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| author | Erik de Castro Lopo <erikd@mega-nerd.com> | 2007-05-14 19:55:24 +1000 |
|---|---|---|
| committer | Erik de Castro Lopo <erikd@mega-nerd.com> | 2007-05-14 19:55:24 +1000 |
| commit | cb979e10a703033864f8f42c94e9d1d335e5be40 (patch) | |
| tree | 6bb359e4b64f1719b7afcd887da975e1021405ec /doc/dither.html | |
First snapshot of the public project.
Diffstat (limited to 'doc/dither.html')
| -rw-r--r-- | doc/dither.html | 1024 |
1 files changed, 1024 insertions, 0 deletions
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 @@ +<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> +<HTML> + +<HEAD> + <TITLE> + libsndfile : the sf_command function. + </TITLE> + <META NAME="Author" CONTENT="Erik de Castro Lopo (erikd AT mega-nerd DOT com)"> + <!-- Another version at the bottom of the page. --> + <META NAME="Description" CONTENT="The libsndfile API."> + <META NAME="Keywords" CONTENT="WAV AIFF AU libsndfile sound audio dsp Linux"> + <LINK REL=StyleSheet HREF="libsndfile.css" TYPE="text/css" MEDIA="all"> +</HEAD> + +<BODY> + +<H1><B>sf_command</B></H1> +<PRE> + + int sf_command (SNDFILE *sndfile, int cmd, void *data, int datasize) ; +</PRE> +<P> + 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. +</P> +<P> + 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. +</P> +<P> + The available commands are as follows: +</P> + +<CENTER> +<TABLE BORDER="0" WIDTH="90%" CELLPADDING="4"> +<TR> + <TD><A HREF="#SFC_GET_LIB_VERSION">SFC_GET_LIB_VERSION</A></TD> + <TD>Retrieve the version of the library.</TD> +</TR> +<TR> + <TD><A HREF="#SFC_GET_LOG_INFO">SFC_GET_LOG_INFO</A></TD> + <TD>Retrieve the internal per-file operation log.</TD> +</TR> +<TR> + <TD><A HREF="#SFC_CALC_SIGNAL_MAX">SFC_CALC_SIGNAL_MAX</A></TD> + <TD>Retrieve the measured maximum signal value.</TD> +</TR> +<TR> + <TD><A HREF="#SFC_CALC_NORM_SIGNAL_MAX">SFC_CALC_NORM_SIGNAL_MAX</A></TD> + <TD>Retrieve the measured normalised maximum signal value.</TD> +</TR> +<TR> + <TD><A HREF="#SFC_CALC_MAX_ALL_CHANNELS">SFC_CALC_MAX_ALL_CHANNELS</A></TD> + <TD>Calculate peaks for all channels.</TD> +</TR> +<TR> + <TD><A HREF="#SFC_CALC_NORM_MAX_ALL_CHANNELS">SFC_CALC_NORM_MAX_ALL_CHANNELS</A></TD> + <TD>Calculate normalised peaks for all channels.</TD> +</TR> + +<TR> + <TD><A HREF="#SFC_SET_NORM_FLOAT">SFC_SET_NORM_FLOAT</A></TD> + <TD>Modify the normalisation behaviour of the floating point reading and writing functions.</TD> +</TR> +<TR> + <TD><A HREF="#SFC_SET_NORM_DOUBLE">SFC_SET_NORM_DOUBLE</A></TD> + <TD>Modify the normalisation behaviour of the double precision floating point reading and writing functions.</TD> +</TR> +<TR> + <TD><A HREF="#SFC_GET_NORM_FLOAT">SFC_GET_NORM_FLOAT</A></TD> + <TD>Retrieve the current normalisation behaviour of the floating point reading and writing functions.</TD> +</TR> +<TR> + <TD><A HREF="#SFC_GET_NORM_DOUBLE">SFC_GET_NORM_DOUBLE</A></TD> + <TD>Retrieve the current normalisation behaviour of the double precision floating point reading and writing functions.</TD> +</TR> +<TR> + <TD><A HREF="#SFC_GET_SIMPLE_FORMAT_COUNT">SFC_GET_SIMPLE_FORMAT_COUNT</A></TD> + <TD>Retrieve the number of simple formats supported by libsndfile.</TD> +</TR> +<TR> + <TD><A HREF="#SFC_GET_SIMPLE_FORMAT">SFC_GET_SIMPLE_FORMAT</A></TD> + <TD>Retrieve information about a simple format.</TD> +</TR> + +<TR> + <TD><A HREF="#SFC_GET_FORMAT_INFO">SFC_GET_FORMAT_INFO</A></TD> + <TD>Retrieve information about a major or subtype format.</TD> +</TR> + +<TR> + <TD><A HREF="#SFC_GET_FORMAT_MAJOR_COUNT">SFC_GET_FORMAT_MAJOR_COUNT</A></TD> + <TD>Retrieve the number of major formats.