:</DT> |
| 216 | <DD><DD>This call will return the length of the retrieved version string. |
| 217 | </DL> |
| 218 | <DL> |
| 219 | <DT>Notes:</DT> |
| 220 | <DD> |
| 221 | The string returned in the buffer passed to this function will not overflow |
| 222 | the buffer and will always be null terminated . |
| 223 | </DL> |
| 224 | |
| 225 | <!-- ========================================================================= --> |
| 226 | <A NAME="SFC_CALC_SIGNAL_MAX"></A> |
| 227 | <H2><BR><B>SFC_CALC_SIGNAL_MAX</B></H2> |
| 228 | <P> |
| 229 | Retrieve the measured maximum signal value. This involves reading through |
| 230 | the whole file which can be slow on large files. |
| 231 | </P> |
| 232 | <P> |
| 233 | Parameters: |
| 234 | <PRE> |
| 235 | sndfile : A valid SNDFILE* pointer |
| 236 | cmd : SFC_CALC_SIGNAL_MAX |
| 237 | data : A pointer to a double |
| 238 | datasize : sizeof (double) |
| 239 | </PRE> |
| 240 | <P> |
| 241 | Example: |
| 242 | </P> |
| 243 | <PRE> |
| 244 | double max_val ; |
| 245 | sf_command (sndfile, SFC_CALC_SIGNAL_MAX, &max_val, sizeof (max_val)) ; |
| 246 | </PRE> |
| 247 | |
| 248 | <DL> |
| 249 | <DT>Return value:</DT> |
| 250 | <DD><DD>Zero on success, non-zero otherwise. |
| 251 | </DL> |
| 252 | |
| 253 | <!-- ========================================================================= --> |
| 254 | <A NAME="SFC_CALC_NORM_SIGNAL_MAX"></A> |
| 255 | <H2><BR><B>SFC_CALC_NORM_SIGNAL_MAX</B></H2> |
| 256 | <P> |
| 257 | Retrieve the measured normailised maximum signal value. This involves reading |
| 258 | through the whole file which can be slow on large files. |
| 259 | </P> |
| 260 | <P> |
| 261 | Parameters: |
| 262 | <PRE> |
| 263 | sndfile : A valid SNDFILE* pointer |
| 264 | cmd : SFC_CALC_NORM_SIGNAL_MAX |
| 265 | data : A pointer to a double |
| 266 | datasize : sizeof (double) |
| 267 | </PRE> |
| 268 | <P> |
| 269 | Example: |
| 270 | </P> |
| 271 | <PRE> |
| 272 | double max_val ; |
| 273 | sf_command (sndfile, SFC_CALC_NORM_SIGNAL_MAX, &max_val, sizeof (max_val)) ; |
| 274 | </PRE> |
| 275 | |
| 276 | <DL> |
| 277 | <DT>Return value:</DT> |
| 278 | <DD><DD>Zero on success, non-zero otherwise. |
| 279 | </DL> |
| 280 | |
| 281 | <!-- ========================================================================= --> |
| 282 | <A NAME="SFC_CALC_MAX_ALL_CHANNELS"></A> |
| 283 | <H2><BR><B>SFC_CALC_MAX_ALL_CHANNELS</B></H2> |
| 284 | <P> |
| 285 | Calculate peaks for all channels. This involves reading through |
| 286 | the whole file which can be slow on large files. |
| 287 | </P> |
| 288 | <P> |
| 289 | Parameters: |
| 290 | <PRE> |
| 291 | sndfile : A valid SNDFILE* pointer |
| 292 | cmd : SFC_CALC_MAX_ALL_CHANNELS |
| 293 | data : A pointer to a double |
| 294 | datasize : sizeof (double) * number_of_channels |
| 295 | </PRE> |
| 296 | <P> |
| 297 | Example: |
| 298 | </P> |
| 299 | <PRE> |
| 300 | double peaks [number_of_channels] ; |
| 301 | sf_command (sndfile, SFC_CALC_MAX_ALL_CHANNELS, peaks, sizeof (peaks)) ; |
| 302 | </PRE> |
| 303 | <DL> |
| 304 | <DT>Return value:</DT> |
| 305 | <DD>Zero if peaks have been calculated successfully and non-zero otherwise. |
| 306 | </DL> |
| 307 | |
| 308 | |
| 309 | <!-- ========================================================================= --> |
| 310 | <A NAME="SFC_CALC_NORM_MAX_ALL_CHANNELS"></A> |
| 311 | <H2><BR><B>SFC_CALC_NORM_MAX_ALL_CHANNELS</B></H2> |
| 312 | <P> |
| 313 | Calculate normalised peaks for all channels. This involves reading through |
| 314 | the whole file which can be slow on large files. |
| 315 | </P> |
| 316 | <P> |
| 317 | Parameters: |
| 318 | <PRE> |
