ref: 97bea98f87382d6abf885bd2e671dee845cad43b
dir: /src/example2.c/
/* Simple example of using SoX libraries
*
* Copyright (c) 2008 robs@users.sourceforge.net
*
* 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.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#ifdef NDEBUG /* N.B. assert used with active statements so enable always. */
#undef NDEBUG /* Must undef above assert.h or other that might include it. */
#endif
#include "sox.h"
#include "util.h"
#include <stdio.h>
#include <math.h>
#include <assert.h>
/*
* Reads input file and displays a few seconds of wave-form, starting from
* a given time through the audio. E.g. example2 song2.au 30.75 1
*/
int main(int argc, char * argv[])
{
sox_format_t * in;
sox_sample_t * buf;
size_t blocks, block_size;
/* Period of audio over which we will measure its volume in order to
* display the wave-form: */
static const double block_period = 0.025; /* seconds */
double start_secs = 0, period = 2;
char dummy;
uint64_t seek;
/* All libSoX applications must start by initialising the SoX library */
assert(sox_init() == SOX_SUCCESS);
assert(argc > 1);
++argv, --argc; /* Move to 1st parameter */
/* Open the input file (with default parameters) */
assert(in = sox_open_read(*argv, NULL, NULL, NULL));
++argv, --argc; /* Move past this parameter */
if (argc) { /* If given, read the start time: */
assert(sscanf(*argv, "%lf%c", &start_secs, &dummy) == 1);
++argv, --argc; /* Move past this parameter */
}
if (argc) { /* If given, read the period of time to display: */
assert(sscanf(*argv, "%lf%c", &period, &dummy) == 1);
++argv, --argc; /* Move past this parameter */
}
/* Calculate the start position in number of samples: */
seek = start_secs * in->signal.rate * in->signal.channels + .5;
/* Make sure that this is at a `wide sample' boundary: */
seek -= seek % in->signal.channels;
/* Move the file pointer to the desired starting position */
assert(sox_seek(in, seek, SOX_SEEK_SET) == SOX_SUCCESS);
/* Convert block size (in seconds) to a number of samples: */
block_size = block_period * in->signal.rate * in->signal.channels + .5;
/* Make sure that this is at a `wide sample' boundary: */
block_size -= block_size % in->signal.channels;
/* Allocate a block of memory to store the block of audio samples: */
assert(buf = malloc(sizeof(sox_sample_t) * block_size));
/* This example program requires that the audio has precisely 2 channels: */
assert(in->signal.channels == 2);
/* Read and process blocks of audio for the selected period or until EOF: */
for (blocks = 0; sox_read(in, buf, block_size) == block_size && blocks * block_period < period; ++blocks) {
double left = 0, right = 0;
size_t i;
static const char line[] = "===================================";
int l, r;
for (i = 0; i < block_size; ++i) {
SOX_SAMPLE_LOCALS;
/* convert the sample from SoX's internal format to a `double' for
* processing in this application: */
double sample = SOX_SAMPLE_TO_FLOAT_64BIT(buf[i],);
/* The samples for each channel are interleaved; in this example
* we allow only stereo audio, so the left channel audio can be found in
* even-numbered samples, and the right channel audio in odd-numbered
* samples: */
if (i & 1)
right = max(right, fabs(sample)); /* Find the peak volume in the block */
else
left = max(left, fabs(sample)); /* Find the peak volume in the block */
}
/* Build up the wave form by displaying the left & right channel
* volume as a line length: */
l = (1 - left) * 35 + .5;
r = (1 - right) * 35 + .5;
printf("%8.3f%36s|%s\n", start_secs + blocks * block_period, line + l, line + r);
}
/* All done; tidy up: */
free(buf);
sox_close(in);
sox_quit();
return 0;
}