firstNZsample.c

/* firstNZsample.c - print time of first non-zero audio sample 
 *
 * (C) 2009 Robin Gareus <[email protected]> 
 * GPLv2 https://www.gnu.org/licenses/gpl-2.0.html
 *
 * compile with:
 *   gcc -o firstNZsample firstNZsample.c -Wall -lsndfile
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sndfile.h>

int main (int argc, char **argv)
{
	int      chn = -1;
	char*    filename;
	SF_INFO  nfo;
	SNDFILE* sndfile;

	if (argc < 2) {
		fprintf(stderr, "Usage: %s <audio-file> [chn]\n\n", argv[0]);
		fprintf(stderr, "This tool prints the time of the first non-zero audio-sample.\n\n");
		return -1;
	}

	filename = argv[1];

	if (argc > 2) {
		chn = atoi (argv[2]) - 1;
	}

	memset (&nfo, 0, sizeof(SF_INFO));

	if ((sndfile = sf_open (filename, SFM_READ, &nfo)) == 0) {
		return -1;
	}
	if (!sndfile) {
		return -1;
	}

	float* buf = (float*) malloc (nfo.channels * sizeof(float));

	if (!buf) return -1;

	for (int s = 0; s < nfo.frames; ++s) {
		sf_readf_float (sndfile, buf, 1);
		for (int c = 0; c < nfo.channels; ++c) {
			if (chn >= 0 && c != chn) {
				continue;
			}
			if (buf[c] != 0) {
				printf ("First non-zero sample: %d (chn:%d)\n", s, c + 1);
				goto end;
			}
		}
	}
	printf ("All samples are zero.\n");

end:
	sf_close(sndfile);
	free(buf);
	return 0;
}