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Update Vamp plugin SDK to 2.5
author Chris Cannam
date Thu, 09 May 2013 10:52:46 +0100
parents c7265573341e
children
rev   line source
Chris@0 1 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
Chris@0 2 <HTML>
Chris@0 3
Chris@0 4 <HEAD>
Chris@0 5 <TITLE>
Chris@0 6 The libsndfile API
Chris@0 7 </TITLE>
Chris@0 8 <META NAME="Author" CONTENT="Erik de Castro Lopo (erikd AT mega-nerd DOT com)">
Chris@0 9 <META NAME="Description" CONTENT="The libsndfile API.">
Chris@0 10 <META NAME="Keywords" CONTENT="WAV AIFF AU libsndfile sound audio dsp Linux">
Chris@0 11 <LINK REL="stylesheet" HREF="libsndfile.css" TYPE="text/css" MEDIA="all">
Chris@0 12 <LINK REL="stylesheet" HREF="print.css" TYPE="text/css" MEDIA="print">
Chris@0 13 </HEAD>
Chris@0 14
Chris@0 15 <BODY>
Chris@0 16
Chris@0 17 <BR>
Chris@0 18 <H1><B>libsndfile</B></H1>
Chris@0 19 <P>
Chris@0 20 Libsndfile is a library designed to allow the reading and writing of many
Chris@0 21 different sampled sound file formats (such as MS Windows WAV and the Apple/SGI
Chris@0 22 AIFF format) through one standard library interface.
Chris@0 23 </P>
Chris@0 24 <!-- pepper -->
Chris@0 25 <P>
Chris@0 26 During read and write operations, formats are seamlessly converted between the
Chris@0 27 format the application program has requested or supplied and the file's data
Chris@0 28 format. The application programmer can remain blissfully unaware of issues
Chris@0 29 such as file endian-ness and data format. See <A HREF="#note1">Note 1</A> and
Chris@0 30 <A HREF="#note2">Note 2</A>.
Chris@0 31 </P>
Chris@0 32 <!-- pepper -->
Chris@0 33 <P>
Chris@0 34 Every effort is made to keep these documents up-to-date, error free and
Chris@0 35 unambiguous.
Chris@0 36 However, since maintaining the documentation is the least fun part of working
Chris@0 37 on libsndfile, these docs can and do fall behind the behaviour of library.
Chris@0 38 If any errors, omissions or ambiguities are found, please notify me (erikd)
Chris@0 39 at mega-nerd dot com.
Chris@0 40 </P>
Chris@0 41 <!-- pepper -->
Chris@0 42 <P>
Chris@0 43 To supplement this reference documentation, there are simple example programs
Chris@0 44 included in the source code tarball.
Chris@0 45 The test suite which is also part of the source code tarball is also a good
Chris@0 46 place to look for the correct usage of the library functions.
Chris@0 47 </P>
Chris@0 48 <!-- pepper -->
Chris@0 49 <P>
Chris@0 50 <B> Finally, if you think there is some feature missing from libsndfile, check that
Chris@0 51 it isn't already implemented (and documented)
Chris@0 52 <A HREF="command.html">here</A>.
Chris@0 53 </B>
Chris@0 54 </P>
Chris@0 55
Chris@0 56 <H2><B>Synopsis</B></H2>
Chris@0 57 <P>
Chris@0 58 The functions of libsndfile are defined as follows:
Chris@0 59 </P>
Chris@0 60 <!-- pepper -->
Chris@0 61 <PRE>
Chris@0 62 #include &lt;stdio.h&gt;
Chris@0 63 #include &lt;sndfile.h&gt;
Chris@0 64
Chris@0 65 SNDFILE* <A HREF="#open">sf_open</A> (const char *path, int mode, SF_INFO *sfinfo) ;
Chris@0 66 SNDFILE* <A HREF="#open_fd">sf_open_fd</A> (int fd, int mode, SF_INFO *sfinfo, int close_desc) ;
Chris@0 67 SNDFILE* <A HREF="#open_virtual">sf_open_virtual</A> (SF_VIRTUAL_IO *sfvirtual, int mode, SF_INFO *sfinfo, void *user_data) ;
Chris@0 68 int <A HREF="#check">sf_format_check</A> (const SF_INFO *info) ;
Chris@0 69
Chris@0 70 sf_count_t <A HREF="#seek">sf_seek</A> (SNDFILE *sndfile, sf_count_t frames, int whence) ;
Chris@0 71
Chris@0 72 int <A HREF="command.html">sf_command</A> (SNDFILE *sndfile, int cmd, void *data, int datasize) ;
Chris@0 73
Chris@0 74 int <A HREF="#error">sf_error</A> (SNDFILE *sndfile) ;
Chris@0 75 const char* <A HREF="#error">sf_strerror</A> (SNDFILE *sndfile) ;
Chris@0 76 const char* <A HREF="#error">sf_error_number</A> (int errnum) ;
Chris@0 77
Chris@0 78 int <A HREF="#error">sf_perror</A> (SNDFILE *sndfile) ;
Chris@0 79 int <A HREF="#error">sf_error_str</A> (SNDFILE *sndfile, char* str, size_t len) ;
Chris@0 80
Chris@0 81 int <A HREF="#close">sf_close</A> (SNDFILE *sndfile) ;
Chris@0 82 void <A HREF="#write_sync">sf_write_sync</A> (SNDFILE *sndfile) ;
Chris@0 83
Chris@0 84 sf_count_t <A HREF="#read">sf_read_short</A> (SNDFILE *sndfile, short *ptr, sf_count_t items) ;
Chris@0 85 sf_count_t <A HREF="#read">sf_read_int</A> (SNDFILE *sndfile, int *ptr, sf_count_t items) ;
