Chris@40: Libsndfile is a library designed to allow the reading and writing of many Chris@40: different sampled sound file formats (such as MS Windows WAV and the Apple/SGI Chris@40: AIFF format) through one standard library interface. Chris@40:
Chris@40: Chris@40:Chris@40: During read and write operations, formats are seamlessly converted between the Chris@40: format the application program has requested or supplied and the file's data Chris@40: format. The application programmer can remain blissfully unaware of issues Chris@40: such as file endian-ness and data format. See Note 1 and Chris@40: Note 2. Chris@40:
Chris@40: Chris@40:Chris@40: Every effort is made to keep these documents up-to-date, error free and Chris@40: unambiguous. Chris@40: However, since maintaining the documentation is the least fun part of working Chris@40: on libsndfile, these docs can and do fall behind the behaviour of the library. Chris@40: If any errors, omissions or ambiguities are found, please notify me (erikd) Chris@40: at mega-nerd dot com. Chris@40:
Chris@40: Chris@40:Chris@40: To supplement this reference documentation, there are simple example programs Chris@40: included in the source code tarball. Chris@40: The test suite which is also part of the source code tarball is also a good Chris@40: place to look for the correct usage of the library functions. Chris@40:
Chris@40: Chris@40:Chris@40: Finally, if you think there is some feature missing from libsndfile, check that Chris@40: it isn't already implemented (and documented) Chris@40: here. Chris@40: Chris@40:
Chris@40: Chris@40:Chris@40: The functions of libsndfile are defined as follows: Chris@40:
Chris@40: Chris@40:Chris@40: #include <stdio.h> Chris@40: #include <sndfile.h> Chris@40: Chris@40: SNDFILE* sf_open (const char *path, int mode, SF_INFO *sfinfo) ; Chris@40: SNDFILE* sf_wchar_open (LPCWSTR wpath, int mode, SF_INFO *sfinfo) ; Chris@40: SNDFILE* sf_open_fd (int fd, int mode, SF_INFO *sfinfo, int close_desc) ; Chris@40: SNDFILE* sf_open_virtual (SF_VIRTUAL_IO *sfvirtual, int mode, SF_INFO *sfinfo, void *user_data) ; Chris@40: int sf_format_check (const SF_INFO *info) ; Chris@40: Chris@40: sf_count_t sf_seek (SNDFILE *sndfile, sf_count_t frames, int whence) ; Chris@40: Chris@40: int sf_command (SNDFILE *sndfile, int cmd, void *data, int datasize) ; Chris@40: Chris@40: int sf_error (SNDFILE *sndfile) ; Chris@40: const char* sf_strerror (SNDFILE *sndfile) ; Chris@40: const char* sf_error_number (int errnum) ; Chris@40: Chris@40: int sf_perror (SNDFILE *sndfile) ; Chris@40: int sf_error_str (SNDFILE *sndfile, char* str, size_t len) ; Chris@40: Chris@40: int sf_close (SNDFILE *sndfile) ; Chris@40: void sf_write_sync (SNDFILE *sndfile) ; Chris@40: Chris@40: sf_count_t sf_read_short (SNDFILE *sndfile, short *ptr, sf_count_t items) ; Chris@40: sf_count_t sf_read_int (SNDFILE *sndfile, int *ptr, sf_count_t items) ; Chris@40: sf_count_t sf_read_float (SNDFILE *sndfile, float *ptr, sf_count_t items) ; Chris@40: sf_count_t sf_read_double (SNDFILE *sndfile, double *ptr, sf_count_t items) ; Chris@40: Chris@40: sf_count_t sf_readf_short (SNDFILE *sndfile, short *ptr, sf_count_t frames) ; Chris@40: sf_count_t sf_readf_int (SNDFILE *sndfile, int *ptr, sf_count_t frames) ; Chris@40: sf_count_t sf_readf_float (SNDFILE *sndfile, float *ptr, sf_count_t frames) ; Chris@40: sf_count_t sf_readf_double (SNDFILE *sndfile, double *ptr, sf_count_t frames) ; Chris@40: Chris@40: sf_count_t sf_write_short (SNDFILE *sndfile, short *ptr, sf_count_t items) ; Chris@40: sf_count_t sf_write_int (SNDFILE *sndfile, int *ptr, sf_count_t items) ; Chris@40: sf_count_t sf_write_float (SNDFILE *sndfile, float *ptr, sf_count_t items) ; Chris@40: sf_count_t sf_write_double (SNDFILE *sndfile, double *ptr, sf_count_t items) ; Chris@40: Chris@40: sf_count_t sf_writef_short (SNDFILE *sndfile, short *ptr, sf_count_t frames) ; Chris@40: sf_count_t sf_writef_int (SNDFILE *sndfile, int *ptr, sf_count_t frames) ; Chris@40: sf_count_t sf_writef_float (SNDFILE *sndfile, float *ptr, sf_count_t frames) ; Chris@40: sf_count_t sf_writef_double (SNDFILE *sndfile, double *ptr, sf_count_t frames) ; Chris@40: Chris@40: sf_count_t sf_read_raw (SNDFILE *sndfile, void *ptr, sf_count_t bytes) ; Chris@40: sf_count_t sf_write_raw (SNDFILE *sndfile, void *ptr, sf_count_t bytes) ; Chris@40: Chris@40: const char* sf_get_string (SNDFILE *sndfile, int str_type) ; Chris@40: int sf_set_string (SNDFILE *sndfile, int str_type, const char* str) ; Chris@40: Chris@40:Chris@40: Chris@40:
Chris@40: SNDFILE* is an anonymous pointer to data which is private to the library. Chris@40:
Chris@40: Chris@40: Chris@40: Chris@40:Chris@40: SNDFILE* sf_open (const char *path, int mode, SF_INFO *sfinfo) ; Chris@40:Chris@40: Chris@40:
Chris@40: The sf_open() function opens the sound file at the specified path. Chris@40: The filename is byte encoded, but may be utf-8 on Linux, while on Mac OS X it Chris@40: will use the filesystem character set. Chris@40: On Windows, there is also a Windows specific sf_wchar_open() that takes a Chris@40: UTF16_BE encoded filename. Chris@40:
Chris@40: Chris@40:Chris@40: SNDFILE* sf_wchar_open (LPCWSTR wpath, int mode, SF_INFO *sfinfo) ; Chris@40:Chris@40: Chris@40:
Chris@40: The SF_INFO structure is for passing data between the calling function and the library Chris@40: when opening a file for reading or writing. It is defined in sndfile.h as follows: Chris@40:
Chris@40: Chris@40:
Chris@40: typedef struct
Chris@40: { sf_count_t frames ; /* Used to be called samples. */
Chris@40: int samplerate ;
Chris@40: int channels ;
Chris@40: int format ;
Chris@40: int sections ;
Chris@40: int seekable ;
Chris@40: } SF_INFO ;
Chris@40:
Chris@40:
Chris@40: Chris@40: The mode parameter for this function can be any one of the following three values: Chris@40:
Chris@40: Chris@40:Chris@40: SFM_READ - read only mode Chris@40: SFM_WRITE - write only mode Chris@40: SFM_RDWR - read/write mode Chris@40:Chris@40: Chris@40:
Chris@40: When opening a file for read, the format field should be set to zero before Chris@40: calling sf_open(). Chris@40: The only exception to this is the case of RAW files where the caller has to set Chris@40: the samplerate, channels and format fields to valid values. Chris@40: All other fields of the structure are filled in by the library. Chris@40:
Chris@40: Chris@40:Chris@40: When opening a file for write, the caller must fill in structure members samplerate, Chris@40: channels, and format. Chris@40:
Chris@40: Chris@40:Chris@40: The format field in the above SF_INFO structure is made up of the bit-wise OR of a Chris@40: major format type (values between 0x10000 and 0x08000000), a minor format type Chris@40: (with values less than 0x10000) and an optional endian-ness value. Chris@40: The currently understood formats are listed in sndfile.h as follows and also include Chris@40: bitmasks for separating major and minor file types. Chris@40: Not all combinations of endian-ness and major and minor file types are valid. Chris@40:
Chris@40: Chris@40:
Chris@40: enum
Chris@40: { /* Major formats. */
Chris@40: SF_FORMAT_WAV = 0x010000, /* Microsoft WAV format (little endian). */
Chris@40: SF_FORMAT_AIFF = 0x020000, /* Apple/SGI AIFF format (big endian). */