| 319 | sndfile : A valid SNDFILE* pointer |
| 320 | cmd : SFC_CALC_NORM_MAX_ALL_CHANNELS |
| 321 | data : A pointer to a double |
| 322 | datasize : sizeof (double) * number_of_channels |
| 323 | </PRE> |
| 324 | <P> |
| 325 | Example: |
| 326 | </P> |
| 327 | <PRE> |
| 328 | double peaks [number_of_channels] ; |
| 329 | sf_command (sndfile, SFC_CALC_NORM_MAX_ALL_CHANNELS, peaks, sizeof (peaks)) ; |
| 330 | </PRE> |
| 331 | <DL> |
| 332 | <DT>Return value:</DT> |
| 333 | <DD>Zero if peaks have been calculated successfully and non-zero otherwise. |
| 334 | </DL> |
| 335 | |
| 336 | |
| 337 | |
| 338 | |
| 339 | |
| 340 | <!-- ========================================================================= --> |
| 341 | <!-- |
| 342 | <A NAME="read-text"></A> |
| 343 | <H2><BR><B>Read text</B></H2> |
| 344 | <P> |
| 345 | Many sound file formats contain allow the inclusion of a text string describing the nature |
| 346 | of the file. If a file contains such a string, this functions will return it to the caller. |
| 347 | </P> |
| 348 | <P> |
| 349 | It should be noted that the way the string is added to the file is file format dependant |
| 350 | but that any string added with <A HREF="#write-text">write text</A> will be returned by |
| 351 | <A HREF="#read-text">read text</A>. |
| 352 | </P> |
| 353 | <P> |
| 354 | <P> |
| 355 | Parameters: |
| 356 | </P> |
| 357 | <PRE> |
| 358 | sndfile : A valid SNDFILE* pointer |
| 359 | cmd : The text string "read text". |
| 360 | data : A pointer to a char buffer. |
| 361 | datasize : The size of the the buffer. |
| 362 | </PRE> |
| 363 | <P> |
| 364 | Example: |
| 365 | </P> |
| 366 | <PRE> |
| 367 | char buffer [128] ; |
| 368 | sf_command (sndfile, "read text", buffer, sizeof (buffer)) ; |
| 369 | </PRE> |
| 370 | <DL> |
| 371 | <DT>Return value:</DT> |
| 372 | <DD>If a text string is found, this call will return the length of the retrieved text |
| 373 | string. |
| 374 | <DD>If no text string is found, zero will be returned and the first element in the |
| 375 | buffer will be set to the null character. |
| 376 | <DT>Notes:</DT> |
| 377 | <DD>The string returned in the buffer passed to this function will not overflow |
| 378 | the buffer and will be correctly null terminated . |
| 379 | </DL> |
| 380 | |
| 381 | <A NAME="write-text"></A> |
| 382 | <H2><BR><B>Write text</B></H2> |
| 383 | <P> |
| 384 | Add a text string to a file. The text string added can be retrieved when the file is |
| 385 | read using <A HREF="#read-text">read text</A>. |
| 386 | </P> |
| 387 | <P> |
| 388 | Parameters: |
| 389 | </P> |
| 390 | <PRE> |
| 391 | sndfile : A valid SNDFILE* pointer |
| 392 | cmd : The text string "write text". |
| 393 | data : A pointer to the string to be added. |
| 394 | datasize : Not used. |
| 395 | </PRE> |
| 396 | <P> |
| 397 | Example: |
| 398 | </P> |
| 399 | <PRE> |
| 400 | char text = "The sound of one hand clapping." ; |
| 401 | sf_command (sndfile, "write text", text, strlen (text)) ; |
| 402 | </PRE> |
| 403 | <DL> |
| 404 | <DT>Return value: </DT> |
| 405 | <DD>If the current file format allows the addition of text strings, the string will |
| 406 | be added and the length of the string will be returned. |
| 407 | <DD>If the file format does not allow the addition of text strings zero will be returned. |
| 408 | <DD>If this function is called after the file is openned but before |
| 409 | </DL> |
| 410 | --> |
| 411 | |
| 412 | |
| 413 | <!-- ========================================================================= --> |
| 414 | <A NAME="SFC_SET_NORM_FLOAT"></A> |
| 415 | <H2><BR><B>SFC_SET_NORM_FLOAT</B></H2> |
| 416 | <P> |