Chris@0 86 sf_count_t <A HREF="#read">sf_read_float</A> (SNDFILE *sndfile, float *ptr, sf_count_t items) ;
Chris@0 87 sf_count_t <A HREF="#read">sf_read_double</A> (SNDFILE *sndfile, double *ptr, sf_count_t items) ;
Chris@0 88
Chris@0 89 sf_count_t <A HREF="#readf">sf_readf_short</A> (SNDFILE *sndfile, short *ptr, sf_count_t frames) ;
Chris@0 90 sf_count_t <A HREF="#readf">sf_readf_int</A> (SNDFILE *sndfile, int *ptr, sf_count_t frames) ;
Chris@0 91 sf_count_t <A HREF="#readf">sf_readf_float</A> (SNDFILE *sndfile, float *ptr, sf_count_t frames) ;
Chris@0 92 sf_count_t <A HREF="#readf">sf_readf_double</A> (SNDFILE *sndfile, double *ptr, sf_count_t frames) ;
Chris@0 93
Chris@0 94 sf_count_t <A HREF="#write">sf_write_short</A> (SNDFILE *sndfile, short *ptr, sf_count_t items) ;
Chris@0 95 sf_count_t <A HREF="#write">sf_write_int</A> (SNDFILE *sndfile, int *ptr, sf_count_t items) ;
Chris@0 96 sf_count_t <A HREF="#write">sf_write_float</A> (SNDFILE *sndfile, float *ptr, sf_count_t items) ;
Chris@0 97 sf_count_t <A HREF="#write">sf_write_double</A> (SNDFILE *sndfile, double *ptr, sf_count_t items) ;
Chris@0 98
Chris@0 99 sf_count_t <A HREF="#writef">sf_writef_short</A> (SNDFILE *sndfile, short *ptr, sf_count_t frames) ;
Chris@0 100 sf_count_t <A HREF="#writef">sf_writef_int</A> (SNDFILE *sndfile, int *ptr, sf_count_t frames) ;
Chris@0 101 sf_count_t <A HREF="#writef">sf_writef_float</A> (SNDFILE *sndfile, float *ptr, sf_count_t frames) ;
Chris@0 102 sf_count_t <A HREF="#writef">sf_writef_double</A> (SNDFILE *sndfile, double *ptr, sf_count_t frames) ;
Chris@0 103
Chris@0 104 sf_count_t <A HREF="#raw">sf_read_raw</A> (SNDFILE *sndfile, void *ptr, sf_count_t bytes) ;
Chris@0 105 sf_count_t <A HREF="#raw">sf_write_raw</A> (SNDFILE *sndfile, void *ptr, sf_count_t bytes) ;
Chris@0 106
Chris@0 107 const char* <A HREF="#string">sf_get_string</A> (SNDFILE *sndfile, int str_type) ;
Chris@0 108 int <A HREF="#string">sf_set_string</A> (SNDFILE *sndfile, int str_type, const char* str) ;
Chris@0 109
Chris@0 110 </PRE>
Chris@0 111 <!-- pepper -->
Chris@0 112 <P>
Chris@0 113 SNDFILE* is an anonymous pointer to data which is private to the library.
Chris@0 114 </P>
Chris@0 115
Chris@0 116
Chris@0 117 <A NAME="open"></A>
Chris@0 118 <H2><B>File Open Function</B></H2>
Chris@0 119
Chris@0 120 <PRE>
Chris@0 121 SNDFILE* sf_open (const char *path, int mode, SF_INFO *sfinfo) ;
Chris@0 122 </PRE>
Chris@0 123
Chris@0 124 <P>
Chris@0 125 The SF_INFO structure is for passing data between the calling function and the library
Chris@0 126 when opening a file for reading or writing. It is defined in sndfile.h as follows:
Chris@0 127 </P>
Chris@0 128 <!-- pepper -->
Chris@0 129 <PRE>
Chris@0 130 typedef struct
Chris@0 131 { sf_count_t frames ; /* Used to be called samples. */
Chris@0 132 int samplerate ;
Chris@0 133 int channels ;
Chris@0 134 int format ;
Chris@0 135 int sections ;
Chris@0 136 int seekable ;
Chris@0 137 } SF_INFO ;
Chris@0 138 </PRE>
Chris@0 139
Chris@0 140 <P>
Chris@0 141 The mode parameter for this function can be any one of the following three values:
Chris@0 142 </P>
Chris@0 143 <!-- pepper -->
Chris@0 144 <PRE>
Chris@0 145 SFM_READ - read only mode
Chris@0 146 SFM_WRITE - write only mode
Chris@0 147 SFM_RDWR - read/write mode
Chris@0 148 </PRE>
Chris@0 149
Chris@0 150 <P>
Chris@0 151 When opening a file for read, the <b>format</B> field should be set to zero before
Chris@0 152 calling sf_open().
Chris@0 153 The only exception to this is the case of RAW files where the caller has to set
Chris@0 154 the samplerate, channels and format fields to valid values.
Chris@0 155 All other fields of the structure are filled in by the library.
Chris@0 156 </P>
Chris@0 157 <!-- pepper -->
Chris@0 158 <P>
Chris@0 159 When opening a file for write, the caller must fill in structure members samplerate,
Chris@0 160 channels, and format.
Chris@0 161 </P>
Chris@0 162 <!-- pepper -->
Chris@0 163 <P>
Chris@0 164 The format field in the above SF_INFO structure is made up of the bit-wise OR of a
Chris@0 165 major format type (values between 0x10000 and 0x08000000), a minor format type
Chris@0 166 (with values less than 0x10000) and an optional endian-ness value.
Chris@0 167 The currently understood formats are listed in sndfile.h as follows and also include
Chris@0 168 bitmasks for separating major and minor file types.
Chris@0 169 Not all combinations of endian-ness and major and minor file types are valid.
