bridging.h

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 2007 - 2009, Digium, Inc.
 *
 * Joshua Colp <jcolp@digium.com>
 *
 * 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.
 */

/*! \file
 * \brief Channel Bridging API
 * \author Joshua Colp <jcolp@digium.com>
 * \ref AstBridging
 */

/*!
 * \page AstBridging Channel Bridging API
 *
 * The purpose of this API is to provide an easy and flexible way to bridge
 * channels of different technologies with different features.
 *
 * Bridging technologies provide the mechanism that do the actual handling
 * of frames between channels. They provide capability information, codec information,
 * and preference value to assist the bridging core in choosing a bridging technology when
 * creating a bridge. Different bridges may use different bridging technologies based on needs
 * but once chosen they all operate under the same premise; they receive frames and send frames.
 *
 * Bridges are a combination of bridging technology, channels, and features. A
 * developer creates a new bridge based on what they are currently expecting to do
 * with it or what they will do with it in the future. The bridging core determines what
 * available bridging technology will best fit the requirements and creates a new bridge.
 * Once created, channels can be added to the bridge in a blocking or non-blocking fashion.
 *
 * Features are such things as channel muting or DTMF based features such as attended transfer,
 * blind transfer, and hangup. Feature information must be set at the most granular level, on
 * the channel. While you can use features on a global scope the presence of a feature structure
 * on the channel will override the global scope. An example would be having the bridge muted
 * at global scope and attended transfer enabled on a channel. Since the channel itself is not muted
 * it would be able to speak.
 *
 * Feature hooks allow a developer to tell the bridging core that when a DTMF string
 * is received from a channel a callback should be called in their application. For
 * example, a conference bridge application may want to provide an IVR to control various
 * settings on the conference bridge. This can be accomplished by attaching a feature hook
 * that calls an IVR function when a DTMF string is entered.
 *
 */

#ifndef _ASTERISK_BRIDGING_H
#define _ASTERISK_BRIDGING_H

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

#include "asterisk/bridging_features.h"
#include "asterisk/dsp.h"

/*! \brief Capabilities for a bridge technology */
enum ast_bridge_capability {
   /*! Bridge is only capable of mixing 2 channels */
   AST_BRIDGE_CAPABILITY_1TO1MIX = (1 << 1),
   /*! Bridge is capable of mixing 2 or more channels */
   AST_BRIDGE_CAPABILITY_MULTIMIX = (1 << 2),
   /*! Bridge should natively bridge two channels if possible */
   AST_BRIDGE_CAPABILITY_NATIVE = (1 << 3),
   /*! Bridge should run using the multithreaded model */
   AST_BRIDGE_CAPABILITY_MULTITHREADED = (1 << 4),
   /*! Bridge should run a central bridge thread */
   AST_BRIDGE_CAPABILITY_THREAD = (1 << 5),
   /*! Bridge technology can do video mixing (or something along those lines) */
   AST_BRIDGE_CAPABILITY_VIDEO = (1 << 6),
   /*! Bridge technology can optimize things based on who is talking */
   AST_BRIDGE_CAPABILITY_OPTIMIZE = (1 << 7),
};

/*! \brief State information about a bridged channel */
enum ast_bridge_channel_state {
   /*! Waiting for a signal */
   AST_BRIDGE_CHANNEL_STATE_WAIT = 0,
   /*! Bridged channel has ended itself (it has hung up) */
   AST_BRIDGE_CHANNEL_STATE_END,
   /*! Bridged channel should be hung up */
   AST_BRIDGE_CHANNEL_STATE_HANGUP,
   /*! Bridged channel should be removed from the bridge without being hung up */
   AST_BRIDGE_CHANNEL_STATE_DEPART,
   /*! Bridged channel is executing a feature hook */
   AST_BRIDGE_CHANNEL_STATE_FEATURE,
   /*! Bridged channel is sending a DTMF stream out */
   AST_BRIDGE_CHANNEL_STATE_DTMF,
   /*! Bridged channel began talking */
   AST_BRIDGE_CHANNEL_STATE_START_TALKING,
   /*! Bridged channel has stopped talking */
   AST_BRIDGE_CHANNEL_STATE_STOP_TALKING,
};

