From bab7a6ac29462969c05b1638f7a7a81d95485c04 Mon Sep 17 00:00:00 2001
From: "sgunderson@bigfoot.com" <>
Date: Thu, 28 Dec 2006 03:01:43 +0100
Subject: [PATCH] Add a program to skew an input using a skew control signal.

---
 do-skew.c | 74 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 74 insertions(+)
 create mode 100644 do-skew.c

diff --git a/do-skew.c b/do-skew.c
new file mode 100644
index 0000000..6062999
--- /dev/null
+++ b/do-skew.c
@@ -0,0 +1,74 @@
+#include <stdio.h>
+#include <string.h>
+#include <math.h>
+#include <stdlib.h>
+
+double frac(double x)
+{
+	return x - (int)x;
+}
+
+int main(int argc, char **argv)
+{
+	FILE *in, *skew, *out;
+
+	// open input
+	if (strcmp(argv[1], "-") == 0) {
+		in = stdin;
+	} else {
+		in = fopen(argv[1], "rb");
+		if (in == NULL) {
+			perror(argv[1]);
+			exit(1);
+		}
+	}
+
+	// open skew
+	if (strcmp(argv[2], "-") == 0) {
+		skew = stdin;
+	} else {
+		skew = fopen(argv[2], "rb");
+		if (skew == NULL) {
+			perror(argv[2]);
+			exit(1);
+		}
+	}
+
+	// open output
+	if (strcmp(argv[3], "-") == 0) {
+		out = stderr;
+	} else {
+		out = fopen(argv[3], "wb");
+		if (in == NULL) {
+			perror(argv[3]);
+			exit(1);
+		}
+	}
+
+	short prev_sample, sample = 0;
+	unsigned in_pos = -1;
+	double p = -1.0;
+
+	while (!feof(in) && !feof(skew)) {
+		double delta_p;
+		if (fread(&delta_p, sizeof(double), 1, skew) != 1) {
+			exit(0);
+		}
+
+		p += delta_p;
+
+		// read samples until we're at the right position
+		while ((unsigned)(ceil(p)) > in_pos) {
+			prev_sample = sample;
+			if (fread(&sample, sizeof(short), 1, in) != 1) {
+				exit(0);
+			}
+		}
+
+		// linear interpolation (works well since delta_p varies so slowly)
+		double t = frac(p);
+		short intp_sample = prev_sample * (1.0 - t) + sample * t;
+
+		fwrite(&intp_sample, sizeof(short), 1, out);
+	}
+}
-- 
2.39.2