Chris@0 170 </P>
Chris@0 171 <!-- pepper -->
Chris@0 172 <PRE>
Chris@0 173 enum
Chris@0 174 { /* Major formats. */
Chris@0 175 SF_FORMAT_WAV = 0x010000, /* Microsoft WAV format (little endian). */
Chris@0 176 SF_FORMAT_AIFF = 0x020000, /* Apple/SGI AIFF format (big endian). */
Chris@0 177 SF_FORMAT_AU = 0x030000, /* Sun/NeXT AU format (big endian). */
Chris@0 178 SF_FORMAT_RAW = 0x040000, /* RAW PCM data. */
Chris@0 179 SF_FORMAT_PAF = 0x050000, /* Ensoniq PARIS file format. */
Chris@0 180 SF_FORMAT_SVX = 0x060000, /* Amiga IFF / SVX8 / SV16 format. */
Chris@0 181 SF_FORMAT_NIST = 0x070000, /* Sphere NIST format. */
Chris@0 182 SF_FORMAT_VOC = 0x080000, /* VOC files. */
Chris@0 183 SF_FORMAT_IRCAM = 0x0A0000, /* Berkeley/IRCAM/CARL */
Chris@0 184 SF_FORMAT_W64 = 0x0B0000, /* Sonic Foundry's 64 bit RIFF/WAV */
Chris@0 185 SF_FORMAT_MAT4 = 0x0C0000, /* Matlab (tm) V4.2 / GNU Octave 2.0 */
Chris@0 186 SF_FORMAT_MAT5 = 0x0D0000, /* Matlab (tm) V5.0 / GNU Octave 2.1 */
Chris@0 187 SF_FORMAT_PVF = 0x0E0000, /* Portable Voice Format */
Chris@0 188 SF_FORMAT_XI = 0x0F0000, /* Fasttracker 2 Extended Instrument */
Chris@0 189 SF_FORMAT_HTK = 0x100000, /* HMM Tool Kit format */
Chris@0 190 SF_FORMAT_SDS = 0x110000, /* Midi Sample Dump Standard */
Chris@0 191 SF_FORMAT_AVR = 0x120000, /* Audio Visual Research */
Chris@0 192 SF_FORMAT_WAVEX = 0x130000, /* MS WAVE with WAVEFORMATEX */
Chris@0 193 SF_FORMAT_SD2 = 0x160000, /* Sound Designer 2 */
Chris@0 194 SF_FORMAT_FLAC = 0x170000, /* FLAC lossless file format */
Chris@0 195 SF_FORMAT_CAF = 0x180000, /* Core Audio File format */
Chris@0 196 SF_FORMAT_WVE = 0x190000, /* Psion WVE format */
Chris@0 197 SF_FORMAT_OGG = 0x200000, /* Xiph OGG container */
Chris@0 198 SF_FORMAT_MPC2K = 0x210000, /* Akai MPC 2000 sampler */
Chris@0 199 SF_FORMAT_RF64 = 0x220000, /* RF64 WAV file */
Chris@0 200
Chris@0 201 /* Subtypes from here on. */
Chris@0 202
Chris@0 203 SF_FORMAT_PCM_S8 = 0x0001, /* Signed 8 bit data */
Chris@0 204 SF_FORMAT_PCM_16 = 0x0002, /* Signed 16 bit data */
Chris@0 205 SF_FORMAT_PCM_24 = 0x0003, /* Signed 24 bit data */
Chris@0 206 SF_FORMAT_PCM_32 = 0x0004, /* Signed 32 bit data */
Chris@0 207
Chris@0 208 SF_FORMAT_PCM_U8 = 0x0005, /* Unsigned 8 bit data (WAV and RAW only) */
Chris@0 209
Chris@0 210 SF_FORMAT_FLOAT = 0x0006, /* 32 bit float data */
Chris@0 211 SF_FORMAT_DOUBLE = 0x0007, /* 64 bit float data */
Chris@0 212
Chris@0 213 SF_FORMAT_ULAW = 0x0010, /* U-Law encoded. */
Chris@0 214 SF_FORMAT_ALAW = 0x0011, /* A-Law encoded. */
Chris@0 215 SF_FORMAT_IMA_ADPCM = 0x0012, /* IMA ADPCM. */
Chris@0 216 SF_FORMAT_MS_ADPCM = 0x0013, /* Microsoft ADPCM. */
Chris@0 217
Chris@0 218 SF_FORMAT_GSM610 = 0x0020, /* GSM 6.10 encoding. */
Chris@0 219 SF_FORMAT_VOX_ADPCM = 0x0021, /* Oki Dialogic ADPCM encoding. */
Chris@0 220
Chris@0 221 SF_FORMAT_G721_32 = 0x0030, /* 32kbs G721 ADPCM encoding. */
Chris@0 222 SF_FORMAT_G723_24 = 0x0031, /* 24kbs G723 ADPCM encoding. */
Chris@0 223 SF_FORMAT_G723_40 = 0x0032, /* 40kbs G723 ADPCM encoding. */
Chris@0 224
Chris@0 225 SF_FORMAT_DWVW_12 = 0x0040, /* 12 bit Delta Width Variable Word encoding. */
Chris@0 226 SF_FORMAT_DWVW_16 = 0x0041, /* 16 bit Delta Width Variable Word encoding. */
Chris@0 227 SF_FORMAT_DWVW_24 = 0x0042, /* 24 bit Delta Width Variable Word encoding. */
Chris@0 228 SF_FORMAT_DWVW_N = 0x0043, /* N bit Delta Width Variable Word encoding. */
Chris@0 229
Chris@0 230 SF_FORMAT_DPCM_8 = 0x0050, /* 8 bit differential PCM (XI only) */
Chris@0 231 SF_FORMAT_DPCM_16 = 0x0051, /* 16 bit differential PCM (XI only) */
Chris@0 232
Chris@0 233 SF_FORMAT_VORBIS = 0x0060, /* Xiph Vorbis encoding. */
Chris@0 234
Chris@0 235 /* Endian-ness options. */
Chris@0 236
Chris@0 237 SF_ENDIAN_FILE = 0x00000000, /* Default file endian-ness. */
Chris@0 238 SF_ENDIAN_LITTLE = 0x10000000, /* Force little endian-ness. */
Chris@0 239 SF_ENDIAN_BIG = 0x20000000, /* Force big endian-ness. */
Chris@0 240 SF_ENDIAN_CPU = 0x30000000, /* Force CPU endian-ness. */
Chris@0 241
Chris@0 242 SF_FORMAT_SUBMASK = 0x0000FFFF,
Chris@0 243 SF_FORMAT_TYPEMASK = 0x0FFF0000,
Chris@0 244 SF_FORMAT_ENDMASK = 0x30000000
Chris@0 245 } ;
Chris@0 246 </PRE>
Chris@0 247 <!-- pepper -->
Chris@0 248 <P>
Chris@0 249 Every call to sf_open() should be matched with a call to sf_close() to free up
Chris@0 250 memory allocated during the call to sf_open().