| 417 | This command only affects data read from or written to using the floating point functions: |
| 418 | </P> |
| 419 | <PRE> |
| 420 | size_t <A HREF="api.html#read">sf_read_float</A> (SNDFILE *sndfile, float *ptr, size_t items) ; |
| 421 | size_t <A HREF="api.html#readf">sf_readf_float</A> (SNDFILE *sndfile, float *ptr, size_t frames) ; |
| 422 | |
| 423 | size_t <A HREF="api.html#write">sf_write_float</A> (SNDFILE *sndfile, float *ptr, size_t items) ; |
| 424 | size_t <A HREF="api.html#writef">sf_writef_float</A> (SNDFILE *sndfile, float *ptr, size_t frames) ; |
| 425 | </PRE> |
| 426 | <P> |
| 427 | Parameters: |
| 428 | </P> |
| 429 | <PRE> |
| 430 | sndfile : A valid SNDFILE* pointer |
| 431 | cmd : SFC_SET_NORM_FLOAT |
| 432 | data : NULL |
| 433 | datasize : SF_TRUE or SF_FALSE |
| 434 | </PRE> |
| 435 | <P> |
| 436 | For read operations setting normalisation to SF_TRUE means that the data from all |
| 437 | subsequent reads will be be normalised to the range [-1.0, 1.0]. |
| 438 | </P> |
| 439 | <P> |
| 440 | For write operations, setting normalisation to SF_TRUE means than all data supplied |
| 441 | to the float write functions should be in the range [-1.0, 1.0] and will be scaled |
| 442 | for the file format as necessary. |
| 443 | </P> |
| 444 | <P> |
| 445 | For both cases, setting normalisation to SF_FALSE means that no scaling will take place. |
| 446 | </P> |
| 447 | <P> |
| 448 | Example: |
| 449 | </P> |
| 450 | <PRE> |
| 451 | sf_command (sndfile, SFC_SET_NORM_FLOAT, NULL, SF_TRUE) ; |
| 452 | |
| 453 | sf_command (sndfile, SFC_SET_NORM_FLOAT, NULL, SF_FALSE) ; |
| 454 | </PRE> |
| 455 | <DL> |
| 456 | <DT>Return value: </DT> |
| 457 | <DD>Returns 1 on success or 0 for failure. |
| 458 | </DL> |
| 459 | |
| 460 | <!-- ========================================================================= --> |
| 461 | <A NAME="SFC_SET_NORM_DOUBLE"></A> |
| 462 | <H2><BR><B>SFC_SET_NORM_DOUBLE</B></H2> |
| 463 | <P> |
| 464 | This command only affects data read from or written to using the double precision |
| 465 | floating point functions: |
| 466 | </P> |
| 467 | <PRE> |
| 468 | size_t <A HREF="api.html#read">sf_read_double</A> (SNDFILE *sndfile, double *ptr, size_t items) ; |
| 469 | size_t <A HREF="api.html#readf">sf_readf_double</A> (SNDFILE *sndfile, double *ptr, size_t frames) ; |
| 470 | |
| 471 | size_t <A HREF="api.html#write">sf_write_double</A> (SNDFILE *sndfile, double *ptr, size_t items) ; |
| 472 | size_t <A HREF="api.html#writef">sf_writef_double</A> (SNDFILE *sndfile, double *ptr, size_t frames) ; |
| 473 | </PRE> |
| 474 | <P> |
| 475 | Parameters: |
| 476 | </P> |
| 477 | <PRE> |
| 478 | sndfile : A valid SNDFILE* pointer |
| 479 | cmd : SFC_SET_NORM_DOUBLE |
| 480 | data : NULL |
| 481 | datasize : SF_TRUE or SF_FALSE |
| 482 | </PRE> |
| 483 | <P> |
| 484 | For read operations setting normalisation to SF_TRUE means that the data |
| 485 | from all subsequent reads will be be normalised to the range [-1.0, 1.0]. |
| 486 | </P> |
| 487 | <P> |
| 488 | For write operations, setting normalisation to SF_TRUE means than all data supplied |
| 489 | to the double write functions should be in the range [-1.0, 1.0] and will be scaled |
| 490 | for the file format as necessary. |
| 491 | </P> |
| 492 | <P> |
| 493 | For both cases, setting normalisation to SF_FALSE means that no scaling will take place. |
| 494 | </P> |
| 495 | <P> |
| 496 | Example: |
| 497 | </P> |
| 498 | <PRE> |
| 499 | sf_command (sndfile, SFC_SET_NORM_DOUBLE, NULL, SF_TRUE) ; |
| 500 | |
| 501 | sf_command (sndfile, SFC_SET_NORM_DOUBLE, NULL, SF_FALSE) ; |
| 502 | </PRE> |
| 503 | <DL> |
| 504 | <DT>Return value: </DT> |
