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layout: page title: 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 an integer identifier which is defined in sndfile.h. All of the valid command identifiers have names beginning 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:

Name	Description
SFC_GET_LIB_VERSION	Retrieve the version of the library as a string.
SFC_GET_LOG_INFO	Retrieve the internal per-file operation log.
SFC_GET_CURRENT_SF_INFO	Retrieve `SF_INFO` struct of opened file.
SFC_CALC_SIGNAL_MAX	Calculate the measured maximum signal value.
SFC_CALC_NORM_SIGNAL_MAX	Calculate the measured normalised maximum signal value.
SFC_CALC_MAX_ALL_CHANNELS	Calculate the peak value for each channel.
SFC_CALC_NORM_MAX_ALL_CHANNELS	Calculate the normalised peak for each channel.
SFC_GET_SIGNAL_MAX	Retrieve the peak value for the file.
SFC_GET_MAX_ALL_CHANNELS	Retrieve the peak value for each channel.
SFC_SET_NORM_FLOAT	Set float normalisation behaviour.
SFC_SET_NORM_DOUBLE	Set double normalisation behaviour.
SFC_GET_NORM_FLOAT	Get float normalisation behaviour.
SFC_GET_NORM_DOUBLE	Get double normalisation behaviour.
SFC_SET_SCALE_FLOAT_INT_READ	Control scale factor on read.
SFC_SET_SCALE_INT_FLOAT_WRITE	Control scale factor on write.
SFC_GET_SIMPLE_FORMAT_COUNT	Get simple formats count.
SFC_GET_SIMPLE_FORMAT	Get information about a simple format.
SFC_GET_FORMAT_INFO	Get information about a major or subtype format.
SFC_GET_FORMAT_MAJOR_COUNT	Get the number of major formats.
SFC_GET_FORMAT_MAJOR	Get information about a major format type.
SFC_GET_FORMAT_SUBTYPE_COUNT	Get the number of subformats.
SFC_GET_FORMAT_SUBTYPE	Get information about a subformat.
SFC_SET_ADD_PEAK_CHUNK	Control PEAK chunk write to WAV and AIFF.
SFC_UPDATE_HEADER_NOW	Update the file header in write mode on demand.
SFC_SET_UPDATE_HEADER_AUTO	Update the file header on each write.
SFC_FILE_TRUNCATE	Truncate a file open for write or for read/write.
SFC_SET_RAW_START_OFFSET	Change the data start offset for raw files.
SFC_SET_DITHER_ON_WRITE	Not implemented.
SFC_SET_DITHER_ON_READ	Not implemented.
SFC_GET_DITHER_INFO_COUNT	Not implemented.
SFC_GET_DITHER_INFO	Not implemented.
SFC_SET_CLIPPING	Control automatic clipping behaviour.
SFC_GET_CLIPPING	Get current clipping setting.
SFC_GET_EMBED_FILE_INFO	Get information about embedded audio files.
SFC_WAVEX_GET_AMBISONIC	Test a WAVEX file for Ambisonic format.
SFC_WAVEX_SET_AMBISONIC	Modify a WAVEX header for Ambisonic format.
SFC_SET_VBR_ENCODING_QUALITY	Set the Variable Bit Rate encoding quality.
SFC_SET_OGG_PAGE_LATENCY_MS	Set Ogg page latency for Opus file.
SFC_SET_COMPRESSION_LEVEL	Set the compression level.
SFC_RAW_DATA_NEEDS_ENDSWAP	Determine if raw data needs endswapping.
SFC_GET_BROADCAST_INFO	Get the Broadcast Chunk info.
SFC_SET_BROADCAST_INFO	Set the Broadcast Chunk info.
SFC_GET_CHANNEL_MAP_INFO	Get the channel map info.
SFC_SET_CHANNEL_MAP_INFO	Set the channel map info.
SFC_SET_CART_INFO	Set the Cart Chunk info.
SFC_GET_CART_INFO	Get the Cart Chunk info.
SFC_GET_LOOP_INFO	Get loop info.
SFC_GET_INSTRUMENT	Get instrument info.
SFC_SET_INSTRUMENT	Set instrument info.
SFC_GET_CUE_COUNT	Get the cue marker count.
SFC_GET_CUE	Get cue marker info.
SFC_SET_CUE	Set cue marker info.
SFC_RF64_AUTO_DOWNGRADE	Set auto downgrade from RF64 to WAV.
SFC_GET_ORIGINAL_SAMPLERATE	Get original samplerate metadata.
SFC_SET_ORIGINAL_SAMPLERATE	Set original samplerate metadata.
SFC_GET_BITRATE_MODE	Get bitrate mode.
SFC_SET_BITRATE_MODE	Set bitrate mode.

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 buffer

Examples

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 internal per-file operation log.

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 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_GET_CURRENT_SF_INFO

Retrieve SF_INFO struct of opened file.

SFC_GET_CURRENT_SF_INFO command copies SF_INFO struct of sndfile object to provided buffer.

Parameters

sndfile: A valid SNDFILE* pointer
cmd: SFC_GET_CURRENT_SF_INFO
data: A pointer to a valid SF_INFO* pointer
datasize: sizeof (SF_INFO)

Examples

SF_INFO  sfinfo ;
sf_command (sndfile, SFC_GET_CURRENT_SF_INFO, sfinfo, sizeof (SF_INFO)) ;

Return value

Zero on success, non-zero otherwise.

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)

Examples

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 normalised 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)

Examples

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 the peak value (ie a single number) for each channel. 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

Examples

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 the normalised peak for each channel. 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

Examples

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_GET_SIGNAL_MAX

Retrieve the peak value for the file as stored in the file header.

Parameters

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

Examples

double   max_peak ;
sf_command (sndfile, SFC_GET_SIGNAL_MAX, &max_peak, sizeof (max_peak)) ;

Return value

SF_TRUE if the file header contained the peak value. SF_FALSE otherwise.

SFC_GET_MAX_ALL_CHANNELS

Retrieve the peak value for the file as stored in the file header.

Parameters

sndfile: A valid SNDFILE* pointer
cmd: SFC_GET_SIGNAL_MAX
data: A pointer to an array of doubles
datasize: sizeof (double) * number_of_channels

Example

double   peaks [number_of_channels] ;
sf_command (sndfile, SFC_GET_MAX_ALL_CHANNELS, peaks, sizeof (peaks)) ;

Return value

SF_TRUE if the file header contains per channel peak values for the file, SF_FALSE 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.

Examples

sf_command (sndfile, SFC_SET_NORM_FLOAT, NULL, SF_TRUE) ;

sf_command (sndfile, SFC_SET_NORM_FLOAT, NULL, SF_FALSE) ;

Return value

Returns the previous float normalisation mode.

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.

Examples

sf_command (sndfile, SFC_SET_NORM_DOUBLE, NULL, SF_TRUE) ;

sf_command (sndfile, SFC_SET_NORM_DOUBLE, NULL, SF_FALSE) ;

Return value

Returns the previous double normalisation mode.

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

Examples

normalisation = sf_command (sndfile, SFC_GET_NORM_FLOAT, NULL, 0) ;

Return value

Returns TRUE if normalisation 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_SET_SCALE_FLOAT_INT_READ

Set/clear the scale factor when integer (short/int) data is read from a file containing floating point data.

Parameters

sndfile: A valid SNDFILE* pointer

cmd: SFC_SET_SCALE_FLOAT_INT_READ

data: NULL
datasize: TRUE or FALSE

Example:

sf_command (sndfile, SFC_SET_SCALE_FLOAT_INT_READ, NULL, SF_TRUE) ;

Return value

Returns the previous SFC_SET_SCALE_FLOAT_INT_READ setting for this file.

SFC_SET_SCALE_INT_FLOAT_WRITE

Set/clear the scale factor when integer (short/int) data is written to a file as floating point data.

Parameters

sndfile: A valid SNDFILE* pointer
cmd: SFC_SET_SCALE_INT_FLOAT_WRITE
data: NULL
datasize: TRUE or FALSE

Examples

sf_command (sndfile, SFC_SET_SCALE_INT_FLOAT_WRITE, NULL, SF_TRUE) ;

Return value

Returns the previous SFC_SET_SCALE_INT_FLOAT_WRITE setting for this file.

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)

Examples

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).

Examples

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 a 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, eg. "WAV (Microsoft 16 bit PCM)". The extension 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.

Examples

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)

Examples

int  count ;
sf_command (sndfile, SFC_GET_FORMAT_MAJOR_COUNT, &count, sizeof (int)) ;

Return value

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)

Examples

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 be one of the major format identifiers such as SF_FORMAT_WAV or SF_FORMAT_AIFF. The name field will contain a char* pointer to the name of the string, eg. "WAV (Microsoft)". The extension 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)

Examples

int   count ;
sf_command (sndfile, SFC_GET_FORMAT_SUBTYPE_COUNT, &count, sizeof (int)) ;

Return value

Returns zero.

SFC_GET_FORMAT_SUBTYPE

Enumerate the subtypes (this function does not translate a subtype into a string describing that subtype). A typical use case might be retrieving a string description of all subtypes so that a dialog box can be filled in.

Parameters

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

Examples

Example 1: Retrieve all sybtypes supported by the WAV format.

SF_FORMAT_INFO  format_info ;
int             k, count ;

sf_command (sndfile, SFC_GET_FORMAT_SUBTYPE_COUNT, &count, sizeof (int)) ;

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.format | SF_FORMAT_WAV))
        continue ;
    printf ("%08x  %s\n", format_info.format, format_info.name) ;
    } ;

Example 2: Print a string describing the SF_FORMAT_PCM_16 subtype.

SF_FORMAT_INFO  format_info ;
int             k, count ;

sf_command (sndfile, SFC_GET_FORMAT_SUBTYPE_COUNT, &count, sizeof (int)) ;

for (k = 0 ; k < count ; k++)
{   format_info.format = k ;
    sf_command (sndfile, SFC_GET_FORMAT_SUBTYPE, &format_info, sizeof (format_info)) ;
    if (format_info.format == SF_FORMAT_PCM_16)
    {   printf ("%08x  %s\n", format_info.format, format_info.name) ;
        break ;
        } ;
    } ;

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 be one of the major format identifiers such as SF_FORMAT_WAV or 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 extension 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.

Examples

/* 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.

Examples

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

Return value

Returns zero.

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_SET_UPDATE_HEADER_AUTO
data: Not used (should be NULL)
datasize: SF_TRUE or SF_FALSE

Examples

/* 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 that was opened for write or 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.

Examples

/* 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.

Examples

/* 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 success, non-zero otherwise.

SFC_SET_CLIPPING

Turn on/off automatic clipping when doing floating point to integer conversion.

Parameters

sndfile: A valid SNDFILE* pointer
cmd: SFC_SET_CLIPPING
data: NULL
datasize: SF_TRUE or SF_FALSE.

Turn on (datasize == SF_TRUE) or off (datasize == SF_FALSE) clipping.

Examples

sf_command (sndfile, SFC_SET_CLIPPING, NULL, SF_TRUE) ;

Return value

Clipping mode (SF_TRUE or SF_FALSE).

SFC_GET_CLIPPING

Turn on/off automatic clipping when doing floating point to integer conversion.

Parameters

sndfile: A valid SNDFILE* pointer
cmd: SFC_GET_CLIPPING
data: NULL
datasize: 0

Retrieve the current cliiping setting.

Examples

sf_command (sndfile, SFC_GET_CLIPPING, NULL, 0) ;

Return value

Clipping mode (SF_TRUE or SF_FALSE).

SFC_GET_EMBED_FILE_INFO

Get the file offset and file length of a file enbedded within another larger file.

Parameters

sndfile: A valid SNDFILE* pointer
cmd: SFC_GET_EMBED_FILE_INFO
data: a pointer to an SF_EMBED_FILE_INFO struct
datasize: sizeof (SF_EMBED_FILE_INFO)

The SF_EMBED_FILE_INFO struct is defined in sndfile.h as:

typedef struct
{   sf_count_t  offset ;
    sf_count_t  length ;
} SF_EMBED_FILE_INFO ;

Return value

0 on success and non-zero otherwise.

The value of the offset field of the SF_EMBED_FILE_INFO struct will be the offsets in bytes from the start of the outer file to the start of the audio file. The value of the offset field of the SF_EMBED_FILE_INFO struct will be the length in bytes of the embedded file.

SFC_WAVEX_GET_AMBISONIC

Test if the current file has the GUID of a WAVEX file for any of the Ambisonic formats.

Parameters

sndfile: A valid SNDFILE* pointer
cmd: SFC_WAVEX_GET_AMBISONIC
data: NULL
datasize: 0

The Ambisonic WAVEX formats are defined here: http://dream.cs.bath.ac.uk/researchdev/wave-ex/bformat.html.

Return value

SF_AMBISONIC_NONE(0x40) or SF_AMBISONIC_B_FORMAT(0x41) or zero if the file format does not support ambisonic formats.

SFC_WAVEX_SET_AMBISONIC

Set the GUID of a new WAVEX file to indicate an Ambisonics format.

Parameters

sndfile: A valid SNDFILE* pointer
cmd: SFC_WAVEX_SET_AMBISONIC
data: NULL
datasize: SF_AMBISONIC_NONE or SF_AMBISONIC_B_FORMAT

Turn on (SF_AMBISONIC_B_FORMAT(0x41)) or off (SF_AMBISONIC_NONE(0x40)) encoding. This command is currently only supported for files with SF_FORMAT_WAVEX format.

The Ambisonic WAVEX formats are defined here:

http://dream.cs.bath.ac.uk/researchdev/wave-ex/bformat.html.

Return value

Return the ambisonic value that has just been set or zero if the file format does not support ambisonic encoding.

SFC_SET_VBR_ENCODING_QUALITY

Set the Variable Bit Rate encoding quality. The encoding quality value should be between 0.0 (lowest quality) and 1.0 (highest quality). Currenly this command is only implemented for FLAC and Ogg/Vorbis files. It has no effect on un-compressed file formats.

Parameters

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

The command must be sent before any audio data is written to the file.

Return value

SF_TRUE if VBR encoding quality was set. SF_FALSE otherwise.

SFC_SET_OGG_PAGE_LATENCY_MS

Set page latency for Ogg Opus file in milliseconds. The value should be between 50.0 and 1600.0. This command is only implemented for Ogg Opus files.

Parameters

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

Return value

0 on success and non-zero otherwise.

SFC_SET_COMPRESSION_LEVEL

Set the compression level. The compression level should be between 0.0 (minimum compression level) and 1.0 (highest compression level). Currenly this command is only implemented for FLAC and Ogg/Vorbis files. It has no effect on uncompressed file formats.

Parameters

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

The command must be sent before any audio data is written to the file.

Return value

SF_TRUE if compression level was set. SF_FALSE otherwise.

SFC_RAW_DATA_NEEDS_ENDSWAP

Determine if raw data read using sf_read_raw() needs to be end swapped on the host CPU.

For instance, will return SF_TRUE on when reading WAV containing SF_FORMAT_PCM_16 data on a big endian machine and SF_FALSE on a little endian machine.

Parameters

sndfile: A valid SNDFILE* pointer
cmd: SFC_RAW_DATA_NEEDS_ENDSWAP
data: NULL
datasize: 0

Return value

SF_TRUE or SF_FALSE.

SFC_GET_BROADCAST_INFO

Retrieve the Broadcast Extension Chunk from WAV (and related) files.

Parameters

sndfile: A valid SNDFILE* pointer
cmd: SFC_GET_BROADCAST_INFO
data: a pointer to an SF_BROADCAST_INFO struct
datasize: sizeof (SF_BROADCAST_INFO)

The SF_BROADCAST_INFO struct is defined in sndfile.h as:

typedef struct
{   char            description [256] ;
    char            originator [32] ;
    char            originator_reference [32] ;
    char            origination_date [10] ;
    char            origination_time [8] ;
    unsigned int    time_reference_low ;
    unsigned int    time_reference_high ;
    short           version ;
    char            umid [64] ;
    char            reserved [190] ;
    unsigned int    coding_history_size ;
    char            coding_history [256] ;
} SF_BROADCAST_INFO ;

Return value

SF_TRUE if the file contained a Broadcast Extension chunk or SF_FALSE otherwise.

SFC_SET_BROADCAST_INFO

Set the Broadcast Extension Chunk for WAV (and related) files.

Parameters

sndfile: A valid SNDFILE* pointer
cmd: SFC_SET_BROADCAST_INFO
data: a pointer to an SF_BROADCAST_INFO struct
datasize: sizeof (SF_BROADCAST_INFO)

Return value

SF_TRUE if setting the Broadcast Extension chunk was successful and SF_FALSE otherwise.

SFC_GET_CHANNEL_MAP_INFO

Retrieve the channel map contained in an AIFF or CAF Channel Layout chunk.

Parameters

sndfile: A valid SNDFILE* pointer
cmd: SFC_GET_CHANNEL_MAP_INFO
data: a pointer to an array of int, the same size as the number of channels in the file
datasize: number of channels * sizeof (int)

Channel map positions are defined in an enum in sndfile.h:

Name	Value	Description
SF_CHANNEL_MAP_INVALID	0
SF_CHANNEL_MAP_MONO	1
SF_CHANNEL_MAP_LEFT	2	Apple calls this 'Left'
SF_CHANNEL_MAP_RIGHT	3	Apple calls this 'Right'
SF_CHANNEL_MAP_CENTER	4	Apple calls this 'Center'
SF_CHANNEL_MAP_FRONT_LEFT	5
SF_CHANNEL_MAP_FRONT_RIGHT	6
SF_CHANNEL_MAP_FRONT_CENTER	7
SF_CHANNEL_MAP_REAR_CENTER	8	Apple calls this 'Center Surround', Msft calls this 'Back Center'
SF_CHANNEL_MAP_REAR_LEFT	9	Apple calls this 'Left Surround', Msft calls this 'Back Left'
SF_CHANNEL_MAP_REAR_RIGHT	10	Apple calls this 'Right Surround', Msft calls this 'Back Right'
SF_CHANNEL_MAP_LFE	11	Apple calls this 'LFEScreen', Msft calls this 'Low Frequency'
SF_CHANNEL_MAP_FRONT_LEFT_OF_CENTER	12	Apple calls this 'Left Center'
SF_CHANNEL_MAP_FRONT_RIGHT_OF_CENTER	13	Apple calls this 'Right Center'
SF_CHANNEL_MAP_SIDE_LEFT	14	Apple calls this 'Left Surround Direct'
SF_CHANNEL_MAP_SIDE_RIGHT	15	Apple calls this 'Right Surround Direct'
SF_CHANNEL_MAP_TOP_CENTER	16	Apple calls this 'Top Center Surround'
SF_CHANNEL_MAP_TOP_FRONT_LEFT	17	Apple calls this 'Vertical Height Left'
SF_CHANNEL_MAP_TOP_FRONT_RIGHT	18	Apple calls this 'Vertical Height Right'
SF_CHANNEL_MAP_TOP_FRONT_CENTER	19	Apple calls this 'Vertical Height Center'
SF_CHANNEL_MAP_TOP_REAR_LEFT	20	Apple and MS call this 'Top Back Left'
SF_CHANNEL_MAP_TOP_REAR_RIGHT	21	Apple and MS call this 'Top Back Right'
SF_CHANNEL_MAP_TOP_REAR_CENTER	22	Apple and MS call this 'Top Back Center'
SF_CHANNEL_MAP_AMBISONIC_B_W	23
SF_CHANNEL_MAP_AMBISONIC_B_X	24
SF_CHANNEL_MAP_AMBISONIC_B_Y	25
SF_CHANNEL_MAP_AMBISONIC_B_Z	26
SF_CHANNEL_MAP_MAX	27

Return value

SF_TRUE if the file contained a Channel Layout chunk or SF_FALSE otherwise.

SFC_SET_CHANNEL_MAP_INFO

Set the channel map contained in an AIFF or CAF Channel Layout chunk.

Parameters

sndfile: A valid SNDFILE* pointer
cmd: SFC_SET_CHANNEL_MAP_INFO
data: a pointer to an array of int, the same size as the number of channels in the file
datasize: number of channels * sizeof (int)

Return value

SF_TRUE if setting the Channel Layout chunk was successful and SF_FALSE otherwise.

SFC_GET_CART_INFO

Retrieve the Cart Chunk from WAV (and related) files. Based on AES46 standard for CartChunk (see CartChunk.org for more information.

Parameters

sndfile: A valid SNDFILE* pointer
cmd: SFC_GET_CART_INFO
data: a pointer to an SF_CART_INFO struct
datasize: sizeof (SF_CART_INFO)

The SF_CART_INFO struct is defined in sndfile.h as:

#define SF_CART_INFO_VAR(p_tag_text_size) \
    struct
    {       char            version [4] ;
            char            title [64] ;
            char            artist [64] ;
            char            cut_id [64] ;
            char            client_id [64] ;
            char            category [64] ;
            char            classification [64] ;
            char            out_cue [64] ;
            char            start_date [10] ;
            char            start_time [8] ;
            char            end_date [10] ;
            char            end_time [8] ;
            char            producer_app_id [64] ;
            char            producer_app_version [64] ;
            char            user_def [64] ;
            long    level_reference ;
            SF_CART_TIMER   post_timers [8] ;
            char            reserved [276] ;
            char            url [1024] ;
            unsigned int    tag_text_size ;
            char            tag_text[p_tag_text_size] ;
    }

Return value

SF_TRUE if the file contained a Cart chunk or SF_FALSE otherwise.

SFC_SET_CART_INFO

Set the Cart Chunk for WAV (and related) files.

Parameters

sndfile: A valid SNDFILE* pointer
cmd: SFC_SET_CART_INFO
data: a pointer to an SF_CART_INFO struct
datasize: sizeof (SF_CART_INFO)

Return value

SF_TRUE if setting the Cart chunk was successful and SF_FALSE otherwise.

SFC_GET_LOOP_INFO

Retrieve loop information for file including time signature, length in beats and original MIDI base note

Parameters

sndfile: A valid SNDFILE* pointer
cmd: SFC_GET_LOOP_INFO
data: a pointer to an SF_LOOP_INFO struct
datasize: sizeof (SF_LOOP_INFO)

The SF_LOOP_INFO struct is defined in sndfile.h as:

typedef struct
{   short    time_sig_num ;   /* any positive integer    > 0  */
    short    time_sig_den ;   /* any positive power of 2 > 0  */
    int        loop_mode ;    /* see SF_LOOP enum             */

    int        num_beats ;    /* this is NOT the amount of quarter notes !!!*/
                              /* a full bar of 4/4 is 4 beats */
                              /* a full bar of 7/8 is 7 beats */

    float    bpm ;            /* suggestion, as it can be calculated using other fields:*/
                              /* file's lenght, file's sampleRate and our time_sig_den*/
                              /* -> bpms are always the amount of _quarter notes_ per minute */

    int    root_key ;         /* MIDI note, or -1 for None */
    int future [6] ;
} SF_LOOP_INFO ;

Examples

SF_LOOP_INFO loop;
sf_command (sndfile, SFC_GET_LOOP_INFO, &loop, sizeof (loop)) ;

Return value

SF_TRUE if the file header contains loop information for the file, SF_FALSE otherwise.

SFC_GET_INSTRUMENT

Retrieve instrument information from file including MIDI base note, keyboard mapping and looping informations(start/stop and mode).

Parameters

sndfile: A valid SNDFILE* pointer
cmd: SFC_GET_INSTRUMENT
data: a pointer to an SF_INSTRUMENT struct
datasize: sizeof (SF_INSTRUMENT)

The SF_INSTRUMENT struct is defined in sndfile.h as:

typedef struct
{   int gain ;
    char basenote, detune ;
    char velocity_lo, velocity_hi ;
    char key_lo, key_hi ;
    int loop_count ;

    struct
    {   int mode ;
        unsigned int start ;
        unsigned int end ;
        unsigned int count ;
    } loops [16] ; /* make variable in a sensible way */
} SF_INSTRUMENT ;

mode values are defined as:

Name	Value	Description
SF_LOOP_NONE	800
SF_LOOP_FORWARD	801
SF_LOOP_BACKWARD	802
SF_LOOP_ALTERNATING	803

Examples

SF_INSTRUMENT inst ;
sf_command (sndfile, SFC_GET_INSTRUMENT, &inst, sizeof (inst)) ;

Return value

SF_TRUE if the file header contains instrument information for the file, SF_FALSE otherwise.

SFC_SET_INSTRUMENT

Set the instrument information for the file.

Parameters

sndfile: A valid SNDFILE* pointer
cmd: SFC_SET_INSTRUMENT
data: a pointer to an SF_INSTRUMENT struct
datasize: sizeof (SF_INSTRUMENT)

Examples

SF_INSTRUMENT inst ;
sf_command (sndfile, SFC_SET_INSTRUMENT, &inst, sizeof (inst)) ;

Return value

SF_TRUE if the file header contains instrument information for the file, SF_FALSE otherwise.

SFC_GET_CUE_COUNT

Retrieve the number of cue markers available for retrieval using the SFC_GET_CUE command.

Parameters

sndfile: A valid SNDFILE* pointer
cmd: SFC_GET_CUE_COUNT
data: a pointer to a uint32_t
datasize: sizeof (uint32_t)

Examples

uint32_t cue_count ;
sf_command (sndfile, SFC_GET_CUE_COUNT, &cue_count, sizeof (cue_count)) ;

Return value

SF_TRUE if the file header contains cue marker information for the file, SF_FALSE otherwise.

SFC_GET_CUE

Retrieve cue marker information from file.

Parameters

sndfile: A valid SNDFILE* pointer
cmd: SFC_GET_CUE
data: a pointer to an SF_CUES struct
datasize: sizeof (SF_CUES)

The SF_CUES struct is defined in sndfile.h as:

typedef struct
{   int cue_count ;

    struct
    {   int32_t   indx ;
        uint32_t  position ;
        int32_t   fcc_chunk ;
        int32_t   chunk_start ;
        int32_t   block_start ;
        uint32_t  sample_offset ;
        char name [256] ;
    } cue_points [100] ;
} SF_CUES ;

There is also an SF_CUES_VAR #define that allows reading/writing more than 100 cue markers.

Examples

SF_CUES cues ;
sf_command (sndfile, SFC_GET_CUE, &cues, sizeof (cues)) ;

Return value

SF_TRUE if the file header contains cue marker information for the file, SF_FALSE otherwise.

SFC_SET_CUE

Set the cue marker information for the file.

Parameters

sndfile: A valid SNDFILE* pointer
cmd: SFC_SET_CUE
data: a pointer to an SF_CUES struct
datasize: sizeof (SF_CUES)

Examples

SF_CUES cues ;
sf_command (sndfile, SFC_SET_CUE, &cues, sizeof (cues)) ;

Return value

SF_TRUE if the file header contains cue marker information for the file, SF_FALSE otherwise.

SFC_RF64_AUTO_DOWNGRADE

Enable auto downgrade from RF64 to WAV.

The EBU recomendation is that when writing RF64 files and the resulting file is less than 4Gig in size, it should be downgraded to a WAV file (WAV files have a maximum size of 4Gig). libsndfile doesn't follow the EBU recommendations exactly, mainly because the test suite needs to be able test reading/writing RF64 files without having to generate files larger than 4 gigabytes.

Note: This command should be issued before the first bit of audio data has been written to the file. Calling this command after audio data has been written will return the current value of this setting, but will not allow it to be changed.

Parameters

sndfile: A valid SNDFILE* pointer
cmd: SFC_RF64_AUTO_DOWNGRADE
data: NULL
datasize: SF_TRUE or SF_FALSE

Examples

/* Enable auto downgrade on file close. */
sf_command (sndfile, SFC_RF64_AUTO_DOWNGRADE, NULL, SF_TRUE) ;

Return value

Returns SF_TRUE if SFC_RF64_AUTO_DOWNGRADE is set and SF_FALSE otherwise.

SFC_GET_ORIGINAL_SAMPLERATE

Get original samplerate metadata.

The Opus audio codec stores audio data independent of samplerate, but only supports encoding or decoding at 8000Hz, 12000Hz, 16000Hz, 24000Hz or 48000Hz. Opus includes a header field to record the original source input samplerate, and a samplerate converter may be used if needed.

This command gets the original samplerate header field. It does not enable any (non-existent) samplerate conversion, nor change the current decoder samplerate.

Parameters

sndfile: A valid SNDFILE* pointer
cmd: SFC_GET_ORIGINAL_SAMPLERATE
data: pointer to an integer
datasize: sizeof (int)

Examples

/* Get the original sample rate */
int original_samplerate ;
sf_command (sndfile, SFC_GET_ORIGINAL_SAMPLERATE, &original_samplerate, sizeof (original_samplerate)) ;

Return value

Returns SF_TRUE on success, SF_FALSE otherwise.

The passed integer is set to the value of the original samplerate.

SFC_SET_ORIGINAL_SAMPLERATE

Set original samplerate metadata.

When writing an Opus file this command sets the original samplerate header field to the provided value, which is then stored in the file. This has no effect on the current encoder samplerate.

When reading an Opus file this command overrides the original samplerate value as read from the file. libsndfile uses this value to choose what samplerate to decode at, rounding up to the nearest valid Opus samplerate. After a successful call, the file samplerate and frames count may have changed.

Note: This command should be issued before the first bit of audio data has been read from or written to the file.

Parameters

sndfile: A valid SNDFILE* pointer
cmd: SFC_SET_ORIGINAL_SAMPLERATE
data: pointer to an integer
datasize: sizeof (int)

Examples

/* Store the original sample rate as 44100 */
int original_samplerate 44100;
sf_command (sndfile, SFC_SET_ORIGINAL_SAMPLERATE, &original_samplerate, sizeof (input_samplerate)) ;

Return value

Returns SF_TRUE on success, SF_FALSE otherwise.

On write, can only succeed if no data has been written. On read, if successful, SFC_GET_CURRENT_SF_INFO should be called to determine the new frames count and samplerate

SFC_GET_BITRATE_MODE

Get bitrate mode.

The bitrate mode is one of:

Name	Value	Description
SF_BITRATE_MODE_CONSTANT	800	Constant bitrate.
SF_BITRATE_MODE_AVERAGE	801	Average bitrate.
SF_BITRATE_MODE_VARIABLE	802	Variable bitrate.

Parameters

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

Return value

Returns one of SF_BITRATE_MODE_XXX on success, -1 otherwise.

SFC_SET_BITRATE_MODE

Set bitrate mode.

The bitrate mode is one of:

Name	Value	Description
SF_BITRATE_MODE_CONSTANT	800	Constant bitrate.
SF_BITRATE_MODE_AVERAGE	801	Average bitrate.
SF_BITRATE_MODE_VARIABLE	802	Variable bitrate.

Parameters

sndfile: A valid SNDFILE* pointer
cmd: SFC_SET_BITRATE_MODE
data: pointer to an integer
datasize: sizeof (int)

Return value

Returns SF_TRUE on success, SF_FALSE otherwise.

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sf_command

SFC_GET_LIB_VERSION

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SFC_GET_LOG_INFO

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SFC_GET_CURRENT_SF_INFO

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SFC_CALC_SIGNAL_MAX

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SFC_CALC_NORM_SIGNAL_MAX

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SFC_CALC_MAX_ALL_CHANNELS

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SFC_CALC_NORM_MAX_ALL_CHANNELS

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SFC_GET_SIGNAL_MAX

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SFC_GET_MAX_ALL_CHANNELS

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SFC_SET_NORM_FLOAT

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SFC_SET_NORM_DOUBLE

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SFC_GET_NORM_FLOAT

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SFC_GET_NORM_DOUBLE

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SFC_SET_SCALE_FLOAT_INT_READ

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SFC_SET_SCALE_INT_FLOAT_WRITE

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SFC_GET_SIMPLE_FORMAT_COUNT

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SFC_GET_SIMPLE_FORMAT

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SFC_GET_FORMAT_INFO

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SFC_GET_FORMAT_MAJOR_COUNT

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SFC_GET_FORMAT_MAJOR

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