Chris@0 251 </P>
Chris@0 252 <!-- pepper -->
Chris@0 253 <P>
Chris@0 254 On success, the sf_open function returns a non-NULL pointer which should be
Chris@0 255 passed as the first parameter to all subsequent libsndfile calls dealing with
Chris@0 256 that audio file.
Chris@0 257 On fail, the sf_open function returns a NULL pointer.
Chris@0 258 An explanation of the error can obtained by passing NULL to
Chris@0 259 <A HREF="#error">sf_strerror</A>.
Chris@0 260 </P>
Chris@0 261
Chris@0 262 <A NAME="open_fd"></A>
Chris@0 263 <H3><B>File Descriptor Open</B></H3>
Chris@0 264
Chris@0 265 <PRE>
Chris@0 266 SNDFILE* sf_open_fd (int fd, int mode, SF_INFO *sfinfo, int close_desc) ;
Chris@0 267 </PRE>
Chris@0 268
Chris@0 269 <P>
Chris@0 270 <b>Note:</b> On Microsoft Windows, this function does not work if the
Chris@0 271 application and the libsndfile DLL are linked to different versions of the
Chris@0 272 Microsoft C runtime DLL.
Chris@0 273 </P>
Chris@0 274 <P>
Chris@0 275 The second open function takes a file descriptor of a file that has already been
Chris@0 276 opened.
Chris@0 277 Care should be taken to ensure that the mode of the file represented by the
Chris@0 278 descriptor matches the mode argument.
Chris@0 279 This function is useful in the following circumstances:
Chris@0 280 </P>
Chris@0 281
Chris@0 282 <UL>
Chris@0 283 <LI>Opening temporary files securely (ie use the tmpfile() to return a
Chris@0 284 FILE* pointer and then using fileno() to retrieve the file descriptor
Chris@0 285 which is then passed to libsndfile).
Chris@0 286 <LI>Opening files with file names using OS specific character encodings
Chris@0 287 and then passing the file descriptor to sf_open_fd().
Chris@0 288 <LI>Opening sound files embedded within larger files.
Chris@0 289 <A HREF="embedded_files.html">More info</A>.
Chris@0 290 </UL>
Chris@0 291
Chris@0 292 <P>
Chris@0 293 Every call to sf_open_fd() should be matched with a call to sf_close() to free up
Chris@0 294 memory allocated during the call to sf_open().
Chris@0 295 </P>
Chris@0 296
Chris@0 297 <P>
Chris@0 298 When sf_close() is called, the file descriptor is only closed if the <B>close_desc</B>
Chris@0 299 parameter was TRUE when the sf_open_fd() function was called.
Chris@0 300 </P>
Chris@0 301
Chris@0 302 <P>
Chris@0 303 On success, the sf_open_fd function returns a non-NULL pointer which should be
Chris@0 304 passed as the first parameter to all subsequent libsndfile calls dealing with
Chris@0 305 that audio file.
Chris@0 306 On fail, the sf_open_fd function returns a NULL pointer.
Chris@0 307 </P>
Chris@0 308
Chris@0 309 <A NAME="open_virtual"></A>
Chris@0 310 <h3><b>Virtual File Open Function</b></h3>
Chris@0 311 <pre>
Chris@0 312 SNDFILE* sf_open_virtual (SF_VIRTUAL_IO *sfvirtual, int mode, SF_INFO *sfinfo, void *user_data) ;
Chris@0 313 </pre>
Chris@0 314 <p>
Chris@0 315 Opens a soundfile from a virtual file I/O context which is provided
Chris@0 316 by the caller. This is usually used to interface libsndfile to a stream or buffer
Chris@0 317 based system. Apart from the sfvirtual and the user_data parameters this function behaves
Chris@0 318 like <a href="#open">sf_open</a>.
Chris@0 319 </p>
Chris@0 320
Chris@0 321 <pre>
Chris@0 322 typedef struct
Chris@0 323 { sf_vio_get_filelen get_filelen ;
Chris@0 324 sf_vio_seek seek ;
Chris@0 325 sf_vio_read read ;
Chris@0 326 sf_vio_write write ;
Chris@0 327 sf_vio_tell tell ;
Chris@0 328 } SF_VIRTUAL_IO ;
Chris@0 329 </pre>
Chris@0 330 <p>
Chris@0 331 Libsndfile calls the callbacks provided by the SF_VIRTUAL_IO structure when opening, reading
Chris@0 332 and writing to the virtual file context. The user_data pointer is a user defined context which
Chris@0 333 will be available in the callbacks.
