1 files changed, 34 insertions, 0 deletions
diff --git a/libavcodec/adx.c b/libavcodec/adx.c
new file mode 100644
index 0000000000..bc3e8825ca
--- /dev/null
+++ b/libavcodec/adx.c
@@ -0,0 +1,34 @@
+/*
+ * Copyright (c) 2011  Justin Ruggles
+ *
+ * This file is part of Libav.
+ *
+ * Libav is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * Libav 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with Libav; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "libavutil/mathematics.h"
+#include "adx.h"
+
+void ff_adx_calculate_coeffs(int cutoff, int sample_rate, int bits, int *coeff)
+{
+    double a, b, c;
+
+    a = M_SQRT2 - cos(2.0 * M_PI * cutoff / sample_rate);
+    b = M_SQRT2 - 1.0;
+    c = (a - sqrt((a + b) * (a - b))) / b;
+
+    coeff[0] = lrintf(c * 2.0  * (1 << bits));
+    coeff[1] = lrintf(-(c * c) * (1 << bits));
+}