</TD> +</TR> +<TR> + <TD><A HREF="#SFC_GET_FORMAT_MAJOR">SFC_GET_FORMAT_MAJOR</A></TD> + <TD>Retrieve information about a major format type.</TD> +</TR> +<TR> + <TD><A HREF="#SFC_GET_FORMAT_SUBTYPE_COUNT">SFC_GET_FORMAT_SUBTYPE_COUNT</A></TD> + <TD>Retrieve the number of subformats.</TD> +</TR> +<TR> + <TD><A HREF="#SFC_GET_FORMAT_SUBTYPE">SFC_GET_FORMAT_SUBTYPE</A></TD> + <TD>Retrieve information about a subformat.</TD> +</TR> + +<TR> + <TD><A HREF="#SFC_SET_ADD_PEAK_CHUNK">SFC_SET_ADD_PEAK_CHUNK</A></TD> + <TD>Switch the code for adding the PEAK chunk to WAV and AIFF files on or off.</TD> +</TR> + +<TR> + <TD><A HREF="#SFC_UPDATE_HEADER_NOW">SFC_UPDATE_HEADER_NOW</A></TD> + <TD>Used when a file is open for write, this command will update the file + header to reflect the data written so far.</TD> +</TR> +<TR> + <TD><A HREF="#SFC_SET_UPDATE_HEADER_AUTO">SFC_SET_UPDATE_HEADER_AUTO</A></TD> + <TD>Used when a file is open for write, this command will cause the file header + to be updated after each write to the file.</TD> +</TR> + +<TR> + <TD><A HREF="#SFC_FILE_TRUNCATE">SFC_FILE_TRUNCATE</A></TD> + <TD>Truncate a file open for write or for read/write.</TD> +</TR> + +<TR> + <TD><A HREF="#SFC_SET_RAW_START_OFFSET">SFC_SET_RAW_START_OFFSET</A></TD> + <TD>Change the data start offset for files opened up as SF_FORMAT_RAW.</TD> +</TR> + + + +<!-- +<TR> + <TD><A HREF="#add-dither">add dither</A></TD> + <TD>Add dither to output on write.</TD> +</TR> +--> +</TABLE> +</CENTER> + +<BR><BR> + +<HR> + +<!-- ========================================================================= --> +<A NAME="SFC_GET_LIB_VERSION"></A> +<H2><BR><B>SFC_GET_LIB_VERSION</B></H2> +<P> +Retrieve the version of the library as a string. +</P> +<P> +Parameters: +<PRE> + sndfile : Not used + cmd : SFC_GET_LIB_VERSION + data : A pointer to a char buffer + datasize : The size of the the buffer +</PRE> +<P> +Example: +</P> +<PRE> + char buffer [128] ; + sf_command (NULL, SFC_GET_LIB_VERSION, buffer, sizeof (buffer)) ; +</PRE> + +<DL> +<DT>Return value:</DT> + <DD><DD>This call will return the length of the retrieved version string. +</DL> +<DL> +<DT>Notes:</DT> +<DD> +The string returned in the buffer passed to this function will not overflow +the buffer and will always be null terminated . +</DL> + +<!-- ========================================================================= --> +<A NAME="SFC_GET_LOG_INFO"></A> +<H2><BR><B>SFC_GET_LOG_INFO</B></H2> +<P> +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. +</P> +<P> +Parameters: +<PRE> + sndfile : A valid SNDFILE* pointer + cmd : SFC_GET_LOG_INFO + data : A pointer to a char buffer + datasize : The size of the the buffer +</PRE> +<P> +Example: +</P> +<PRE> + char buffer [2048] ; + sf_command (sndfile, SFC_GET_LOG_INFO, buffer, sizeof (buffer)) ; +</PRE> + +<DL> +<DT>Return value:</DT> + <DD><DD>This call will return the length of the retrieved version string. +</DL> +<DL> +<DT>Notes:</DT> +<DD> +The string returned in the buffer passed to this function will not overflow +the buffer and will always be null terminated . +</DL> + +<!-- ========================================================================= --> +<A NAME="SFC_CALC_SIGNAL_MAX"></A> +<H2><BR><B>SFC_CALC_SIGNAL_MAX</B></H2> +<P> +Retrieve the measured maximum signal value. This involves reading through +the whole file which can be slow on large files. +</P> +<P> +Parameters: +<PRE> + sndfile : A valid SNDFILE* pointer + cmd : SFC_CALC_SIGNAL_MAX + data : A pointer to a double + datasize : sizeof (double) +</PRE> +<P> +Example: +</P> +<PRE> + double max_val ; + sf_command (sndfile, SFC_CALC_SIGNAL_MAX, &max_val, sizeof (max_val)) ; +</PRE> + +<DL> +<DT>Return value:</DT> + <DD><DD>Zero on success, non-zero otherwise. +</DL> + +<!