Chris@40: SF_FORMAT_AU = 0x030000, /* Sun/NeXT AU format (big endian). */
Chris@40: SF_FORMAT_RAW = 0x040000, /* RAW PCM data. */
Chris@40: SF_FORMAT_PAF = 0x050000, /* Ensoniq PARIS file format. */
Chris@40: SF_FORMAT_SVX = 0x060000, /* Amiga IFF / SVX8 / SV16 format. */
Chris@40: SF_FORMAT_NIST = 0x070000, /* Sphere NIST format. */
Chris@40: SF_FORMAT_VOC = 0x080000, /* VOC files. */
Chris@40: SF_FORMAT_IRCAM = 0x0A0000, /* Berkeley/IRCAM/CARL */
Chris@40: SF_FORMAT_W64 = 0x0B0000, /* Sonic Foundry's 64 bit RIFF/WAV */
Chris@40: SF_FORMAT_MAT4 = 0x0C0000, /* Matlab (tm) V4.2 / GNU Octave 2.0 */
Chris@40: SF_FORMAT_MAT5 = 0x0D0000, /* Matlab (tm) V5.0 / GNU Octave 2.1 */
Chris@40: SF_FORMAT_PVF = 0x0E0000, /* Portable Voice Format */
Chris@40: SF_FORMAT_XI = 0x0F0000, /* Fasttracker 2 Extended Instrument */
Chris@40: SF_FORMAT_HTK = 0x100000, /* HMM Tool Kit format */
Chris@40: SF_FORMAT_SDS = 0x110000, /* Midi Sample Dump Standard */
Chris@40: SF_FORMAT_AVR = 0x120000, /* Audio Visual Research */
Chris@40: SF_FORMAT_WAVEX = 0x130000, /* MS WAVE with WAVEFORMATEX */
Chris@40: SF_FORMAT_SD2 = 0x160000, /* Sound Designer 2 */
Chris@40: SF_FORMAT_FLAC = 0x170000, /* FLAC lossless file format */
Chris@40: SF_FORMAT_CAF = 0x180000, /* Core Audio File format */
Chris@40: SF_FORMAT_WVE = 0x190000, /* Psion WVE format */
Chris@40: SF_FORMAT_OGG = 0x200000, /* Xiph OGG container */
Chris@40: SF_FORMAT_MPC2K = 0x210000, /* Akai MPC 2000 sampler */
Chris@40: SF_FORMAT_RF64 = 0x220000, /* RF64 WAV file */
Chris@40:
Chris@40: /* Subtypes from here on. */
Chris@40:
Chris@40: SF_FORMAT_PCM_S8 = 0x0001, /* Signed 8 bit data */
Chris@40: SF_FORMAT_PCM_16 = 0x0002, /* Signed 16 bit data */
Chris@40: SF_FORMAT_PCM_24 = 0x0003, /* Signed 24 bit data */
Chris@40: SF_FORMAT_PCM_32 = 0x0004, /* Signed 32 bit data */
Chris@40:
Chris@40: SF_FORMAT_PCM_U8 = 0x0005, /* Unsigned 8 bit data (WAV and RAW only) */
Chris@40:
Chris@40: SF_FORMAT_FLOAT = 0x0006, /* 32 bit float data */
Chris@40: SF_FORMAT_DOUBLE = 0x0007, /* 64 bit float data */
Chris@40:
Chris@40: SF_FORMAT_ULAW = 0x0010, /* U-Law encoded. */
Chris@40: SF_FORMAT_ALAW = 0x0011, /* A-Law encoded. */
Chris@40: SF_FORMAT_IMA_ADPCM = 0x0012, /* IMA ADPCM. */
Chris@40: SF_FORMAT_MS_ADPCM = 0x0013, /* Microsoft ADPCM. */
Chris@40:
Chris@40: SF_FORMAT_GSM610 = 0x0020, /* GSM 6.10 encoding. */
Chris@40: SF_FORMAT_VOX_ADPCM = 0x0021, /* Oki Dialogic ADPCM encoding. */
Chris@40:
Chris@40: SF_FORMAT_G721_32 = 0x0030, /* 32kbs G721 ADPCM encoding. */
Chris@40: SF_FORMAT_G723_24 = 0x0031, /* 24kbs G723 ADPCM encoding. */
Chris@40: SF_FORMAT_G723_40 = 0x0032, /* 40kbs G723 ADPCM encoding. */
Chris@40:
Chris@40: SF_FORMAT_DWVW_12 = 0x0040, /* 12 bit Delta Width Variable Word encoding. */
Chris@40: SF_FORMAT_DWVW_16 = 0x0041, /* 16 bit Delta Width Variable Word encoding. */
Chris@40: SF_FORMAT_DWVW_24 = 0x0042, /* 24 bit Delta Width Variable Word encoding. */
Chris@40: SF_FORMAT_DWVW_N = 0x0043, /* N bit Delta Width Variable Word encoding. */
Chris@40:
Chris@40: SF_FORMAT_DPCM_8 = 0x0050, /* 8 bit differential PCM (XI only) */
Chris@40: SF_FORMAT_DPCM_16 = 0x0051, /* 16 bit differential PCM (XI only) */
Chris@40:
Chris@40: SF_FORMAT_VORBIS = 0x0060, /* Xiph Vorbis encoding. */
Chris@40:
Chris@40: /* Endian-ness options. */
Chris@40:
Chris@40: SF_ENDIAN_FILE = 0x00000000, /* Default file endian-ness. */
Chris@40: SF_ENDIAN_LITTLE = 0x10000000, /* Force little endian-ness. */
Chris@40: SF_ENDIAN_BIG = 0x20000000, /* Force big endian-ness. */
Chris@40: SF_ENDIAN_CPU = 0x30000000, /* Force CPU endian-ness. */
Chris@40:
Chris@40: SF_FORMAT_SUBMASK = 0x0000FFFF,
