abstract_jb.h

Go to the documentation of this file.

/*
 * abstract_jb: common implementation-independent jitterbuffer stuff
 *
 * Copyright (C) 2005, Attractel OOD
 *
 * Contributors:
 * Slav Klenov <slav@securax.org>
 *
 * 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.
 *
 * A license has been granted to Digium (via disclaimer) for the use of
 * this code.
 */

/*! \file
 *
 * \brief Common implementation-independent jitterbuffer stuff.
 * 
 * \author Slav Klenov <slav@securax.org>
 */

#ifndef _ABSTRACT_JB_H_
#define _ABSTRACT_JB_H_

#include <sys/time.h>

#include "asterisk/format.h"

#if defined(__cplusplus) || defined(c_plusplus)
extern "C" {
#endif

struct ast_frame;

/* Configuration flags */
enum {
   AST_JB_ENABLED = (1 << 0),
   AST_JB_FORCED =  (1 << 1),
   AST_JB_LOG =     (1 << 2)
};

enum ast_jb_type {
   AST_JB_FIXED,
   AST_JB_ADAPTIVE,
};

/*! Abstract return codes */
enum {
   AST_JB_IMPL_OK,
   AST_JB_IMPL_DROP,
   AST_JB_IMPL_INTERP,
   AST_JB_IMPL_NOFRAME
};

#define AST_JB_IMPL_NAME_SIZE 12

/*!
 * \brief General jitterbuffer configuration.
 */
struct ast_jb_conf
{
   /*! \brief Combination of the AST_JB_ENABLED, AST_JB_FORCED and AST_JB_LOG flags. */
   unsigned int flags;
   /*! \brief Max size of the jitterbuffer implementation. */
   long max_size;
   /*! \brief Resynchronization threshold of the jitterbuffer implementation. */
   long resync_threshold;
   /*! \brief Name of the jitterbuffer implementation to be used. */
   char impl[AST_JB_IMPL_NAME_SIZE];
   /*! \brief amount of additional jitterbuffer adjustment */
   long target_extra;
};


/* Jitterbuffer configuration property names */
#define AST_JB_CONF_PREFIX "jb"
#define AST_JB_CONF_ENABLE "enable"
#define AST_JB_CONF_FORCE "force"
#define AST_JB_CONF_MAX_SIZE "maxsize"
#define AST_JB_CONF_RESYNCH_THRESHOLD "resyncthreshold"
#define AST_JB_CONF_TARGET_EXTRA "targetextra"
#define AST_JB_CONF_IMPL "impl"
#define AST_JB_CONF_LOG "log"

/* Hooks for the abstract jb implementation */
/*! \brief Create */
typedef void * (*jb_create_impl)(struct ast_jb_conf *general_config);
/*! \brief Destroy */
typedef void (*jb_destroy_impl)(void *jb);
/*! \brief Put first frame */
typedef int (*jb_put_first_impl)(void *jb, struct ast_frame *fin, long now);
/*! \brief Put frame */
typedef int (*jb_put_impl)(void *jb, struct ast_frame *fin, long now);
/*! \brief Get frame for now */
typedef int (*jb_get_impl)(void *jb, struct ast_frame **fout, long now, long interpl);
/*! \brief Get next */
typedef long (*jb_next_impl)(void *jb);
/*! \brief Remove first frame */
typedef int (*jb_remove_impl)(void *jb, struct ast_frame **fout);
/*! \brief Force resynch */
typedef void (*jb_force_resynch_impl)(void *jb);
/*! \brief Empty and reset jb */
typedef void (*jb_empty_and_reset_impl)(void *jb);


/*!
 * \brief Jitterbuffer implementation struct.
 */
struct ast_jb_impl
{
   char name[AST_JB_IMPL_NAME_SIZE];
   enum ast_jb_type type;
   jb_create_impl create;
   jb_destroy_impl destroy;
   jb_put_first_impl put_first;
   jb_put_impl put;
   jb_get_impl get;
   jb_next_impl next;
   jb_remove_impl remove;
   jb_force_resynch_impl force_resync;
   jb_empty_and_reset_impl empty_and_reset;
};

/*!
 * \brief General jitterbuffer state.
 */
struct ast_jb
{
   /*! \brief Jitterbuffer configuration. */
   struct ast_jb_conf conf;
   /*! \brief Jitterbuffer implementation to be used. */
   const struct ast_jb_impl *impl;
   /*! \brief Jitterbuffer object, passed to the implementation. */
   void *jbobj;
   /*! \brief The time the jitterbuffer was created. */
   struct timeval timebase;
   /*! \brief The time the next frame should be played. */
   long next;
   /*! \brief Voice format of the last frame in. */
   struct ast_format last_format;
   /*! \brief File for frame timestamp tracing. */
   FILE *logfile;
   /*! \brief Jitterbuffer internal state flags. */
   unsigned int flags;
};


