- Libsndfile is a library designed to allow the reading and writing of many - different sampled sound file formats (such as MS Windows WAV and the Apple/SGI - AIFF format) through one standard library interface. -
- -- During read and write operations, formats are seamlessly converted between the - format the application program has requested or supplied and the file's data - format. The application programmer can remain blissfully unaware of issues - such as file endian-ness and data format. See Note 1 and - Note 2. -
- -- Every effort is made to keep these documents up-to-date, error free and - unambiguous. - However, since maintaining the documentation is the least fun part of working - on libsndfile, these docs can and do fall behind the behaviour of library. - If any errors, omissions or ambiguities are found, please notify me (erikd) - at mega-nerd dot com. -
- -- To supplement this reference documentation, there are simple example programs - included in the source code tarball. - The test suite which is also part of the source code tarball is also a good - place to look for the correct usage of the library functions. -
- -- Finally, if you think there is some feature missing from libsndfile, check that - it isn't already implemented (and documented) - here. - -
- --The functions of libsndfile are defined as follows: -
- -- #include <stdio.h> - #include <sndfile.h> - - SNDFILE* sf_open (const char *path, int mode, SF_INFO *sfinfo) ; - SNDFILE* sf_open_fd (int fd, int mode, SF_INFO *sfinfo, int close_desc) ; - SNDFILE* sf_open_virtual (SF_VIRTUAL_IO *sfvirtual, int mode, SF_INFO *sfinfo, void *user_data) ; - int sf_format_check (const SF_INFO *info) ; - - sf_count_t sf_seek (SNDFILE *sndfile, sf_count_t frames, int whence) ; - - int sf_command (SNDFILE *sndfile, int cmd, void *data, int datasize) ; - - int sf_error (SNDFILE *sndfile) ; - const char* sf_strerror (SNDFILE *sndfile) ; - const char* sf_error_number (int errnum) ; - - int sf_perror (SNDFILE *sndfile) ; - int sf_error_str (SNDFILE *sndfile, char* str, size_t len) ; - - int sf_close (SNDFILE *sndfile) ; - void sf_write_sync (SNDFILE *sndfile) ; - - sf_count_t sf_read_short (SNDFILE *sndfile, short *ptr, sf_count_t items) ; - sf_count_t sf_read_int (SNDFILE *sndfile, int *ptr, sf_count_t items) ; - sf_count_t sf_read_float (SNDFILE *sndfile, float *ptr, sf_count_t items) ; - sf_count_t sf_read_double (SNDFILE *sndfile, double *ptr, sf_count_t items) ; - - sf_count_t sf_readf_short (SNDFILE *sndfile, short *ptr, sf_count_t frames) ; - sf_count_t sf_readf_int (SNDFILE *sndfile, int *ptr, sf_count_t frames) ; - sf_count_t sf_readf_float (SNDFILE *sndfile, float *ptr, sf_count_t frames) ; - sf_count_t sf_readf_double (SNDFILE *sndfile, double *ptr, sf_count_t frames) ; - - sf_count_t sf_write_short (SNDFILE *sndfile, short *ptr, sf_count_t items) ; - sf_count_t sf_write_int (SNDFILE *sndfile, int *ptr, sf_count_t items) ; - sf_count_t sf_write_float (SNDFILE *sndfile, float *ptr, sf_count_t items) ; - sf_count_t sf_write_double (SNDFILE *sndfile, double *ptr, sf_count_t items) ; - - sf_count_t sf_writef_short (SNDFILE *sndfile, short *ptr, sf_count_t frames) ; - sf_count_t sf_writef_int (SNDFILE *sndfile, int *ptr, sf_count_t frames) ; - sf_count_t sf_writef_float (SNDFILE *sndfile, float *ptr, sf_count_t frames) ; - sf_count_t sf_writef_double (SNDFILE *sndfile, double *ptr, sf_count_t frames) ; - - sf_count_t sf_read_raw (SNDFILE *sndfile, void *ptr, sf_count_t bytes) ; - sf_count_t sf_write_raw (SNDFILE *sndfile, void *ptr, sf_count_t bytes) ; - - const char* sf_get_string (SNDFILE *sndfile, int str_type) ; - int sf_set_string (SNDFILE *sndfile, int str_type, const char* str) ; - -- -
-SNDFILE* is an anonymous pointer to data which is private to the library. -