Chris@40: SF_FORMAT_TYPEMASK = 0x0FFF0000,
Chris@40: SF_FORMAT_ENDMASK = 0x30000000
Chris@40: } ;
Chris@40:
Chris@40:
Chris@40: Chris@40: Every call to sf_open() should be matched with a call to sf_close() to free up Chris@40: memory allocated during the call to sf_open(). Chris@40:
Chris@40: Chris@40:Chris@40: On success, the sf_open function returns a non-NULL pointer which should be Chris@40: passed as the first parameter to all subsequent libsndfile calls dealing with Chris@40: that audio file. Chris@40: On fail, the sf_open function returns a NULL pointer. Chris@40: An explanation of the error can obtained by passing NULL to Chris@40: sf_strerror. Chris@40:
Chris@40: Chris@40: Chris@40:Chris@40: SNDFILE* sf_open_fd (int fd, int mode, SF_INFO *sfinfo, int close_desc) ; Chris@40:Chris@40: Chris@40:
Chris@40: Note: On Microsoft Windows, this function does not work if the Chris@40: application and the libsndfile DLL are linked to different versions of the Chris@40: Microsoft C runtime DLL. Chris@40:
Chris@40:Chris@40: The second open function takes a file descriptor of a file that has already been Chris@40: opened. Chris@40: Care should be taken to ensure that the mode of the file represented by the Chris@40: descriptor matches the mode argument. Chris@40: This function is useful in the following circumstances: Chris@40:
Chris@40: Chris@40:Chris@40: Every call to sf_open_fd() should be matched with a call to sf_close() to free up Chris@40: memory allocated during the call to sf_open(). Chris@40:
Chris@40: Chris@40:Chris@40: When sf_close() is called, the file descriptor is only closed if the close_desc Chris@40: parameter was TRUE when the sf_open_fd() function was called. Chris@40:
Chris@40: Chris@40:Chris@40: On success, the sf_open_fd function returns a non-NULL pointer which should be Chris@40: passed as the first parameter to all subsequent libsndfile calls dealing with Chris@40: that audio file. Chris@40: On fail, the sf_open_fd function returns a NULL pointer. Chris@40:
Chris@40: Chris@40: Chris@40:Chris@40: SNDFILE* sf_open_virtual (SF_VIRTUAL_IO *sfvirtual, int mode, SF_INFO *sfinfo, void *user_data) ; Chris@40:Chris@40:
Chris@40: Opens a soundfile from a virtual file I/O context which is provided Chris@40: by the caller. This is usually used to interface libsndfile to a stream or buffer Chris@40: based system. Apart from the sfvirtual and the user_data parameters this function behaves Chris@40: like sf_open. Chris@40:
Chris@40: Chris@40:
Chris@40: typedef struct
Chris@40: { sf_vio_get_filelen get_filelen ;
Chris@40: sf_vio_seek seek ;
Chris@40: sf_vio_read read ;
Chris@40: sf_vio_write write ;
Chris@40: sf_vio_tell tell ;
Chris@40: } SF_VIRTUAL_IO ;
Chris@40:
Chris@40: Chris@40: Libsndfile calls the callbacks provided by the SF_VIRTUAL_IO structure when opening, reading Chris@40: and writing to the virtual file context. The user_data pointer is a user defined context which Chris@40: will be available in the callbacks. Chris@40:
Chris@40:Chris@40: typedef sf_count_t (*sf_vio_get_filelen) (void *user_data) ; Chris@40: typedef sf_count_t (*sf_vio_seek) (sf_count_t offset, int whence, void *user_data) ; Chris@40: typedef sf_count_t (*sf_vio_read) (void *ptr, sf_count_t count, void *user_data) ; Chris@40: typedef sf_count_t (*sf_vio_write) (const void *ptr, sf_count_t count, void *user_data) ; Chris@40: typedef sf_count_t (*sf_vio_tell) (void *user_data) ; Chris@40:Chris@40:
Chris@40: typedef sf_count_t (*sf_vio_get_filelen) (void *user_data) ; Chris@40:Chris@40:
Chris@40: The virtual file contex must return the length of the virtual file in bytes.
