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Asterisk developer's documentation


abstract_jb.h

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00001 /*
00002  * abstract_jb: common implementation-independent jitterbuffer stuff
00003  *
00004  * Copyright (C) 2005, Attractel OOD
00005  *
00006  * Contributors:
00007  * Slav Klenov <slav@securax.org>
00008  *
00009  * See http://www.asterisk.org for more information about
00010  * the Asterisk project. Please do not directly contact
00011  * any of the maintainers of this project for assistance;
00012  * the project provides a web site, mailing lists and IRC
00013  * channels for your use.
00014  *
00015  * This program is free software, distributed under the terms of
00016  * the GNU General Public License Version 2. See the LICENSE file
00017  * at the top of the source tree.
00018  *
00019  * A license has been granted to Digium (via disclaimer) for the use of
00020  * this code.
00021  */
00022 
00023 /*! \file
00024  *
00025  * \brief Common implementation-independent jitterbuffer stuff.
00026  * 
00027  * \author Slav Klenov <slav@securax.org>
00028  */
00029 
00030 #ifndef _ABSTRACT_JB_H_
00031 #define _ABSTRACT_JB_H_
00032 
00033 #include <sys/time.h>
00034 
00035 #if defined(__cplusplus) || defined(c_plusplus)
00036 extern "C" {
00037 #endif
00038 
00039 struct ast_frame;
00040 
00041 /* Configuration flags */
00042 enum {
00043    AST_JB_ENABLED = (1 << 0),
00044    AST_JB_FORCED =  (1 << 1),
00045    AST_JB_LOG =     (1 << 2)
00046 };
00047 
00048 #define AST_JB_IMPL_NAME_SIZE 12
00049 
00050 /*!
00051  * \brief General jitterbuffer configuration.
00052  */
00053 struct ast_jb_conf
00054 {
00055    /*! \brief Combination of the AST_JB_ENABLED, AST_JB_FORCED and AST_JB_LOG flags. */
00056    unsigned int flags;
00057    /*! \brief Max size of the jitterbuffer implementation. */
00058    long max_size;
00059    /*! \brief Resynchronization threshold of the jitterbuffer implementation. */
00060    long resync_threshold;
00061    /*! \brief Name of the jitterbuffer implementation to be used. */
00062    char impl[AST_JB_IMPL_NAME_SIZE];
00063    /*! \brief amount of additional jitterbuffer adjustment */
00064    long target_extra;
00065 };
00066 
00067 
00068 /* Jitterbuffer configuration property names */
00069 #define AST_JB_CONF_PREFIX "jb"
00070 #define AST_JB_CONF_ENABLE "enable"
00071 #define AST_JB_CONF_FORCE "force"
00072 #define AST_JB_CONF_MAX_SIZE "maxsize"
00073 #define AST_JB_CONF_RESYNCH_THRESHOLD "resyncthreshold"
00074 #define AST_JB_CONF_TARGET_EXTRA "targetextra"
00075 #define AST_JB_CONF_IMPL "impl"
00076 #define AST_JB_CONF_LOG "log"
00077 
00078 
00079 struct ast_jb_impl;
00080 
00081 
00082 /*!
00083  * \brief General jitterbuffer state.
00084  */
00085 struct ast_jb
00086 {
00087    /*! \brief Jitterbuffer configuration. */
00088    struct ast_jb_conf conf;
00089    /*! \brief Jitterbuffer implementation to be used. */
00090    struct ast_jb_impl *impl;
00091    /*! \brief Jitterbuffer object, passed to the implementation. */
00092    void *jbobj;
00093    /*! \brief The time the jitterbuffer was created. */
00094    struct timeval timebase;
00095    /*! \brief The time the next frame should be played. */
00096    long next;
00097    /*! \brief Voice format of the last frame in. */
00098    int last_format;
00099    /*! \brief File for frame timestamp tracing. */
00100    FILE *logfile;
00101    /*! \brief Jitterbuffer internal state flags. */
00102    unsigned int flags;
00103 };
00104 
00105 
00106 /*!
00107  * \brief Checks the need of a jb use in a generic bridge.
00108  * \param c0 first bridged channel.
00109  * \param c1 second bridged channel.
00110  *
00111  * Called from ast_generic_bridge() when two channels are entering in a bridge.
00112  * The function checks the need of a jitterbuffer, depending on both channel's
00113  * configuration and technology properties. As a result, this function sets
00114  * appropriate internal jb flags to the channels, determining further behaviour
00115  * of the bridged jitterbuffers.
00116  *
00117  * \retval zero if there are no jitter buffers in use
00118  * \retval non-zero if there are
00119  */
00120 int ast_jb_do_usecheck(struct ast_channel *c0, struct ast_channel *c1);
00121 
00122 
00123 /*!