- - - -- SNDFILE* sf_open (const char *path, int mode, SF_INFO *sfinfo) ; -- -
-The SF_INFO structure is for passing data between the calling function and the library -when opening a file for reading or writing. It is defined in sndfile.h as follows: -
- -
- typedef struct
- { sf_count_t frames ; /* Used to be called samples. */
- int samplerate ;
- int channels ;
- int format ;
- int sections ;
- int seekable ;
- } SF_INFO ;
-
-
--The mode parameter for this function can be any one of the following three values: -
- -- SFM_READ - read only mode - SFM_WRITE - write only mode - SFM_RDWR - read/write mode -- -
-When opening a file for read, the format field should be set to zero before -calling sf_open(). -The only exception to this is the case of RAW files where the caller has to set -the samplerate, channels and format fields to valid values. -All other fields of the structure are filled in by the library. -
- --When opening a file for write, the caller must fill in structure members samplerate, -channels, and format. -
- --The format field in the above SF_INFO structure is made up of the bit-wise OR of a -major format type (values between 0x10000 and 0x08000000), a minor format type -(with values less than 0x10000) and an optional endian-ness value. -The currently understood formats are listed in sndfile.h as follows and also include -bitmasks for separating major and minor file types. -Not all combinations of endian-ness and major and minor file types are valid. -
- -
- enum
- { /* Major formats. */
- SF_FORMAT_WAV = 0x010000, /* Microsoft WAV format (little endian). */
- SF_FORMAT_AIFF = 0x020000, /* Apple/SGI AIFF format (big endian). */
- SF_FORMAT_AU = 0x030000, /* Sun/NeXT AU format (big endian). */
- SF_FORMAT_RAW = 0x040000, /* RAW PCM data. */
- SF_FORMAT_PAF = 0x050000, /* Ensoniq PARIS file format. */
- SF_FORMAT_SVX = 0x060000, /* Amiga IFF / SVX8 / SV16 format. */
- SF_FORMAT_NIST = 0x070000, /* Sphere NIST format. */
- SF_FORMAT_VOC = 0x080000, /* VOC files. */
- SF_FORMAT_IRCAM = 0x0A0000, /* Berkeley/IRCAM/CARL */
- SF_FORMAT_W64 = 0x0B0000, /* Sonic Foundry's 64 bit RIFF/WAV */
- SF_FORMAT_MAT4 = 0x0C0000, /* Matlab (tm) V4.2 / GNU Octave 2.0 */
- SF_FORMAT_MAT5 = 0x0D0000, /* Matlab (tm) V5.0 / GNU Octave 2.1 */
- SF_FORMAT_PVF = 0x0E0000, /* Portable Voice Format */
- SF_FORMAT_XI = 0x0F0000, /* Fasttracker 2 Extended Instrument */
- SF_FORMAT_HTK = 0x100000, /* HMM Tool Kit format */
- SF_FORMAT_SDS = 0x110000, /* Midi Sample Dump Standard */
- SF_FORMAT_AVR = 0x120000, /* Audio Visual Research */
- SF_FORMAT_WAVEX = 0x130000, /* MS WAVE with WAVEFORMATEX */
- SF_FORMAT_SD2 = 0x160000, /* Sound Designer 2 */
- SF_FORMAT_FLAC = 0x170000, /* FLAC lossless file format */
- SF_FORMAT_CAF = 0x180000, /* Core Audio File format */
- SF_FORMAT_WVE = 0x190000, /* Psion WVE format */
- SF_FORMAT_OGG = 0x200000, /* Xiph OGG container */
- SF_FORMAT_MPC2K = 0x210000, /* Akai MPC 2000 sampler */
- SF_FORMAT_RF64 = 0x220000, /* RF64 WAV file */
-
- /* Subtypes from here on. */
-
- SF_FORMAT_PCM_S8 = 0x0001, /* Signed 8 bit data */
- SF_FORMAT_PCM_16 = 0x0002, /* Signed 16 bit data */
- SF_FORMAT_PCM_24 = 0x0003, /* Signed 24 bit data */
- SF_FORMAT_PCM_32 = 0x0004, /* Signed 32 bit data */
-
- SF_FORMAT_PCM_U8 = 0x0005, /* Unsigned 8 bit data (WAV and RAW only) */
-
- SF_FORMAT_FLOAT = 0x0006, /* 32 bit float data */
- SF_FORMAT_DOUBLE = 0x0007, /* 64 bit float data */
-
- SF_FORMAT_ULAW = 0x0010, /* U-Law encoded. */
- SF_FORMAT_ALAW = 0x0011, /* A-Law encoded. */
- SF_FORMAT_IMA_ADPCM = 0x0012, /* IMA ADPCM. */
- SF_FORMAT_MS_ADPCM = 0x0013, /* Microsoft ADPCM. */
-
- SF_FORMAT_GSM610 = 0x0020, /* GSM 6.10 encoding. */
- SF_FORMAT_VOX_ADPCM = 0x0021, /* Oki Dialogic ADPCM encoding. */
-
- SF_FORMAT_G721_32 = 0x0030, /* 32kbs G721 ADPCM encoding. */