/*! \brief Return values for bridge technology write function */
enum ast_bridge_write_result {
   /*! Bridge technology wrote out frame fine */
   AST_BRIDGE_WRITE_SUCCESS = 0,
   /*! Bridge technology attempted to write out the frame but failed */
   AST_BRIDGE_WRITE_FAILED,
   /*! Bridge technology does not support writing out a frame of this type */
   AST_BRIDGE_WRITE_UNSUPPORTED,
};

struct ast_bridge_technology;
struct ast_bridge;

/*!
 * \brief Structure specific to bridge technologies capable of
 * performing talking optimizations.
 */
struct ast_bridge_tech_optimizations {
   /*! The amount of time in ms that talking must be detected before
    *  the dsp determines that talking has occurred */
   unsigned int talking_threshold;
   /*! The amount of time in ms that silence must be detected before
    *  the dsp determines that talking has stopped */
   unsigned int silence_threshold;
   /*! Whether or not the bridging technology should drop audio
    *  detected as silence from the mix. */
   unsigned int drop_silence:1;
};

/*!
 * \brief Structure that contains information regarding a channel in a bridge
 */
struct ast_bridge_channel {
   /*! Lock to protect this data structure */
   ast_mutex_t lock;
   /*! Condition, used if we want to wake up a thread waiting on the bridged channel */
   ast_cond_t cond;
   /*! Current bridged channel state */
   enum ast_bridge_channel_state state;
   /*! Asterisk channel participating in the bridge */
   struct ast_channel *chan;
   /*! Asterisk channel we are swapping with (if swapping) */
   struct ast_channel *swap;
   /*! Bridge this channel is participating in */
   struct ast_bridge *bridge;
   /*! Private information unique to the bridge technology */
   void *bridge_pvt;
   /*! Thread handling the bridged channel */
   pthread_t thread;
   /*! Additional file descriptors to look at */
   int fds[4];
   /*! Bit to indicate whether the channel is suspended from the bridge or not */
   unsigned int suspended:1;
   /*! Bit to indicate if a imparted channel is allowed to get hungup after leaving the bridge by the bridging core. */
   unsigned int allow_impart_hangup:1;
   /*! Features structure for features that are specific to this channel */
   struct ast_bridge_features *features;
   /*! Technology optimization parameters used by bridging technologies capable of
    *  optimizing based upon talk detection. */
   struct ast_bridge_tech_optimizations tech_args;
   /*! Queue of DTMF digits used for DTMF streaming */
   char dtmf_stream_q[8];
   /*! Call ID associated with bridge channel */
   struct ast_callid *callid;
   /*! Linked list information */
   AST_LIST_ENTRY(ast_bridge_channel) entry;
};

enum ast_bridge_video_mode_type {
   /*! Video is not allowed in the bridge */
   AST_BRIDGE_VIDEO_MODE_NONE = 0,
   /*! A single user is picked as the only distributed of video across the bridge */
   AST_BRIDGE_VIDEO_MODE_SINGLE_SRC,
   /*! A single user's video feed is distributed to all bridge channels, but
    *  that feed is automatically picked based on who is talking the most. */
   AST_BRIDGE_VIDEO_MODE_TALKER_SRC,
};

/*! This is used for both SINGLE_SRC mode to set what channel
 *  should be the current single video feed */
struct ast_bridge_video_single_src_data {
   /*! Only accept video coming from this channel */
   struct ast_channel *chan_vsrc;
};

/*! This is used for both SINGLE_SRC_TALKER mode to set what channel
 *  should be the current single video feed */
struct ast_bridge_video_talker_src_data {
   /*! Only accept video coming from this channel */
   struct ast_channel *chan_vsrc;
   int average_talking_energy;

   /*! Current talker see's this person */
   struct ast_channel *chan_old_vsrc;
};

struct ast_bridge_video_mode {
   enum ast_bridge_video_mode_type mode;
   /* Add data for all the video modes here. */
   union {
      struct ast_bridge_video_single_src_data single_src_data;
      struct ast_bridge_video_talker_src_data talker_src_data;
   } mode_data;
};