| 505 | <DD>Returns 1 on success or 0 for failure. |
| 506 | </DL> |
| 507 | |
| 508 | <!-- ========================================================================= --> |
| 509 | <A NAME="SFC_GET_NORM_FLOAT"></A> |
| 510 | <H2><BR><B>SFC_GET_NORM_FLOAT</B></H2> |
| 511 | <P> |
| 512 | Retrieve the current float normalisation mode. |
| 513 | </P> |
| 514 | <P> |
| 515 | Parameters: |
| 516 | </P> |
| 517 | <PRE> |
| 518 | sndfile : A valid SNDFILE* pointer |
| 519 | cmd : SFC_GET_NORM_FLOAT |
| 520 | data : NULL |
| 521 | datasize : anything |
| 522 | </PRE> |
| 523 | <P> |
| 524 | Example: |
| 525 | </P> |
| 526 | <PRE> |
| 527 | normalisation = sf_command (sndfile, SFC_GET_NORM_FLOAT, NULL, 0) ; |
| 528 | </PRE> |
| 529 | <DL> |
| 530 | <DT>Return value: </DT> |
| 531 | <DD>Returns TRUE if normaisation is on and FALSE otherwise. |
| 532 | </DL> |
| 533 | |
| 534 | <!-- ========================================================================= --> |
| 535 | <A NAME="SFC_GET_NORM_DOUBLE"></A> |
| 536 | <H2><BR><B>SFC_GET_NORM_DOUBLE</B></H2> |
| 537 | <P> |
| 538 | Retrieve the current float normalisation mode. |
| 539 | </P> |
| 540 | <P> |
| 541 | Parameters: |
| 542 | </P> |
| 543 | <PRE> |
| 544 | sndfile : A valid SNDFILE* pointer |
| 545 | cmd : SFC_GET_NORM_DOUBLE |
| 546 | data : NULL |
| 547 | datasize : anything |
| 548 | </PRE> |
| 549 | <P> |
| 550 | Example: |
| 551 | </P> |
| 552 | <PRE> |
| 553 | normalisation = sf_command (sndfile, SFC_GET_NORM_DOUBLE, NULL, 0) ; |
| 554 | </PRE> |
| 555 | <DL> |
| 556 | <DT>Return value: </DT> |
| 557 | <DD>Returns TRUE if normalisation is on and FALSE otherwise. |
| 558 | </DL> |
| 559 | |
| 560 | <!-- ========================================================================= --> |
| 561 | <A NAME="SFC_GET_SIMPLE_FORMAT_COUNT"></A> |
| 562 | <H2><BR><B>SFC_GET_SIMPLE_FORMAT_COUNT</B></H2> |
| 563 | <P> |
| 564 | Retrieve the number of simple formats supported by libsndfile. |
| 565 | </P> |
| 566 | <P> |
| 567 | Parameters: |
| 568 | </P> |
| 569 | <PRE> |
| 570 | sndfile : Not used. |
| 571 | cmd : SFC_GET_SIMPLE_FORMAT_COUNT |
| 572 | data : a pointer to an int |
| 573 | datasize : sizeof (int) |
| 574 | </PRE> |
| 575 | <P> |
| 576 | Example: |
| 577 | </P> |
| 578 | <PRE> |
| 579 | int count ; |
| 580 | sf_command (sndfile, SFC_GET_SIMPLE_FORMAT_COUNT, &count, sizeof (int)) ; |
| 581 | </PRE> |
| 582 | <DL> |
| 583 | <DT>Return value: </DT> |
| 584 | <DD>0 |
| 585 | </DL> |
| 586 | |
| 587 | <!-- ========================================================================= --> |
| 588 | <A NAME="SFC_GET_SIMPLE_FORMAT"></A> |
| 589 | <H2><BR><B>SFC_GET_SIMPLE_FORMAT</B></H2> |
| 590 | <P> |
| 591 | Retrieve information about a simple format. |
| 592 | </P> |
| 593 | <P> |
| 594 | Parameters: |
| 595 | </P> |
| 596 | <PRE> |
| 597 | sndfile : Not used. |
| 598 | cmd : SFC_GET_SIMPLE_FORMAT |
| 599 | data : a pointer to an SF_FORMAT_INFO struct |
| 600 | datasize : sizeof (SF_FORMAT_INFO) |
| 601 | </PRE> |
| 602 | <P> |
| 603 | The SF_FORMAT_INFO struct is defined in <sndfile.h> as: |
| 604 | </P> |
| 605 | <PRE> |
| 606 | typedef struct |
| 607 | { int format ; |
| 608 | const char *name ; |
| 609 | const char *extension ; |
| 610 | } SF_FORMAT_INFO ; |
| 611 | </PRE> |
| 612 | <P> |
| 613 | When sf_command() is called with SF_GET_SIMPLE_FORMAT, the value of the format |
| 614 | field should be the format number (ie 0 <= format <= count value obtained using |
| 615 | SF_GET_SIMPLE_FORMAT_COUNT). |
| 616 | </P> |
| 617 | <P> |
| 618 | Example: |
| 619 | </P> |
| 620 | <PRE> |
| 621 | SF_FORMAT_INFO format_info ; |
