Wed Oct 28 11:51:08 2009

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  * \ref translate.c
00022  */
00023 
00024 #ifndef _ASTERISK_TRANSLATE_H
00025 #define _ASTERISK_TRANSLATE_H
00026 
00027 #define MAX_AUDIO_FORMAT 15 /* Do not include video here */
00028 #define MAX_FORMAT 32   /* Do include video here */
00029 
00030 #if defined(__cplusplus) || defined(c_plusplus)
00031 extern "C" {
00032 #endif
00033 
00034 #if 1 /* need lots of stuff... */
00035 #include "asterisk/frame.h"
00036 #include "asterisk/plc.h"
00037 #include "asterisk/linkedlists.h"
00038 // XXX #include "asterisk/module.h"
00039 #endif
00040 
00041 struct ast_trans_pvt;   /* declared below */
00042 
00043 /*! \brief
00044  * Descriptor of a translator. 
00045  *
00046  * Name, callbacks, and various options
00047  * related to run-time operation (size of buffers, auxiliary
00048  * descriptors, etc).
00049  *
00050  * A codec registers itself by filling the relevant fields
00051  * of a structure and passing it as an argument to
00052  * ast_register_translator(). The structure should not be
00053  * modified after a successful registration, and its address
00054  * must be used as an argument to ast_unregister_translator().
00055  *
00056  * As a minimum, a translator should supply name, srcfmt and dstfmt,
00057  * the required buf_size (in bytes) and buffer_samples (in samples),
00058  * and a few callbacks (framein, frameout, sample).
00059  * The outbuf is automatically prepended by AST_FRIENDLY_OFFSET
00060  * spare bytes so generic routines can place data in there.
00061  *
00062  * Note, the translator is not supposed to do any memory allocation
00063  * or deallocation, nor any locking, because all of this is done in
00064  * the generic code.
00065  *
00066  * Translators using generic plc (packet loss concealment) should
00067  * supply a non-zero plc_samples indicating the size (in samples)
00068  * of artificially generated frames and incoming data.
00069  * Generic plc is only available for dstfmt = SLINEAR
00070  */
00071 struct ast_translator {
00072    const char name[80];    /*!< Name of translator */
00073    int srcfmt;       /*!< Source format (note: bit position,
00074                  converted to index during registration) */
00075    int dstfmt;       /*!< Destination format (note: bit position,
00076                  converted to index during registration) */
00077 
00078    int (*newpvt)(struct ast_trans_pvt *); /*!< initialize private data 
00079                associated with the translator */
00080 
00081    int (*framein)(struct ast_trans_pvt *pvt, struct ast_frame *in);
00082                /*!< Input frame callback. Store 
00083                     (and possibly convert) input frame. */
00084 
00085    struct ast_frame * (*frameout)(struct ast_trans_pvt *pvt);
00086                /*!< Output frame callback. Generate a frame 
00087                    with outbuf content. */
00088 
00089    void (*destroy)(struct ast_trans_pvt *pvt);
00090                /*!< cleanup private data, if needed 
00091                   (often unnecessary). */
00092 
00093    struct ast_frame * (*sample)(void); /*!< Generate an example frame */
00094 
00095    /*! \brief size of outbuf, in samples. Leave it 0 if you want the framein
00096     * callback deal with the frame. Set it appropriately if you
00097     * want the code to checks if the incoming frame fits the
00098     * outbuf (this is e.g. required for plc).
00099     */
00100    int buffer_samples;  /*< size of outbuf, in samples */
00101 
00102    /*! \brief size of outbuf, in bytes. Mandatory. The wrapper code will also
00103     * allocate an AST_FRIENDLY_OFFSET space before.
00104     */
00105    int buf_size;
00106 
00107    int desc_size;       /*!< size of private descriptor in pvt->pvt, if any */
00108    int plc_samples;     /*!< set to the plc block size if used, 0 otherwise */
00109    int useplc;       /*!< current status of plc, changed at runtime */
00110    int native_plc;         /*!< true if the translator can do native plc */
00111 
00112    struct ast_module *module; /* opaque reference to the parent module */
00113 
00114    int cost;         /*!< Cost in milliseconds for encoding/decoding 1 second of sound */
00115    int active;       /*!< Whether this translator should be used or not */
00116    AST_LIST_ENTRY(ast_translator) list;   /*!< link field */
00117 };
00118 
00119 /*! \brief
00120  * Default structure for translators, with the basic fields and buffers,
00121  * all allocated as part of the same chunk of memory. The buffer is
00122  * preceded by \ref AST_FRIENDLY_OFFSET bytes in front of the user portion.
00123  * 'buf' points right after this space.
00124  *
00125  * *_framein() routines operate in two ways:
00126  * 1. some convert on the fly and place the data directly in outbuf;
00127  *    in this case 'samples' and 'datalen' contain the number of samples
00128  *    and number of bytes available in the buffer.
00129  *    In this case we can use a generic *_frameout() routine that simply
00130  *    takes whatever is there and places it into the output frame.
00131  * 2. others simply store the (unconverted) samples into a working
00132  *    buffer, and leave the conversion task to *_frameout().