Chris@0 334 </p>
Chris@0 335 <pre>
Chris@0 336 typedef sf_count_t (*sf_vio_get_filelen) (void *user_data) ;
Chris@0 337 typedef sf_count_t (*sf_vio_seek) (sf_count_t offset, int whence, void *user_data) ;
Chris@0 338 typedef sf_count_t (*sf_vio_read) (void *ptr, sf_count_t count, void *user_data) ;
Chris@0 339 typedef sf_count_t (*sf_vio_write) (const void *ptr, sf_count_t count, void *user_data) ;
Chris@0 340 typedef sf_count_t (*sf_vio_tell) (void *user_data) ;
Chris@0 341 </pre>
Chris@0 342 <h4>sf_vio_get_filelen</h4>
Chris@0 343 <pre>
Chris@0 344 typedef sf_count_t (*sf_vio_get_filelen) (void *user_data) ;
Chris@0 345 </pre>
Chris@0 346 <p>
Chris@0 347 The virtual file contex must return the length of the virtual file in bytes.<br>
Chris@0 348 </p>
Chris@0 349 <h4>sf_vio_seek</h4>
Chris@0 350 <pre>
Chris@0 351 typedef sf_count_t (*sf_vio_seek) (sf_count_t offset, int whence, void *user_data) ;
Chris@0 352 </pre>
Chris@0 353 <p>
Chris@0 354 The virtual file context must seek to offset using the seek mode provided by whence which is one of<br>
Chris@0 355 </p>
Chris@0 356 <pre>
Chris@0 357 SEEK_CUR
Chris@0 358 SEEK_SET
Chris@0 359 SEEK_END
Chris@0 360 </pre>
Chris@0 361 <p>
Chris@0 362 The return value must contain the new offset in the file.
Chris@0 363 </p>
Chris@0 364 <h4>sf_vio_read</h4>
Chris@0 365 <pre>
Chris@0 366 typedef sf_count_t (*sf_vio_read) (void *ptr, sf_count_t count, void *user_data) ;
Chris@0 367 </pre>
Chris@0 368 <p>
Chris@0 369 The virtual file context must copy ("read") "count" bytes into the
Chris@0 370 buffer provided by ptr and return the count of actually copied bytes.
Chris@0 371 </p>
Chris@0 372 <h4>sf_vio_write</h4>
Chris@0 373 <pre>
Chris@0 374 typedef sf_count_t (*sf_vio_write) (const void *ptr, sf_count_t count, void *user_data) ;
Chris@0 375 </pre>
Chris@0 376 <p>
Chris@0 377 The virtual file context must process "count" bytes stored in the
Chris@0 378 buffer passed with ptr and return the count of actually processed bytes.<br>
Chris@0 379 </p>
Chris@0 380 <h4>sf_vio_tell</h4>
Chris@0 381 <pre>
Chris@0 382 typedef sf_count_t (*sf_vio_tell) (void *user_data) ;
Chris@0 383 </pre>
Chris@0 384 <p>
Chris@0 385 Return the current position of the virtual file context.<br>
Chris@0 386 </p>
Chris@0 387
Chris@0 388
Chris@0 389 <A NAME="check"></A>
Chris@0 390 <BR><H2><B>Format Check Function</B></H2>
Chris@0 391
Chris@0 392 <PRE>
Chris@0 393 int sf_format_check (const SF_INFO *info) ;
Chris@0 394 </PRE>
Chris@0 395 <!-- pepper -->
Chris@0 396 <P>
Chris@0 397 This function allows the caller to check if a set of parameters in the SF_INFO struct
Chris@0 398 is valid before calling sf_open (SFM_WRITE).
Chris@0 399 </P>
Chris@0 400 <P>
Chris@0 401 sf_format_check returns TRUE if the parameters are valid and FALSE otherwise.
Chris@0 402 </P>
Chris@0 403
Chris@0 404 <A NAME="seek"></A>
Chris@0 405 <BR><H2><B>File Seek Functions</B></H2>
Chris@0 406
Chris@0 407 <PRE>
Chris@0 408 sf_count_t sf_seek (SNDFILE *sndfile, sf_count_t frames, int whence) ;
Chris@0 409 </PRE>
Chris@0 410
Chris@0 411 <P>
Chris@0 412 The file seek functions work much like lseek in unistd.h with the exception that
Chris@0 413 the non-audio data is ignored and the seek only moves within the audio data section of
Chris@0 414 the file.
Chris@0 415 In addition, seeks are defined in number of (multichannel) frames.
Chris@0 416 Therefore, a seek in a stereo file from the current position forward with an offset
Chris@0 417 of 1 would skip forward by one sample of both channels.
Chris@0 418 </P>
Chris@0 419
Chris@0 420 <P>
Chris@0 421 like lseek(), the whence parameter can be any one of the following three values:
Chris@0 422 </P>
Chris@0 423
Chris@0 424 <PRE>
Chris@0 425 SEEK_SET - The offset is set to the start of the audio data plus offset (multichannel) frames.
Chris@0 426 SEEK_CUR - The offset is set to its current location plus offset (multichannel) frames.
Chris@0 427 SEEK_END - The offset is set to the end of the data plus offset (multichannel) frames.
Chris@0 428 </PRE>
Chris@0 429 <!-- pepper -->
Chris@0 430 <P>
Chris@0 431 Internally, libsndfile keeps track of the read and write locations using separate
Chris@0 432 read and write pointers.
Chris@0 433 If a file has been opened with a mode of SFM_RDWR, bitwise OR-ing the standard whence
Chris@0 434 values above with either SFM_READ or SFM_WRITE allows the read and write pointers to
Chris@0 435 be modified separately.
Chris@0 436 If the SEEK_* values are used on their own, the read and write pointers are
Chris@0 437 both modified.
Chris@0 438 </P>
Chris@0 439
Chris@0 440 <P>
Chris@0 441 Note that the frames offset can be negative and in fact should be when SEEK_END is used for the
Chris@0 442 whence parameter.
Chris@0 443 </P>
Chris@0 444 <P>
Chris@0 445 sf_seek will return the offset in (multichannel) frames from the start of the audio data
Chris@0 446 or -1 if an error occured (ie an attempt is made to seek beyond the start or end of the file).
Chris@0 447 </P>
Chris@0 448
Chris@0 449 <A NAME="error"></A>
Chris@0 450 <H2><BR><B>Error Reporting Functions</B></H2>
Chris@0 451
Chris@0 452
Chris@0 453 <PRE>
Chris@0 454 int sf_error (SNDFILE *sndfile) ;
Chris@0 455 </PRE>
Chris@0 456 <P>
Chris@0 457 This function returns the current error number for the given SNDFILE.