| 622 | int k, count ; |
| 623 | |
| 624 | sf_command (sndfile, SFC_GET_SIMPLE_FORMAT_COUNT, &count, sizeof (int)) ; |
| 625 | |
| 626 | for (k = 0 ; k < count ; k++) |
| 627 | { format_info.format = k ; |
| 628 | sf_command (sndfile, SFC_GET_SIMPLE_FORMAT, &format_info, sizeof (format_info)) ; |
| 629 | printf ("%08x %s %s\n", format_info.format, format_info.name, format_info.extension) ; |
| 630 | } ; |
| 631 | </PRE> |
| 632 | <DL> |
| 633 | <DT>Return value: </DT> |
| 634 | <DD>0 on success and non-zero otherwise. |
| 635 | <DD>The value of the format field of the SF_FORMAT_INFO struct will be an value which |
| 636 | can be placed in the format field of an SF_INFO struct when a file is to be opened |
| 637 | for write. |
| 638 | <DD>The name field will contain a char* pointer to the name of the string ie "WAV (Microsoft 16 bit PCM)". |
| 639 | <DD>The extention field will contain the most commonly used file extension for that file type. |
| 640 | </DL> |
| 641 | |
| 642 | <!-- ========================================================================= --> |
| 643 | <A NAME="SFC_GET_FORMAT_INFO"></A> |
| 644 | <H2><BR><B>SFC_GET_FORMAT_INFO</B></H2> |
| 645 | <P> |
| 646 | Retrieve information about a major or subtype format. |
| 647 | </P> |
| 648 | <P> |
| 649 | Parameters: |
| 650 | </P> |
| 651 | <PRE> |
| 652 | sndfile : Not used. |
| 653 | cmd : SFC_GET_FORMAT_INFO |
| 654 | data : a pointer to an SF_FORMAT_INFO struct |
| 655 | datasize : sizeof (SF_FORMAT_INFO) |
| 656 | </PRE> |
| 657 | <P> |
| 658 | The SF_FORMAT_INFO struct is defined in <sndfile.h> as: |
| 659 | </P> |
| 660 | <PRE> |
| 661 | typedef struct |
| 662 | { int format ; |
| 663 | const char *name ; |
| 664 | const char *extension ; |
| 665 | } SF_FORMAT_INFO ; |
| 666 | </PRE> |
| 667 | <P> |
| 668 | When sf_command() is called with SF_GET_FORMAT_INFO, the format field is |
| 669 | examined and if (format & SF_FORMAT_TYPEMASK) is a valid format then the struct |
| 670 | is filled in with information about the given major type. |
| 671 | If (format & SF_FORMAT_TYPEMASK) is FALSE and (format & SF_FORMAT_SUBMASK) is a |
| 672 | valid subtype format then the struct is filled in with information about the given |
| 673 | subtype. |
| 674 | </P> |
| 675 | <P> |
| 676 | Example: |
| 677 | </P> |
| 678 | <PRE> |
| 679 | SF_FORMAT_INFO format_info ; |
| 680 | |
| 681 | format_info.format = SF_FORMAT_WAV ; |
| 682 | sf_command (sndfile, SFC_GET_FORMAT_INFO, &format_info, sizeof (format_info)) ; |
| 683 | printf ("%08x %s %s\n", format_info.format, format_info.name, format_info.extension) ; |
| 684 | |
| 685 | format_info.format = SF_FORMAT_ULAW ; |
| 686 | sf_command (sndfile, SFC_GET_FORMAT_INFO, &format_info, sizeof (format_info)) ; |
| 687 | printf ("%08x %s\n", format_info.format, format_info.name) ; |
| 688 | </PRE> |
| 689 | <DL> |
| 690 | <DT>Return value: </DT> |
| 691 | <DD>0 on success and non-zero otherwise. |
| 692 | </DL> |
| 693 | <!-- ========================================================================= --> |
| 694 | <A NAME="SFC_GET_FORMAT_MAJOR_COUNT"></A> |
| 695 | <H2><BR><B>SFC_GET_FORMAT_MAJOR_COUNT</B></H2> |
| 696 | <P> |
| 697 | Retrieve the number of major formats. |
| 698 | </P> |
| 699 | <P> |
| 700 | Parameters: |
| 701 | </P> |
| 702 | <PRE> |
| 703 | sndfile : Not used. |
| 704 | cmd : SFC_GET_FORMAT_MAJOR_COUNT |
| 705 | data : a pointer to an int |
| 706 | datasize : sizeof (int) |
| 707 | </PRE> |
| 708 | <P> |
| 709 | Example: |
| 710 | </P> |
| 711 | <PRE> |
| 712 | int count ; |
| 713 | sf_command (sndfile, SFC_GET_FORMAT_MAJOR_COUNT, &count, sizeof (int)) ; |
| 714 | </PRE> |
| 715 | <DL> |