00133  *    In this case, the intermediate buffer must be in the private
00134  *    descriptor, 'datalen' is left to 0, while 'samples' is still
00135  *    updated with the number of samples received.
00136  */
00137 struct ast_trans_pvt {
00138    struct ast_translator *t;
00139    struct ast_frame f;         /*!< used in frameout */
00140    int samples;                /*!< samples available in outbuf */
00141    /*! \brief actual space used in outbuf */
00142    int datalen;
00143    void *pvt;                  /*!< more private data, if any */
00144    union {
00145       char *c;                /*!< the useful portion of the buffer */
00146       unsigned char *uc;      /*!< the useful portion of the buffer */
00147       int16_t *i16;
00148       uint8_t *ui8;
00149    } outbuf; 
00150    plc_state_t *plc;           /*!< optional plc pointer */
00151    struct ast_trans_pvt *next; /*!< next in translator chain */
00152    struct timeval nextin;
00153    struct timeval nextout;
00154 };
00155 
00156 /*! \brief generic frameout function */
00157 struct ast_frame *ast_trans_frameout(struct ast_trans_pvt *pvt,
00158         int datalen, int samples);
00159 
00160 struct ast_trans_pvt;
00161 
00162 /*!
00163  * \brief Register a translator
00164  * This registers a codec translator with asterisk
00165  * \param t populated ast_translator structure
00166  * \param module handle to the module that owns this translator
00167  * \return 0 on success, -1 on failure
00168  */
00169 int __ast_register_translator(struct ast_translator *t, struct ast_module *module);
00170 
00171 /*! \brief See \ref __ast_register_translator() */
00172 #define ast_register_translator(t) __ast_register_translator(t, ast_module_info->self)
00173 
00174 /*!
00175  * \brief Unregister a translator
00176  * Unregisters the given tranlator
00177  * \param t translator to unregister
00178  * \return 0 on success, -1 on failure
00179  */
00180 int ast_unregister_translator(struct ast_translator *t);
00181 
00182 /*!
00183  * \brief Activate a previously deactivated translator
00184  * \param t translator to activate
00185  * \return nothing
00186  *
00187  * Enables the specified translator for use.
00188  */
00189 void ast_translator_activate(struct ast_translator *t);
00190 
00191 /*!
00192  * \brief Deactivate a translator
00193  * \param t translator to deactivate
00194  * \return nothing
00195  *
00196  * Disables the specified translator from being used.
00197  */
00198 void ast_translator_deactivate(struct ast_translator *t);
00199 
00200 /*!
00201  * \brief Chooses the best translation path
00202  *
00203  * Given a list of sources, and a designed destination format, which should
00204  * I choose? 
00205  * \return Returns 0 on success, -1 if no path could be found.  
00206  * \note Modifies dests and srcs in place 
00207  */
00208 int ast_translator_best_choice(int *dsts, int *srcs);
00209 
00210 /*! 
00211  * \brief Builds a translator path
00212  * Build a path (possibly NULL) from source to dest 
00213  * \param dest destination format
00214  * \param source source format
00215  * \return ast_trans_pvt on success, NULL on failure
00216  * */
00217 struct ast_trans_pvt *ast_translator_build_path(int dest, int source);
00218 
00219 /*!
00220  * \brief Frees a translator path
00221  * Frees the given translator path structure
00222  * \param tr translator path to get rid of
00223  */
00224 void ast_translator_free_path(struct ast_trans_pvt *tr);
00225 
00226 /*!
00227  * \brief translates one or more frames
00228  * Apply an input frame into the translator and receive zero or one output frames.  Consume
00229  * determines whether the original frame should be freed
00230  * \param tr translator structure to use for translation
00231  * \param f frame to translate
00232  * \param consume Whether or not to free the original frame
00233  * \return an ast_frame of the new translation format on success, NULL on failure
00234  */
00235 struct ast_frame *ast_translate(struct ast_trans_pvt *tr, struct ast_frame *f, int consume);
00236 
00237 /*!
00238  * \brief Returns the number of steps required to convert from 'src' to 'dest'.
00239  * \param dest destination format
00240  * \param src source format
00241  * \return the number of translation steps required, or -1 if no path is available
00242  */
00243 unsigned int ast_translate_path_steps(unsigned int dest, unsigned int src);
00244 
00245 /*!
00246  * \brief Mask off unavailable formats from a format bitmask
00247  * \param dest possible destination formats
00248  * \param src source formats
00249  * \return the destination formats that are available in the source or translatable
00250  *
00251  * The result will include all formats from 'dest' that are either present
00252  * in 'src' or translatable from a format present in 'src'.
00253  *
00254  * \note Only a single audio format and a single video format can be
00255  * present in 'src', or the function will produce unexpected results.
00256  */
00257 unsigned int ast_translate_available_formats(unsigned int dest, unsigned int src);
00258 
00259 #if defined(__cplusplus) || defined(c_plusplus)
00260 }
00261 #endif
00262 
00263 #endif /* _ASTERISK_TRANSLATE_H */

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