-- ========================================================================= --> +<A NAME="SFC_CALC_NORM_SIGNAL_MAX"></A> +<H2><BR><B>SFC_CALC_NORM_SIGNAL_MAX</B></H2> +<P> +Retrieve the measured normailised maximum signal value. This involves reading +through the whole file which can be slow on large files. +</P> +<P> +Parameters: +<PRE> + sndfile : A valid SNDFILE* pointer + cmd : SFC_CALC_NORM_SIGNAL_MAX + data : A pointer to a double + datasize : sizeof (double) +</PRE> +<P> +Example: +</P> +<PRE> + double max_val ; + sf_command (sndfile, SFC_CALC_NORM_SIGNAL_MAX, &max_val, sizeof (max_val)) ; +</PRE> + +<DL> +<DT>Return value:</DT> + <DD><DD>Zero on success, non-zero otherwise. +</DL> + +<!-- ========================================================================= --> +<A NAME="SFC_CALC_MAX_ALL_CHANNELS"></A> +<H2><BR><B>SFC_CALC_MAX_ALL_CHANNELS</B></H2> +<P> +Calculate peaks for all channels. This involves reading through +the whole file which can be slow on large files. +</P> +<P> +Parameters: +<PRE> + sndfile : A valid SNDFILE* pointer + cmd : SFC_CALC_MAX_ALL_CHANNELS + data : A pointer to a double + datasize : sizeof (double) * number_of_channels +</PRE> +<P> +Example: +</P> +<PRE> + double peaks [number_of_channels] ; + sf_command (sndfile, SFC_CALC_MAX_ALL_CHANNELS, peaks, sizeof (peaks)) ; +</PRE> +<DL> +<DT>Return value:</DT> + <DD>Zero if peaks have been calculated successfully and non-zero otherwise. +</DL> + + +<!-- ========================================================================= --> +<A NAME="SFC_CALC_NORM_MAX_ALL_CHANNELS"></A> +<H2><BR><B>SFC_CALC_NORM_MAX_ALL_CHANNELS</B></H2> +<P> +Calculate normalised peaks for all channels. This involves reading through +the whole file which can be slow on large files. +</P> +<P> +Parameters: +<PRE> + sndfile : A valid SNDFILE* pointer + cmd : SFC_CALC_NORM_MAX_ALL_CHANNELS + data : A pointer to a double + datasize : sizeof (double) * number_of_channels +</PRE> +<P> +Example: +</P> +<PRE> + double peaks [number_of_channels] ; + sf_command (sndfile, SFC_CALC_NORM_MAX_ALL_CHANNELS, peaks, sizeof (peaks)) ; +</PRE> +<DL> +<DT>Return value:</DT> + <DD>Zero if peaks have been calculated successfully and non-zero otherwise. +</DL> + + + + + +<!-- ========================================================================= --> +<!-- +<A NAME="read-text"></A> +<H2><BR><B>Read text</B></H2> +<P> +Many sound file formats contain allow the inclusion of a text string describing the nature +of the file. If a file contains such a string, this functions will return it to the caller. +</P> +<P> +It should be noted that the way the string is added to the file is file format dependant +but that any string added with <A HREF="#write-text">write text</A> will be returned by +<A HREF="#read-text">read text</A>. +</P> +<P> +<P> +Parameters: +</P> +<PRE> + sndfile : A valid SNDFILE* pointer + cmd : The text string "read text". + data : A pointer to a char buffer. + datasize : The size of the the buffer. +</PRE> +<P> +Example: +</P> +<PRE> + char buffer [128] ; + sf_command (sndfile, "read text", buffer, sizeof (buffer)) ; +</PRE> +<DL> +<DT>Return value:</DT> +<DD>If a text string is found, this call will return the length of the retrieved text + string. + <DD>If no text string is found, zero will be returned and the first element in the + buffer will be set to the null character. +<DT>Notes:</DT> +<DD>The string returned in the buffer