From cb979e10a703033864f8f42c94e9d1d335e5be40 Mon Sep 17 00:00:00 2001 From: Erik de Castro Lopo Date: Mon, 14 May 2007 19:55:24 +1000 Subject: First snapshot of the public project. --- doc/dither.html | 1024 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 1024 insertions(+) create mode 100644 doc/dither.html (limited to 'doc/dither.html') diff --git a/doc/dither.html b/doc/dither.html new file mode 100644 index 0000000..16ca2de --- /dev/null +++ b/doc/dither.html @@ -0,0 +1,1024 @@ + + + + + + libsndfile : the sf_command function. + + + + + + + + + + +

sf_command

+
+
+        int    sf_command (SNDFILE *sndfile, int cmd, void *data, int datasize) ;
+
+

+ This function allows the caller to retrieve information from or change aspects of the + library behaviour. + Examples include retrieving a string containing the library version or changing the + scaling applied to floating point sample data during read and write. + Most of these operations are performed on a per-file basis. +

+

+ The cmd parameter is a integer identifier which is defined in <sndfile.h>. + All of the valid command identifiers have names begining with "SFC_". + Data is passed to and returned from the library by use of a void pointer. + The library will not read or write more than datasize bytes from the void pointer. + For some calls no data is required in which case data should be NULL and datasize + may be used for some other purpose. +

+

+ The available commands are as follows: +

+ +
+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +
SFC_GET_LIB_VERSIONRetrieve the version of the library.
SFC_GET_LOG_INFORetrieve the internal per-file operation log.
SFC_CALC_SIGNAL_MAXRetrieve the measured maximum signal value.
SFC_CALC_NORM_SIGNAL_MAXRetrieve the measured normalised maximum signal value.
SFC_CALC_MAX_ALL_CHANNELSCalculate peaks for all channels.
SFC_CALC_NORM_MAX_ALL_CHANNELSCalculate normalised peaks for all channels.
SFC_SET_NORM_FLOATModify the normalisation behaviour of the floating point reading and writing functions.
SFC_SET_NORM_DOUBLEModify the normalisation behaviour of the double precision floating point reading and writing functions.
SFC_GET_NORM_FLOATRetrieve the current normalisation behaviour of the floating point reading and writing functions.
SFC_GET_NORM_DOUBLERetrieve the current normalisation behaviour of the double precision floating point reading and writing functions.
SFC_GET_SIMPLE_FORMAT_COUNTRetrieve the number of simple formats supported by libsndfile.
SFC_GET_SIMPLE_FORMATRetrieve information about a simple format.
SFC_GET_FORMAT_INFORetrieve information about a major or subtype format.
SFC_GET_FORMAT_MAJOR_COUNTRetrieve the number of major formats.
SFC_GET_FORMAT_MAJORRetrieve information about a major format type.
SFC_GET_FORMAT_SUBTYPE_COUNTRetrieve the number of subformats.
SFC_GET_FORMAT_SUBTYPERetrieve information about a subformat.
SFC_SET_ADD_PEAK_CHUNKSwitch the code for adding the PEAK chunk to WAV and AIFF files on or off.
SFC_UPDATE_HEADER_NOWUsed when a file is open for write, this command will update the file + header to reflect the data written so far.
SFC_SET_UPDATE_HEADER_AUTOUsed when a file is open for write, this command will cause the file header + to be updated after each write to the file.
SFC_FILE_TRUNCATETruncate a file open for write or for read/write.
SFC_SET_RAW_START_OFFSETChange the data start offset for files opened up as SF_FORMAT_RAW.
+
+ +

+ +
+ + + +


SFC_GET_LIB_VERSION

+

+Retrieve the version of the library as a string. +

+

+Parameters: +

+        sndfile  : Not used
+        cmd      : SFC_GET_LIB_VERSION
+        data     : A pointer to a char buffer
+        datasize : The size of the the buffer
+
+

+Example: +

+
+        char  buffer [128] ;
+        sf_command (NULL, SFC_GET_LIB_VERSION, buffer, sizeof (buffer)) ;
+
+ +
+
Return value:
+
This call will return the length of the retrieved version string. +
+
+
Notes:
+
+The string returned in the buffer passed to this function will not overflow +the buffer and will always be null terminated . +
+ + + +


