ref: 1d48e533e1c6de212ad1520ed6481b222727e7a6
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; }