Sat Aug 6 00:39:32 2011

Asterisk developer's documentation


translate.h

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00001 /*
00002  * Asterisk -- An open source telephony toolkit.
00003  *
00004  * Copyright (C) 1999 - 2006, 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 Support for translation of data formats.
00021  */
00022 
00023 #ifndef _ASTERISK_TRANSLATE_H
00024 #define _ASTERISK_TRANSLATE_H
00025 
00026 #define MAX_AUDIO_FORMAT 15 /* Do not include video here */
00027 #define MAX_FORMAT 32   /* Do include video here */
00028 
00029 #if defined(__cplusplus) || defined(c_plusplus)
00030 extern "C" {
00031 #endif
00032 
00033 #if 1 /* need lots of stuff... */
00034 #include "asterisk/frame.h"
00035 #include "asterisk/plc.h"
00036 #include "asterisk/linkedlists.h"
00037 // XXX #include "asterisk/module.h"
00038 #endif
00039 
00040 struct ast_trans_pvt;   /* declared below */
00041 
00042 /*! \brief
00043  * Descriptor of a translator. Name, callbacks, and various options
00044  * related to run-time operation (size of buffers, auxiliary
00045  * descriptors, etc).
00046  *
00047  * A coded registers itself by filling the relevant fields
00048  * of a structure and passing it as an argument to
00049  * ast_register_translator(). The structure should not be
00050  * modified after a successful registration, and its address
00051  * must be used as an argument to ast_unregister_translator().
00052  *
00053  * As a minimum, a translator should supply name, srcfmt and dstfmt,
00054  * the required buf_size (in bytes) and buffer_samples (in samples),
00055  * and a few callbacks (framein, frameout, sample).
00056  * The outbuf is automatically prepended by AST_FRIENDLY_OFFSET
00057  * spare bytes so generic routines can place data in there.
00058  *
00059  * Note, the translator is not supposed to do any memory allocation
00060  * or deallocation, nor any locking, because all of this is done in
00061  * the generic code.
00062  *
00063  */
00064 struct ast_translator {
00065    const char name[80];    /*!< Name of translator */
00066    int srcfmt;       /*!< Source format (note: bit position,
00067                  converted to index during registration) */
00068    int dstfmt;       /*!< Destination format (note: bit position,
00069                  converted to index during registration) */
00070 
00071    int (*newpvt)(struct ast_trans_pvt *); /*!< initialize private data 
00072                associated with the translator */
00073 
00074    int (*framein)(struct ast_trans_pvt *pvt, struct ast_frame *in);
00075                /*!< Input frame callback. Store 
00076                     (and possibly convert) input frame. */
00077 
00078    struct ast_frame * (*frameout)(struct ast_trans_pvt *pvt);
00079                /*!< Output frame callback. Generate a frame 
00080                    with outbuf content. */
00081 
00082    void (*destroy)(struct ast_trans_pvt *pvt);
00083                /*!< cleanup private data, if needed 
00084                   (often unnecessary). */
00085 
00086    struct ast_frame * (*sample)(void); /*!< Generate an example frame */
00087 
00088    /*! \brief size of outbuf, in samples. Leave it 0 if you want the framein
00089     * callback deal with the frame. Set it appropriately if you
00090     * want the code to checks if the incoming frame fits the
00091     * outbuf (this is e.g. required for plc).
00092     */
00093    int buffer_samples;  /*< size of outbuf, in samples */
00094 
00095    /*! \brief size of outbuf, in bytes. Mandatory. The wrapper code will also
00096     * allocate an AST_FRIENDLY_OFFSET space before.
00097     */
00098    int buf_size;
00099 
00100    int desc_size;       /*!< size of private descriptor in pvt->pvt, if any */
00101    int plc_samples; /* Unused. Kept for ABI purposes */
00102    int useplc; /* Unused. Kept for ABI purposes */
00103    int native_plc;         /*!< true if the translator can do native plc */
00104 
00105    struct ast_module *module; /* opaque reference to the parent module */
00106 
00107    int cost;         /*!< Cost in milliseconds for encoding/decoding 1 second of sound */
00108    int active;       /*!< Whether this translator should be used or not */
00109    AST_LIST_ENTRY(ast_translator) list;   /*!< link field */
00110 };
00111 
00112 /*! \brief
00113  * Default structure for translators, with the basic fields and buffers,
00114  * all allocated as part of the same chunk of memory. The buffer is
00115  * preceded by AST_FRIENDLY_OFFSET bytes in front of the user portion.
00116  * 'buf' points right after this space.
00117  *
00118  * *_framein() routines operate in two ways:
00119  * 1. some convert on the fly and place the data directly in outbuf;
00120  *    in this case 'samples' and 'datalen' contain the number of samples
00121  *    and number of bytes available in the buffer.
00122  *    In this case we can use a generic *_frameout() routine that simply
00123  *    takes whatever is there and places it into the output frame.
00124  * 2. others simply store the (unconverted) samples into a working
