1 files changed, 65 insertions, 0 deletions

diff --git a/drivers/isdn/mISDN/dsp_biquad.h b/drivers/isdn/mISDN/dsp_biquad.h
new file mode 100644
index 000000000000..038191bc45f5
--- /dev/null
+++ b/drivers/isdn/mISDN/dsp_biquad.h
@@ -0,0 +1,65 @@
+/*
+ * SpanDSP - a series of DSP components for telephony
+ *
+ * biquad.h - General telephony bi-quad section routines (currently this just
+ *            handles canonic/type 2 form)
+ *
+ * Written by Steve Underwood <steveu@coppice.org>
+ *
+ * Copyright (C) 2001 Steve Underwood
+ *
+ * All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ */
+
+struct biquad2_state {
+        int32_t gain;
+        int32_t a1;
+        int32_t a2;
+        int32_t b1;
+        int32_t b2;
+
+        int32_t z1;
+        int32_t z2;
+};
+
+static inline void biquad2_init(struct biquad2_state *bq,
+    int32_t gain, int32_t a1, int32_t a2, int32_t b1, int32_t b2)
+{
+        bq->gain = gain;
+        bq->a1 = a1;
+        bq->a2 = a2;
+        bq->b1 = b1;
+        bq->b2 = b2;
+
+        bq->z1 = 0;
+        bq->z2 = 0;
+}
+
+static inline int16_t biquad2(struct biquad2_state *bq, int16_t sample)
+{
+        int32_t y;
+        int32_t z0;
+
+        z0 = sample*bq->gain + bq->z1*bq->a1 + bq->z2*bq->a2;
+        y = z0 + bq->z1*bq->b1 + bq->z2*bq->b2;
+
+        bq->z2 = bq->z1;
+        bq->z1 = z0 >> 15;
+        y >>= 15;
+        return  y;
+}