- SF_FORMAT_G723_24 = 0x0031, /* 24kbs G723 ADPCM encoding. */
- SF_FORMAT_G723_40 = 0x0032, /* 40kbs G723 ADPCM encoding. */
-
- SF_FORMAT_DWVW_12 = 0x0040, /* 12 bit Delta Width Variable Word encoding. */
- SF_FORMAT_DWVW_16 = 0x0041, /* 16 bit Delta Width Variable Word encoding. */
- SF_FORMAT_DWVW_24 = 0x0042, /* 24 bit Delta Width Variable Word encoding. */
- SF_FORMAT_DWVW_N = 0x0043, /* N bit Delta Width Variable Word encoding. */
-
- SF_FORMAT_DPCM_8 = 0x0050, /* 8 bit differential PCM (XI only) */
- SF_FORMAT_DPCM_16 = 0x0051, /* 16 bit differential PCM (XI only) */
-
- SF_FORMAT_VORBIS = 0x0060, /* Xiph Vorbis encoding. */
-
- /* Endian-ness options. */
-
- SF_ENDIAN_FILE = 0x00000000, /* Default file endian-ness. */
- SF_ENDIAN_LITTLE = 0x10000000, /* Force little endian-ness. */
- SF_ENDIAN_BIG = 0x20000000, /* Force big endian-ness. */
- SF_ENDIAN_CPU = 0x30000000, /* Force CPU endian-ness. */
-
- SF_FORMAT_SUBMASK = 0x0000FFFF,
- SF_FORMAT_TYPEMASK = 0x0FFF0000,
- SF_FORMAT_ENDMASK = 0x30000000
- } ;
-
-
--Every call to sf_open() should be matched with a call to sf_close() to free up -memory allocated during the call to sf_open(). -
- --On success, the sf_open function returns a non-NULL pointer which should be -passed as the first parameter to all subsequent libsndfile calls dealing with -that audio file. -On fail, the sf_open function returns a NULL pointer. -An explanation of the error can obtained by passing NULL to - sf_strerror. -
- - -- SNDFILE* sf_open_fd (int fd, int mode, SF_INFO *sfinfo, int close_desc) ; -- -
-Note: On Microsoft Windows, this function does not work if the -application and the libsndfile DLL are linked to different versions of the -Microsoft C runtime DLL. -
--The second open function takes a file descriptor of a file that has already been -opened. -Care should be taken to ensure that the mode of the file represented by the -descriptor matches the mode argument. -This function is useful in the following circumstances: -
- --Every call to sf_open_fd() should be matched with a call to sf_close() to free up -memory allocated during the call to sf_open(). -
- --When sf_close() is called, the file descriptor is only closed if the close_desc -parameter was TRUE when the sf_open_fd() function was called. -
- --On success, the sf_open_fd function returns a non-NULL pointer which should be -passed as the first parameter to all subsequent libsndfile calls dealing with -that audio file. -On fail, the sf_open_fd function returns a NULL pointer. -
- - -- SNDFILE* sf_open_virtual (SF_VIRTUAL_IO *sfvirtual, int mode, SF_INFO *sfinfo, void *user_data) ; --
- Opens a soundfile from a virtual file I/O context which is provided - by the caller. This is usually used to interface libsndfile to a stream or buffer - based system. Apart from the sfvirtual and the user_data parameters this function behaves - like sf_open. -
- -
- typedef struct
- { sf_vio_get_filelen get_filelen ;
- sf_vio_seek seek ;
- sf_vio_read read ;
- sf_vio_write write ;
- sf_vio_tell tell ;
- } SF_VIRTUAL_IO ;
-
--Libsndfile calls the callbacks provided by the SF_VIRTUAL_IO structure when opening, reading -and writing to the virtual file context. The user_data pointer is a user defined context which -will be available in the callbacks. -
-- typedef sf_count_t (*sf_vio_get_filelen) (void *user_data) ; - typedef sf_count_t (*sf_vio_seek) (sf_count_t offset, int whence, void *user_data) ; - typedef sf_count_t (*sf_vio_read) (void *ptr, sf_count_t count, void *user_data) ; - typedef sf_count_t (*sf_vio_write) (const void *ptr, sf_count_t count, void *user_data) ; - typedef sf_count_t (*sf_vio_tell) (void *user_data) ; --
- typedef sf_count_t (*sf_vio_get_filelen) (void *user_data) ; --
-The virtual file contex must return the length of the virtual file in bytes.