00124  * \brief Calculates the time, left to the closest delivery moment in a bridge.
00125  * \param c0 first bridged channel.
00126  * \param c1 second bridged channel.
00127  * \param time_left bridge time limit, or -1 if not set.
00128  *
00129  * Called from ast_generic_bridge() to determine the maximum time to wait for
00130  * activity in ast_waitfor_n() call. If neihter of the channels is using jb,
00131  * this function returns the time limit passed.
00132  *
00133  * \return maximum time to wait.
00134  */
00135 int ast_jb_get_when_to_wakeup(struct ast_channel *c0, struct ast_channel *c1, int time_left);
00136 
00137 
00138 /*!
00139  * \brief Puts a frame into a channel jitterbuffer.
00140  * \param chan channel.
00141  * \param f frame.
00142  *
00143  * Called from ast_generic_bridge() to put a frame into a channel's jitterbuffer.
00144  * The function will successfuly enqueue a frame if and only if:
00145  * 1. the channel is using a jitterbuffer (as determined by ast_jb_do_usecheck()),
00146  * 2. the frame's type is AST_FRAME_VOICE,
00147  * 3. the frame has timing info set and has length >= 2 ms,
00148  * 4. there is no some internal error happened (like failed memory allocation).
00149  * Frames, successfuly queued, should be delivered by the channel's jitterbuffer,
00150  * when their delivery time has came.
00151  * Frames, not successfuly queued, should be delivered immediately.
00152  * Dropped by the jb implementation frames are considered successfuly enqueued as
00153  * far as they should not be delivered at all.
00154  *
00155  * \retval 0 if the frame was queued
00156  * \retval -1 if not
00157  */
00158 int ast_jb_put(struct ast_channel *chan, struct ast_frame *f);
00159 
00160 
00161 /*!
00162  * \brief Deliver the queued frames that should be delivered now for both channels.
00163  * \param c0 first bridged channel.
00164  * \param c1 second bridged channel.
00165  *
00166  * Called from ast_generic_bridge() to deliver any frames, that should be delivered
00167  * for the moment of invocation. Does nothing if neihter of the channels is using jb
00168  * or has any frames currently queued in. The function delivers frames usig ast_write()
00169  * each of the channels.
00170  */
00171 void ast_jb_get_and_deliver(struct ast_channel *c0, struct ast_channel *c1);
00172 
00173 
00174 /*!
00175  * \brief Destroys jitterbuffer on a channel.
00176  * \param chan channel.
00177  *
00178  * Called from ast_channel_free() when a channel is destroyed.
00179  */
00180 void ast_jb_destroy(struct ast_channel *chan);
00181 
00182 
00183 /*!
00184  * \brief Sets jitterbuffer configuration property.
00185  * \param conf configuration to store the property in.
00186  * \param varname property name.
00187  * \param value property value.
00188  *
00189  * Called from a channel driver to build a jitterbuffer configuration typically when
00190  * reading a configuration file. It is not necessary for a channel driver to know
00191  * each of the jb configuration property names. The jitterbuffer itself knows them.
00192  * The channel driver can pass each config var it reads through this function. It will
00193  * return 0 if the variable was consumed from the jb conf.
00194  *
00195  * \return zero if the property was set to the configuration, -1 if not.
00196  */
00197 int ast_jb_read_conf(struct ast_jb_conf *conf, const char *varname, const char *value);
00198 
00199 
00200 /*!
00201  * \brief Configures a jitterbuffer on a channel.
00202  * \param chan channel to configure.
00203  * \param conf configuration to apply.
00204  *
00205  * Called from a channel driver when a channel is created and its jitterbuffer needs
00206  * to be configured.
00207  */
00208 void ast_jb_configure(struct ast_channel *chan, const struct ast_jb_conf *conf);
00209 
00210 
00211 /*!
00212  * \brief Copies a channel's jitterbuffer configuration.
00213  * \param chan channel.
00214  * \param conf destination.
00215  */
00216 void ast_jb_get_config(const struct ast_channel *chan, struct ast_jb_conf *conf);
00217 
00218 /*!
00219  * \brief drops all frames from a jitterbuffer and resets it
00220  * \param c0 one channel of a bridge
00221  * \param c1 the other channel of the bridge
00222  */
00223 void ast_jb_empty_and_reset(struct ast_channel *c0, struct ast_channel *c1);
00224 
00225 #if defined(__cplusplus) || defined(c_plusplus)
00226 }
00227 #endif
00228 
00229 #endif /* _ABSTRACT_JB_H_ */