/*!
 * \brief Structure that contains information about a bridge
 */
struct ast_bridge {
   /*! Number of channels participating in the bridge */
   int num;
   /*! The video mode this bridge is using */
   struct ast_bridge_video_mode video_mode;
   /*! The internal sample rate this bridge is mixed at when multiple channels are being mixed.
    *  If this value is 0, the bridge technology may auto adjust the internal mixing rate. */
   unsigned int internal_sample_rate;
   /*! The mixing interval indicates how quickly the bridges internal mixing should occur
    * for bridge technologies that mix audio. When set to 0, the bridge tech must choose a
    * default interval for itself. */
   unsigned int internal_mixing_interval;
   /*! Bit to indicate that the bridge thread is waiting on channels in the bridge array */
   unsigned int waiting:1;
   /*! Bit to indicate the bridge thread should stop */
   unsigned int stop:1;
   /*! Bit to indicate the bridge thread should refresh itself */
   unsigned int refresh:1;
   /*! Bridge flags to tweak behavior */
   struct ast_flags feature_flags;
   /*! Bridge technology that is handling the bridge */
   struct ast_bridge_technology *technology;
   /*! Private information unique to the bridge technology */
   void *bridge_pvt;
   /*! Thread running the bridge */
   pthread_t thread;
   /*! Enabled features information */
   struct ast_bridge_features features;
   /*! Array of channels that the bridge thread is currently handling */
   struct ast_channel **array;
   /*! Number of channels in the above array */
   size_t array_num;
   /*! Number of channels the array can handle */
   size_t array_size;
   /*! Call ID associated with the bridge */
   struct ast_callid *callid;
   /*! Linked list of channels participating in the bridge */
   AST_LIST_HEAD_NOLOCK(, ast_bridge_channel) channels;
   };

/*! \brief Create a new bridge
 *
 * \param capabilities The capabilities that we require to be used on the bridge
 * \param flags Flags that will alter the behavior of the bridge
 *
 * \retval a pointer to a new bridge on success
 * \retval NULL on failure
 *
 * Example usage:
 *
 * \code
 * struct ast_bridge *bridge;
 * bridge = ast_bridge_new(AST_BRIDGE_CAPABILITY_1TO1MIX, AST_BRIDGE_FLAG_DISSOLVE);
 * \endcode
 *
 * This creates a simple two party bridge that will be destroyed once one of
 * the channels hangs up.
 */
struct ast_bridge *ast_bridge_new(uint32_t capabilities, int flags);

/*! \brief See if it is possible to create a bridge
 *
 * \param capabilities The capabilities that the bridge will use
 *
 * \retval 1 if possible
 * \retval 0 if not possible
 *
 * Example usage:
 *
 * \code
 * int possible = ast_bridge_check(AST_BRIDGE_CAPABILITY_1TO1MIX);
 * \endcode
 *
 * This sees if it is possible to create a bridge capable of bridging two channels
 * together.
 */
int ast_bridge_check(uint32_t capabilities);

/*! \brief Destroy a bridge
 *
 * \param bridge Bridge to destroy
 *
 * \retval 0 on success
 * \retval -1 on failure
 *
 * Example usage:
 *
 * \code
 * ast_bridge_destroy(bridge);
 * \endcode
 *
 * This destroys a bridge that was previously created using ast_bridge_new.
 */
int ast_bridge_destroy(struct ast_bridge *bridge);

/*! \brief Join (blocking) a channel to a bridge
 *
 * \param bridge Bridge to join
 * \param chan Channel to join
 * \param swap Channel to swap out if swapping
 * \param features Bridge features structure
 * \param (Optional) Bridging tech optimization parameters for this channel.
 *
 * \retval state that channel exited the bridge with
 *
 * Example usage:
 *
 * \code
 * ast_bridge_join(bridge, chan, NULL, NULL);
 * \endcode
 *
 * This adds a channel pointed to by the chan pointer to the bridge pointed to by
 * the bridge pointer. This function will not return until the channel has been
 * removed from the bridge, swapped out for another channel, or has hung up.
 *
 * If this channel will be replacing another channel the other channel can be specified
 * in the swap parameter. The other channel will be thrown out of the bridge in an
 * atomic fashion.
 *
 * If channel specific features are enabled a pointer to the features structure
 * can be specified in the features parameter.
 */
enum ast_bridge_channel_state ast_bridge_join(struct ast_bridge *bridge,
   struct ast_channel *chan,
   struct ast_channel *swap,
   struct ast_bridge_features *features,
   struct ast_bridge_tech_optimizations *tech_args);