| 716 | <DT>Return value: </DT> |
| 717 | <DD>0 |
| 718 | </DL> |
| 719 | |
| 720 | <!-- ========================================================================= --> |
| 721 | <A NAME="SFC_GET_FORMAT_MAJOR"></A> |
| 722 | <H2><BR><B>SFC_GET_FORMAT_MAJOR</B></H2> |
| 723 | <P> |
| 724 | Retrieve information about a major format type. |
| 725 | </P> |
| 726 | <P> |
| 727 | Parameters: |
| 728 | </P> |
| 729 | <PRE> |
| 730 | sndfile : Not used. |
| 731 | cmd : SFC_GET_FORMAT_MAJOR |
| 732 | data : a pointer to an SF_FORMAT_INFO struct |
| 733 | datasize : sizeof (SF_FORMAT_INFO) |
| 734 | </PRE> |
| 735 | <P> |
| 736 | Example: |
| 737 | </P> |
| 738 | <PRE> |
| 739 | SF_FORMAT_INFO format_info ; |
| 740 | int k, count ; |
| 741 | |
| 742 | sf_command (sndfile, SFC_GET_FORMAT_MAJOR_COUNT, &count, sizeof (int)) ; |
| 743 | |
| 744 | for (k = 0 ; k < count ; k++) |
| 745 | { format_info.format = k ; |
| 746 | sf_command (sndfile, SFC_GET_FORMAT_MAJOR, &format_info, sizeof (format_info)) ; |
| 747 | printf ("%08x %s %s\n", format_info.format, format_info.name, format_info.extension) ; |
| 748 | } ; |
| 749 | </PRE> |
| 750 | <P> |
| 751 | For a more comprehensive example, see the program list_formats.c in the examples/ |
| 752 | directory of the libsndfile source code distribution. |
| 753 | </P> |
| 754 | <DL> |
| 755 | <DT>Return value: </DT> |
| 756 | <DD>0 on success and non-zero otherwise. |
| 757 | <DD>The value of the format field will one of the major format identifiers suc as SF_FORMAT_WAV |
| 758 | SF_FORMAT_AIFF. |
| 759 | <DD>The name field will contain a char* pointer to the name of the string ie "WAV (Microsoft)". |
| 760 | <DD>The extention field will contain the most commonly used file extension for that file type. |
| 761 | </DL> |
| 762 | |
| 763 | <!-- ========================================================================= --> |
| 764 | <A NAME="SFC_GET_FORMAT_SUBTYPE_COUNT"></A> |
| 765 | <H2><BR><B>SFC_GET_FORMAT_SUBTYPE_COUNT</B></H2> |
| 766 | <P> |
| 767 | Retrieve the number of subformats. |
| 768 | </P> |
| 769 | <P> |
| 770 | Parameters: |
| 771 | </P> |
| 772 | <PRE> |
| 773 | sndfile : Not used. |
| 774 | cmd : SFC_GET_FORMAT_SUBTYPE_COUNT |
| 775 | data : a pointer to an int |
| 776 | datasize : sizeof (int) |
| 777 | </PRE> |
| 778 | <P> |
| 779 | Example: |
| 780 | </P> |
| 781 | <PRE> |
| 782 | int count ; |
| 783 | sf_command (sndfile, SFC_GET_FORMAT_SUBTYPE_COUNT, &count, sizeof (int)) ; |
| 784 | </PRE> |
| 785 | <DL> |
| 786 | <DT>Return value: </DT> |
| 787 | <DD>0 |
| 788 | </DL> |
| 789 | |
| 790 | <!-- ========================================================================= --> |
| 791 | <A NAME="SFC_GET_FORMAT_SUBTYPE"></A> |
| 792 | <H2><BR><B>SFC_GET_FORMAT_SUBTYPE</B></H2> |
| 793 | <P> |
| 794 | Retrieve information about a subformat. |
| 795 | </P> |
| 796 | <P> |
| 797 | Parameters: |
| 798 | </P> |
| 799 | <PRE> |
| 800 | sndfile : Not used. |
| 801 | cmd : SFC_GET_FORMAT_SUBTYPE |
| 802 | data : a pointer to an SF_FORMAT_INFO struct |
| 803 | datasize : sizeof (SF_FORMAT_INFO) |
| 804 | </PRE> |
| 805 | <P> |
| 806 | Example: |
| 807 | </P> |
| 808 | <PRE> |
| 809 | SF_FORMAT_INFO format_info ; |
| 810 | int k, count ; |
| 811 | |
| 812 | sf_command (sndfile, SFC_GET_FORMAT_SUBTYPE_COUNT, &count, sizeof (int)) ; |
| 813 | |
| 814 | /* Retrieve all the subtypes supported by the WAV format. */ |
| 815 | for (k = 0 ; k < count ; k++) |
| 816 | { format_info.format = k ; |
| 817 | sf_command (sndfile, SFC_GET_FORMAT_SUBTYPE, &format_info, sizeof (format_info)) ; |
| 818 | if (! sf_format_check (format.info | SF_FORMAT_WAV)) |