Chris@0 458 The error number may be one of the following:
Chris@0 459 </P>
Chris@0 460 <PRE>
Chris@0 461 enum
Chris@0 462 { SF_ERR_NO_ERROR = 0,
Chris@0 463 SF_ERR_UNRECOGNISED_FORMAT = 1,
Chris@0 464 SF_ERR_SYSTEM = 2,
Chris@0 465 SF_ERR_MALFORMED_FILE = 3,
Chris@0 466 SF_ERR_UNSUPPORTED_ENCODING = 4
Chris@0 467 } ;
Chris@0 468 </PRE>
Chris@0 469 <!-- pepper -->
Chris@0 470 <P>
Chris@0 471 or any one of many other internal error values.
Chris@0 472 Applications should only test the return value against error values defined in
Chris@0 473 &lt;sndfile.h&gt; as the internal error values are subject to change at any
Chris@0 474 time.
Chris@0 475 For errors not in the above list, the function sf_error_number() can be used to
Chris@0 476 convert it to an error string.
Chris@0 477 </P>
Chris@0 478
Chris@0 479 <PRE>
Chris@0 480 const char* sf_strerror (SNDFILE *sndfile) ;
Chris@0 481 const char* sf_error_number (int errnum) ;
Chris@0 482 </PRE>
Chris@0 483
Chris@0 484 <P>
Chris@0 485 The error functions sf_strerror() and sf_error_number() convert the library's internal
Chris@0 486 error enumerations into text strings.
Chris@0 487 </P>
Chris@0 488 <PRE>
Chris@0 489 int sf_perror (SNDFILE *sndfile) ;
Chris@0 490 int sf_error_str (SNDFILE *sndfile, char* str, size_t len) ;
Chris@0 491 </PRE>
Chris@0 492
Chris@0 493 <P>
Chris@0 494 The functions sf_perror() and sf_error_str() are deprecated and will be dropped
Chris@0 495 from the library at some later date.
Chris@0 496 </P>
Chris@0 497
Chris@0 498 <A NAME="close"></A>
Chris@0 499 <H2><BR><B>File Close Function</B></H2>
Chris@0 500
Chris@0 501 <PRE>
Chris@0 502 int sf_close (SNDFILE *sndfile) ;
Chris@0 503 </PRE>
Chris@0 504 <!-- pepper -->
Chris@0 505 <P>
Chris@0 506 The close function closes the file, deallocates its internal buffers and returns
Chris@0 507 0 on success or an error value otherwise.
Chris@0 508 </P>
Chris@0 509 <BR>
Chris@0 510
Chris@0 511 <A NAME="write_sync"></A>
Chris@0 512 <H2><BR><B>Write Sync Function</B></H2>
Chris@0 513
Chris@0 514 <PRE>
Chris@0 515 void sf_write_sync (SNDFILE *sndfile) ;
Chris@0 516 </PRE>
Chris@0 517 <!-- pepper -->
Chris@0 518 <P>
Chris@0 519 If the file is opened SFM_WRITE or SFM_RDWR, call the operating system's function
Chris@0 520 to force the writing of all file cache buffers to disk. If the file is opened
Chris@0 521 SFM_READ no action is taken.
Chris@0 522 </P>
Chris@0 523 <BR>
Chris@0 524
Chris@0 525
Chris@0 526 <A NAME="read"></A>
Chris@0 527 <H2><BR><B>File Read Functions (Items)</B></H2>
Chris@0 528
Chris@0 529 <PRE>
Chris@0 530 sf_count_t sf_read_short (SNDFILE *sndfile, short *ptr, sf_count_t items) ;
Chris@0 531 sf_count_t sf_read_int (SNDFILE *sndfile, int *ptr, sf_count_t items) ;
Chris@0 532 sf_count_t sf_read_float (SNDFILE *sndfile, float *ptr, sf_count_t items) ;
Chris@0 533 sf_count_t sf_read_double (SNDFILE *sndfile, double *ptr, sf_count_t items) ;
Chris@0 534 </PRE>
Chris@0 535
Chris@0 536 <P>
Chris@0 537 The file read items functions fill the array pointed to by ptr with the requested
Chris@0 538 number of items. The items parameter must be an integer product of the number
Chris@0 539 of channels or an error will occur.
Chris@0 540 </P>
Chris@0 541 <!-- pepper -->
Chris@0 542 <P>
Chris@0 543 It is important to note that the data type used by the calling program and the data
Chris@0 544 format of the file do not need to be the same. For instance, it is possible to open
Chris@0 545 a 16 bit PCM encoded WAV file and read the data using sf_read_float(). The library
Chris@0 546 seamlessly converts between the two formats on-the-fly. See
Chris@0 547 <A HREF="#note1">Note 1</A>.
Chris@0 548 </P>
Chris@0 549 <!-- pepper -->
Chris@0 550 <P>
Chris@0 551 The sf_read_XXXX functions return the number of items read.
Chris@0 552 Unless the end of the file was reached during the read, the return value should
Chris@0 553 equal the number of items requested.
Chris@0 554 Attempts to read beyond the end of the file will not result in an error but will
Chris@0 555 cause the sf_read_XXXX functions to return less than the number of items requested
Chris@0 556 or 0 if already at the end of the file.
Chris@0 557 </P>
Chris@0 558
Chris@0 559 <A NAME="readf"></A>
Chris@0 560 <H2><BR><B>File Read Functions (Frames)</B></H2>
Chris@0 561
Chris@0 562 <PRE>
Chris@0 563 sf_count_t sf_readf_short (SNDFILE *sndfile, short *ptr, sf_count_t frames) ;
Chris@0 564 sf_count_t sf_readf_int (SNDFILE *sndfile, int *ptr, sf_count_t frames) ;
Chris@0 565 sf_count_t sf_readf_float (SNDFILE *sndfile, float *ptr, sf_count_t frames) ;
Chris@0 566 sf_count_t sf_readf_double (SNDFILE *sndfile, double *ptr, sf_count_t frames) ;
Chris@0 567 </PRE>
Chris@0 568 <!-- pepper -->
Chris@0 569 <P>
Chris@0 570 The file read frames functions fill the array pointed to by ptr with the requested
Chris@0 571 number of frames of data. The array must be large enough to hold the product of
Chris@0 572 frames and the number of channels.