/*!
 * \brief Checks the need of a jb use in a generic bridge.
 * \param c0 first bridged channel.
 * \param c1 second bridged channel.
 *
 * Called from ast_generic_bridge() when two channels are entering in a bridge.
 * The function checks the need of a jitterbuffer, depending on both channel's
 * configuration and technology properties. As a result, this function sets
 * appropriate internal jb flags to the channels, determining further behaviour
 * of the bridged jitterbuffers.
 *
 * \retval zero if there are no jitter buffers in use
 * \retval non-zero if there are
 */
int ast_jb_do_usecheck(struct ast_channel *c0, struct ast_channel *c1);


/*!
 * \brief Calculates the time, left to the closest delivery moment in a bridge.
 * \param c0 first bridged channel.
 * \param c1 second bridged channel.
 * \param time_left bridge time limit, or -1 if not set.
 *
 * Called from ast_generic_bridge() to determine the maximum time to wait for
 * activity in ast_waitfor_n() call. If neihter of the channels is using jb,
 * this function returns the time limit passed.
 *
 * \return maximum time to wait.
 */
int ast_jb_get_when_to_wakeup(struct ast_channel *c0, struct ast_channel *c1, int time_left);


/*!
 * \brief Puts a frame into a channel jitterbuffer.
 * \param chan channel.
 * \param f frame.
 *
 * Called from ast_generic_bridge() to put a frame into a channel's jitterbuffer.
 * The function will successfuly enqueue a frame if and only if:
 * 1. the channel is using a jitterbuffer (as determined by ast_jb_do_usecheck()),
 * 2. the frame's type is AST_FRAME_VOICE,
 * 3. the frame has timing info set and has length >= 2 ms,
 * 4. there is no some internal error happened (like failed memory allocation).
 * Frames, successfuly queued, should be delivered by the channel's jitterbuffer,
 * when their delivery time has came.
 * Frames, not successfuly queued, should be delivered immediately.
 * Dropped by the jb implementation frames are considered successfuly enqueued as
 * far as they should not be delivered at all.
 *
 * \retval 0 if the frame was queued
 * \retval -1 if not
 */
int ast_jb_put(struct ast_channel *chan, struct ast_frame *f);


/*!
 * \brief Deliver the queued frames that should be delivered now for both channels.
 * \param c0 first bridged channel.
 * \param c1 second bridged channel.
 *
 * Called from ast_generic_bridge() to deliver any frames, that should be delivered
 * for the moment of invocation. Does nothing if neihter of the channels is using jb
 * or has any frames currently queued in. The function delivers frames usig ast_write()
 * each of the channels.
 */
void ast_jb_get_and_deliver(struct ast_channel *c0, struct ast_channel *c1);


/*!
 * \brief Destroys jitterbuffer on a channel.
 * \param chan channel.
 *
 * Called from ast_channel_free() when a channel is destroyed.
 */
void ast_jb_destroy(struct ast_channel *chan);


/*!
 * \brief Sets jitterbuffer configuration property.
 * \param conf configuration to store the property in.
 * \param varname property name.
 * \param value property value.
 *
 * Called from a channel driver to build a jitterbuffer configuration typically when
 * reading a configuration file. It is not necessary for a channel driver to know
 * each of the jb configuration property names. The jitterbuffer itself knows them.
 * The channel driver can pass each config var it reads through this function. It will
 * return 0 if the variable was consumed from the jb conf.
 *
 * \return zero if the property was set to the configuration, -1 if not.
 */
int ast_jb_read_conf(struct ast_jb_conf *conf, const char *varname, const char *value);


/*!
 * \brief Configures a jitterbuffer on a channel.
 * \param chan channel to configure.
 * \param conf configuration to apply.
 *
 * Called from a channel driver when a channel is created and its jitterbuffer needs
 * to be configured.
 */
void ast_jb_configure(struct ast_channel *chan, const struct ast_jb_conf *conf);


/*!
 * \brief Copies a channel's jitterbuffer configuration.
 * \param chan channel.
 * \param conf destination.
 */
void ast_jb_get_config(const struct ast_channel *chan, struct ast_jb_conf *conf);

/*!
 * \brief drops all frames from a jitterbuffer and resets it
 * \param c0 one channel of a bridge
 * \param c1 the other channel of the bridge
 */
void ast_jb_empty_and_reset(struct ast_channel *c0, struct ast_channel *c1);

const struct ast_jb_impl *ast_jb_get_impl(enum ast_jb_type type);

#if defined(__cplusplus) || defined(c_plusplus)
}
#endif

#endif /* _ABSTRACT_JB_H_ */