--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/spandsp-0.0.6pre17/src/spandsp/dtmf.h	Fri Jun 25 15:50:58 2010 +0200
@@ -0,0 +1,218 @@
+/*
+ * SpanDSP - a series of DSP components for telephony
+ *
+ * dtmf.h - DTMF tone generation and detection.
+ *
+ * Written by Steve Underwood <steveu@coppice.org>
+ *
+ * Copyright (C) 2001, 2005 Steve Underwood
+ *
+ * All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License version 2.1,
+ * as published by the Free Software Foundation.
+ *
+ * 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 Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ * $Id: dtmf.h,v 1.32 2009/02/10 13:06:47 steveu Exp $
+ */
+
+#if !defined(_SPANDSP_DTMF_H_)
+#define _SPANDSP_DTMF_H_
+
+/*! \page dtmf_rx_page DTMF receiver
+\section dtmf_rx_page_sec_1 What does it do?
+The DTMF receiver detects the standard DTMF digits. It is compliant with
+ITU-T Q.23, ITU-T Q.24, and the local DTMF specifications of most administrations.
+Its passes the test suites. It also scores *very* well on the standard
+talk-off tests. 
+
+The current design uses floating point extensively. It is not tolerant of DC.
+It is expected that a DC restore stage will be placed before the DTMF detector.
+Unless the dial tone filter is switched on, the detector has poor tolerance
+of dial tone. Whether this matter depends on your application. If you are using
+the detector in an IVR application you will need proper echo cancellation to
+get good performance in the presence of speech prompts, so dial tone will not
+exist. If you do need good dial tone tolerance, a dial tone filter can be
+enabled in the detector.
+
+The DTMF receiver's design assumes the channel is free of any DC component.
+
+\section dtmf_rx_page_sec_2 How does it work?
+Like most other DSP based DTMF detector's, this one uses the Goertzel algorithm
+to look for the DTMF tones. What makes each detector design different is just how
+that algorithm is used.
+
+Basic DTMF specs:
+    - Minimum tone on = 40ms
+    - Minimum tone off = 50ms
+    - Maximum digit rate = 10 per second
+    - Normal twist <= 8dB accepted
+    - Reverse twist <= 4dB accepted
+    - S/N >= 15dB will detect OK
+    - Attenuation <= 26dB will detect OK
+    - Frequency tolerance +- 1.5% will detect, +-3.5% will reject
+
+TODO:
+*/
+
+/*! \page dtmf_tx_page DTMF tone generation
+\section dtmf_tx_page_sec_1 What does it do?
+
+The DTMF tone generation module provides for the generation of the
+repertoire of 16 DTMF dual tones. 
+
+\section dtmf_tx_page_sec_2 How does it work?
+*/
+
+#define MAX_DTMF_DIGITS 128
+
+typedef void (*digits_rx_callback_t)(void *user_data, const char *digits, int len);
+
+/*!
+    DTMF generator state descriptor. This defines the state of a single
+    working instance of a DTMF generator.
+*/
+typedef struct dtmf_tx_state_s dtmf_tx_state_t;
+
+/*!
+    DTMF digit detector descriptor.
+*/
+typedef struct dtmf_rx_state_s dtmf_rx_state_t;
+
+#if defined(__cplusplus)
+extern "C"
+{
+#endif
+
+/*! \brief Generate a buffer of DTMF tones.
+    \param s The DTMF generator context.
+    \param amp The buffer for the generated signal.
+    \param max_samples The required number of generated samples.
+    \return The number of samples actually generated. This may be less than 
+            max_samples if the input buffer empties. */
+SPAN_DECLARE(int) dtmf_tx(dtmf_tx_state_t *s, int16_t amp[], int max_samples);
+
+/*! \brief Put a string of digits in a DTMF generator's input buffer.
+    \param s The DTMF generator context.
+    \param digits The string of digits to be added.
+    \param len The length of the string of digits. If negative, the string is
+           assumed to be a NULL terminated string.
+    \return The number of digits actually added. This may be less than the
+            length of the digit string, if the buffer fills up. */
+SPAN_DECLARE(int) dtmf_tx_put(dtmf_tx_state_t *s, const char *digits, int len);
+
+/*! \brief Change the transmit level for a DTMF tone generator context.
+    \param s The DTMF generator context.
+    \param level The level of the low tone, in dBm0.
+    \param twist The twist, in dB. */
+SPAN_DECLARE(void) dtmf_tx_set_level(dtmf_tx_state_t *s, int level, int twist);
+
+/*! \brief Change the transmit on and off time for a DTMF tone generator context.
+    \param s The DTMF generator context.
+    \param on-time The on time, in ms.
