1 files changed, 110 insertions, 0 deletions

diff --git a/drivers/isdn/mISDN/dsp_ecdis.h b/drivers/isdn/mISDN/dsp_ecdis.h
new file mode 100644
index 000000000000..8a20af43308b
--- /dev/null
+++ b/drivers/isdn/mISDN/dsp_ecdis.h
@@ -0,0 +1,110 @@
+/*
+ * SpanDSP - a series of DSP components for telephony
+ *
+ * ec_disable_detector.h - A detector which should eventually meet the
+ *                         G.164/G.165 requirements for detecting the
+ *                         2100Hz echo cancellor disable tone.
+ *
+ * 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.
+ *
+ */
+
+#include "dsp_biquad.h"
+
+struct ec_disable_detector_state {
+        struct biquad2_state notch;
+        int notch_level;
+        int channel_level;
+        int tone_present;
+        int tone_cycle_duration;
+        int good_cycles;
+        int hit;
+};
+
+
+#define FALSE 0
+#define TRUE (!FALSE)
+
+static inline void
+echo_can_disable_detector_init(struct ec_disable_detector_state *det)
+{
+    /* Elliptic notch */
+    /* This is actually centred at 2095Hz, but gets the balance we want, due
+       to the asymmetric walls of the notch */
+        biquad2_init(&det->notch,
+                (int32_t) (-0.7600000*32768.0),
+                (int32_t) (-0.1183852*32768.0),
+                (int32_t) (-0.5104039*32768.0),
+                (int32_t) (0.1567596*32768.0),
+                (int32_t) (1.0000000*32768.0));
+
+        det->channel_level = 0;
+        det->notch_level = 0;
+        det->tone_present = FALSE;
+        det->tone_cycle_duration = 0;
+        det->good_cycles = 0;
+        det->hit = 0;
+}
+/*- End of function --------------------------------------------------------*/
+
+static inline int
+echo_can_disable_detector_update(struct ec_disable_detector_state *det,
+int16_t amp)
+{
+        int16_t notched;
+
+        notched = biquad2(&det->notch, amp);
+        /* Estimate the overall energy in the channel, and the energy in
+           the notch (i.e. overall channel energy - tone energy => noise).
+           Use abs instead of multiply for speed (is it really faster?).
+           Damp the overall energy a little more for a stable result.
+           Damp the notch energy a little less, so we don't damp out the
+           blip every time the phase reverses */
+        det->channel_level += ((abs(amp) - det->channel_level) >> 5);
+        det->notch_level += ((abs(notched) - det->notch_level) >> 4);
+        if (det->channel_level > 280) {
+                /* There is adequate energy in the channel.
+                 Is it mostly at 2100Hz? */
+                if (det->notch_level*6 < det->channel_level) {
+                        /* The notch says yes, so we have the tone. */
+                        if (!det->tone_present) {
+                                /* Do we get a kick every 450+-25ms? */
+                                if (det->tone_cycle_duration >= 425*8
+                                        && det->tone_cycle_duration <= 475*8) {
+                                        det->good_cycles++;
+                                        if (det->good_cycles > 2)
+                                        det->hit = TRUE;
+                                }
+                                det->tone_cycle_duration = 0;
+                        }
+                        det->tone_present = TRUE;
+                } else
+                        det->tone_present = FALSE;
+                det->tone_cycle_duration++;
+        } else {
+                det->tone_present = FALSE;
+                det->tone_cycle_duration = 0;
+                det->good_cycles = 0;
+        }
+        return det->hit;
+}
+/*- End of function --------------------------------------------------------*/
+/*- End of file ------------------------------------------------------------*/