/*! \brief Impart (non-blocking) a channel on a bridge
 *
 * \param bridge Bridge to impart on
 * \param chan Channel to impart
 * \param swap Channel to swap out if swapping
 * \param features Bridge features structure
 * \param allow_hangup  Indicates if the bridge thread should manage hanging up of the channel or not.
 *
 * \retval 0 on success
 * \retval -1 on failure
 *
 * Example usage:
 *
 * \code
 * ast_bridge_impart(bridge, chan, NULL, NULL, 0);
 * \endcode
 *
 * This adds a channel pointed to by the chan pointer to the bridge pointed to by
 * the bridge pointer. This function will return immediately and will not wait
 * until the channel is no longer part of the bridge.
 *
 * If this channel will be replacing another channel the other channel can be specified
 * in the swap parameter. The other channel will be thrown out of the bridge in an
 * atomic fashion.
 *
 * If channel specific features are enabled a pointer to the features structure
 * can be specified in the features parameter.
 */
int ast_bridge_impart(struct ast_bridge *bridge, struct ast_channel *chan, struct ast_channel *swap, struct ast_bridge_features *features, int allow_hangup);

/*! \brief Depart a channel from a bridge
 *
 * \param bridge Bridge to depart from
 * \param chan Channel to depart
 *
 * \retval 0 on success
 * \retval -1 on failure
 *
 * Example usage:
 *
 * \code
 * ast_bridge_depart(bridge, chan);
 * \endcode
 *
 * This removes the channel pointed to by the chan pointer from the bridge
 * pointed to by the bridge pointer and gives control to the calling thread.
 * This does not hang up the channel.
 *
 * \note This API call can only be used on channels that were added to the bridge
 *       using the ast_bridge_impart API call.
 */
int ast_bridge_depart(struct ast_bridge *bridge, struct ast_channel *chan);

/*! \brief Remove a channel from a bridge
 *
 * \param bridge Bridge that the channel is to be removed from
 * \param chan Channel to remove
 *
 * \retval 0 on success
 * \retval -1 on failure
 *
 * Example usage:
 *
 * \code
 * ast_bridge_remove(bridge, chan);
 * \endcode
 *
 * This removes the channel pointed to by the chan pointer from the bridge
 * pointed to by the bridge pointer and requests that it be hung up. Control
 * over the channel will NOT be given to the calling thread.
 *
 * \note This API call can be used on channels that were added to the bridge
 *       using both ast_bridge_join and ast_bridge_impart.
 */
int ast_bridge_remove(struct ast_bridge *bridge, struct ast_channel *chan);

/*! \brief Merge two bridges together
 *
 * \param bridge0 First bridge
 * \param bridge1 Second bridge
 *
 * \retval 0 on success
 * \retval -1 on failure
 *
 * Example usage:
 *
 * \code
 * ast_bridge_merge(bridge0, bridge1);
 * \endcode
 *
 * This merges the bridge pointed to by bridge1 with the bridge pointed to by bridge0.
 * In reality all of the channels in bridge1 are simply moved to bridge0.
 *
 * \note The second bridge specified is not destroyed when this operation is
 *       completed.
 */
int ast_bridge_merge(struct ast_bridge *bridge0, struct ast_bridge *bridge1);