| 819 | continue ; |
| 820 | printf ("%08x %s\n", format_info.format, format_info.name) ; |
| 821 | } ; |
| 822 | </PRE> |
| 823 | <P> |
| 824 | For a more comprehensive example, see the program list_formats.c in the examples/ |
| 825 | directory of the libsndfile source code distribution. |
| 826 | </P> |
| 827 | <DL> |
| 828 | <DT>Return value: </DT> |
| 829 | <DD>0 on success and non-zero otherwise. |
| 830 | <DD>The value of the format field will one of the major format identifiers such as SF_FORMAT_WAV |
| 831 | SF_FORMAT_AIFF. |
| 832 | <DD>The name field will contain a char* pointer to the name of the string; for instance |
| 833 | "WAV (Microsoft)" or "AIFF (Apple/SGI)". |
| 834 | <DD>The extention field will be a NULL pointer. |
| 835 | </DL> |
| 836 | |
| 837 | <!-- ========================================================================= --> |
| 838 | <A NAME="SFC_SET_ADD_PEAK_CHUNK"></A> |
| 839 | <H2><BR><B>SFC_SET_ADD_PEAK_CHUNK</B></H2> |
| 840 | <P> |
| 841 | By default, WAV and AIFF files which contain floating point data (subtype SF_FORMAT_FLOAT |
| 842 | or SF_FORMAT_DOUBLE) have a PEAK chunk. |
| 843 | By using this command, the addition of a PEAK chunk can be turned on or off. |
| 844 | </P> |
| 845 | <P> |
| 846 | Note : This call must be made before any data is written to the file. |
| 847 | </P> |
| 848 | <P> |
| 849 | Parameters: |
| 850 | <PRE> |
| 851 | sndfile : A valid SNDFILE* pointer |
| 852 | cmd : SFC_SET_ADD_PEAK_CHUNK |
| 853 | data : Not used (should be NULL) |
| 854 | datasize : TRUE or FALSE. |
| 855 | </PRE> |
| 856 | <P> |
| 857 | Example: |
| 858 | </P> |
| 859 | <PRE> |
| 860 | /* Turn on the PEAK chunk. */ |
| 861 | sf_command (sndfile, SFC_SET_ADD_PEAK_CHUNK, NULL, SF_TRUE) ; |
| 862 | |
| 863 | /* Turn off the PEAK chunk. */ |
| 864 | sf_command (sndfile, SFC_SET_ADD_PEAK_CHUNK, NULL, SF_FALSE) ; |
| 865 | </PRE> |
| 866 | <DL> |
| 867 | <DT>Return value:</DT> |
| 868 | <DD>Returns SF_TRUE if the peak chunk will be written after this call. |
| 869 | <DD>Returns SF_FALSE if the peak chunk will not be written after this call. |
| 870 | </DL> |
| 871 | |
| 872 | <!-- ========================================================================= --> |
| 873 | <A NAME="SFC_UPDATE_HEADER_NOW"></A> |
| 874 | <H2><BR><B>SFC_UPDATE_HEADER_NOW</B></H2> |
| 875 | <P> |
| 876 | The header of an audio file is normally written by libsndfile when the file is |
| 877 | closed using <B>sf_close()</B>. |
| 878 | </P> |
| 879 | <P> |
| 880 | There are however situations where large files are being generated and it would |
| 881 | be nice to have valid data in the header before the file is complete. |
| 882 | Using this command will update the file header to reflect the amount of data written |
| 883 | to the file so far. |
| 884 | Other programs opening the file for read (before any more data is written) will |
| 885 | then read a valid sound file header. |
| 886 | </P> |
| 887 | <P> |
| 888 | Parameters: |
| 889 | <PRE> |
| 890 | sndfile : A valid SNDFILE* pointer |
| 891 | cmd : SFC_UPDATE_HEADER_NOW |
| 892 | data : Not used (should be NULL) |
| 893 | datasize : Not used. |
| 894 | </PRE> |
| 895 | <P> |
| 896 | Example: |
| 897 | </P> |
| 898 | <PRE> |
| 899 | /* Update the header now. */ |
| 900 | sf_command (sndfile, SFC_UPDATE_HEADER_NOW, NULL, 0) ; |
| 901 | </PRE> |
| 902 | <DL> |
| 903 | <DT>Return value:</DT> |
| 904 | <DD>0 |
| 905 | </DL> |
| 906 | |
| 907 | <!-- ========================================================================= --> |
| 908 | <A NAME="SFC_SET_UPDATE_HEADER_AUTO"></A> |
| 909 | <H2><BR><B>SFC_SET_UPDATE_HEADER_AUTO</B></H2> |
| 910 | <P> |