SFC_GET_LOG_INFO

+

+Retrieve the log buffer generated when opening a file as a string. This log +buffer can often contain a good reason for why libsndfile failed to open a +particular file. +

+

+Parameters: +

+        sndfile  : A valid SNDFILE* pointer
+        cmd      : SFC_GET_LOG_INFO
+        data     : A pointer to a char buffer
+        datasize : The size of the the buffer
+
+

+Example: +

+
+        char  buffer [2048] ;
+        sf_command (sndfile, SFC_GET_LOG_INFO, buffer, sizeof (buffer)) ;
+
+ +
+
Return value:
+
This call will return the length of the retrieved version string. +
+
+
Notes:
+
+The string returned in the buffer passed to this function will not overflow +the buffer and will always be null terminated . +
+ + + +


SFC_CALC_SIGNAL_MAX

+

+Retrieve the measured maximum signal value. This involves reading through +the whole file which can be slow on large files. +

+

+Parameters: +

+        sndfile  : A valid SNDFILE* pointer
+        cmd      : SFC_CALC_SIGNAL_MAX
+        data     : A pointer to a double
+        datasize : sizeof (double)
+
+

+Example: +

+
+        double   max_val ;
+        sf_command (sndfile, SFC_CALC_SIGNAL_MAX, &max_val, sizeof (max_val)) ;
+
+ +
+
Return value:
+
Zero on success, non-zero otherwise. +
+ + + +


SFC_CALC_NORM_SIGNAL_MAX

+

+Retrieve the measured normailised maximum signal value. This involves reading +through the whole file which can be slow on large files. +

+

+Parameters: +

+        sndfile  : A valid SNDFILE* pointer
+        cmd      : SFC_CALC_NORM_SIGNAL_MAX
+        data     : A pointer to a double
+        datasize : sizeof (double)
+
+

+Example: +

+
+        double   max_val ;
+        sf_command (sndfile, SFC_CALC_NORM_SIGNAL_MAX, &max_val, sizeof (max_val)) ;
+
+ +
+
Return value:
+
Zero on success, non-zero otherwise. +
+ + + +


SFC_CALC_MAX_ALL_CHANNELS

+

+Calculate peaks for all channels. This involves reading through +the whole file which can be slow on large files. +

+

+Parameters: +

+        sndfile  : A valid SNDFILE* pointer
+        cmd      : SFC_CALC_MAX_ALL_CHANNELS
+        data     : A pointer to a double
+        datasize : sizeof (double) * number_of_channels
+
+

+Example: +

+
+        double   peaks [number_of_channels] ;
+        sf_command (sndfile, SFC_CALC_MAX_ALL_CHANNELS, peaks, sizeof (peaks)) ;
+
+
+
Return value:
+
Zero if peaks have been calculated successfully and non-zero otherwise. +
+ + + + +


SFC_CALC_NORM_MAX_ALL_CHANNELS

+

+Calculate normalised peaks for all channels. This involves reading through +the whole file which can be slow on large files. +

+

+Parameters: +

+        sndfile  : A valid SNDFILE* pointer
+        cmd      : SFC_CALC_NORM_MAX_ALL_CHANNELS
+        data     : A pointer to a double
+        datasize : sizeof (double) * number_of_channels
+
+

+Example: +

+
+        double   peaks [number_of_channels] ;
+        sf_command (sndfile, SFC_CALC_NORM_MAX_ALL_CHANNELS, peaks, sizeof (peaks)) ;
+
+
+
Return value:
+
Zero if peaks have been calculated successfully and non-zero otherwise. +
+ + + + + + + + + + + +


SFC_SET_NORM_FLOAT

+

+This command only affects data read from or written to using the floating point functions: +

+
+	size_t    sf_read_float    (SNDFILE *sndfile, float *ptr, size_t items) ;
+	size_t    sf_readf_float   (SNDFILE *sndfile, float *ptr, size_t frames) ;
+
+	size_t    sf_write_float   (SNDFILE *sndfile, float *ptr, size_t items) ;
+	size_t    sf_writef_float  (SNDFILE *sndfile, float *ptr, size_t frames) ;
+
+