/*! \brief Suspend a channel temporarily from a bridge
 *
 * \param bridge Bridge to suspend the channel from
 * \param chan Channel to suspend
 *
 * \retval 0 on success
 * \retval -1 on failure
 *
 * Example usage:
 *
 * \code
 * ast_bridge_suspend(bridge, chan);
 * \endcode
 *
 * This suspends the channel pointed to by chan from the bridge pointed to by bridge temporarily.
 * Control of the channel is given to the calling thread. This differs from ast_bridge_depart as
 * the channel will not be removed from the bridge.
 *
 * \note This API call can be used on channels that were added to the bridge
 *       using both ast_bridge_join and ast_bridge_impart.
 */
int ast_bridge_suspend(struct ast_bridge *bridge, struct ast_channel *chan);

/*! \brief Unsuspend a channel from a bridge
 *
 * \param bridge Bridge to unsuspend the channel from
 * \param chan Channel to unsuspend
 *
 * \retval 0 on success
 * \retval -1 on failure
 *
 * Example usage:
 *
 * \code
 * ast_bridge_unsuspend(bridge, chan);
 * \endcode
 *
 * This unsuspends the channel pointed to by chan from the bridge pointed to by bridge.
 * The bridge will go back to handling the channel once this function returns.
 *
 * \note You must not mess with the channel once this function returns.
 *       Doing so may result in bad things happening.
 */
int ast_bridge_unsuspend(struct ast_bridge *bridge, struct ast_channel *chan);

/*! \brief Change the state of a bridged channel
 *
 * \param bridge_channel Channel to change the state on
 * \param new_state The new state to place the channel into
 *
 * Example usage:
 *
 * \code
 * ast_bridge_change_state(bridge_channel, AST_BRIDGE_CHANNEL_STATE_WAIT);
 * \endcode
 *
 * This places the channel pointed to by bridge_channel into the state
 * AST_BRIDGE_CHANNEL_STATE_WAIT.
 *
 * \note This API call is only meant to be used in feature hook callbacks to
 *       make sure the channel either hangs up or returns to the bridge.
 */
void ast_bridge_change_state(struct ast_bridge_channel *bridge_channel, enum ast_bridge_channel_state new_state);

/*! \brief Adjust the internal mixing sample rate of a bridge used during
 *         multimix mode.
 *
 * \param bridge_channel Channel to change the sample rate on.
 * \param sample rate, the sample rate to change to. If a
 *        value of 0 is passed here, the bridge will be free to pick
 *        what ever sample rate it chooses.
 *
 */
void ast_bridge_set_internal_sample_rate(struct ast_bridge *bridge, unsigned int sample_rate);

/*! \brief Adjust the internal mixing interval of a bridge used during
 *         multimix mode.
 *
 * \param bridge_channel Channel to change the sample rate on.
 * \param mixing_interval, the sample rate to change to.  If 0 is set
 * the bridge tech is free to choose any mixing interval it uses by default.
 */
void ast_bridge_set_mixing_interval(struct ast_bridge *bridge, unsigned int mixing_interval);

/*!
 * \brief Set a bridge to feed a single video source to all participants.
 */
void ast_bridge_set_single_src_video_mode(struct ast_bridge *bridge, struct ast_channel *video_src_chan);

/*!
 * \brief Set the bridge to pick the strongest talker supporting
 * video as the single source video feed
 */
void ast_bridge_set_talker_src_video_mode(struct ast_bridge *bridge);

/*!
 * \brief Update information about talker energy for talker src video mode.
 */
void ast_bridge_update_talker_src_video_mode(struct ast_bridge *bridge, struct ast_channel *chan, int talker_energy, int is_keyfame);

/*!
 * \brief Returns the number of video sources currently active in the bridge
 */
int ast_bridge_number_video_src(struct ast_bridge *bridge);

/*!
 * \brief Determine if a channel is a video src for the bridge
 *
 * \retval 0 Not a current video source of the bridge.
 * \retval None 0, is a video source of the bridge, The number
 *         returned represents the priority this video stream has
 *         on the bridge where 1 is the highest priority.
 */
int ast_bridge_is_video_src(struct ast_bridge *bridge, struct ast_channel *chan);

/*!
 * \brief remove a channel as a source of video for the bridge.
 */
void ast_bridge_remove_video_src(struct ast_bridge *bridge, struct ast_channel *chan);

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

#endif /* _ASTERISK_BRIDGING_H */