Chris@0 573 </P>
Chris@0 574
Chris@0 575 <P><B>
Chris@0 576 Care must be taken to ensure that there is enough space in the array pointed to by
Chris@0 577 ptr, to take (frames * channels) number of items (shorts, ints, floats or doubles).
Chris@0 578 </B></P>
Chris@0 579
Chris@0 580 <P>
Chris@0 581 The sf_readf_XXXX functions return the number of frames read.
Chris@0 582 Unless the end of the file was reached during the read, the return value should equal
Chris@0 583 the number of frames requested.
Chris@0 584 Attempts to read beyond the end of the file will not result in an error but will cause
Chris@0 585 the sf_readf_XXXX functions to return less than the number of frames requested or 0 if
Chris@0 586 already at the end of the file.
Chris@0 587 </P>
Chris@0 588
Chris@0 589 <A NAME="write"></A>
Chris@0 590 <H2><BR><B>File Write Functions (Items)</B></H2>
Chris@0 591
Chris@0 592 <PRE>
Chris@0 593 sf_count_t sf_write_short (SNDFILE *sndfile, short *ptr, sf_count_t items) ;
Chris@0 594 sf_count_t sf_write_int (SNDFILE *sndfile, int *ptr, sf_count_t items) ;
Chris@0 595 sf_count_t sf_write_float (SNDFILE *sndfile, float *ptr, sf_count_t items) ;
Chris@0 596 sf_count_t sf_write_double (SNDFILE *sndfile, double *ptr, sf_count_t items) ;
Chris@0 597 </PRE>
Chris@0 598
Chris@0 599 <P>
Chris@0 600 The file write items functions write the data in the array pointed to by ptr to the file.
Chris@0 601 The items parameter must be an integer product of the number of channels or an error
Chris@0 602 will occur.
Chris@0 603 </P>
Chris@0 604 <!-- pepper -->
Chris@0 605 <P>
Chris@0 606 It is important to note that the data type used by the calling program and the data
Chris@0 607 format of the file do not need to be the same. For instance, it is possible to open
Chris@0 608 a 16 bit PCM encoded WAV file and write the data using sf_write_float(). The library
Chris@0 609 seamlessly converts between the two formats on-the-fly. See
Chris@0 610 <A HREF="#note1">Note 1</A>.
Chris@0 611 </P>
Chris@0 612 <P>
Chris@0 613 The sf_write_XXXX functions return the number of items written (which should be the
Chris@0 614 same as the items parameter).
Chris@0 615 </P>
Chris@0 616
Chris@0 617 <A NAME="writef"></A>
Chris@0 618 <H2><BR><B>File Write Functions (Frames)</B></H2>
Chris@0 619
Chris@0 620 <PRE>
Chris@0 621 sf_count_t sf_writef_short (SNDFILE *sndfile, short *ptr, sf_count_t frames) ;
Chris@0 622 sf_count_t sf_writef_int (SNDFILE *sndfile, int *ptr, sf_count_t frames) ;
Chris@0 623 sf_count_t sf_writef_float (SNDFILE *sndfile, float *ptr, sf_count_t frames) ;
Chris@0 624 sf_count_t sf_writef_double (SNDFILE *sndfile, double *ptr, sf_count_t frames) ;
Chris@0 625 </PRE>
Chris@0 626
Chris@0 627 <P>
Chris@0 628 The file write frames functions write the data in the array pointed to by ptr to the file.
Chris@0 629 The array must be large enough to hold the product of frames and the number of channels.
Chris@0 630 </P>
Chris@0 631 <P>
Chris@0 632 The sf_writef_XXXX functions return the number of frames written (which should be the
Chris@0 633 same as the frames parameter).
Chris@0 634 </P>
Chris@0 635
Chris@0 636 <A NAME="raw"></A>
Chris@0 637 <H2><BR><B>Raw File Read and Write Functions</B></H2>
Chris@0 638 <!-- pepper -->
Chris@0 639 <PRE>
Chris@0 640 sf_count_t sf_read_raw (SNDFILE *sndfile, void *ptr, sf_count_t bytes) ;
Chris@0 641 sf_count_t sf_write_raw (SNDFILE *sndfile, void *ptr, sf_count_t bytes) ;
Chris@0 642 </PRE>
Chris@0 643
Chris@0 644 <P>
Chris@0 645 <b>Note:</b> Unless you are writing an external decoder/encode that uses
Chris@0 646 libsndfile to handle the file headers, you should not be using these
Chris@0 647 functions.
Chris@0 648 </P>
Chris@0 649
Chris@0 650 <P>
Chris@0 651 The raw read and write functions read raw audio data from the audio file (not to be
Chris@0 652 confused with reading RAW header-less PCM files). The number of bytes read or written
Chris@0 653 must always be an integer multiple of the number of channels multiplied by the number
Chris@0 654 of bytes required to represent one sample from one channel.
Chris@0 655 </P>
Chris@0 656 <!-- pepper -->
Chris@0 657 <P>
Chris@0 658 The raw read and write functions return the number of bytes read or written (which
Chris@0 659 should be the same as the bytes parameter).
Chris@0 660 </P>
Chris@0 661
Chris@0 662 <P>
Chris@0 663 <B>
Chris@0 664 Note : The result of using of both regular reads/writes and raw reads/writes on
Chris@0 665 compressed file formats other than SF_FORMAT_ALAW and SF_FORMAT_ULAW is undefined.
