Convert to PCM using libsndfile.

topcm.c

#include <stdio.h>
#include <sndfile.h>
#include <string.h>

// gcc topcm.c -lsndfile -o topcm

int main(int argc, char **argv) {

	if (argc < 3) {
		printf("Usage: %s in-filename out-filename\n", argv[0]); return 0;
	}

	SF_INFO readInfo, writeInfo;
	readInfo.format = 0;

	char *inFilename = argv[1];
	char *outFilename = argv[2];

	SNDFILE *in = sf_open(inFilename, SFM_READ, &readInfo);
	if (in == NULL) {
		printf("Can't open file for reading!\n"); return 1;
	}

	writeInfo.format = SF_FORMAT_WAV | SF_FORMAT_PCM_16;
	writeInfo.samplerate = readInfo.samplerate;
	writeInfo.channels   = readInfo.channels;
	SNDFILE *out = sf_open(outFilename, SFM_WRITE, &writeInfo);
	if (out == NULL) {
		printf("Can't open file for writing!\n"); return 2;
	}

	short samples[2048];
	for (;;) {
		int items = sf_read_short(in, samples, 2048);
		if (items > 0) {
			sf_write_short(out, samples, items);
		} else {
			break;
		}
	}

	sf_close(in);
	sf_close(out);

	return 0;

}