+Parameters: +

+
+        sndfile  : A valid SNDFILE* pointer
+        cmd      : SFC_SET_NORM_FLOAT
+        data     : NULL
+        datasize : SF_TRUE or SF_FALSE
+
+

+For read operations setting normalisation to SF_TRUE means that the data from all +subsequent reads will be be normalised to the range [-1.0, 1.0]. +

+

+For write operations, setting normalisation to SF_TRUE means than all data supplied +to the float write functions should be in the range [-1.0, 1.0] and will be scaled +for the file format as necessary. +

+

+For both cases, setting normalisation to SF_FALSE means that no scaling will take place. +

+

+Example: +

+
+        sf_command (sndfile, SFC_SET_NORM_FLOAT, NULL, SF_TRUE) ;
+
+        sf_command (sndfile, SFC_SET_NORM_FLOAT, NULL, SF_FALSE) ;
+
+
+
Return value:
+
Returns 1 on success or 0 for failure. +
+ + + +


SFC_SET_NORM_DOUBLE

+

+This command only affects data read from or written to using the double precision +floating point functions: +

+
+	size_t    sf_read_double    (SNDFILE *sndfile, double *ptr, size_t items) ;
+	size_t    sf_readf_double   (SNDFILE *sndfile, double *ptr, size_t frames) ;
+
+	size_t    sf_write_double   (SNDFILE *sndfile, double *ptr, size_t items) ;
+	size_t    sf_writef_double  (SNDFILE *sndfile, double *ptr, size_t frames) ;
+
+

+Parameters: +

+
+        sndfile  : A valid SNDFILE* pointer
+        cmd      : SFC_SET_NORM_DOUBLE
+        data     : NULL
+        datasize : SF_TRUE or SF_FALSE
+
+

+For read operations setting normalisation to SF_TRUE means that the data +from all subsequent reads will be be normalised to the range [-1.0, 1.0]. +

+

+For write operations, setting normalisation to SF_TRUE means than all data supplied +to the double write functions should be in the range [-1.0, 1.0] and will be scaled +for the file format as necessary. +

+

+For both cases, setting normalisation to SF_FALSE means that no scaling will take place. +

+

+Example: +

+
+        sf_command (sndfile, SFC_SET_NORM_DOUBLE, NULL, SF_TRUE) ;
+
+        sf_command (sndfile, SFC_SET_NORM_DOUBLE, NULL, SF_FALSE) ;
+
+
+
Return value:
+
Returns 1 on success or 0 for failure. +
+ + + +


SFC_GET_NORM_FLOAT

+

+Retrieve the current float normalisation mode. +

+

+Parameters: +

+
+        sndfile  : A valid SNDFILE* pointer
+        cmd      : SFC_GET_NORM_FLOAT
+        data     : NULL
+        datasize : anything
+
+

+Example: +

+
+        normalisation = sf_command (sndfile, SFC_GET_NORM_FLOAT, NULL, 0) ;
+
+
+
Return value:
+
Returns TRUE if normaisation is on and FALSE otherwise. +
+ + + +


SFC_GET_NORM_DOUBLE

+

+Retrieve the current float normalisation mode. +

+

+Parameters: +

+
+        sndfile  : A valid SNDFILE* pointer
+        cmd      : SFC_GET_NORM_DOUBLE
+        data     : NULL
+        datasize : anything
+
+

+Example: +

+
+        normalisation = sf_command (sndfile, SFC_GET_NORM_DOUBLE, NULL, 0) ;
+
+
+
Return value:
+
Returns TRUE if normalisation is on and FALSE otherwise. +
+ + + +


SFC_GET_SIMPLE_FORMAT_COUNT

+

+Retrieve the number of simple formats supported by libsndfile. +

+

+Parameters: +

+
+        sndfile  : Not used.
+        cmd      : SFC_GET_SIMPLE_FORMAT_COUNT
+        data     : a pointer to an int
+        datasize : sizeof (int)
+
+