Chris@0 666 </B>
Chris@0 667 </P>
Chris@0 668
Chris@0 669 <p>
Chris@0 670 See also : <a href="command.html#SFC_RAW_NEEDS_ENDSWAP">SFC_RAW_NEEDS_ENDSWAP</a>
Chris@0 671 </p>
Chris@0 672
Chris@0 673 <A NAME="string"></A>
Chris@0 674 <H2><BR><B>Functions for Reading and Writing String Data</B></H2>
Chris@0 675
Chris@0 676
Chris@0 677 <PRE>
Chris@0 678 const char* sf_get_string (SNDFILE *sndfile, int str_type) ;
Chris@0 679 int sf_set_string (SNDFILE *sndfile, int str_type, const char* str) ;
Chris@0 680 </PRE>
Chris@0 681
Chris@0 682 <P>
Chris@0 683 These functions allow strings to be set on files opened for write and to be
Chris@0 684 retrieved from files opened for read where supported by the given file type.
Chris@0 685 The <B>str_type</B> parameter can be any one of the following string types:
Chris@0 686 </P>
Chris@0 687
Chris@0 688 <PRE>
Chris@0 689 enum
Chris@0 690 { SF_STR_TITLE,
Chris@0 691 SF_STR_COPYRIGHT,
Chris@0 692 SF_STR_SOFTWARE,
Chris@0 693 SF_STR_ARTIST,
Chris@0 694 SF_STR_COMMENT,
Chris@0 695 SF_STR_DATE,
Chris@0 696 SF_STR_ALBUM,
Chris@0 697 SF_STR_LICENSE,
Chris@0 698 SF_STR_TRACKNUMBER,
Chris@0 699 SF_STR_GENRE
Chris@0 700 } ;
Chris@0 701 </PRE>
Chris@0 702
Chris@0 703 <P>
Chris@0 704 The sf_get_string() function returns the specified string if it exists and a
Chris@0 705 NULL pointer otherwise.
Chris@0 706 In addition to the string ids above, SF_STR_FIRST (== SF_STR_TITLE) and
Chris@0 707 SF_STR_LAST (always the same as the highest numbers string id) are also
Chris@0 708 available to allow iteration over all the available string ids.
Chris@0 709 </P>
Chris@0 710
Chris@0 711 <P>
Chris@0 712 The sf_set_string() function sets the string data.
Chris@0 713 It returns zero on success and non-zero on error.
Chris@0 714 The error code can be converted to a string using sf_error_number().
Chris@0 715 </P>
Chris@0 716
Chris@0 717
Chris@0 718 <P>
Chris@0 719
Chris@0 720 </P>
Chris@0 721
Chris@0 722 <HR>
Chris@0 723
Chris@0 724 <A NAME="note1"></A>
Chris@0 725 <H2><BR><B>Note 1</B></H2>
Chris@0 726 <!-- pepper -->
Chris@0 727 <P>
Chris@0 728 When converting between integer PCM formats of differing size (ie using sf_read_int()
Chris@0 729 to read a 16 bit PCM encoded WAV file) libsndfile obeys one simple rule:
Chris@0 730 </P>
Chris@0 731
Chris@0 732 <P CLASS=indent_block>
Chris@0 733 Whenever integer data is moved from one sized container to another sized container,
Chris@0 734 the most significant bit in the source container will become the most significant bit
Chris@0 735 in the destination container.
Chris@0 736 </P>
Chris@0 737
Chris@0 738 <P>
Chris@0 739 When converting between integer data and floating point data, different rules apply.
Chris@0 740 The default behaviour when reading floating point data (sf_read_float() or
Chris@0 741 sf_read_double ()) from a file with integer data is normalisation. Regardless of
Chris@0 742 whether data in the file is 8, 16, 24 or 32 bit wide, the data will be read as
Chris@0 743 floating point data in the range [-1.0, 1.0]. Similarly, data in the range [-1.0, 1.0]
Chris@0 744 will be written to an integer PCM file so that a data value of 1.0 will be the largest
Chris@0 745 allowable integer for the given bit width. This normalisation can be turned on or off
Chris@0 746 using the <A HREF="command.html">sf_command</A> interface.
Chris@0 747 </P>
Chris@0 748
Chris@0 749 <A NAME="note2"></A>
Chris@0 750 <H2><BR><B>Note 2</B></H2>
Chris@0 751
Chris@0 752 <P>
Chris@0 753 Reading a file containg floating point data (allowable with WAV, AIFF, AU and other
Chris@0 754 file formats) using integer read methods (sf_read_short() or sf_read_int()) can
Chris@0 755 produce unexpected results.
Chris@0 756 For instance the data in the file may have a maximum absolute value &lt; 1.0 which
Chris@0 757 would mean that all sample values read from the file will be zero.
Chris@0 758 In order to read these files correctly using integer read methods, it is recommended
Chris@0 759 that you use the
Chris@0 760 <A HREF="command.html">sf_command</A>
Chris@0 761 interface, a command of
Chris@0 762 <A HREF="command.html#SFC_SET_SCALE_FLOAT_INT_READ">SFC_SET_SCALE_FLOAT_INT_READ</A>
Chris@0 763 and a parameter of SF_TRUE to force correct scaling.
Chris@0 764 </P>
Chris@0 765 <!-- pepper -->
Chris@0 766 <HR>
Chris@0 767 <!-- pepper -->
Chris@0 768 <P>
Chris@0 769 The libsndfile home page is
Chris@0 770 <A HREF="http://www.mega-nerd.com/libsndfile/">here</A>.
Chris@0 771 </P>
Chris@0 772 <P>
Chris@0 773 Version : 1.0.25
Chris@0 774 </P>
Chris@0 775 <!-- pepper -->
Chris@0 776 <!-- pepper -->
Chris@0 777 <!-- pepper -->
Chris@0 778 <!-- pepper -->
Chris@0 779
Chris@0 780 </BODY>
Chris@0 781 </HTML>