sfprocess.c

Audacity是一款用於錄音和編輯聲音的、免費的開放源碼軟體。它可以執行於Mac OS X、Microsoft Windows、GNU/Linux和其它作業系統

/*
** Copyright (C) 2001-2004 Erik de Castro Lopo <[e-mail]>
**
** 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 ;
    const char	*infilename = "input.wav" ;
    const 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 */


/*
** Do not edit or modify anything in this comment block.
** The arch-tag line is a file identity tag for the GNU Arch
** revision control system.
**
** arch-tag: de9fdd1e-b807-41ef-9d51-075ba383e536
*/