+Example: +

+
+        int  count ;
+        sf_command (sndfile, SFC_GET_SIMPLE_FORMAT_COUNT, &count, sizeof (int)) ;
+
+
+
Return value:
+
0 +
+ + + +


SFC_GET_SIMPLE_FORMAT

+

+Retrieve information about a simple format. +

+

+Parameters: +

+
+        sndfile  : Not used.
+        cmd      : SFC_GET_SIMPLE_FORMAT
+        data     : a pointer to an  SF_FORMAT_INFO struct
+        datasize : sizeof (SF_FORMAT_INFO)
+
+

+The SF_FORMAT_INFO struct is defined in <sndfile.h> as: +

+
+        typedef struct
+        {   int         format ;
+            const char  *name ;
+            const char  *extension ;
+        } SF_FORMAT_INFO ;
+
+

+When sf_command() is called with SF_GET_SIMPLE_FORMAT, the value of the format +field should be the format number (ie 0 <= format <= count value obtained using +SF_GET_SIMPLE_FORMAT_COUNT). +

+

+Example: +

+
+        SF_FORMAT_INFO	format_info ;
+        int             k, count ;
+
+        sf_command (sndfile, SFC_GET_SIMPLE_FORMAT_COUNT, &count, sizeof (int)) ;
+
+        for (k = 0 ; k < count ; k++)
+        {   format_info.format = k ;
+            sf_command (sndfile, SFC_GET_SIMPLE_FORMAT, &format_info, sizeof (format_info)) ;
+            printf ("%08x  %s %s\n", format_info.format, format_info.name, format_info.extension) ;
+            } ;
+
+
+
Return value:
+
0 on success and non-zero otherwise. +
The value of the format field of the SF_FORMAT_INFO struct will be an value which + can be placed in the format field of an SF_INFO struct when a file is to be opened + for write. +
The name field will contain a char* pointer to the name of the string ie "WAV (Microsoft 16 bit PCM)". +
The extention field will contain the most commonly used file extension for that file type. +
+ + + +


SFC_GET_FORMAT_INFO

+

+Retrieve information about a major or subtype format. +

+

+Parameters: +

+
+        sndfile  : Not used.
+        cmd      : SFC_GET_FORMAT_INFO
+        data     : a pointer to an SF_FORMAT_INFO struct
+        datasize : sizeof (SF_FORMAT_INFO)
+
+

+The SF_FORMAT_INFO struct is defined in <sndfile.h> as: +

+
+        typedef struct
+        {   int         format ;
+            const char  *name ;
+            const char  *extension ;
+        } SF_FORMAT_INFO ;
+
+

+When sf_command() is called with SF_GET_FORMAT_INFO, the format field is +examined and if (format & SF_FORMAT_TYPEMASK) is a valid format then the struct +is filled in with information about the given major type. +If (format & SF_FORMAT_TYPEMASK) is FALSE and (format & SF_FORMAT_SUBMASK) is a +valid subtype format then the struct is filled in with information about the given +subtype. +

+

+Example: +

+
+        SF_FORMAT_INFO	format_info ;
+
+        format_info.format = SF_FORMAT_WAV ;
+        sf_command (sndfile, SFC_GET_FORMAT_INFO, &format_info, sizeof (format_info)) ;
+        printf ("%08x  %s %s\n", format_info.format, format_info.name, format_info.extension) ;
+
+        format_info.format = SF_FORMAT_ULAW ;
+        sf_command (sndfile, SFC_GET_FORMAT_INFO, &format_info, sizeof (format_info)) ;
+        printf ("%08x  %s\n", format_info.format, format_info.name) ;
+
+
+
Return value:
+
0 on success and non-zero otherwise. +
+ + +


SFC_GET_FORMAT_MAJOR_COUNT

+

+Retrieve the number of major formats. +

+

+Parameters: +

+
+        sndfile  : Not used.
+        cmd      : SFC_GET_FORMAT_MAJOR_COUNT
+        data     : a pointer to an int
+        datasize : sizeof (int)
+
+

+Example: +

+
+        int  count ;
+        sf_command (sndfile, SFC_GET_FORMAT_MAJOR_COUNT, &count, sizeof (int)) ;
+
+
+
Return value:
+
0 +
+ + + +


