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/*
* Asterisk -- An open source telephony toolkit.
*
* Copyright (C) 1999 - 2005, Digium, Inc.
*
* Mark Spencer <markster@digium.com>
*
* See http://www.asterisk.org for more information about
* the Asterisk project. Please do not directly contact
* any of the maintainers of this project for assistance;
* the project provides a web site, mailing lists and IRC
* channels for your use.
*
* This program is free software, distributed under the terms of
* the GNU General Public License Version 2. See the LICENSE file
* at the top of the source tree.
*/
/*! \file
* \brief TTY/TDD Generation support
* \note Includes code and algorithms from the Zapata library.
*/
#ifndef _ASTERISK_TDD_H
#define _ASTERISK_TDD_H
#define TDD_BYTES_PER_CHAR 2700
struct tdd_state;
typedef struct tdd_state TDDSTATE;
/*! CallerID Initialization
* Initializes the TDD system. Mostly stuff for inverse FFT
*/
void tdd_init(void);
/*! Generates a CallerID FSK stream in ulaw format suitable for transmission.
* \param tdd tdd structure
* \param buf Buffer to use. This needs to be large enough to accomodate all the generated samples.
* \param string This is the string to send.
* This function creates a stream of TDD data in ulaw format. It returns the size
* (in bytes) of the data (if it returns a size of 0, there is probably an error)
*/
int tdd_generate(struct tdd_state *tdd, unsigned char *buf, const char *string);
/*! Create a TDD state machine
* This function returns a malloc'd instance of the tdd_state data structure.
* Returns a pointer to a malloc'd tdd_state structure, or NULL on error.
*/
struct tdd_state *tdd_new(void);
/*! Read samples into the state machine, and return character (if any).
* \param tdd Which state machine to act upon
* \param ubuf containing your samples
* \param samples number of samples contained within the buffer.
*
* Send received audio to the TDD demodulator.
* Returns -1 on error, 0 for "needs more samples",
* and > 0 (the character) if reception of a character is complete.
*/
int tdd_feed(struct tdd_state *tdd, unsigned char *ubuf, int samples);
/*! Free a TDD state machine
* \param tdd This is the tdd_state state machine to free
* This function frees tdd_state tdd.
*/
void tdd_free(struct tdd_state *tdd);
/*! Generate Echo Canceller disable tone (2100HZ)
* \param outbuf This is the buffer to receive the tone data
* \param len This is the length (in samples) of the tone data to generate
* Returns 0 if no error, and -1 if error.
*/
int ast_tdd_gen_ecdisa(unsigned char *outbuf, int len);
#endif /* _ASTERISK_TDD_H */
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