Mon Oct 8 12:38:58 2012

Asterisk developer's documentation


bridge_softmix.c

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00001 /*
00002  * Asterisk -- An open source telephony toolkit.
00003  *
00004  * Copyright (C) 2007, Digium, Inc.
00005  *
00006  * Joshua Colp <jcolp@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  *
00021  * \brief Multi-party software based channel mixing
00022  *
00023  * \author Joshua Colp <jcolp@digium.com>
00024  *
00025  * \ingroup bridges
00026  *
00027  * \todo This bridge operates in 8 kHz mode unless a define is uncommented.
00028  * This needs to be improved so the bridge moves between the dominant codec as needed depending
00029  * on channels present in the bridge and transcoding capabilities.
00030  */
00031 
00032 /*** MODULEINFO
00033    <support_level>core</support_level>
00034  ***/
00035 
00036 #include "asterisk.h"
00037 
00038 ASTERISK_FILE_VERSION(__FILE__, "$Revision: 328209 $")
00039 
00040 #include <stdio.h>
00041 #include <stdlib.h>
00042 #include <string.h>
00043 #include <sys/time.h>
00044 #include <signal.h>
00045 #include <errno.h>
00046 #include <unistd.h>
00047 
00048 #include "asterisk/module.h"
00049 #include "asterisk/channel.h"
00050 #include "asterisk/bridging.h"
00051 #include "asterisk/bridging_technology.h"
00052 #include "asterisk/frame.h"
00053 #include "asterisk/options.h"
00054 #include "asterisk/logger.h"
00055 #include "asterisk/slinfactory.h"
00056 #include "asterisk/astobj2.h"
00057 #include "asterisk/timing.h"
00058 
00059 /*! \brief Interval at which mixing will take place. Valid options are 10, 20, and 40. */
00060 #define SOFTMIX_INTERVAL 20
00061 
00062 /*! \brief Size of the buffer used for sample manipulation */
00063 #define SOFTMIX_DATALEN (160 * (SOFTMIX_INTERVAL / 10))
00064 
00065 /*! \brief Number of samples we are dealing with */
00066 #define SOFTMIX_SAMPLES (SOFTMIX_DATALEN / 2)
00067 
00068 /*! \brief Define used to turn on 16 kHz audio support */
00069 /* #define SOFTMIX_16_SUPPORT */
00070 
00071 /*! \brief Structure which contains per-channel mixing information */
00072 struct softmix_channel {
00073    /*! Lock to protect this structure */
00074    ast_mutex_t lock;
00075    /*! Factory which contains audio read in from the channel */
00076    struct ast_slinfactory factory;
00077    /*! Frame that contains mixed audio to be written out to the channel */
00078    struct ast_frame frame;
00079    /*! Bit used to indicate that the channel provided audio for this mixing interval */
00080    int have_audio:1;
00081    /*! Bit used to indicate that a frame is available to be written out to the channel */
00082    int have_frame:1;
00083    /*! Buffer containing final mixed audio from all sources */
00084    short final_buf[SOFTMIX_DATALEN];
00085    /*! Buffer containing only the audio from the channel */
00086    short our_buf[SOFTMIX_DATALEN];
00087 };
00088 
00089 /*! \brief Function called when a bridge is created */
00090 static int softmix_bridge_create(struct ast_bridge *bridge)
00091 {
00092    struct ast_timer *timer;
00093 
00094    if (!(timer = ast_timer_open())) {
00095       return -1;
00096    }
00097 
00098    bridge->bridge_pvt = timer;
00099 
00100    return 0;
00101 }
00102 
00103 /*! \brief Function called when a bridge is destroyed */
00104 static int softmix_bridge_destroy(struct ast_bridge *bridge)
00105 {
00106    if (!bridge->bridge_pvt) {
00107       return -1;
00108    }
00109    ast_timer_close((struct ast_timer *) bridge->bridge_pvt);
00110 
00111    return 0;
00112 }
00113 
00114 /*! \brief Function called when a channel is joined into the bridge */
00115 static int softmix_bridge_join(struct ast_bridge *bridge, struct ast_bridge_channel *bridge_channel)
00116 {
00117    struct softmix_channel *sc = NULL;
00118 
00119    /* Create a new softmix_channel structure and allocate various things on it */
00120    if (!(sc = ast_calloc(1, sizeof(*sc)))) {
00121       return -1;
00122    }
00123 
00124    /* Can't forget the lock */
00125    ast_mutex_init(&sc->lock);
00126 
00127    /* Setup smoother */
00128    ast_slinfactory_init(&sc->factory);
00129 
00130    /* Setup frame parameters */
00131    sc->frame.frametype = AST_FRAME_VOICE;
00132 #ifdef SOFTMIX_16_SUPPORT
00133    sc->frame.subclass.codec = AST_FORMAT_SLINEAR16;
00134 #else
00135    sc->frame.subclass.codec = AST_FORMAT_SLINEAR;
00136 #endif
00137    sc->frame.data.ptr = sc->final_buf;
00138    sc->frame.datalen = SOFTMIX_DATALEN;
00139    sc->frame.samples = SOFTMIX_SAMPLES;
00140 
00141    /* Can't forget to record our pvt structure within the bridged channel structure */
00142    bridge_channel->bridge_pvt = sc;
00143 
00144    return 0;
00145 }
00146 
00147 /*! \brief Function called when a channel leaves the bridge */
00148 static int softmix_bridge_leave(struct ast_bridge *bridge, struct ast_bridge_channel *bridge_channel)
00149 {
00150    struct softmix_channel *sc = bridge_channel->bridge_pvt;
