LIBSOX_NG(3)

NAME
libsox_ng - another audio file format and effect library

SYNOPSIS
#include <sox_ng.h>

cc -o file file.c -lsox_ng

DESCRIPTION
libsox_ng is a library of sound sample file format readers/writers and sound effects processors. It is mainly developed to be used by SoX but any audio application might find it useful.

If you want to dive straight in reading and writing audio files, look at the start of GENERIC FUNCTIONS and the section on READING AND WRITING AUDIO FILES.

#include <sox_ng.h>
    Declarations for all of the below (and a lot more!). However, you should only use items whose names begin with sox_ or SOX_; the lsx_ and LSX_ items are intended for internal use by SoX's format and effect handlers. They are exported by libsox so that dynamically-loaded format handlers and custom format and effect handlers can use them but should not be used by libSoX-based applications. Programs should normally include <sox.h> to be portable to systems that have not upgraded to sox_ng yet; those that have upgraded should provide <sox.h> as an alias for <sox_ng.h> and the interface is unlikely to change.

cc -o file file.c -lsox_ng
    Ensure that if a program includes <sox.h>, it is linked with -lsox, and <sox_ng.h> with -lsox_ng as some software distributions (or you) may choose to install them both side by side and the contents of their internal data structures differ.

BASIC TYPES

sox_int8_t | Signed twos-complement 8-bit type
sox_uint8_t | Unsigned 8-bit type
sox_int16_t | Signed twos-complement 16-bit type
sox_uint16_t | Unsigned 16-bit type
sox_int32_t | Signed twos-complement 32-bit type
sox_uint32_t | Unsigned 32-bit type
sox_int64_t | Signed twos-complement 64-bit type
sox_uint64_t | Unsigned 64-bit type
sox_int24_t | Alias for sox_int32_t (beware of the extra byte)
sox_uint24_t | Alias for sox_uint32_t (beware of the extra byte)
sox_sample_t | Native SoX audio sample type (alias for sox_int32_t)
sox_rate_t | Samples per second are stored as a double
sox_bool | Boolean type: sox_false (= 0) or sox_true (= 1)

ERROR HANDLING
Most of the functions in libSoX return an integer error code which is SOX_SUCCESS if the functions succeeded or a sox_error_t which can take the following values:
    SOX_SUCCESS | Function succeeded = 0
    SOX_EOF | End Of File or other error
    SOX_EHDR | Invalid Audio Header
    SOX_EFMT | Unsupported data format
    SOX_ENOMEM | Can't alloc memory
    SOX_EPERM | Operation not permitted
    SOX_ENOTSUP | Operation not supported
    SOX_EINVAL | Invalid argument
    SOX_ENOKEYMAP | No such keymap
    SOX_ENOEFFECT | No such effect
or other values mapped from errno(3).

char *sox_strerror(int sox_errno)
    Converts a SoX error code into an error string and returns the error string corresponding to the specified error code, or a generic message if the error code is not recognized.

GENERIC FUNCTIONS

int sox_init(void)
    Initialize the effects library. Returns SOX_SUCCESS if successful.

int sox_format_init(void)
    Find and load format handler plugins. Returns SOX_SUCCESS if successful.

void sox_format_quit(void)
    Unload format handler plugins.

int sox_quit(void)
    Close the effects library and unload format handler plugins. Returns SOX_SUCCESS if successful.

char *sox_version(void)
    Returns the version number string of libSoX, for example, "14.4.0".

sox_version_info_t *sox_version_info(void)
    Returns information about this build of libSoX, containing:

    size_t size
        Structure size = sizeof(sox_version_info_t)

    sox_version_flags_t flags
        Feature flags bits indicating whether optional features are present in this build of libSoX, the logical OR of:

        sox_version_none
            No special features (= 0).

        sox_version_have_popen
            Pipes are available to fetch URLs with wget or curl, to use external codec programs like ffmpeg and for piped inputs like "|sox_ng -n -p synth 1".

        sox_version_have_magic
            libmagic is in use to autodetect the formats of files.

        sox_version_have_threads
            OpenMP support is included, so effects and channels will run in parallel if sox_get_globals()->use_threads has not been set to sox_false.

        sox_version_have_memopen
            sox_open_mem_read(), sox_open_mem_write() and sox_open_memstream_write() do what it says on the box. If fmemopen(3) is not available, they fall back to sox_open_read() and sox_open_write().

    sox_uint32_t version_code
        Version number, for example 0x0E0402.

    char *version
        Version string, for example, "14.4.2".

    char *version_extra
        Version extra info or NULL, set by PACKAGE_EXTRA, for example, "beta".

    char *distro
        Distro or NULL, set by DISTRO, for example, "Debian".

    char *compiler
        Compiler info or NULL, for example, "msvc 160040219".

    char *arch
        Architecture-dependent feature code. For example, "1248 48 44 L OMP" where the first four digits give the sizes in bytes of char, short, long and off_t, the next two the sizes of float and double, the next two the sizes of a data pointer and a function pointer, followed by L if the machine is little-endian or B if big-endian, and OMP if multi-threading is available using OpenMP.

sox_globals_t *sox_get_globals(void)
    Returns a pointer to the structure with global settings for formats and effects, containing:

    char *myname
        The name the program was invoked as, for error reporting. sox_ng sets this to the bare program name without a directory path (or a .exe extension on Windows) as "sox_ng", "soxi_ng", "play_ng" or "rec_ng", or "sox", "soxi", "play" or "rec" when it replaces sox. Other programs using libsox_ng can set it to argv[0] on startup if they wish, but it is only used by libSoX when creating error messages for lsx_fail() when there are syntax errors in effects' options and leaving it NULL is harmless.

    unsigned verbosity
        Messages are output by the default output message handler if sox_get_globals()->verbosity >= level.

    sox_output_message_handler_t output_message_handler
        The address of a client-specified message output handling function of type void message_handler(unsigned level, char *filename, char *fmt, va_list ap)

        level
            1=FAIL, 2=WARN, 3=INFO, 4=DEBUG, 5=DEBUG_MORE, 6=DEBUG_MOST.

        filename
            Source code __FILENAME__ from which a message originates.

        fmt Message format string.

        ap  Message format parameters.

        For examples of how to use it, see src/example3.c and demo/soxcopy.c.

    sox_bool repeatable
        Use pre-determined timestamps and random number generator seed.

    size_t bufsiz
        Default size (in bytes) used by libSoX for blocks of sample data. Plugins should use similarly-sized buffers to get best performance.

    size_t input_bufsiz
        Default size (in bytes) used by libSoX for blocks of input sample data. Plugins should use similarly-sized buffers to get best performance.

    sox_int32_t ranqd1
        Can be used to re-seed libSoX's random number generator.

    size_t log2_dft_min_size
        Log to base 2 of the minimum size used by libSoX for DFT filtering. Plugins should use similarly-sized DFTs to get best performance.

    float A4
        The frequency in Hz of A above middle C, usually 440, that is used when converting note names to frequencies.

FILE FORMAT HANDLERS
Format handlers deal with decoding and encoding audio files and are accessed with the following types and functions:

sox_format_handler_t
    Handler structure defined by each format, containing:

    unsigned sox_lib_version_code
        Checked when loading format handler plugins.

    char *description
        A short description of the format.

    char **names
        Null-terminated array of filename extensions handled by this format.

    unsigned int flags
        File flags, the logical OR of:

        SOX_FILE_NOSTDIO | Does not use stdio routines
        SOX_FILE_DEVICE | File is an audio device
        SOX_FILE_PHONY | Phony file/device (for example /dev/null)
        SOX_FILE_REWIND | File should be rewound to write header
        SOX_FILE_BIT_REV | Is the file bit-reversed?
        SOX_FILE_NIB_REV | Is the file nibble-reversed?
        SOX_FILE_ENDIAN | Is the file format endian?
        SOX_FILE_ENDBIG | For an endian file format, is it big endian?
        SOX_FILE_MONO | Do channel restrictions allow mono?
        SOX_FILE_STEREO | Do channel restrictions allow stereo?
        SOX_FILE_QUAD | Do channel restrictions allow quad?
        SOX_FILE_LIT_END | A mask to OR in if the file is little-endian
        SOX_FILE_BIG_END | A mask to OR in if the file is big-endian
        SOX_FILE_CHANS | A mask to interrogate channels restrictions. If flags & SOX_FILE_CHANS is 0, there are no restrictions.

    int (*startread)(sox_format_t *ft)
        The function to initialize the decoder. If it is NULL, the format cannot be read.

    size_t (*read)(sox_format_t *ft, sox_sample_t *buf, size_t len)
        Decode a block of samples.

    int (*stopread)(sox_format_t *ft)
        Close reader (decoder); NULL if no closing necessary.

    int (*startwrite)(sox_format_t *ft)
        The function to initialize the encoder. If it is NULL, the format cannot be written.

    size_t (*write)(sox_format_t *ft, sox_sample_t *buf, size_t len);
        Encode a block of sample.

    int (*stopwrite)(sox_format_t *ft)
        Close writer (decoder); NULL if no closing necessary.

    int (*seek)(sox_format_t *ft, sox_uint64_t offset)
        Reposition reader; NULL if not supported.

    unsigned *write_formats
        An array of values indicating the encodings and precisions supported for writing. The data format is encoding, precision, precision, ..., 0, repeat, and end with 0. The default precision is given first. An example for a format supporting signed values at 16 and 24 bits, defaulting to 16 bits, and unsigned at 8 bits:
          unsigned *formats = {
            SOX_ENCODING_SIGN2, 16, 24, 0,
            SOX_ENCODING_UNSIGNED, 8, 0,
            0
          }

    sox_rate_t *write_rates
        A null-terminated array of sample rates supported for writing, NULL if all (or almost all) rates are supported.

    size_t priv_size
        SoX automatically allocates a buffer in which the handler can store data, of this size in bytes.

sox_format_t
    Data passed to and from format handlers, containing:

    char *filename
        The file's name.

    sox_signalinfo_t signal
        Signal specifications for the reader (decoder) or the writer (encoder): sample rate, number of channels, precision, length, headroom multiplier. Info will be SOX_UNSPEC if the user provided no info.

    sox_encodinginfo_t encoding
        Encoding specifications for the reader or writer.

    char *filetype
        The type of the file, as determined by inspection of the file's header or by libmagic.

    sox_oob_t oob
        Out-Of-Band data: comments (ID3 tags), instrument info, loop info.

    sox_bool seekable
        Can seek on this file.

    sox_bool last_byte_was_zero
        The last byte written was a zero.

    char mode
        Read or write mode ('r' or 'w').

    sox_uint64_t olength
        Samples *chans written to file.

    sox_uint64_t clips
        Incremented if clipping occurs.

    int sox_errno
        Failure error code.

    char sox_errstr[256]
        Failure error text.

    void *fp
        File stream pointer.

    sox_uint8_t *pending_buffer
        Buffer of unreturned read bytes.

    sox_uint8_t *pending_bytes
        Bytes read but not returned yet.

    size_t pending_count
        How many bytes read but not returned.

    lsx_io_type io_type
        Whether this stream is a file, a pipe or a URL, one of:

        lsx_io_file
            Stream is a real file.

        lsx_io_pipe
            Stream is a pipe.

        lsx_io_url
            Stream is a URL.

    sox_uint64_t tell_off
        Current offset within file.

    sox_uint64_t data_start
        Offset at which sound data begins.

    sox_format_handler_t handler
        The format handler for this file.

    void *priv
        The format handler's private data area.

sox_encodinginfo_t
    How samples are encoded, containing:

    sox_encoding_t encoding
        The encoding used for samples.

    unsigned bits_per_sample
        0 if unknown or variable; uncompressed value if lossless; compressed value if lossy.

    double compression
        Compression factor (where applicable).

    sox_option_t reverse_bytes
        Should bytes be reversed?

    sox_option_t reverse_nibbles
        Should nibbles be reversed?

    sox_option_t reverse_bits
        Should bits be reversed?

    sox_bool opposite_endian
        If set to true, the format should reverse its default endianness.

    If the reverse_ fields are sox_option_default during sox_open_read() or sox_open_write(), libSoX will set them to either sox_option_no or sox_option_yes according to the default of the machine or format.

sox_option_t
    The type of the sox_encodinginfo_t.reverse_* fields, one of:

    sox_option_no
        Option specified as no (= 0).

    sox_option_yes
        Option specified as yes.

    sox_option_default
        Option unspecified, usually implies some kind of auto-detect logic.

sox_format_tab_t *sox_get_format_fns(void)
    Returns a null-terminated table of information about the loaded format handlers, of which each entry contains:

    char *name
        The name of the format handler.

    sox_format_handler_t *(*fn)(void)
        The function to call to get a pointer to the format handler's data.

sox_format_handler_t *sox_find_format(char *name, sox_bool ignore_devices)
    Finds a format handler by name and returns it, or NULL if it is not found.

sox_bool sox_format_supports_encoding(char *path, char *filetype, sox_encodinginfo_t *encoding)

path
    Path to file to be examined (required if filetype is NULL).

filetype
    A previously-determined file type, or NULL to use the extension of path.

encoding
    Encoding for which the format handler should be queried.

Returns true if the format handler for the specified file type supports the specified encoding.

sox_format_handler_t sox_write_handler(char *path, char *filetype, char **filetype1)
    Gets the format handler for a specified file type. Returns the found format handler, or NULL if not found.

    path
        Path to file (required if filetype is NULL).

    filetype
        Filetype for which handler is needed, or NULL to use the extension from path.

    filetype1
        Receives the filetype that was detected. Pass NULL if not needed.

ENCODINGS

sox_encoding_t
    The format of encoded sample data, one of:

    SOX_ENCODING_UNKNOWN | Encoding has not yet been determined
    SOX_ENCODING_SIGN2 | Signed linear 2's compliment
    SOX_ENCODING_UNSIGNED | Unsigned linear: Sound Blaster
    SOX_ENCODING_FLOAT | Floating point (binary format)
    SOX_ENCODING_FLOAT_TEXT | Floating point (text format)
    SOX_ENCODING_FLAC | FLAC compression
    SOX_ENCODING_HCOM | Mac FSSD files with Huffman compression
    SOX_ENCODING_WAVPACK | WavPack with integer samples
    SOX_ENCODING_WAVPACKF | WavPack with float samples
    SOX_ENCODING_ULAW | Mu-law signed logs: US telephony
    SOX_ENCODING_ALAW | A-law signed logs: non-US telephony
    SOX_ENCODING_G721 | G.721 4-bit ADPCM
    SOX_ENCODING_G723 | G.723 3 or 5 bit ADPCM
    SOX_ENCODING_CL_ADPCM | Creative Labs 8->2,3,4 bit compressed PCM
    SOX_ENCODING_CL_ADPCM16 | Creative Labs 16->4 bit compressed PCM
    SOX_ENCODING_MS_ADPCM | Microsoft Compressed PCM
    SOX_ENCODING_IMA_ADPCM | IMA Compressed PCM
    SOX_ENCODING_OKI_ADPCM | Dialogic/OKI Compressed PCM
    SOX_ENCODING_DPCM | Differential PCM: Fasttracker 2 (xi format)
    SOX_ENCODING_DWVW | Delta Width Variable Word
    SOX_ENCODING_DWVWN | Delta Width Variable Word N-bit
    SOX_ENCODING_GSM | GSM 6.10 33byte frame lossy compression
    SOX_ENCODING_MP1 | MPEG 1 Layer 1 compression
    SOX_ENCODING_MP2 | MPEG 1 Layer 2 compression
    SOX_ENCODING_MP3 | MPEG 1 Layer 3 compression
    SOX_ENCODING_VORBIS | Vorbis compression
    SOX_ENCODING_AMR_WB | AMR-WB compression
    SOX_ENCODING_AMR_NB | AMR-NB compression
    SOX_ENCODING_CVSD | Continuously Variable Slope Delta
    SOX_ENCODING_LPC10 | Linear Predictive Coding
    SOX_ENCODING_OPUS | Opus compression
    SOX_ENCODING_DSD | Direct Stream Digital
    SOX_ENCODINGS | End of list marker

sox_encodings_info_t *sox_get_encodings_info(void)
    Returns a pointer to a null-terminated list of available encodings, containing:

    sox_encodings_flags_t flags
        How lossy the format is, one of:

        sox_encodings_none
            No flags specified (implies lossless encoding).

        sox_encodings_lossy1
            Encode, decode: lossy once.

        sox_encodings_lossy2
            Encode, decode, encode, decode: lossy twice.

    char *name
        Short name for the encoding.

    char *desc
        Description of the encoding.

void sox_init_encodinginfo(sox_encodinginfo_t *e)
    Fills in a sox_encodinginfo_t with default values.

unsigned sox_precision(sox_encoding_t encoding, unsigned bits)
    Given an encoding and the encoded bits_per_sample, returns the number of useful bits per sample in the decoded data, or 0 to indicate that the value returned by the format handler should be used instead of a pre-determined precision.

    encoding
        Encoding for which to lookup precision information.

    bits
        The number of encoded bits per sample.

READING AND WRITING AUDIO FILES

sox_format_t *sox_open_read(char *path, sox_signalinfo_t *signal, sox_encodinginfo_t *encoding, char *filetype)
    Opens a decoding session for a file.

    path
        Path to file to be opened (required).

    signal
        Information already known about audio stream, or NULL if none.

    encoding
        Information already known about sample encoding, or NULL if none.

    filetype
        Previously-determined file type, or NULL to auto-detect.

    Returns the handle for the new session, which must be closed with sox_close(), or NULL on failure.

sox_format_t *sox_open_mem_read(void *buffer, size_t size, sox_signalinfo_t *signal, sox_encodinginfo_t *encoding, char *filetype)
    Opens a decoding session for a memory buffer.

    buffer
        Pointer to audio data buffer (required).

    size
        Number of bytes to read from audio data buffer.

    signal
        Information already known about audio stream, or NULL if none.

    encoding
        Information already known about sample encoding, or NULL if none.

    filetype
        Previously-determined file type, or NULL to auto-detect.

    Returns a handle for the new session, which must be closed with sox_close(), or NULL on failure.

size_t sox_read(sox_format_t *ft, sox_sample_t *buf, size_t len)
    Reads samples from a decoding session into a sample buffer.

    buf Buffer from which to read samples.

    len Number of samples available in buf.

    Returns the number of samples decoded, or 0 on EOF or a read error. If it was the end of the file, errno will be zero, non-zero if there was a read error.

int sox_seek(sox_format_t *ft, sox_uint64_t offset, int whence)
    Sets the location at which the next samples will be decoded.

    offset
        Sample offset at which to position reader.

    whence
        Only SOX_SEEK_SET is currently supported.

    Returns SOX_SUCCESS if successful.

sox_format_t *sox_open_write(char *path, sox_signalinfo_t *signal, sox_encodinginfo_t *encoding, char *filetype, sox_oob_t *oob, sox_bool (*overwrite)(char *filename))
    Opens an encoding session for a file.

    path
        Path to file to be written (required).

    signal
        Information about desired audio stream (required).

    encoding
        Information about desired sample encoding, or NULL to use defaults.

    filetype
        Previously-determined file type, or NULL to auto-detect.

    oob Out-of-band data to add to file, or NULL if none.

    overwrite
        Called if file exists to determine whether overwrite is ok.

    Returns the new session handle, which must be closed with sox_close(), or NULL on failure.

sox_format_t *sox_open_mem_write(void *buffer, size_t size, sox_signalinfo_t *signal, sox_encodinginfo_t *encoding, char *filetype, sox_oob_t *oob)
    Opens an encoding session for a memory buffer.

    buffer
        A pointer to the audio data buffer that receives data (required).

    size
        The maximum number of bytes to write to audio data buffer.

    signal
        Information about the desired audio stream (required).

    encoding
        Information about the desired sample encoding, or NULL to use defaults.

    filetype
        The previously-determined file type, or NULL to auto-detect.

    oob Out-of-band data to add to file, or NULL if none.

    Returns the new session handle, which must be closed with sox_close(), or NULL on failure.

sox_format_t *sox_open_memstream_write(char **buffer_p, size_t *size_p, sox_signalinfo_t *signal, sox_encodinginfo_t *encoding, char *filetype, sox_oob_t *oob)
    Opens an encoding session for a memstream buffer.

    buffer_p
        Receives pointer to audio data buffer that receives data (required).

    size_p
        Receives size of data written to audio data buffer (required).

    signal
        Information about desired audio stream (required).

    encoding
        Information about desired sample encoding, or NULL to use defaults.

    filetype
        Previously-determined file type, or NULL to auto-detect.

    oob Out-of-band data to add to file, or NULL if none.

    Returns the new session handle, which must be closed with sox_close(), or NULL on failure.

size_t sox_write(sox_format_t *ft, sox_sample_t *buf, size_t len)
    Writes samples to an encoding session from a sample buffer.

    buf Buffer from which to read samples.

    len Number of samples available in buf.

    Returns the number of samples encoded, or zero if a write error occurred (for the reason, check errno(3).)

int sox_close(sox_format_t *ft)
    Closes an encoding or decoding session. Returns SOX_SUCCESS if successful.

EFFECTS AND EFFECTS CHAINS
The following types and functions are used to access libSoX's powerful effects.

sox_effect_t
    Effect information, containing:

    sox_effects_globals_t *global_info
        Global effects parameters, containing:

        sox_plot_t plot
            The type of plot requested, one of:

            sox_plot_off
                No plot.

            sox_plot_octave
                Octave plot.

            sox_plot_gnuplot
                Gnuplot plot.

            sox_plot_data
                Output the plot data as text.

        sox_globals_t *global_info
            A pointer to the associated sox_globals_t.

    sox_signalinfo_t in_signal
        Info about the incoming data stream.

    sox_signalinfo_t out_signal
        Info about the outgoing data stream.

    sox_encodinginfo_t *in_encoding
        Info about the incoming data encoding.

    sox_encodinginfo_t *out_encoding
        Info about the outgoing data encoding.

    sox_effect_handler_t handler
        The handler for this effect.

    sox_uint64_t clips
        Incremented when clipping occurs.

    size_t flows
        1 if handler.flags & SOX_EFF_MCHAN, or the number of channels otherwise.

    size_t flow
        Flow number.

    void *priv
        The effect's private data area (each flow has a separate copy).

sox_signalinfo_t
    Signal parameters, containing:

    sox_rate_t rate
        Samples per second, 0 if unknown.

    unsigned channels
        Number of sound channels, 0 if unknown.

    unsigned precision
        Bits per sample, 0 if unknown.

    sox_uint64_t length
        Samples in the file (sample frames × channels), SOX_UNSPEC (= 0) if the actual value is not yet known, SOX_UNKNOWN_LEN is used within the effects chain if the actual length is not known. Format handlers use SOX_UNSPEC instead. SOX_IGNORE_LENGTH to indicate that a format handler should ignore length information in file headers.

    double *mult
        Effects headroom multiplier; may be NULL.

    Members are SOX_UNSPEC (= 0) if the actual value is not yet known.

sox_effect_handler_t
    Effect handler information, containing:

    char *name
        The effect's name.

    char *usage
        One-line effect usage and parameters.

    char **extra_usage
        Additional lines of usage, null-terminated.

    unsigned int flags
        The logical OR of:

        SOX_EFF_CHAN
            The effect might alter the number of channels.

        SOX_EFF_RATE
            The effect might alter sample rate.

        SOX_EFF_PREC
            The effect does its own calculation of output sample precision (otherwise a default value is taken, depending on the presence of SOX_EFF_MODIFY).

        SOX_EFF_LENGTH
            The effect might alter audio length (as measured in time units, not necessarily in samples).

        SOX_EFF_MCHAN
            The effect handles multiple channels internally.

        SOX_EFF_NULL
            The effect does nothing and can be optimized out of the chain.

        SOX_EFF_GAIN
            The effect does not support gain -r.

        SOX_EFF_MODIFY
            The effect does not modify sample values (but it might remove or duplicate samples or insert zeros).

        SOX_EFF_INTERNAL
            The effect is present in libSoX but is not valid for use by SoX command-line tools.

    int (*getopts)(sox_effect_t *effp, int argc, char **argv)
        The effect's function to parse command-line arguments, called once per effect.

    int (*start)(sox_effect_t *effp)
        The function to initialize effect, called once per flow.

    int (*flow)(sox_effect_t *effp, sox_sample_t *ibuf, sox_sample_t *obuf, size_t *isamp, size_t *osamp)
        The function to process samples.

        ibuf
            Buffer from which to read samples

        obuf
            Buffer to which samples are written.

        isamp
            On entry, contains the capacity of ibuf in samples; on exit, contains the number of samples consumed.

        osamp
            On entry, contains the capacity of obuf in samples; on exit, contains the number of samples written.

    int (*drain)(sox_effect_t *effp, sox_sample_t *obuf, size_t *osamp)
        The function to output after input is complete. Parameters are as for flow.

    int (*stop)(sox_effect_t *effp)
        The function to shut the effect down (called once per flow).

    int (*kill)(sox_effect_t *effp)
        The function to shut the effect down (called once per effect).

    char *(*get)(sox_effect_t *effp, char *field)
        Pointer to a function to read the current value of an effect's parameter, returning NULL if there is no readable parameter of that name, or a pointer to mallocked memory containing a string value sprintfed with "%g" which it is the caller's responsibility to free.

    char *(*set)(sox_effect_t *effp, char *field, char *value)
        Pointer to a function to set the value of an effect's parameter, returning NULL if that parameter cannot be set or if the value is garbage, or a pointer to mallocked memory containing the new value sprintfed with "%g". Values outside the parameter's range set the minimum or maximum value and return that.

    size_t priv_size
        The size of the effect's private data.

sox_effects_chain_t
    A chain of effects to be applied to a stream, containing:

    sox_effect_t **effects
        Table of effects to be applied to a stream.

    size_t length
        Number of effects to be applied.

    sox_effects_globals_t global_info
        Copy of global effects settings.

    sox_encodinginfo_t *in_enc
        Input encoding.

    sox_encodinginfo_t *out_enc
        Output encoding.

sox_effects_globals_t *sox_get_effects_globals(void)
    Returns global parameters for effects.

sox_effect_handler_t *sox_find_effect(char *name)
    Finds the effect handler with the given name. Returns an effect pointer, or NULL if not found.

sox_effect_t *sox_create_effect(sox_effect_handler_t *eh)
    Creates an effect using the given handler. Returns the new effect, or NULL if not found.

int sox_effect_options(sox_effect_t *effp, int argc, char **argv)
    Applies the command-line options to the effect. Returns the number of arguments consumed.

sox_effect_handler_t *sox_get_effect_fns(void)
    Returns an null-terminated array of the known effect handlers.

sox_effects_chain_t *sox_create_effects_chain(sox_encodinginfo_t *in_enc, sox_encodinginfo_t *out_enc)
    Initializes an effects chain.

    in_enc
        Input encoding.

    out_enc
        Output encoding.
Returns a handle, which must be closed with sox_delete_effects_chain(). or NULL on failure.

void sox_delete_effects_chain(sox_effects_chain_t *chain)
    Closes an effects chain and deletes all the effects in it.

int sox_add_effect(sox_effects_chain_t *chain, sox_effect_t *effp, sox_signalinfo_t *in, sox_signalinfo_t *out)
    Adds an effect to the end of the effects chain. Returns SOX_SUCCESS if successful.

    in  Characteristics of the input signal to the chain.

    out Characteristics of the output signal from the chain.

int sox_flow_effects(sox_effects_chain_t *chain, int (*callback)(sox_bool all_done, void *data), void *data)
    Runs the effects chain. Returns SOX_SUCCESS if successful.

    chain
        Effects chain to run.

    callback
        If not NULL, a pointer to a function for monitoring flow progress, called between processing each block of data. It is handed a copy of the client_data pointer that was passed to sox_flow_effects and if the callback returns anything other than SOX_SUCCESS, the flow is stopped.

    data
        A pointer that is pass to the callback.

sox_uint64_t sox_effects_clips(sox_effects_chain_t *chain)
    Returns the number of clips that occurred while running an effects chain.

sox_uint64_t sox_stop_effect(sox_effect_t *effp)
    Shuts down an effect (calls stop on each of its flows) and returns the number of clips from all flows.

void sox_push_effect_last(sox_effects_chain_t *chain, sox_effect_t *effp)
    Adds an already-initialized effect to the end of the chain.

sox_effect_t *sox_pop_effect_last(sox_effects_chain_t *chain)
    Removes and returns an effect from the end of the chain. Returns the removed effect, or NULL if the chain has no effects.

void sox_delete_effect(sox_effect_t *effp)
    Shut down and delete an effect.

void sox_delete_effect_last(sox_effects_chain_t *chain)
    Shut down and delete the last effect in the chain.

void sox_delete_effects(sox_effects_chain_t *chain)
    Shut down and delete all effects in the chain.

EFFECT-SPECIFIC FUNCTIONS
For both of these, *effp should be a trim effect.

sox_uint64_t sox_trim_get_start(sox_effect_t *effp)
    Gets the sample offset of the start of the trim, useful for efficiently skipping the part that will be trimmed anyway (get trim start, seek, then clear trim start). Returns the sample offset of the start of the trim.

void sox_trim_clear_start(sox_effect_t *effp)
    Clears the start of the trim to 0.

OUT-OF-BAND DATA

sox_oob_t
    Out-Of-Band data: comments, instrument info and loop info, containing:

    sox_comments_t comments
        File's metadata as comment strings in id=value format, accessed via the sox_*_comments functions below.

    sox_instrinfo_t instr
        Instrument specification, containing:

        signed char MIDInote
            For unity pitch playback.

        signed char MIDIlow
            MIDI pitch-bend low range.

        signed char MIDIhi
            MIDI pitch-bend high range.

        unsigned char loopmode
            Loop modes: the lower 4 bits describe the loop behaviour, one of:

            sox_loop_none
                Single-shot.

            sox_loop_forward
                Forward loop.

            sox_loop_forward_back.
                Forward/back loop.

            and the upper 4 bits mask the loop blass, the logical OR of

            sox_loop_8
                8 loops (??).

            sox_loop_sustain_decay
                AIFF style, one sustain & one decay loop.

        unsigned nloops
            Number of active loops (max SOX_MAX_NLOOPS = 8).

    sox_loopinfo_t loops[SOX_MAX_NLOOPS];
        Looping specifications, containing:

        sox_uint64_t start
            First sample.

        sox_uint64_t length
            Length of loop.

        unsigned count
            Number of repeats, 0=forever.

        unsigned char type
            Bits with the same meaning as loopmode above.

COMMENTS

size_t sox_num_comments(sox_comments_t comments)
    Returns the number of items in the metadata block.

void sox_append_comment(sox_comments_t *comments, char *item)
    Adds an item to the metadata block, in "id=value" format.

void sox_append_comments(sox_comments_t *comments, char *items)
    Adds a newline-separated list of "id=value" items to the metadata block, for example "id1=value1\nid2=value2".

sox_comments_t sox_copy_comments(sox_comments_t comments)
    Duplicates the metadata block and returns the copy.

void sox_delete_comments(sox_comments_t *comments)
    Frees the metadata block.

char *sox_find_comment(sox_comments_t comments, char *id)
    If "id=value" is found in the comments, returns a pointer to its value, or NULL if the id was not found.

PLAYLIST FUNCTIONS

sox_bool sox_is_playlist(char *filename)
    Returns true if the specified file is a known playlist file type.

int sox_parse_playlist(int (*callback)(void *data, char *filename), void *data, char *listname)
    Parses the specified playlist file. Returns SOX_SUCCESS if successful.

    callback
        The function to call for each item in the playlist.

    data
        A pointer to client data, passed to the callback function.

    listname
        The name of the playlist file.

KEYMAPS
Keymaps are the mechanism by which SoX allows you to modify effects' internal parameters on the fly by mapping keys with --keymap and then pressing them while in --interactive mode (e.g. when using play or with -d as the output filename.)

void sox_keymap_add(char *key, char *effect, char *field, char op, double step)
    Add a keymap.

    key The string name of the key to map, for example "D".

    effect
        The name of the effect to affect. "echo" will affect all echoes in the effects chain; "echo2" will only affect the second instance of it.

    field
        The name of the parameter in the effect's priv_t to change. For effects with multiple stages, "decay" will affect the decay of all stages and "decay2" will only affect the decay of the scond stage.

    op 10
        How to affect the parameter: '+', '-', '*', '/' or '='.

    step 10
        How much to add or subtract from the parameter, to muliply or divide it by, or to set its value to.

extern sox_bool sox_is_keymapped(char *key)
    See if a key or an effect.field is used in a keymap

int sox_keymap_apply(sox_effects_chain_t *effp, char *key)
    Apply a keymap. Returns SOX_SUCCESS on successful application, SOX_ENOEFFECT if the effect was not found in the chain or it was found but doesn't have a keymappable parameter of that name, SOX_ENOKEYMAP if the key was not mapped to anything.

void sox_keymap_free(void)
    Forget all keymaps.

MISCELLANEOUS UTILITY FUNCTIONS

size_t sox_basename(char *buffer, size_t len, char *filename)
    Gets the basename of the specified file; for example, the basename of "/a/b/c.d" would be "c". Returns the number of characters written to the buffer, excluding the final nul character, or 0 on failure.

    buffer
        Buffer into which basename should be written.

    len Size of buffer, in bytes.

    filename
        Filename from which to extract basename.

GENERIC MACROS

SOX_LIB_VERSION(a, b, c)
    Compute a 32-bit integer API version from three 8-bit parts. a is the major version number, b the minor version and c the micro or bugfix version. Returns a 32-bit integer API version like 0x000a0b0c.

SOX_LIB_VERSION_CODE
    The current API version as a 32-bit integer which follows the version number of SoX.

SOX_INT_MIN(bits)
    Returns the smallest (most negative) value storable in a twos-complement signed integer with the specified number of bits, cast to an unsigned integer. For example, SOX_INT_MIN(8) = 0x80, SOX_INT_MIN(16) = 0x8000, etc.

    bits
        The size of value for which to calculate minimum and maximum values.

SOX_INT_MAX(bits)
    Returns the largest (positive) value storable in a twos-complement signed integer with the specified number of bits, cast to an unsigned integer for example, SOX_INT_MAX(8) = 0x7F, SOX_INT_MAX(16) = 0x7FFF, etc.

SOX_UINT_MAX(bits)
    Returns the largest value storable in an unsigned integer with the specified number of bits; for example, SOX_UINT_MAX(8) = 0xFF, SOX_UINT_MAX(16) = 0xFFFF, etc.

SOX_INT8_MAX
    Returns 0x7F.

SOX_INT16_MAX
    Returns 0x7FFF.

SOX_INT24_MAX
    Returns 0x7FFFFF.

SOX_INT32_MAX
    Returns 0x7FFFFFFF.

SOX_SAMPLE_PRECISION
    Bits in a sox_sample_t (= 32).

SOX_SAMPLE_MAX
    The maximum value of a sox_sample_t (= 0x7FFFFFFF).

SOX_SAMPLE_MIN
    The minimum (most negative) value of a sox_sample_t (= 0x80000000).

SOX_SAMPLE_NEG
    The sign bit for sox_sample_t (= 0x80000000).

SOX_SIZE_MAX
    The maximum value of a size_t.

SAMPLE CONVERSION
Linear PCM <--> sox_sample_t
I/O | Input | sox_sample_t | Clips | Input | sox_sample_t | Clips
Format | Minimum | Minimum | I | O | Maximum | Maximum | I | O
Float | -inf | -1 | y | n | inf | 1 - 5e-10 | y | n
Int8 | -128 | -128 | n | n | 127 | 127.9999999 | n | y
Int16 | -32768 | -32768 | n | n | 32767 | 32767.99998 | n | y
Int24 | -8388608 | -8388608 | n | n | 8388607 | 8388607.996 | n | y
Int32 | -2147483648 | -2147483648 | n | n | 2147483647 | 2147483647 | n | n

Conversions are as accurate as possible (with rounding).

Halves are rounded toward +infinity, all others to nearest integer.

Clips shows whether on not there is the possibility of a conversion clipping to the minimum or maximum value when inputting from or outputting to a given type.

Unsigned integers are converted to and from signed integers by flipping the uppermost bit then treating them as signed integers.

Before you use the following SoX sample conversion macros in a function, SOX_SAMPLE_LOCALS declares the temporary local variables they require. For example:
   sox_int16_t sox_sample_to_CD(sox_sample_t sample)
   {
     SOX_SAMPLE_LOCALS
     unsigned clips = 0;
     return SOX_SAMPLE_TO_SIGNED(16, sample, clips);
   }

The following macros return a SoX native sample value and parameters are:

    bits
        The width of the resulting sample (1 through 32).

    d   The value to be converted.

    clips
        A variable that is incremented if the result is too big.
These macros are largely agnostic to the numeric types of their arguments.

SOX_SIGNED_TO_SAMPLE(bits, d)
    Converts a signed integer of width bits to sox_sample_t.

SOX_UNSIGNED_TO_SAMPLE(bits, d)
    Converts an unsigned integer of width bits to sox_sample_t.

SOX_UNSIGNED_8BIT_TO_SAMPLE(sox_uint8_t d, clips)
    Converts an unsigned 8-bit integer to sox_sample_t. The clips parameter is not used.

SOX_SIGNED_8BIT_TO_SAMPLE(sox_int8_t d, clips)
    Converts a signed 8-bit integer to sox_sample_t. The clips parameter is not used.

SOX_UNSIGNED_16BIT_TO_SAMPLE(sox_uint16_t d, clips)
    Converts an unsigned 16-bit integer to sox_sample_t. The clips parameter is not used.

SOX_SIGNED_16BIT_TO_SAMPLE(sox_int16_t d, clips)
    Converts a signed 16-bit integer to sox_sample_t. The clips parameter is not used.

SOX_UNSIGNED_24BIT_TO_SAMPLE(sox_int24_t d, clips)
    Converts an unsigned 24-bit integer to sox_sample_t. The clips parameter is not used.

SOX_SIGNED_24BIT_TO_SAMPLE(sox_int24_t d, clips)
    Converts a signed 24-bit integer to sox_sample_t. The clips parameter is not used.

SOX_UNSIGNED_32BIT_TO_SAMPLE(sox_uint32_t d, clips)
    Converts an unsigned 32-bit integer to sox_sample_t. The clips parameter is not used.

SOX_SIGNED_32BIT_TO_SAMPLE(sox_int32_t d, clips)
    Converts a signed 32-bit integer to sox_sample_t. The clips parameter is not used.

SOX_FLOAT_32BIT_TO_SAMPLE(float d, clips)
    Converts a 32-bit float to sox_sample_t.

SOX_FLOAT_64BIT_TO_SAMPLE(double d, clips)
    Converts a 64-bit float to sox_sample_t.

SOX_SAMPLE_TO_UNSIGNED(bits, sox_sample_t samp, clips)
    Converts a SoX native sample to an unsigned integer of width bits.

SOX_SAMPLE_TO_SIGNED(bits, sox_sample_t samp, clips)
    Converts a SoX native sample to a signed integer of width bits.

SOX_SAMPLE_TO_UNSIGNED_8BIT(sox_sample_t samp, clips)
    Converts a SoX native sample to an unsigned 8-bit integer.

SOX_SAMPLE_TO_SIGNED_8BIT(sox_sample_t samp, clips)
    Converts a SoX native sample to an signed 8-bit integer.

SOX_SAMPLE_TO_UNSIGNED_16BIT(sox_sample_t samp, clips)
    Converts a SoX native sample to an unsigned 16-bit integer.

SOX_SAMPLE_TO_SIGNED_16BIT(sox_sample_t samp, clips)
    Converts a SoX native sample to a signed 16-bit integer.

SOX_SAMPLE_TO_UNSIGNED_24BIT(sox_sample_t samp, clips)
    Converts a SoX native sample to an unsigned 24-bit integer.

SOX_SAMPLE_TO_SIGNED_24BIT(sox_sample_t samp, clips)
    Converts a SoX native sample to a signed 24-bit integer.

SOX_SAMPLE_TO_UNSIGNED_32BIT(sox_sample_t samp, clips)
    Converts a SoX native sample to an unsigned 32-bit integer. The clips parameter is not used.

SOX_SAMPLE_TO_SIGNED_32BIT(sox_sample_t samp, clips)
    Converts a SoX native sample to a signed 32-bit integer. The clips parameter is not used.

SOX_SAMPLE_TO_FLOAT_32BIT(sox_sample_t samp, clips)
    Converts a SoX native sample to a 32-bit float.

SOX_SAMPLE_TO_FLOAT_64BIT(sox_sample_t samp, clips)
    Converts a SoX native sample to a 64-bit float. The clips parameter is not used.

SOX_SAMPLE_CLIP_COUNT(d, clips)
    Clips a value of a type that is larger then sox_sample_t (for example, sox_int64_t) to sox_sample_t's limits and increment a counter if clipping occurs. d is the value (an lvalue) to be clipped, updated as necessary.

SOX_ROUND_CLIP_COUNT(d, clips)
    Clips a value of a type that is larger then sox_sample_t (for example, sox_int64_t) to sox_sample_t's limits and increment a counter if clipping occurs. Returns the clipped value.

SOX_INTEGER_CLIP_COUNT(bits, d, clips)
    Clips a value to the limits of a signed integer of the specified width and increment a counter if clipping occurs. Returns the clipped value.

SOX_16BIT_CLIP_COUNT(d, clips)
    Clips a value to the limits of a 16-bit signed integer and increment a counter if clipping occurs. Returns the clipped value.

SOX_24BIT_CLIP_COUNT(d, clips)
    Clips a value to the limits of a 24-bit signed integer and increments a counter if clipping occurs. Returns the clipped value.

SOX_DEFAULT_CHANNELS
    The default channel count is 2 (stereo).

SOX_DEFAULT_RATE
    The default sample rate is 48000Hz.

SOX_DEFAULT_PRECISION
    The default precision is 16 bits per sample.

SOX_DEFAULT_ENCODING
    The default encoding is SOX_ENCODING_SIGN2 (linear 2's complement PCM).

LINKING
How you link against libsox_ng depends on how SoX was built on your system. For a static build, just link against the library. For a dynamic build, use libtool to link with the correct linker flags. See the libtool manual for details; basically, you use it like this:
   libtool --mode=link gcc -o prog /path/to/libsox_ng.la

COPYRIGHT
Copyright 1991-2015 Lance Norskog, Chris Bagwell and sundry contributors. This library is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License version 2 as published by the Free Software Foundation. This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

AUTHORS
The many authors and contributors are listed in the README file that is distributed with the source code.

SEE ALSO
sox_ng(1), libsoxeffect_ng(3), soxformat_ng(7), src/example*.c and demo/*.c in the SoX source distribution.