SFC_GET_FORMAT_MAJOR

+

+Retrieve information about a major format type. +

+

+Parameters: +

+
+        sndfile  : Not used.
+        cmd      : SFC_GET_FORMAT_MAJOR
+        data     : a pointer to an  SF_FORMAT_INFO struct
+        datasize : sizeof (SF_FORMAT_INFO)
+
+

+Example: +

+
+        SF_FORMAT_INFO	format_info ;
+        int             k, count ;
+
+        sf_command (sndfile, SFC_GET_FORMAT_MAJOR_COUNT, &count, sizeof (int)) ;
+
+        for (k = 0 ; k < count ; k++)
+        {   format_info.format = k ;
+            sf_command (sndfile, SFC_GET_FORMAT_MAJOR, &format_info, sizeof (format_info)) ;
+            printf ("%08x  %s %s\n", format_info.format, format_info.name, format_info.extension) ;
+            } ;
+
+

+For a more comprehensive example, see the program list_formats.c in the examples/ +directory of the libsndfile source code distribution. +

+
+
Return value:
+
0 on success and non-zero otherwise. +
The value of the format field will one of the major format identifiers suc as SF_FORMAT_WAV + SF_FORMAT_AIFF. +
The name field will contain a char* pointer to the name of the string ie "WAV (Microsoft)". +
The extention field will contain the most commonly used file extension for that file type. +
+ + + +


SFC_GET_FORMAT_SUBTYPE_COUNT

+

+Retrieve the number of subformats. +

+

+Parameters: +

+
+        sndfile  : Not used.
+        cmd      : SFC_GET_FORMAT_SUBTYPE_COUNT
+        data     : a pointer to an int
+        datasize : sizeof (int)
+
+

+Example: +

+
+        int   count ;
+        sf_command (sndfile, SFC_GET_FORMAT_SUBTYPE_COUNT, &count, sizeof (int)) ;
+
+
+
Return value:
+
0 +
+ + + +


SFC_GET_FORMAT_SUBTYPE

+

+Retrieve information about a subformat. +

+

+Parameters: +

+
+        sndfile  : Not used.
+        cmd      : SFC_GET_FORMAT_SUBTYPE
+        data     : a pointer to an SF_FORMAT_INFO struct
+        datasize : sizeof (SF_FORMAT_INFO)
+
+

+Example: +

+
+        SF_FORMAT_INFO	format_info ;
+        int             k, count ;
+
+        sf_command (sndfile, SFC_GET_FORMAT_SUBTYPE_COUNT, &count, sizeof (int)) ;
+
+        /* Retrieve all the subtypes supported by the WAV format. */
+        for (k = 0 ; k < count ; k++)
+        {   format_info.format = k ;
+            sf_command (sndfile, SFC_GET_FORMAT_SUBTYPE, &format_info, sizeof (format_info)) ;
+            if (! sf_format_check (format.info | SF_FORMAT_WAV))
+               continue ;
+            printf ("%08x  %s\n", format_info.format, format_info.name) ;
+            } ;
+
+

+For a more comprehensive example, see the program list_formats.c in the examples/ +directory of the libsndfile source code distribution. +

+
+
Return value:
+
0 on success and non-zero otherwise. +
The value of the format field will one of the major format identifiers such as SF_FORMAT_WAV + SF_FORMAT_AIFF. +
The name field will contain a char* pointer to the name of the string; for instance + "WAV (Microsoft)" or "AIFF (Apple/SGI)". +
The extention field will be a NULL pointer. +
+ + + +


SFC_SET_ADD_PEAK_CHUNK

+

+By default, WAV and AIFF files which contain floating point data (subtype SF_FORMAT_FLOAT +or SF_FORMAT_DOUBLE) have a PEAK chunk. +By using this command, the addition of a PEAK chunk can be turned on or off. +

+

+Note : This call must be made before any data is written to the file. +

+

+Parameters: +

+        sndfile  : A valid SNDFILE* pointer
+        cmd      : SFC_SET_ADD_PEAK_CHUNK
+        data     : Not used (should be NULL)
+        datasize : TRUE or FALSE.
+
+