-
- typedef sf_count_t (*sf_vio_seek) (sf_count_t offset, int whence, void *user_data) ; --
-The virtual file context must seek to offset using the seek mode provided by whence which is one of
-
- SEEK_CUR - SEEK_SET - SEEK_END --
-The return value must contain the new offset in the file. -
-- typedef sf_count_t (*sf_vio_read) (void *ptr, sf_count_t count, void *user_data) ; --
-The virtual file context must copy ("read") "count" bytes into the -buffer provided by ptr and return the count of actually copied bytes. -
-- typedef sf_count_t (*sf_vio_write) (const void *ptr, sf_count_t count, void *user_data) ; --
-The virtual file context must process "count" bytes stored in the
-buffer passed with ptr and return the count of actually processed bytes.
-
- typedef sf_count_t (*sf_vio_tell) (void *user_data) ; --
-Return the current position of the virtual file context.
-
- int sf_format_check (const SF_INFO *info) ; -- -
-This function allows the caller to check if a set of parameters in the SF_INFO struct -is valid before calling sf_open (SFM_WRITE). -
--sf_format_check returns TRUE if the parameters are valid and FALSE otherwise. -
- - -- sf_count_t sf_seek (SNDFILE *sndfile, sf_count_t frames, int whence) ; -- -
-The file seek functions work much like lseek in unistd.h with the exception that -the non-audio data is ignored and the seek only moves within the audio data section of -the file. -In addition, seeks are defined in number of (multichannel) frames. -Therefore, a seek in a stereo file from the current position forward with an offset -of 1 would skip forward by one sample of both channels. -
- --like lseek(), the whence parameter can be any one of the following three values: -
- -- SEEK_SET - The offset is set to the start of the audio data plus offset (multichannel) frames. - SEEK_CUR - The offset is set to its current location plus offset (multichannel) frames. - SEEK_END - The offset is set to the end of the data plus offset (multichannel) frames. -- -
-Internally, libsndfile keeps track of the read and write locations using separate -read and write pointers. -If a file has been opened with a mode of SFM_RDWR, bitwise OR-ing the standard whence -values above with either SFM_READ or SFM_WRITE allows the read and write pointers to -be modified separately. -If the SEEK_* values are used on their own, the read and write pointers are -both modified. -
- --Note that the frames offset can be negative and in fact should be when SEEK_END is used for the -whence parameter. -
--sf_seek will return the offset in (multichannel) frames from the start of the audio data -or -1 if an error occured (ie an attempt is made to seek beyond the start or end of the file). -
- - -- int sf_error (SNDFILE *sndfile) ; --
-This function returns the current error number for the given SNDFILE. -The error number may be one of the following: -
-
- enum
- { SF_ERR_NO_ERROR = 0,
- SF_ERR_UNRECOGNISED_FORMAT = 1,
- SF_ERR_SYSTEM = 2,
- SF_ERR_MALFORMED_FILE = 3,
- SF_ERR_UNSUPPORTED_ENCODING = 4
- } ;
-
-
--or any one of many other internal error values. -Applications should only test the return value against error values defined in -<sndfile.h> as the internal error values are subject to change at any -time. -For errors not in the above list, the function sf_error_number() can be used to -convert it to an error string. -
- -- const char* sf_strerror (SNDFILE *sndfile) ; - const char* sf_error_number (int errnum) ; -- -
-The error functions sf_strerror() and sf_error_number() convert the library's internal -error enumerations into text strings. -
-- int sf_perror (SNDFILE *sndfile) ; - int sf_error_str (SNDFILE *sndfile, char* str, size_t len) ; -- -
-The functions sf_perror() and sf_error_str() are deprecated and will be dropped -from the library at some later date. -
- - -- int sf_close (SNDFILE *sndfile) ; -- -
-The close function closes the file, deallocates its internal buffers and returns -0 on success or an error value otherwise. -
