/*
** Copyright (C) 2001-2002 Erik de Castro Lopo <erikd@zip.com.au>
**  
** This program is free software; you can redistribute it and/or modify
** it under the terms of the GNU General Public License as published by
** the Free Software Foundation; either version 2 of the License, or
** (at your option) any later version.
** 
** This program 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.
** 
** You should have received a copy of the GNU General Public License
** along with this program; if not, write to the Free Software 
** Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*/

#include    <stdio.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 stutct 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 ;
    char         *infilename = "input.wav" ;
    char         *outfilename = "output.wav" ;

    /* 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 */