+    \param off_time The off time, in ms. */
+SPAN_DECLARE(void) dtmf_tx_set_timing(dtmf_tx_state_t *s, int on_time, int off_time);
+
+/*! \brief Initialise a DTMF tone generator context.
+    \param s The DTMF generator context.
+    \return A pointer to the DTMF generator context. */
+SPAN_DECLARE(dtmf_tx_state_t *) dtmf_tx_init(dtmf_tx_state_t *s);
+
+/*! \brief Release a DTMF tone generator context.
+    \param s The DTMF tone generator context.
+    \return 0 for OK, else -1. */
+SPAN_DECLARE(int) dtmf_tx_release(dtmf_tx_state_t *s);
+
+/*! \brief Free a DTMF tone generator context.
+    \param s The DTMF tone generator context.
+    \return 0 for OK, else -1. */
+SPAN_DECLARE(int) dtmf_tx_free(dtmf_tx_state_t *s);
+
+/*! Set a optional realtime callback for a DTMF receiver context. This function
+    is called immediately a confirmed state change occurs in the received DTMF. It
+    is called with the ASCII value for a DTMF tone pair, or zero to indicate no tone
+    is being received.
+    \brief Set a realtime callback for a DTMF receiver context.
+    \param s The DTMF receiver context.
+    \param callback Callback routine used to report the start and end of digits.
+    \param user_data An opaque pointer which is associated with the context,
+           and supplied in callbacks. */
+SPAN_DECLARE(void) dtmf_rx_set_realtime_callback(dtmf_rx_state_t *s,
+                                                 tone_report_func_t callback,
+                                                 void *user_data);
+
+/*! \brief Adjust a DTMF receiver context.
+    \param s The DTMF receiver context.
+    \param filter_dialtone TRUE to enable filtering of dialtone, FALSE
+           to disable, < 0 to leave unchanged.
+    \param twist Acceptable twist, in dB. < 0 to leave unchanged.
+    \param reverse_twist Acceptable reverse twist, in dB. < 0 to leave unchanged.
+    \param threshold The minimum acceptable tone level for detection, in dBm0.
+           <= -99 to leave unchanged. */
+SPAN_DECLARE(void) dtmf_rx_parms(dtmf_rx_state_t *s,
+                                 int filter_dialtone,
+                                 int twist,
+                                 int reverse_twist,
+                                 int threshold);
+
+/*! Process a block of received DTMF audio samples.
+    \brief Process a block of received DTMF audio samples.
+    \param s The DTMF receiver context.
+    \param amp The audio sample buffer.
+    \param samples The number of samples in the buffer.
+    \return The number of samples unprocessed. */
+SPAN_DECLARE(int) dtmf_rx(dtmf_rx_state_t *s, const int16_t amp[], int samples);
+
+/*! Get the status of DTMF detection during processing of the last audio
+    chunk.
+    \brief Get the status of DTMF detection during processing of the last
+           audio chunk.
+    \param s The DTMF receiver context.
+    \return The current digit status. Either 'x' for a "maybe" condition, or the
+            digit being detected. */
+SPAN_DECLARE(int) dtmf_rx_status(dtmf_rx_state_t *s);
+
+/*! \brief Get a string of digits from a DTMF receiver's output buffer.
+    \param s The DTMF receiver context.
+    \param digits The buffer for the received digits.
+    \param max The maximum  number of digits to be returned,
+    \return The number of digits actually returned. */
+SPAN_DECLARE(size_t) dtmf_rx_get(dtmf_rx_state_t *s, char *digits, int max);
+
+/*! \brief Initialise a DTMF receiver context.
+    \param s The DTMF receiver context.
+    \param callback An optional callback routine, used to report received digits. If
+           no callback routine is set, digits may be collected, using the dtmf_rx_get()
+           function.
+    \param user_data An opaque pointer which is associated with the context,
+           and supplied in callbacks.
+    \return A pointer to the DTMF receiver context. */
+SPAN_DECLARE(dtmf_rx_state_t *) dtmf_rx_init(dtmf_rx_state_t *s,
+                                             digits_rx_callback_t callback,
+                                             void *user_data);
+
+/*! \brief Release a DTMF receiver context.
+    \param s The DTMF receiver context.
+    \return 0 for OK, else -1. */
+SPAN_DECLARE(int) dtmf_rx_release(dtmf_rx_state_t *s);
+
+/*! \brief Free a DTMF receiver context.
+    \param s The DTMF receiver context.
+    \return 0 for OK, else -1. */
+SPAN_DECLARE(int) dtmf_rx_free(dtmf_rx_state_t *s);
+
+#if defined(__cplusplus)
+}
+#endif
+
+#endif
+/*- End of file ------------------------------------------------------------*/