fileio.h File Reference

Audio file I/O and feature vector writing. More...

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <inttypes.h>
#include <sndfile.h>

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Functions
int	FIO_read_audio (const char *infile, float **indata, size_t *datalen, unsigned *samprate, unsigned donorm)
	Read a single-channel audio file into memory.
int	FIO_write_npy (const char *outfile, const float **outvecs, size_t nvecs, size_t veclen)
	Write a 2D float32 array in NumPy .npy v1.0 format.
int	FIO_write_safetensors (const char *outfile, const float **outvecs, size_t nvecs, size_t veclen)
	Write a 2D float32 array in safetensors format.
int	FIO_write_wav (const char *outfile, const float *data, size_t datalen, unsigned samprate)
	Write mono float audio to a WAV file.
int	FIO_write_htk_feats (const char *outfile, const float **outvecs, size_t nvecs, size_t veclen, unsigned vecsamprate)
	Write feature vectors in HTK binary format.

Detailed Description

Audio file I/O and feature vector writing.

This module provides:

• Reading audio files (WAV, FLAC, AIFF, etc.) via libsndfile.
• Writing audio files (WAV float) via libsndfile.
• Writing feature vectors in NumPy .npy format for Python interop.
• Writing feature vectors in safetensors format for ML pipelines.
• Writing feature vectors in HTK binary format (deprecated).

Definition in file fileio.h.

Function Documentation

FIO_read_audio()

int FIO_read_audio	(	const char *	infile,
		float **	indata,
		size_t *	datalen,
		unsigned *	samprate,
		unsigned	donorm
	)

Read a single-channel audio file into memory.

Parameters

infile	Path to the audio file.
indata	Output: pointer to the audio samples (caller must free).
datalen	Output: number of samples read.
samprate	Output: sampling rate of the file (Hz).
donorm	If 1, normalise samples to [-1.0, 1.0].

Returns

0 on success, -1 on error.

Note

Only single-channel (mono) files are supported. Use the 'sox' utility to split multi-channel files first.

Read a single-channel audio file into memory.

Supported formats include everything that libsndfile can open: WAV, FLAC, AIFF, OGG, and many more.

Parameters

infile	Path to the audio file.
indata	Output: pointer to allocated float array with samples. The caller is responsible for calling free() on this.
datalen	Output: total number of samples read.
samprate	Output: sample rate in Hz.
donorm	1 to normalise samples to [-1.0, 1.0]; 0 for raw values.

Returns

0 on success, -1 on error.

Definition at line 83 of file fileio.c.

FIO_write_htk_feats()

int FIO_write_htk_feats	(	const char *	outfile,
		const float **	outvecs,
		size_t	nvecs,
		size_t	veclen,
		unsigned	vecsamprate
	)

Write feature vectors in HTK binary format.

Deprecated:

Use FIO_write_npy() or FIO_write_safetensors() instead.

Parameters

outfile	Path to the output file.
outvecs	Array of nvecs pointers, each pointing to veclen floats.
nvecs	Number of feature vectors.
veclen	Number of floats per vector.
vecsamprate	Sampling rate of the feature vectors (Hz).

Returns

0 on success, -1 on error.

Write feature vectors in HTK binary format.

The HTK format is: [12-byte header][vector 1][vector 2]...[vector N]

Each vector is a sequence of big-endian 32-bit floats.

Parameters

outfile	Output file path.
outvecs	Array of nvecs pointers, each to veclen floats.
nvecs	Number of feature vectors.
veclen	Number of float elements per vector.
vecsamprate	Feature sampling rate in Hz.

Returns

0 on success, -1 on error.

Definition at line 323 of file fileio.c.

FIO_write_npy()

int FIO_write_npy	(	const char *	outfile,
		const float **	outvecs,
		size_t	nvecs,
		size_t	veclen
	)

Write a 2D float32 array in NumPy .npy v1.0 format.

Produces a file readable by numpy.load(). Data is stored as little-endian float32, row-major (C order).

Parameters

outfile	Path to the output .npy file.
outvecs	Array of nvecs pointers, each pointing to veclen floats.
nvecs	Number of feature vectors (rows).
veclen	Number of floats per vector (columns).

Returns

0 on success, -1 on error.

Definition at line 167 of file fileio.c.

FIO_write_safetensors()

int FIO_write_safetensors	(	const char *	outfile,
		const float **	outvecs,
		size_t	nvecs,
		size_t	veclen
	)

Write a 2D float32 array in safetensors format.

Produces a file readable by the safetensors Python library. The tensor is stored under the key "features" as little-endian float32.

Parameters

outfile	Path to the output .safetensors file.
outvecs	Array of nvecs pointers, each pointing to veclen floats.
nvecs	Number of feature vectors (rows).
veclen	Number of floats per vector (columns).

Returns

0 on success, -1 on error.

Definition at line 236 of file fileio.c.

FIO_write_wav()

int FIO_write_wav	(	const char *	outfile,
		const float *	data,
		size_t	datalen,
		unsigned	samprate
	)

Write mono float audio to a WAV file.

Uses IEEE float format (SF_FORMAT_FLOAT) for lossless DSP round-trips.

Parameters

outfile	Path to the output .wav file.
data	Audio samples.
datalen	Number of samples.
samprate	Sampling rate in Hz.

Returns

0 on success, -1 on error.

Definition at line 282 of file fileio.c.