+Example: +

+
+        /* Turn on the PEAK chunk. */
+        sf_command (sndfile, SFC_SET_ADD_PEAK_CHUNK, NULL, SF_TRUE) ;
+
+        /* Turn off the PEAK chunk. */
+        sf_command (sndfile, SFC_SET_ADD_PEAK_CHUNK, NULL, SF_FALSE) ;
+
+
+
Return value:
+
Returns SF_TRUE if the peak chunk will be written after this call. +
Returns SF_FALSE if the peak chunk will not be written after this call. +
+ + + +


SFC_UPDATE_HEADER_NOW

+

+The header of an audio file is normally written by libsndfile when the file is +closed using sf_close(). +

+

+There are however situations where large files are being generated and it would +be nice to have valid data in the header before the file is complete. +Using this command will update the file header to reflect the amount of data written +to the file so far. +Other programs opening the file for read (before any more data is written) will +then read a valid sound file header. +

+

+Parameters: +

+        sndfile  : A valid SNDFILE* pointer
+        cmd      : SFC_UPDATE_HEADER_NOW
+        data     : Not used (should be NULL)
+        datasize : Not used.
+
+

+Example: +

+
+        /* Update the header now. */
+        sf_command (sndfile, SFC_UPDATE_HEADER_NOW, NULL, 0) ;
+
+
+
Return value:
+
0 +
+ + + +


SFC_SET_UPDATE_HEADER_AUTO

+

+Similar to SFC_UPDATE_HEADER_NOW but updates the header at the end of every call +to the sf_write* functions. +

+

+Parameters: +

+        sndfile  : A valid SNDFILE* pointer
+        cmd      : SFC_UPDATE_HEADER_NOW
+        data     : Not used (should be NULL)
+        datasize : SF_TRUE or SF_FALSE
+
+

+Example: +

+
+        /* Turn on auto header update. */
+        sf_command (sndfile, SFC_SET_UPDATE_HEADER_AUTO, NULL, SF_TRUE) ;
+
+        /* Turn off auto header update. */
+        sf_command (sndfile, SFC_SET_UPDATE_HEADER_AUTO, NULL, SF_FALSE) ;
+
+
+
Return value:
+
TRUE if auto update header is now on; FALSE otherwise. +
+ + + +


SFC_FILE_TRUNCATE

+

+Truncate a file open for write or for read/write. +

+

+Parameters: +

+        sndfile  : A valid SNDFILE* pointer
+        cmd      : SFC_FILE_TRUNCATE
+        data     : A pointer to an sf_count_t.
+        datasize : sizeof (sf_count_t)
+
+ +

+Truncate the file to the number of frames specified by the sf_count_t pointed +to by data. +After this command, both the read and the write pointer will be +at the new end of the file. +This command will fail (returning non-zero) if the requested truncate position +is beyond the end of the file. +

+

+Example: +

+
+        /* Truncate the file to a length of 20 frames. */
+        sf_count_t  frames = 20 ;
+        sf_command (sndfile, SFC_FILE_TRUNCATE, &frames, sizeof (frames)) ;
+
+
+
Return value:
+
Zero on sucess, non-zero otherwise. +
+ + + +


SFC_SET_RAW_START_OFFSET

+

+Change the data start offset for files opened up as SF_FORMAT_RAW. +

+

+Parameters: +

+        sndfile  : A valid SNDFILE* pointer
+        cmd      : SFC_SET_RAW_START_OFFSET
+        data     : A pointer to an sf_count_t.
+        datasize : sizeof (sf_count_t)
+
+ +

+For a file opened as format SF_FORMAT_RAW, set the data offset to the value +given by data. +

+

+Example: +

+
+        /* Reset the data offset to 5 bytes from the start of the file. */
+        sf_count_t  offset = 5 ;
+        sf_command (sndfile, SFC_SET_RAW_START_OFFSET, &offset, sizeof (offset)) ;
+
+
+
Return value:
+
Zero on sucess, non-zero otherwise. +
+ + + +
+

+ The libsndfile home page is here : + + http://www.mega-nerd.com/libsndfile/. +
+Version : 1.0.17 +

+ + + + + -- cgit v1.2.3