00125  *    buffer, and leave the conversion task to *_frameout().
00126  *    In this case, the intermediate buffer must be in the private
00127  *    descriptor, 'datalen' is left to 0, while 'samples' is still
00128  *    updated with the number of samples received.
00129  */
00130 struct ast_trans_pvt {
00131    struct ast_translator *t;
00132    struct ast_frame f;  /*!< used in frameout */
00133    int samples;      /*!< samples available in outbuf */
00134    /*! 
00135     * \brief actual space used in outbuf
00136     */
00137    int datalen;
00138    void *pvt;     /*!< more private data, if any */
00139    char *outbuf;     /*!< the useful portion of the buffer */
00140    plc_state_t *plc; /*!< optional plc pointer */
00141    struct ast_trans_pvt *next;   /*!< next in translator chain */
00142    struct timeval nextin;
00143    struct timeval nextout;
00144 };
00145 
00146 /*! \brief generic frameout function */
00147 struct ast_frame *ast_trans_frameout(struct ast_trans_pvt *pvt,
00148         int datalen, int samples);
00149 
00150 struct ast_trans_pvt;
00151 
00152 /*!
00153  * \brief Register a translator
00154  * This registers a codec translator with asterisk
00155  * \param t populated ast_translator structure
00156  * \param module handle to the module that owns this translator
00157  * \return 0 on success, -1 on failure
00158  */
00159 int __ast_register_translator(struct ast_translator *t, struct ast_module *module);
00160 #define ast_register_translator(t) __ast_register_translator(t, ast_module_info->self)
00161 
00162 /*!
00163  * \brief Unregister a translator
00164  * Unregisters the given tranlator
00165  * \param t translator to unregister
00166  * \return 0 on success, -1 on failure
00167  */
00168 int ast_unregister_translator(struct ast_translator *t);
00169 
00170 /*!
00171  * \brief Activate a previously deactivated translator
00172  * \param t translator to activate
00173  * \return nothing
00174  *
00175  * Enables the specified translator for use.
00176  */
00177 void ast_translator_activate(struct ast_translator *t);
00178 
00179 /*!
00180  * \brief Deactivate a translator
00181  * \param t translator to deactivate
00182  * \return nothing
00183  *
00184  * Disables the specified translator from being used.
00185  */
00186 void ast_translator_deactivate(struct ast_translator *t);
00187 
00188 /*!
00189  * \brief Chooses the best translation path
00190  *
00191  * Given a list of sources, and a designed destination format, which should
00192  * I choose? 
00193  * \return Returns 0 on success, -1 if no path could be found.  
00194  * \note Modifies dests and srcs in place 
00195  */
00196 int ast_translator_best_choice(int *dsts, int *srcs);
00197 
00198 /*! 
00199  * \brief Builds a translator path
00200  * Build a path (possibly NULL) from source to dest 
00201  * \param dest destination format
00202  * \param source source format
00203  * \return ast_trans_pvt on success, NULL on failure
00204  * */
00205 struct ast_trans_pvt *ast_translator_build_path(int dest, int source);
00206 
00207 /*!
00208  * \brief Frees a translator path
00209  * Frees the given translator path structure
00210  * \param tr translator path to get rid of
00211  */
00212 void ast_translator_free_path(struct ast_trans_pvt *tr);
00213 
00214 /*!
00215  * \brief translates one or more frames
00216  * Apply an input frame into the translator and receive zero or one output frames.  Consume
00217  * determines whether the original frame should be freed
00218  * \param tr translator structure to use for translation
00219  * \param f frame to translate
00220  * \param consume Whether or not to free the original frame
00221  * \return an ast_frame of the new translation format on success, NULL on failure
00222  */
00223 struct ast_frame *ast_translate(struct ast_trans_pvt *tr, struct ast_frame *f, int consume);
00224 
00225 /*!
00226  * \brief Returns the number of steps required to convert from 'src' to 'dest'.
00227  * \param dest destination format
00228  * \param src source format
00229  * \return the number of translation steps required, or -1 if no path is available
00230  */
00231 unsigned int ast_translate_path_steps(unsigned int dest, unsigned int src);
00232 
00233 /*!
00234  * \brief Mask off unavailable formats from a format bitmask
00235  * \param dest possible destination formats
00236  * \param src source formats
00237  * \return the destination formats that are available in the source or translatable
00238  *
00239  * The result will include all formats from 'dest' that are either present
00240  * in 'src' or translatable from a format present in 'src'.
00241  *
00242  * Note that only a single audio format and a single video format can be
00243  * present in 'src', or the function will produce unexpected results.
00244  */
00245 unsigned int ast_translate_available_formats(unsigned int dest, unsigned int src);
00246 
00247 #if defined(__cplusplus) || defined(c_plusplus)
00248 }
00249 #endif
00250 
00251 #endif /* _ASTERISK_TRANSLATE_H */

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