Asterisk.org: Developer Documentation (28 Oct 2009)

Wed Oct 28 15:47:56 2009

## Asterisk developer's documentation

# tdd.h

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    00001 /*
    00002  * Asterisk -- An open source telephony toolkit.
    00003  *
    00004  * Copyright (C) 1999 - 2005, Digium, Inc.
    00005  *
    00006  * Mark Spencer <markster@digium.com>
    00007  *
    00008  * See http://www.asterisk.org for more information about
    00009  * the Asterisk project. Please do not directly contact
    00010  * any of the maintainers of this project for assistance;
    00011  * the project provides a web site, mailing lists and IRC
    00012  * channels for your use.
    00013  *
    00014  * This program is free software, distributed under the terms of
    00015  * the GNU General Public License Version 2. See the LICENSE file
    00016  * at the top of the source tree.
    00017  */
    00018
    00019 /*! \file
    00020  * \brief TTY/TDD Generation support
    00021  * \note Includes code and algorithms from the Zapata library.
    00022  */
    00023
    00024 #ifndef _ASTERISK_TDD_H
    00025 #define _ASTERISK_TDD_H
    00026
    00027 #define  TDD_BYTES_PER_CHAR   2700
    00028
    00029 struct tdd_state;
    00030 typedef struct tdd_state TDDSTATE;
    00031
    00032 /*! CallerID Initialization */
    00033 /*!
    00034  * Initializes the TDD system.  Mostly stuff for inverse FFT
    00035  */
    00036 extern void tdd_init(void);
    00037
    00038 /*! Generates a CallerID FSK stream in ulaw format suitable for transmission. */
    00039 /*!
    00040  * \param tdd tdd structure
    00041  * \param buf Buffer to use. This needs to be large enough to accomodate all the generated samples.
    00042  * \param string This is the string to send.
    00043  * This function creates a stream of TDD data in ulaw format. It returns the size
    00044  * (in bytes) of the data (if it returns a size of 0, there is probably an error)
    00045 */
    00046 extern int tdd_generate(struct tdd_state *tdd, unsigned char *buf, const char *string);
    00047
    00048 /*! Create a TDD state machine */
    00049 /*!
    00050  * This function returns a malloc'd instance of the tdd_state data structure.
    00051  * Returns a pointer to a malloc'd tdd_state structure, or NULL on error.
    00052  */
    00053 extern struct tdd_state *tdd_new(void);
    00054
    00055 /*! Read samples into the state machine, and return character (if any). */
    00056 /*!
    00057  * \param tdd Which state machine to act upon
    00058  * \param ubuf containing your samples
    00059  * \param samples number of samples contained within the buffer.
    00060  *
    00061  * Send received audio to the TDD demodulator.
    00062  * Returns -1 on error, 0 for "needs more samples",
    00063  * and > 0 (the character) if reception of a character is complete.
    00064  */
    00065 extern int tdd_feed(struct tdd_state *tdd, unsigned char *ubuf, int samples);
    00066
    00067 /*! Free a TDD state machine */
    00068 /*!
    00069  * \param tdd This is the tdd_state state machine to free
    00070  * This function frees tdd_state tdd.
    00071  */
    00072 extern void tdd_free(struct tdd_state *tdd);
    00073
    00074 /*! Generate Echo Canceller diable tone (2100HZ) */
    00075 /*!
    00076  * \param outbuf This is the buffer to receive the tone data
    00077  * \param len This is the length (in samples) of the tone data to generate
    00078  * Returns 0 if no error, and -1 if error.
    00079  */
    00080 extern int ast_tdd_gen_ecdisa(unsigned char *outbuf, int len);
    00081
    00082 #endif /* _ASTERISK_TDD_H */