passed to this function will not overflow + the buffer and will be correctly null terminated . +</DL> + +<A NAME="write-text"></A> +<H2><BR><B>Write text</B></H2> +<P> +Add a text string to a file. The text string added can be retrieved when the file is +read using <A HREF="#read-text">read text</A>. +</P> +<P> +Parameters: +</P> +<PRE> + sndfile : A valid SNDFILE* pointer + cmd : The text string "write text". + data : A pointer to the string to be added. + datasize : Not used. +</PRE> +<P> +Example: +</P> +<PRE> + char text = "The sound of one hand clapping." ; + sf_command (sndfile, "write text", text, strlen (text)) ; +</PRE> +<DL> +<DT>Return value: </DT> + <DD>If the current file format allows the addition of text strings, the string will + be added and the length of the string will be returned. + <DD>If the file format does not allow the addition of text strings zero will be returned. + <DD>If this function is called after the file is openned but before +</DL> +--> + + +<!-- ========================================================================= --> +<A NAME="SFC_SET_NORM_FLOAT"></A> +<H2><BR><B>SFC_SET_NORM_FLOAT</B></H2> +<P> +This command only affects data read from or written to using the floating point functions: +</P> +<PRE> + size_t <A HREF="api.html#read">sf_read_float</A> (SNDFILE *sndfile, float *ptr, size_t items) ; + size_t <A HREF="api.html#readf">sf_readf_float</A> (SNDFILE *sndfile, float *ptr, size_t frames) ; + + size_t <A HREF="api.html#write">sf_write_float</A> (SNDFILE *sndfile, float *ptr, size_t items) ; + size_t <A HREF="api.html#writef">sf_writef_float</A> (SNDFILE *sndfile, float *ptr, size_t frames) ; +</PRE> +<P> +Parameters: +</P> +<PRE> + sndfile : A valid SNDFILE* pointer + cmd : SFC_SET_NORM_FLOAT + data : NULL + datasize : SF_TRUE or SF_FALSE +</PRE> +<P> +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]. +</P> +<P> +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. +</P> +<P> +For both cases, setting normalisation to SF_FALSE means that no scaling will take place. +</P> +<P> +Example: +</P> +<PRE> + sf_command (sndfile, SFC_SET_NORM_FLOAT, NULL, SF_TRUE) ; + + sf_command (sndfile, SFC_SET_NORM_FLOAT, NULL, SF_FALSE) ; +</PRE> +<DL> +<DT>Return value: </DT> + <DD>Returns 1 on success or 0 for failure. +</DL> + +<!-- ========================================================================= --> +<A NAME="SFC_SET_NORM_DOUBLE"></A> +<H2><BR><B>SFC_SET_NORM_DOUBLE</B></H2> +<P> +This command only affects data read from or written to using the double precision +floating point functions: +</P> +<PRE> + size_t <A HREF="api.html#read">sf_read_double</A> (SNDFILE *sndfile, double *ptr, size_t items) ; + size_t <A HREF="api.html#readf">sf_readf_double</A> (SNDFILE *sndfile, double *ptr, size_t frames) ; + + size_t <A HREF="api.html#write">sf_write_double</A> (SNDFILE *sndfile, double *ptr, size_t items) ; + size_t <A HREF="api.html#writef">sf_writef_double</A> (SNDFILE *sndfile, double *ptr, size_t frames) ; +</PRE> +<P> +Parameters: +</P> +<PRE> + sndfile : A valid SNDFILE* pointer + cmd : SFC_SET_NORM_DOUBLE + data : NULL + datasize : SF_TRUE or SF_FALSE +</PRE> +<P> +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]. +</P> +<P> +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. +</P> +<P> +For both cases, setting normalisation to SF_FALSE means that no scaling will take place. +</P> +<P> +Example: +</P> +<PRE> + sf_command (sndfile, SFC_SET_NORM_DOUBLE, NULL, SF_TRUE) ; + + sf_command (sndfile, SFC_SET_NORM_DOUBLE, NULL, SF_FALSE) ; +</PRE> +<DL> +<DT>Return value: </DT> + <DD>Returns 1 on success or 0 for failure. +</DL> + +<!