Chris@40:
Chris@40: typedef sf_count_t (*sf_vio_seek) (sf_count_t offset, int whence, void *user_data) ; Chris@40:Chris@40:
Chris@40: The virtual file context must seek to offset using the seek mode provided by whence which is one of
Chris@40:
Chris@40: SEEK_CUR Chris@40: SEEK_SET Chris@40: SEEK_END Chris@40:Chris@40:
Chris@40: The return value must contain the new offset in the file. Chris@40:
Chris@40:Chris@40: typedef sf_count_t (*sf_vio_read) (void *ptr, sf_count_t count, void *user_data) ; Chris@40:Chris@40:
Chris@40: The virtual file context must copy ("read") "count" bytes into the Chris@40: buffer provided by ptr and return the count of actually copied bytes. Chris@40:
Chris@40:Chris@40: typedef sf_count_t (*sf_vio_write) (const void *ptr, sf_count_t count, void *user_data) ; Chris@40:Chris@40:
Chris@40: The virtual file context must process "count" bytes stored in the
Chris@40: buffer passed with ptr and return the count of actually processed bytes.
Chris@40:
Chris@40: typedef sf_count_t (*sf_vio_tell) (void *user_data) ; Chris@40:Chris@40:
Chris@40: Return the current position of the virtual file context.
Chris@40:
Chris@40: int sf_format_check (const SF_INFO *info) ; Chris@40:Chris@40: Chris@40:
Chris@40: This function allows the caller to check if a set of parameters in the SF_INFO struct Chris@40: is valid before calling sf_open (SFM_WRITE). Chris@40:
Chris@40:Chris@40: sf_format_check returns TRUE if the parameters are valid and FALSE otherwise. Chris@40:
Chris@40: Chris@40: Chris@40:Chris@40: sf_count_t sf_seek (SNDFILE *sndfile, sf_count_t frames, int whence) ; Chris@40:Chris@40: Chris@40:
Chris@40: The file seek functions work much like lseek in unistd.h with the exception that Chris@40: the non-audio data is ignored and the seek only moves within the audio data section of Chris@40: the file. Chris@40: In addition, seeks are defined in number of (multichannel) frames. Chris@40: Therefore, a seek in a stereo file from the current position forward with an offset Chris@40: of 1 would skip forward by one sample of both channels. Chris@40:
Chris@40: Chris@40:Chris@40: like lseek(), the whence parameter can be any one of the following three values: Chris@40:
Chris@40: Chris@40:Chris@40: SEEK_SET - The offset is set to the start of the audio data plus offset (multichannel) frames. Chris@40: SEEK_CUR - The offset is set to its current location plus offset (multichannel) frames. Chris@40: SEEK_END - The offset is set to the end of the data plus offset (multichannel) frames. Chris@40:Chris@40: Chris@40:
Chris@40: Internally, libsndfile keeps track of the read and write locations using separate Chris@40: read and write pointers. Chris@40: If a file has been opened with a mode of SFM_RDWR, bitwise OR-ing the standard whence Chris@40: values above with either SFM_READ or SFM_WRITE allows the read and write pointers to Chris@40: be modified separately. Chris@40: If the SEEK_* values are used on their own, the read and write pointers are Chris@40: both modified. Chris@40:
Chris@40: Chris@40:Chris@40: Note that the frames offset can be negative and in fact should be when SEEK_END is used for the Chris@40: whence parameter. Chris@40:
Chris@40:Chris@40: sf_seek will return the offset in (multichannel) frames from the start of the audio data Chris@40: or -1 if an error occured (ie an attempt is made to seek beyond the start or end of the file). Chris@40:
Chris@40: Chris@40: Chris@40:Chris@40: int sf_error (SNDFILE *sndfile) ; Chris@40:Chris@40:
Chris@40: This function returns the current error number for the given SNDFILE. Chris@40: The error number may be one of the following: Chris@40:
Chris@40:
Chris@40: enum
Chris@40: { SF_ERR_NO_ERROR = 0,
Chris@40: SF_ERR_UNRECOGNISED_FORMAT = 1,
Chris@40: SF_ERR_SYSTEM = 2,
Chris@40: SF_ERR_MALFORMED_FILE = 3,
Chris@40: SF_ERR_UNSUPPORTED_ENCODING = 4
Chris@40: } ;
Chris@40:
Chris@40:
Chris@40: Chris@40: or any one of many other internal error values. Chris@40: Applications should only test the return value against error values defined in Chris@40: <sndfile.h> as the internal error values are subject to change at any Chris@40: time. Chris@40: For errors not in the above list, the function sf_error_number() can be used to Chris@40: convert it to an error string. Chris@40:
Chris@40: Chris@40:Chris@40: const char* sf_strerror (SNDFILE *sndfile) ; Chris@40: const char* sf_error_number (int errnum) ; Chris@40:Chris@40: Chris@40:
Chris@40: The error functions sf_strerror() and sf_error_number() convert the library's internal Chris@40: error enumerations into text strings. Chris@40:
Chris@40:Chris@40: int sf_perror (SNDFILE *sndfile) ; Chris@40: int sf_error_str (SNDFILE *sndfile, char* str, size_t len) ; Chris@40:Chris@40: Chris@40:
Chris@40: The functions sf_perror() and sf_error_str() are deprecated and will be dropped Chris@40: from the library at some later date. Chris@40:
Chris@40: Chris@40: Chris@40:Chris@40: int sf_close (SNDFILE *sndfile) ; Chris@40:Chris@40: Chris@40:
Chris@40: The close function closes the file, deallocates its internal buffers and returns Chris@40: 0 on success or an error value otherwise. Chris@40:
Chris@40:Chris@40: void sf_write_sync (SNDFILE *sndfile) ; Chris@40:Chris@40: Chris@40:
Chris@40: If the file is opened SFM_WRITE or SFM_RDWR, call the operating system's function Chris@40: to force the writing of all file cache buffers to disk. If the file is opened Chris@40: SFM_READ no action is taken. Chris@40:
Chris@40:Chris@40: sf_count_t sf_read_short (SNDFILE *sndfile, short *ptr, sf_count_t items) ; Chris@40: sf_count_t sf_read_int (SNDFILE *sndfile, int *ptr, sf_count_t items) ; Chris@40: sf_count_t sf_read_float (SNDFILE *sndfile, float *ptr, sf_count_t items) ; Chris@40: sf_count_t sf_read_double (SNDFILE *sndfile, double *ptr, sf_count_t items) ; Chris@40:Chris@40: Chris@40: Chris@40:
Chris@40: sf_count_t sf_readf_short (SNDFILE *sndfile, short *ptr, sf_count_t frames) ; Chris@40: sf_count_t sf_readf_int (SNDFILE *sndfile, int *ptr, sf_count_t frames) ; Chris@40: sf_count_t sf_readf_float (SNDFILE *sndfile, float *ptr, sf_count_t frames) ; Chris@40: sf_count_t sf_readf_double (SNDFILE *sndfile, double *ptr, sf_count_t frames) ; Chris@40:Chris@40: Chris@40:
Chris@40: The file read functions fill the array pointed to by ptr with the Chris@40: requested number of items or frames. Chris@40:
Chris@40: Chris@40:Chris@40: For the frames-count functions, the frames parameter specifies the number Chris@40: of frames. A frame is just a block of samples, one for each Chris@40: channel. Care must be taken to ensure that there is enough space Chris@40: in the array pointed to by ptr, to take (frames * channels) number of Chris@40: items (shorts, ints, floats or doubles). Chris@40:
Chris@40: Chris@40:Chris@40: For the items-count functions, the items parameter must be an integer product Chris@40: of the number of channels or an error will occur. Here, an item is just a Chris@40: sample. Chris@40:
Chris@40: Chris@40:Chris@40: Note: The only difference between the "items" and "frames" versions of Chris@40: each read function is the units in which the object count is specified Chris@40: - calling sf_readf_short with a count argument of N, on a SNDFILE with Chris@40: C channels, is the same as calling sf_read_short with a count argument Chris@40: of N*C. The buffer pointed to by "ptr" should be the same number of Chris@40: bytes in each case. Chris@40:
Chris@40: Chris@40: Chris@40:Chris@40: Note: The data type used by the calling program and the data format of Chris@40: the file do not need to be the same. For instance, it is possible to Chris@40: open a 16 bit PCM encoded WAV file and read the data using Chris@40: sf_read_float(). The library seamlessly converts between the two Chris@40: formats on-the-fly. See Chris@40: Note 1. Chris@40:
Chris@40: Chris@40:Chris@40: The sf_read_XXXX and sf_readf_XXXX functions return the number of Chris@40: items or frames read, respectively. Unless the end of the file was Chris@40: reached during the read, the return value should equal the number of Chris@40: objects requested. Attempts to read beyond the end of the file will Chris@40: not result in an error but will cause the read functions to return Chris@40: less than the number of objects requested or 0 if already at the end Chris@40: of the file. Chris@40:
Chris@40: Chris@40: Chris@40:Chris@40: sf_count_t sf_write_short (SNDFILE *sndfile, short *ptr, sf_count_t items) ; Chris@40: sf_count_t sf_write_int (SNDFILE *sndfile, int *ptr, sf_count_t items) ; Chris@40: sf_count_t sf_write_float (SNDFILE *sndfile, float *ptr, sf_count_t items) ; Chris@40: sf_count_t sf_write_double (SNDFILE *sndfile, double *ptr, sf_count_t items) ; Chris@40:Chris@40: Chris@40: Chris@40:
Chris@40: sf_count_t sf_writef_short (SNDFILE *sndfile, short *ptr, sf_count_t frames) ; Chris@40: sf_count_t sf_writef_int (SNDFILE *sndfile, int *ptr, sf_count_t frames) ; Chris@40: sf_count_t sf_writef_float (SNDFILE *sndfile, float *ptr, sf_count_t frames) ; Chris@40: sf_count_t sf_writef_double (SNDFILE *sndfile, double *ptr, sf_count_t frames) ; Chris@40:Chris@40: Chris@40:
Chris@40: The file write functions write the data in the array pointed to by ptr to the file. Chris@40:
Chris@40: Chris@40:Chris@40: For items-count functions, the items parameter specifies the size of Chris@40: the array and must be an integer product of the number of channels or Chris@40: an error will occur. Chris@40:
Chris@40: Chris@40:Chris@40: For the frames-count functions, the array is expected to be large enough Chris@40: to hold a number of items equal to the product of frames and the Chris@40: number of channels. Chris@40:
Chris@40: Chris@40:As with the read functions above, the only Chris@40: difference in the items and frames version of each write function is Chris@40: the units in which the buffer size is specified. Again, the data type Chris@40: used by the calling program and the data format of the file do not Chris@40: need to be the same (Note 1). Chris@40:
Chris@40: Chris@40:Chris@40: The sf_write_XXXX and sf_writef_XXXX functions respectively return the Chris@40: number of items or frames written (which should be the same as the Chris@40: items or frames parameter). Chris@40:
Chris@40: Chris@40: Chris@40: Chris@40:Chris@40: sf_count_t sf_read_raw (SNDFILE *sndfile, void *ptr, sf_count_t bytes) ; Chris@40: sf_count_t sf_write_raw (SNDFILE *sndfile, void *ptr, sf_count_t bytes) ; Chris@40:Chris@40: Chris@40:
Chris@40: Note: Unless you are writing an external decoder/encode that uses Chris@40: libsndfile to handle the file headers, you should not be using these Chris@40: functions. Chris@40:
Chris@40: Chris@40:Chris@40: The raw read and write functions read raw audio data from the audio file (not to be Chris@40: confused with reading RAW header-less PCM files). The number of bytes read or written Chris@40: must always be an integer multiple of the number of channels multiplied by the number Chris@40: of bytes required to represent one sample from one channel. Chris@40:
Chris@40: Chris@40:Chris@40: The raw read and write functions return the number of bytes read or written (which Chris@40: should be the same as the bytes parameter). Chris@40:
Chris@40: Chris@40:Chris@40: Chris@40: Note : The result of using of both regular reads/writes and raw reads/writes on Chris@40: compressed file formats other than SF_FORMAT_ALAW and SF_FORMAT_ULAW is undefined. Chris@40: Chris@40:
Chris@40: Chris@40:Chris@40: See also : SFC_RAW_NEEDS_ENDSWAP Chris@40:
Chris@40: Chris@40: Chris@40:Chris@40: const char* sf_get_string (SNDFILE *sndfile, int str_type) ; Chris@40: int sf_set_string (SNDFILE *sndfile, int str_type, const char* str) ; Chris@40:Chris@40: Chris@40:
Chris@40: These functions allow strings to be set on files opened for write and to be Chris@40: retrieved from files opened for read where supported by the given file type. Chris@40: The str_type parameter can be any one of the following string types: Chris@40:
Chris@40: Chris@40:
Chris@40: enum
Chris@40: { SF_STR_TITLE,
Chris@40: SF_STR_COPYRIGHT,
Chris@40: SF_STR_SOFTWARE,
Chris@40: SF_STR_ARTIST,
Chris@40: SF_STR_COMMENT,
Chris@40: SF_STR_DATE,
Chris@40: SF_STR_ALBUM,
Chris@40: SF_STR_LICENSE,
Chris@40: SF_STR_TRACKNUMBER,
Chris@40: SF_STR_GENRE
Chris@40: } ;
Chris@40:
Chris@40:
Chris@40: Chris@40: The sf_get_string() function returns the specified string if it exists and a Chris@40: NULL pointer otherwise. Chris@40: In addition to the string ids above, SF_STR_FIRST (== SF_STR_TITLE) and Chris@40: SF_STR_LAST (always the same as the highest numbers string id) are also Chris@40: available to allow iteration over all the available string ids. Chris@40:
Chris@40: Chris@40:Chris@40: The sf_set_string() function sets the string data. Chris@40: It returns zero on success and non-zero on error. Chris@40: The error code can be converted to a string using sf_error_number(). Chris@40:
Chris@40: Chris@40:Chris@40: Strings passed to and retrieved from these two functions are assumed to be Chris@40: utf-8. Chris@40: However, while formats like Ogg/Vorbis and FLAC fully support utf-8, others Chris@40: like WAV and AIFF officially only support ASCII. Chris@40: Writing utf-8 strings to WAV and AIF files with libsndfile will work when read Chris@40: back with libsndfile, but may not work with other programs. Chris@40:
Chris@40: Chris@40:Chris@40: The suggested method of dealing with tags retrived using sf_get_string() is to Chris@40: assume they are utf-8. Chris@40: Similarly if you have a string in some exotic format like utf-16, it should be Chris@40: encoded to utf-8 before being written using libsndfile. Chris@40:
Chris@40: Chris@40:Chris@40: When converting between integer PCM formats of differing size Chris@40: (e.g. using sf_read_int() to read a 16 bit PCM encoded WAV file) Chris@40: libsndfile obeys one simple rule: Chris@40:
Chris@40: Chris@40:Chris@40: Whenever integer data is moved from one sized container to another sized container, Chris@40: the most significant bit in the source container will become the most significant bit Chris@40: in the destination container. Chris@40:
Chris@40: Chris@40:Chris@40: When converting between integer data and floating point data, different rules apply. Chris@40: The default behaviour when reading floating point data (sf_read_float() or Chris@40: sf_read_double ()) from a file with integer data is normalisation. Regardless of Chris@40: whether data in the file is 8, 16, 24 or 32 bit wide, the data will be read as Chris@40: floating point data in the range [-1.0, 1.0]. Similarly, data in the range [-1.0, 1.0] Chris@40: will be written to an integer PCM file so that a data value of 1.0 will be the largest Chris@40: allowable integer for the given bit width. This normalisation can be turned on or off Chris@40: using the sf_command interface. Chris@40:
Chris@40: Chris@40: Chris@40:Chris@40: Reading a file containg floating point data (allowable with WAV, AIFF, AU and other Chris@40: file formats) using integer read methods (sf_read_short() or sf_read_int()) can Chris@40: produce unexpected results. Chris@40: For instance the data in the file may have a maximum absolute value < 1.0 which Chris@40: would mean that all sample values read from the file will be zero. Chris@40: In order to read these files correctly using integer read methods, it is recommended Chris@40: that you use the Chris@40: sf_command Chris@40: interface, a command of Chris@40: SFC_SET_SCALE_FLOAT_INT_READ Chris@40: and a parameter of SF_TRUE to force correct scaling. Chris@40:
Chris@40: Chris@40:Chris@40: The libsndfile home page is Chris@40: here. Chris@40:
Chris@40:Chris@40: Version : 1.0.27 Chris@40:
Chris@40: Chris@40: Chris@40: Chris@40: Chris@40: Chris@40: Chris@40: