sfprocess.c

/*
** Copyright (C) 2001-2013 Erik de Castro Lopo <erikd@mega-nerd.com>
**
** All rights reserved.
**
** Redistribution and use in source and binary forms, with or without
** modification, are permitted provided that the following conditions are
** met:
**
**	 * Redistributions of source code must retain the above copyright
**	   notice, this list of conditions and the following disclaimer.
**	 * Redistributions in binary form must reproduce the above copyright
**	   notice, this list of conditions and the following disclaimer in
**	   the documentation and/or other materials provided with the
**	   distribution.
**	 * Neither the author nor the names of any contributors may be used
**	   to endorse or promote products derived from this software without
**	   specific prior written permission.
**
** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
** TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
** PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
** CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
** EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
** PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
** OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
** WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
** OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
** ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

#include	<stdio.h>
#include	<string.h>

/* Include this header file to use functions from libsndfile. */
#include	<sndfile.h>

/*	This will be the length of the buffer used to hold.frames while
**	we process them.
*/
#define		BUFFER_LEN	1024

/* libsndfile can handle more than 6 channels but we'll restrict it to 6. */
#define		MAX_CHANNELS	6

/* Function prototype. */
static void process_data (double *data, int count, int channels) ;


int
main (void)
{	/* This is a buffer of double precision floating point values
	** which will hold our data while we process it.
	*/
	static double data [BUFFER_LEN] ;

	/* A SNDFILE is very much like a FILE in the Standard C library. The
	** sf_open function return an SNDFILE* pointer when they sucessfully
	** open the specified file.
	*/
	SNDFILE	*infile, *outfile ;

	/* A pointer to an SF_INFO struct is passed to sf_open.
	** On read, the library fills this struct with information about the file.
	** On write, the struct must be filled in before calling sf_open.
	*/
	SF_INFO		sfinfo ;
	int			readcount ;
	const char	*infilename = "input.wav" ;
	const char	*outfilename = "output.wav" ;

	/* The SF_INFO struct must be initialized before using it.
	*/
	memset (&sfinfo, 0, sizeof (sfinfo)) ;

	/* Here's where we open the input file. We pass sf_open the file name and
	** a pointer to an SF_INFO struct.
	** On successful open, sf_open returns a SNDFILE* pointer which is used
	** for all subsequent operations on that file.
	** If an error occurs during sf_open, the function returns a NULL pointer.
	**
	** If you are trying to open a raw headerless file you will need to set the
	** format and channels fields of sfinfo before calling sf_open(). For
	** instance to open a raw 16 bit stereo PCM file you would need the following
	** two lines:
	**
	**		sfinfo.format   = SF_FORMAT_RAW | SF_FORMAT_PCM_16 ;
	**		sfinfo.channels = 2 ;
	*/
	if (! (infile = sf_open (infilename, SFM_READ, &sfinfo)))
	{	/* Open failed so print an error message. */
		printf ("Not able to open input file %s.\n", infilename) ;
		/* Print the error message from libsndfile. */
		puts (sf_strerror (NULL)) ;
		return 1 ;
		} ;

	if (sfinfo.channels > MAX_CHANNELS)
	{	printf ("Not able to process more than %d channels\n", MAX_CHANNELS) ;
		return 1 ;
		} ;
	/* Open the output file. */
	if (! (outfile = sf_open (outfilename, SFM_WRITE, &sfinfo)))
	{	printf ("Not able to open output file %s.\n", outfilename) ;
		puts (sf_strerror (NULL)) ;
		return 1 ;
		} ;

	/* While there are.frames in the input file, read them, process
	** them and write them to the output file.
	*/
	while ((readcount = sf_read_double (infile, data, BUFFER_LEN)))
	{	process_data (data, readcount, sfinfo.channels) ;
		sf_write_double (outfile, data, readcount) ;
		} ;

	/* Close input and output files. */
	sf_close (infile) ;
	sf_close (outfile) ;

	return 0 ;
} /* main */

static void
process_data (double *data, int count, int channels)
{	double channel_gain [MAX_CHANNELS] = { 0.5, 0.8, 0.1, 0.4, 0.4, 0.9 } ;
	int k, chan ;

	/* Process the data here.
	** If the soundfile contains more then 1 channel you need to take care of
	** the data interleaving youself.
	** Current we just apply a channel dependant gain.
	*/

	for (chan = 0 ; chan < channels ; chan ++)
		for (k = chan ; k < count ; k+= channels)
			data [k] *= channel_gain [chan] ;

	return ;
} /* process_data */