-- void sf_write_sync (SNDFILE *sndfile) ; -- -
-If the file is opened SFM_WRITE or SFM_RDWR, call the operating system's function -to force the writing of all file cache buffers to disk. If the file is opened -SFM_READ no action is taken. -
-- sf_count_t sf_read_short (SNDFILE *sndfile, short *ptr, sf_count_t items) ; - sf_count_t sf_read_int (SNDFILE *sndfile, int *ptr, sf_count_t items) ; - sf_count_t sf_read_float (SNDFILE *sndfile, float *ptr, sf_count_t items) ; - sf_count_t sf_read_double (SNDFILE *sndfile, double *ptr, sf_count_t items) ; -- -
-The file read items functions fill the array pointed to by ptr with the requested -number of items. The items parameter must be an integer product of the number -of channels or an error will occur. -
- --It is important to note that the data type used by the calling program and the data -format of the file do not need to be the same. For instance, it is possible to open -a 16 bit PCM encoded WAV file and read the data using sf_read_float(). The library -seamlessly converts between the two formats on-the-fly. See -Note 1. -
- --The sf_read_XXXX functions return the number of items read. -Unless the end of the file was reached during the read, the return value should -equal the number of items requested. -Attempts to read beyond the end of the file will not result in an error but will -cause the sf_read_XXXX functions to return less than the number of items requested -or 0 if already at the end of the file. -
- - -- sf_count_t sf_readf_short (SNDFILE *sndfile, short *ptr, sf_count_t frames) ; - sf_count_t sf_readf_int (SNDFILE *sndfile, int *ptr, sf_count_t frames) ; - sf_count_t sf_readf_float (SNDFILE *sndfile, float *ptr, sf_count_t frames) ; - sf_count_t sf_readf_double (SNDFILE *sndfile, double *ptr, sf_count_t frames) ; -- -
-The file read frames functions fill the array pointed to by ptr with the requested -number of frames of data. The array must be large enough to hold the product of -frames and the number of channels. -
- --Care must be taken to ensure that there is enough space in the array pointed to by -ptr, to take (frames * channels) number of items (shorts, ints, floats or doubles). -
- --The sf_readf_XXXX functions return the number of frames read. -Unless the end of the file was reached during the read, the return value should equal -the number of frames requested. -Attempts to read beyond the end of the file will not result in an error but will cause -the sf_readf_XXXX functions to return less than the number of frames requested or 0 if -already at the end of the file. -
- - -- sf_count_t sf_write_short (SNDFILE *sndfile, short *ptr, sf_count_t items) ; - sf_count_t sf_write_int (SNDFILE *sndfile, int *ptr, sf_count_t items) ; - sf_count_t sf_write_float (SNDFILE *sndfile, float *ptr, sf_count_t items) ; - sf_count_t sf_write_double (SNDFILE *sndfile, double *ptr, sf_count_t items) ; -- -
-The file write items functions write the data in the array pointed to by ptr to the file. -The items parameter must be an integer product of the number of channels or an error -will occur. -
- --It is important to note that the data type used by the calling program and the data -format of the file do not need to be the same. For instance, it is possible to open -a 16 bit PCM encoded WAV file and write the data using sf_write_float(). The library -seamlessly converts between the two formats on-the-fly. See -Note 1. -
--The sf_write_XXXX functions return the number of items written (which should be the -same as the items parameter). -
- - -- sf_count_t sf_writef_short (SNDFILE *sndfile, short *ptr, sf_count_t frames) ; - sf_count_t sf_writef_int (SNDFILE *sndfile, int *ptr, sf_count_t frames) ; - sf_count_t sf_writef_float (SNDFILE *sndfile, float *ptr, sf_count_t frames) ; - sf_count_t sf_writef_double (SNDFILE *sndfile, double *ptr, sf_count_t frames) ; -- -