-- ========================================================================= --> +<A NAME="SFC_GET_NORM_FLOAT"></A> +<H2><BR><B>SFC_GET_NORM_FLOAT</B></H2> +<P> +Retrieve the current float normalisation mode. +</P> +<P> +Parameters: +</P> +<PRE> + sndfile : A valid SNDFILE* pointer + cmd : SFC_GET_NORM_FLOAT + data : NULL + datasize : anything +</PRE> +<P> +Example: +</P> +<PRE> + normalisation = sf_command (sndfile, SFC_GET_NORM_FLOAT, NULL, 0) ; +</PRE> +<DL> +<DT>Return value: </DT> + <DD>Returns TRUE if normaisation is on and FALSE otherwise. +</DL> + +<!-- ========================================================================= --> +<A NAME="SFC_GET_NORM_DOUBLE"></A> +<H2><BR><B>SFC_GET_NORM_DOUBLE</B></H2> +<P> +Retrieve the current float normalisation mode. +</P> +<P> +Parameters: +</P> +<PRE> + sndfile : A valid SNDFILE* pointer + cmd : SFC_GET_NORM_DOUBLE + data : NULL + datasize : anything +</PRE> +<P> +Example: +</P> +<PRE> + normalisation = sf_command (sndfile, SFC_GET_NORM_DOUBLE, NULL, 0) ; +</PRE> +<DL> +<DT>Return value: </DT> + <DD>Returns TRUE if normalisation is on and FALSE otherwise. +</DL> + +<!-- ========================================================================= --> +<A NAME="SFC_GET_SIMPLE_FORMAT_COUNT"></A> +<H2><BR><B>SFC_GET_SIMPLE_FORMAT_COUNT</B></H2> +<P> +Retrieve the number of simple formats supported by libsndfile. +</P> +<P> +Parameters: +</P> +<PRE> + sndfile : Not used. + cmd : SFC_GET_SIMPLE_FORMAT_COUNT + data : a pointer to an int + datasize : sizeof (int) +</PRE> +<P> +Example: +</P> +<PRE> + int count ; + sf_command (sndfile, SFC_GET_SIMPLE_FORMAT_COUNT, &count, sizeof (int)) ; +</PRE> +<DL> +<DT>Return value: </DT> + <DD>0 +</DL> + +<!-- ========================================================================= --> +<A NAME="SFC_GET_SIMPLE_FORMAT"></A> +<H2><BR><B>SFC_GET_SIMPLE_FORMAT</B></H2> +<P> +Retrieve information about a simple format. +</P> +<P> +Parameters: +</P> +<PRE> + sndfile : Not used. + cmd : SFC_GET_SIMPLE_FORMAT + data : a pointer to an SF_FORMAT_INFO struct + datasize : sizeof (SF_FORMAT_INFO) +</PRE> +<P> +The SF_FORMAT_INFO struct is defined in <sndfile.h> as: +</P> +<PRE> + typedef struct + { int format ; + const char *name ; + const char *extension ; + } SF_FORMAT_INFO ; +</PRE> +<P> +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). +</P> +<P> +Example: +</P> +<PRE> + 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) ; + } ; +</PRE> +<DL> +<DT>Return value: </DT> + <DD>0 on success and non-zero otherwise. + <DD>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. + <DD>The name field will contain a char* pointer to the name of the string ie "WAV (Microsoft 16 bit PCM)". + <DD>The extention field will contain the most commonly used file extension for that file type. +</DL> + +<!-- ========================================================================= --> +<A NAME="SFC_GET_FORMAT_INFO"></A> +<H2><BR><B>SFC_GET_FORMAT_INFO</B></H2> +<P> +Retrieve information about a major or subtype format. +</P> +<P> +Parameters: +</P> +<PRE> + sndfile : Not used. + cmd : SFC_GET_FORMAT_INFO + data : a pointer to an SF_FORMAT_INFO struct + datasize : sizeof (SF_FORMAT_INFO) +</PRE> +<P> +The SF_FORMAT_INFO struct is defined in <sndfile.h> as: +</P> +<PRE> + typedef struct + { int format ; + const char *name ; + const char *extension ; + } SF_FORMAT_INFO ; +</PRE> +<P> +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. +</P> +<P> +Example: +</P> +<PRE> + 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) ; +</PRE> +<DL> +<DT>Return value: </DT> + <DD>0 on success and non-zero otherwise. +</DL> +<!-- ========================================================================= --> +<A NAME="SFC_GET_FORMAT_MAJOR_COUNT"></A> +<H2><BR><B>SFC_GET_FORMAT_MAJOR_COUNT</B></H2> +<P> +Retrieve the number of major formats. +</P> +<P> +Parameters: +</P> +<PRE> + sndfile : Not used. + cmd : SFC_GET_FORMAT_MAJOR_COUNT + data : a pointer to an int + datasize : sizeof (int) +</PRE> +<P> +Example: +</P> +<PRE> + int count ; + sf_command (sndfile, SFC_GET_FORMAT_MAJOR_COUNT, &count, sizeof (int)) ; +</PRE> +<DL> +<DT>Return value: </DT> + <DD>0 +</DL> + +<!-- ========================================================================= --> +<A NAME="SFC_GET_FORMAT_MAJOR"></A> +<H2><BR><B>SFC_GET_FORMAT_MAJOR</B></H2> +<P> +Retrieve information about a major format type. +</P> +<P> +Parameters: +</P> +<PRE> + sndfile : Not used. + cmd : SFC_GET_FORMAT_MAJOR + data : a pointer to an SF_FORMAT_INFO struct + datasize : sizeof (SF_FORMAT_INFO) +</PRE> +<P> +Example: +</P> +<PRE> + 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) ; + } ; +</PRE> +<P> +For a more comprehensive example, see the program list_formats.c in the examples/ +directory of the libsndfile source code distribution. +</P> +<DL> +<DT>Return value: </DT> + <DD>0 on success and non-zero otherwise. + <DD>The value of the format field will one of the major format identifiers suc as SF_FORMAT_WAV + SF_FORMAT_AIFF. + <DD>The name field will contain a char* pointer to the name of the string ie "WAV (Microsoft)". + <DD>The extention field will contain the most commonly used file extension for that file type. +</DL> + +<!-- ========================================================================= --> +<A NAME="SFC_GET_FORMAT_SUBTYPE_COUNT"></A> +<H2><BR><B>SFC_GET_FORMAT_SUBTYPE_COUNT</B></H2> +<P> +Retrieve the number of subformats. +</P> +<P> +Parameters: +</P> +<PRE> + sndfile : Not used. + cmd : SFC_GET_FORMAT_SUBTYPE_COUNT + data : a pointer to an int + datasize : sizeof (int) +</PRE> +<P> +Example: +</P> +<PRE> + int count ; + sf_command (sndfile, SFC_GET_FORMAT_SUBTYPE_COUNT, &count, sizeof (int)) ; +</PRE> +<DL> +<DT>Return value: </DT> + <DD>0 +</DL> + +<!-- ========================================================================= --> +<A NAME="SFC_GET_FORMAT_SUBTYPE"></A> +<H2><BR><B>SFC_GET_FORMAT_SUBTYPE</B></H2> +<P> +Retrieve information about a subformat. +</P> +<P> +Parameters: +</P> +<PRE> + sndfile : Not used. + cmd : SFC_GET_FORMAT_SUBTYPE + data : a pointer to an SF_FORMAT_INFO struct + datasize : sizeof (SF_FORMAT_INFO) +</PRE> +<P> +Example: +</P> +<PRE> + 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) ; + } ; +</PRE> +<P> +For a more comprehensive example, see the program list_formats.c in the examples/ +directory of the libsndfile source code distribution. +</P> +<DL> +<DT>Return value: </DT> + <DD>0 on success and non-zero otherwise. + <DD>The value of the format field will one of the major format identifiers such as SF_FORMAT_WAV + SF_FORMAT_AIFF. + <DD>The name field will contain a char* pointer to the name of the string; for instance + "WAV (Microsoft)" or "AIFF (Apple/SGI)". + <DD>The extention field will be a NULL pointer. +</DL> + +<!-- ========================================================================= --> +<A NAME="SFC_SET_ADD_PEAK_CHUNK"></A> +<H2><BR><B>SFC_SET_ADD_PEAK_CHUNK</B></H2> +<P> +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. +</P> +<P> +Note : This call must be made before any data is written to the file. +</P> +<P> +Parameters: +<PRE> + sndfile : A valid SNDFILE* pointer + cmd : SFC_SET_ADD_PEAK_CHUNK + data : Not used (should be NULL) + datasize : TRUE or FALSE. +</PRE> +<P> +Example: +</P> +<PRE> + /* 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) ; +</PRE> +<DL> +<DT>Return value:</DT> +<DD>Returns SF_TRUE if the peak chunk will be written after this call. +<DD>Returns SF_FALSE if the peak chunk will not be written after this call. +</DL> + +<!-- ========================================================================= --> +<A NAME="SFC_UPDATE_HEADER_NOW"></A> +<H2><BR><B>SFC_UPDATE_HEADER_NOW</B></H2> +<P> +The header of an audio file is normally written by libsndfile when the file is +closed using <B>sf_close()</B>. +</P> +<P> +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. +</P> +<P> +Parameters: +<PRE> + sndfile : A valid SNDFILE* pointer + cmd : SFC_UPDATE_HEADER_NOW + data : Not used (should be NULL) + datasize : Not used. +</PRE> +<P> +Example: +</P> +<PRE> + /* Update the header now. */ + sf_command (sndfile, SFC_UPDATE_HEADER_NOW, NULL, 0) ; +</PRE> +<DL> +<DT>Return value:</DT> +<DD>0 +</DL> + +<!-- ========================================================================= --> +<A NAME="SFC_SET_UPDATE_HEADER_AUTO"></A> +<H2><BR><B>SFC_SET_UPDATE_HEADER_AUTO</B></H2> +<P> +Similar to SFC_UPDATE_HEADER_NOW but updates the header at the end of every call +to the <B>sf_write*</B> functions. +</P> +<P> +Parameters: +<PRE> + sndfile : A valid SNDFILE* pointer + cmd : SFC_UPDATE_HEADER_NOW + data : Not used (should be NULL) + datasize : SF_TRUE or SF_FALSE +</PRE> +<P> +Example: +</P> +<PRE> + /* 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) ; +</PRE> +<DL> +<DT>Return value:</DT> +<DD>TRUE if auto update header is now on; FALSE otherwise. +</DL> + +<!-- ========================================================================= --> +<A NAME="SFC_FILE_TRUNCATE"></A> +<H2><BR><B>SFC_FILE_TRUNCATE</B></H2> +<P> +Truncate a file open for write or for read/write. +</P> +<P> +Parameters: +<PRE> + sndfile : A valid SNDFILE* pointer + cmd : SFC_FILE_TRUNCATE + data : A pointer to an sf_count_t. + datasize : sizeof (sf_count_t) +</PRE> + +<P> +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. +</P> +<P> +Example: +</P> +<PRE> + /* Truncate the file to a length of 20 frames. */ + sf_count_t frames = 20 ; + sf_command (sndfile, SFC_FILE_TRUNCATE, &frames, sizeof (frames)) ; +</PRE> +<DL> +<DT>Return value:</DT> + <DD>Zero on sucess, non-zero otherwise. +</DL> + +<!-- ========================================================================= --> +<A NAME="SFC_SET_RAW_START_OFFSET"></A> +<H2><BR><B>SFC_SET_RAW_START_OFFSET</B></H2> +<P> +Change the data start offset for files opened up as SF_FORMAT_RAW. +</P> +<P> +Parameters: +<PRE> + sndfile : A valid SNDFILE* pointer + cmd : SFC_SET_RAW_START_OFFSET + data : A pointer to an sf_count_t. + datasize : sizeof (sf_count_t) +</PRE> + +<P> +For a file opened as format SF_FORMAT_RAW, set the data offset to the value +given by data. +</P> +<P> +Example: +</P> +<PRE> + /* 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)) ; +</PRE> +<DL> +<DT>Return value:</DT> + <DD>Zero on sucess, non-zero otherwise. +</DL> + +<!-- ========================================================================= --> + +<HR> +<P> + The libsndfile home page is here : + <A HREF="http://www.mega-nerd.com/libsndfile/"> + http://www.mega-nerd.com/libsndfile/</A>. +<BR> +Version : 1.0.17 +</P> + +</BODY> +</HTML> + +<!-- + Do not edit or modify anything in this comment block. + The arch-tag line is a file identity tag for the GNU Arch + revision control system. + + arch-tag: e610e74b-9ac0-4255-aff8-97ed229a6a3d +--> |