mqadec: detect correct output sample rate

The output rate returned by ssc_decode_open can be bogus for some files.
Detect the actual rate from the number of output samples instead.

mqadec.c

@@ -36,11 +36,17 @@
 #define BUF_SIZE 4096
 
 static SNDFILE *infile;
+static SF_INFO infmt;
 static uint8_t buf[BUF_SIZE];
 static int buf_pos;
 static int buf_end;
 
+static int samples_in;
+static int samples_out;
+
+static const char *outname;
 static SNDFILE *outfile;
+static SF_INFO outfmt;
 
 static int get_samples(int frame_size, uint8_t **samples, int eof, int *end)
 {
@@ -85,6 +91,7 @@ static int get_samples(int frame_size, uint8_t **samples, int eof, int *end)
 static void consume(int len)
 {
 	buf_pos += len;
+	samples_in += len / (4 * infmt.channels);
 }
 
 static size_t write_samples(void *p, void *buf, size_t len)
@@ -92,6 +99,24 @@ static size_t write_samples(void *p, void *buf, size_t len)
 	int32_t *s = buf;
 	int i;
 
+	samples_out += len;
+
+	if (!outfile) {
+		int rs;
+
+		for (rs = 0; samples_out > samples_in << rs; rs++);
+
+		outfmt.samplerate = infmt.samplerate << rs;
+		outfmt.channels = infmt.channels;
+		outfmt.format = SF_FORMAT_WAV | SF_FORMAT_PCM_24;
+
+		outfile = sf_open(outname, SFM_WRITE, &outfmt);
+		if (!outfile) {
+			fprintf(stderr, "%s: %s\n", outname, sf_strerror(NULL));
+			exit(1);
+		}
+	}
+
 	for (i = 0; i < len * 2; i++)
 		s[i] <<= 8;
 
@@ -106,8 +131,6 @@ static int write_size(void *p)
 int main(int argc, char **argv)
 {
 	struct ssc_decode *sscd;
-	SF_INFO infmt;
-	SF_INFO outfmt;
 	int dummy = 0;
 	int channels = 2;
 	int rate1 = 0;
@@ -145,6 +168,7 @@ int main(int argc, char **argv)
 
 	rate1 = infmt.samplerate;
 	channels = infmt.channels;
+	outname = argv[1];
 
 	sscd = ssc_decode_open(&channels, &rate1, &bits, rate2,
 			       get_samples, consume, write_samples,
@@ -156,17 +180,6 @@ int main(int argc, char **argv)
 		return 1;
 	}
 
-	memset(&outfmt, 0, sizeof(outfmt));
-	outfmt.samplerate = rate1;
-	outfmt.channels = channels;
-	outfmt.format = SF_FORMAT_WAV | SF_FORMAT_PCM_24;
-
-	outfile = sf_open(argv[1], SFM_WRITE, &outfmt);
-	if (!outfile) {
-		fprintf(stderr, "%s: %s\n", argv[1], sf_strerror(NULL));
-		return 1;
-	}
-
 	while (ssc_decode_read(sscd) > 0) {
 		if (!mqa) {
 			const char *s = ssc_decode_status(sscd);