-The file write frames functions write the data in the array pointed to by ptr to the file. -The array must be large enough to hold the product of frames and the number of channels. -
--The sf_writef_XXXX functions return the number of frames written (which should be the -same as the frames parameter). -
- - -- sf_count_t sf_read_raw (SNDFILE *sndfile, void *ptr, sf_count_t bytes) ; - sf_count_t sf_write_raw (SNDFILE *sndfile, void *ptr, sf_count_t bytes) ; -- -
-Note: Unless you are writing an external decoder/encode that uses -libsndfile to handle the file headers, you should not be using these -functions. -
- --The raw read and write functions read raw audio data from the audio file (not to be -confused with reading RAW header-less PCM files). The number of bytes read or written -must always be an integer multiple of the number of channels multiplied by the number -of bytes required to represent one sample from one channel. -
- --The raw read and write functions return the number of bytes read or written (which -should be the same as the bytes parameter). -
- -- -Note : The result of using of both regular reads/writes and raw reads/writes on -compressed file formats other than SF_FORMAT_ALAW and SF_FORMAT_ULAW is undefined. - -
- --See also : SFC_RAW_NEEDS_ENDSWAP -
- - -- const char* sf_get_string (SNDFILE *sndfile, int str_type) ; - int sf_set_string (SNDFILE *sndfile, int str_type, const char* str) ; -- -
-These functions allow strings to be set on files opened for write and to be -retrieved from files opened for read where supported by the given file type. -The str_type parameter can be any one of the following string types: -
- -
- enum
- { SF_STR_TITLE,
- SF_STR_COPYRIGHT,
- SF_STR_SOFTWARE,
- SF_STR_ARTIST,
- SF_STR_COMMENT,
- SF_STR_DATE,
- SF_STR_ALBUM,
- SF_STR_LICENSE,
- SF_STR_TRACKNUMBER,
- SF_STR_GENRE
- } ;
-
-
--The sf_get_string() function returns the specified string if it exists and a -NULL pointer otherwise. -In addition to the string ids above, SF_STR_FIRST (== SF_STR_TITLE) and -SF_STR_LAST (always the same as the highest numbers string id) are also -available to allow iteration over all the available string ids. -
- --The sf_set_string() function sets the string data. -It returns zero on success and non-zero on error. -The error code can be converted to a string using sf_error_number(). -
- - -- -
- --When converting between integer PCM formats of differing size (ie using sf_read_int() -to read a 16 bit PCM encoded WAV file) libsndfile obeys one simple rule: -
- --Whenever integer data is moved from one sized container to another sized container, -the most significant bit in the source container will become the most significant bit -in the destination container. -
- --When converting between integer data and floating point data, different rules apply. -The default behaviour when reading floating point data (sf_read_float() or -sf_read_double ()) from a file with integer data is normalisation. Regardless of -whether data in the file is 8, 16, 24 or 32 bit wide, the data will be read as -floating point data in the range [-1.0, 1.0]. Similarly, data in the range [-1.0, 1.0] -will be written to an integer PCM file so that a data value of 1.0 will be the largest -allowable integer for the given bit width. This normalisation can be turned on or off -using the sf_command interface. -
- - --Reading a file containg floating point data (allowable with WAV, AIFF, AU and other -file formats) using integer read methods (sf_read_short() or sf_read_int()) can -produce unexpected results. -For instance the data in the file may have a maximum absolute value < 1.0 which -would mean that all sample values read from the file will be zero. -In order to read these files correctly using integer read methods, it is recommended -that you use the - sf_command -interface, a command of - SFC_SET_SCALE_FLOAT_INT_READ -and a parameter of SF_TRUE to force correct scaling. -
- -- The libsndfile home page is - here. -
--Version : 1.0.25 -
- - - - - - -