| 911 | Similar to SFC_UPDATE_HEADER_NOW but updates the header at the end of every call |
| 912 | to the <B>sf_write*</B> functions. |
| 913 | </P> |
| 914 | <P> |
| 915 | Parameters: |
| 916 | <PRE> |
| 917 | sndfile : A valid SNDFILE* pointer |
| 918 | cmd : SFC_UPDATE_HEADER_NOW |
| 919 | data : Not used (should be NULL) |
| 920 | datasize : SF_TRUE or SF_FALSE |
| 921 | </PRE> |
| 922 | <P> |
| 923 | Example: |
| 924 | </P> |
| 925 | <PRE> |
| 926 | /* Turn on auto header update. */ |
| 927 | sf_command (sndfile, SFC_SET_UPDATE_HEADER_AUTO, NULL, SF_TRUE) ; |
| 928 | |
| 929 | /* Turn off auto header update. */ |
| 930 | sf_command (sndfile, SFC_SET_UPDATE_HEADER_AUTO, NULL, SF_FALSE) ; |
| 931 | </PRE> |
| 932 | <DL> |
| 933 | <DT>Return value:</DT> |
| 934 | <DD>TRUE if auto update header is now on; FALSE otherwise. |
| 935 | </DL> |
| 936 | |
| 937 | <!-- ========================================================================= --> |
| 938 | <A NAME="SFC_FILE_TRUNCATE"></A> |
| 939 | <H2><BR><B>SFC_FILE_TRUNCATE</B></H2> |
| 940 | <P> |
| 941 | Truncate a file open for write or for read/write. |
| 942 | </P> |
| 943 | <P> |
| 944 | Parameters: |
| 945 | <PRE> |
| 946 | sndfile : A valid SNDFILE* pointer |
| 947 | cmd : SFC_FILE_TRUNCATE |
| 948 | data : A pointer to an sf_count_t. |
| 949 | datasize : sizeof (sf_count_t) |
| 950 | </PRE> |
| 951 | |
| 952 | <P> |
| 953 | Truncate the file to the number of frames specified by the sf_count_t pointed |
| 954 | to by data. |
| 955 | After this command, both the read and the write pointer will be |
| 956 | at the new end of the file. |
| 957 | This command will fail (returning non-zero) if the requested truncate position |
| 958 | is beyond the end of the file. |
| 959 | </P> |
| 960 | <P> |
| 961 | Example: |
| 962 | </P> |
| 963 | <PRE> |
| 964 | /* Truncate the file to a length of 20 frames. */ |
| 965 | sf_count_t frames = 20 ; |
| 966 | sf_command (sndfile, SFC_FILE_TRUNCATE, &frames, sizeof (frames)) ; |
| 967 | </PRE> |
| 968 | <DL> |
| 969 | <DT>Return value:</DT> |
| 970 | <DD>Zero on sucess, non-zero otherwise. |
| 971 | </DL> |
| 972 | |
| 973 | <!-- ========================================================================= --> |
| 974 | <A NAME="SFC_SET_RAW_START_OFFSET"></A> |
| 975 | <H2><BR><B>SFC_SET_RAW_START_OFFSET</B></H2> |
| 976 | <P> |
| 977 | Change the data start offset for files opened up as SF_FORMAT_RAW. |
| 978 | </P> |
| 979 | <P> |
| 980 | Parameters: |
| 981 | <PRE> |
| 982 | sndfile : A valid SNDFILE* pointer |
| 983 | cmd : SFC_SET_RAW_START_OFFSET |
| 984 | data : A pointer to an sf_count_t. |
| 985 | datasize : sizeof (sf_count_t) |
| 986 | </PRE> |
| 987 | |
| 988 | <P> |
| 989 | For a file opened as format SF_FORMAT_RAW, set the data offset to the value |
| 990 | given by data. |
| 991 | </P> |
| 992 | <P> |
| 993 | Example: |
| 994 | </P> |
| 995 | <PRE> |
| 996 | /* Reset the data offset to 5 bytes from the start of the file. */ |
| 997 | sf_count_t offset = 5 ; |
| 998 | sf_command (sndfile, SFC_SET_RAW_START_OFFSET, &offset, sizeof (offset)) ; |
| 999 | </PRE> |
| 1000 | <DL> |
| 1001 | <DT>Return value:</DT> |
| 1002 | <DD>Zero on sucess, non-zero otherwise. |
| 1003 | </DL> |
| 1004 | |
| 1005 | <!-- ========================================================================= --> |
| 1006 | |
| 1007 | <HR> |
| 1008 | <P> |
| 1009 | The libsndfile home page is here : |
| 1010 | <A HREF="http://www.mega-nerd.com/libsndfile/"> |
| 1011 | http://www.mega-nerd.com/libsndfile/</A>. |
| 1012 | <BR> |
| 1013 | Version : 1.0.25 |
| 1014 | </P> |
| 1015 | |
| 1016 | </BODY> |
| 1017 | </HTML> |