00151 
00152    /* Drop mutex lock */
00153    ast_mutex_destroy(&sc->lock);
00154 
00155    /* Drop the factory */
00156    ast_slinfactory_destroy(&sc->factory);
00157 
00158    /* Eep! drop ourselves */
00159    ast_free(sc);
00160 
00161    return 0;
00162 }
00163 
00164 /*! \brief Function called when a channel writes a frame into the bridge */
00165 static enum ast_bridge_write_result softmix_bridge_write(struct ast_bridge *bridge, struct ast_bridge_channel *bridge_channel, struct ast_frame *frame)
00166 {
00167    struct softmix_channel *sc = bridge_channel->bridge_pvt;
00168 
00169    /* Only accept audio frames, all others are unsupported */
00170    if (frame->frametype != AST_FRAME_VOICE) {
00171       return AST_BRIDGE_WRITE_UNSUPPORTED;
00172    }
00173 
00174    ast_mutex_lock(&sc->lock);
00175 
00176    /* If a frame was provided add it to the smoother */
00177 #ifdef SOFTMIX_16_SUPPORT
00178    if (frame->frametype == AST_FRAME_VOICE && frame->subclass.codec == AST_FORMAT_SLINEAR16) {
00179 #else
00180    if (frame->frametype == AST_FRAME_VOICE && frame->subclass.codec == AST_FORMAT_SLINEAR) {
00181 #endif
00182       ast_slinfactory_feed(&sc->factory, frame);
00183    }
00184 
00185    /* If a frame is ready to be written out, do so */
00186    if (sc->have_frame) {
00187       ast_write(bridge_channel->chan, &sc->frame);
00188       sc->have_frame = 0;
00189    }
00190 
00191    /* Alllll done */
00192    ast_mutex_unlock(&sc->lock);
00193 
00194    return AST_BRIDGE_WRITE_SUCCESS;
00195 }
00196 
00197 /*! \brief Function called when the channel's thread is poked */
00198 static int softmix_bridge_poke(struct ast_bridge *bridge, struct ast_bridge_channel *bridge_channel)
00199 {
00200    struct softmix_channel *sc = bridge_channel->bridge_pvt;
00201 
00202    ast_mutex_lock(&sc->lock);
00203 
00204    if (sc->have_frame) {
00205       ast_write(bridge_channel->chan, &sc->frame);
00206       sc->have_frame = 0;
00207    }
00208 
00209    ast_mutex_unlock(&sc->lock);
00210 
00211    return 0;
00212 }
00213 
00214 /*! \brief Function which acts as the mixing thread */
00215 static int softmix_bridge_thread(struct ast_bridge *bridge)
00216 {
00217    struct ast_timer *timer = (struct ast_timer *) bridge->bridge_pvt;
00218    int timingfd = ast_timer_fd(timer);
00219 
00220    ast_timer_set_rate(timer, (1000 / SOFTMIX_INTERVAL));
00221 
00222    while (!bridge->stop && !bridge->refresh && bridge->array_num) {
00223       struct ast_bridge_channel *bridge_channel = NULL;
00224       short buf[SOFTMIX_DATALEN] = {0, };
00225       int timeout = -1;
00226 
00227       /* Go through pulling audio from each factory that has it available */
00228       AST_LIST_TRAVERSE(&bridge->channels, bridge_channel, entry) {
00229          struct softmix_channel *sc = bridge_channel->bridge_pvt;
00230 
00231          ast_mutex_lock(&sc->lock);
00232 
00233          /* Try to get audio from the factory if available */
00234          if (ast_slinfactory_available(&sc->factory) >= SOFTMIX_SAMPLES && ast_slinfactory_read(&sc->factory, sc->our_buf, SOFTMIX_SAMPLES)) {
00235             short *data1, *data2;
00236             int i;
00237 
00238             /* Put into the local final buffer */
00239             for (i = 0, data1 = buf, data2 = sc->our_buf; i < SOFTMIX_DATALEN; i++, data1++, data2++)
00240                ast_slinear_saturated_add(data1, data2);
00241             /* Yay we have our own audio */
00242             sc->have_audio = 1;
00243          } else {
00244             /* Awww we don't have audio ;( */
00245             sc->have_audio = 0;
00246          }
00247          ast_mutex_unlock(&sc->lock);
00248       }
00249 
00250       /* Next step go through removing the channel's own audio and creating a good frame... */
00251       AST_LIST_TRAVERSE(&bridge->channels, bridge_channel, entry) {
00252          struct softmix_channel *sc = bridge_channel->bridge_pvt;
00253          int i = 0;
00254 
00255          /* Copy from local final buffer to our final buffer */
00256          memcpy(sc->final_buf, buf, sizeof(sc->final_buf));
00257 
00258          /* If we provided audio then take it out */
00259          if (sc->have_audio) {
00260             for (i = 0; i < SOFTMIX_DATALEN; i++) {
00261                ast_slinear_saturated_subtract(&sc->final_buf[i], &sc->our_buf[i]);
00262             }
00263          }
00264 
00265          /* The frame is now ready for use... */
00266          sc->have_frame = 1;
00267 
00268          /* Poke bridged channel thread just in case */
00269          pthread_kill(bridge_channel->thread, SIGURG);
00270       }
00271 
00272       ao2_unlock(bridge);
00273 
00274       /* Wait for the timing source to tell us to wake up and get things done */
00275       ast_waitfor_n_fd(&timingfd, 1, &timeout, NULL);
00276 
00277       ast_timer_ack(timer, 1);
00278 
00279       ao2_lock(bridge);
00280    }
00281 
00282    return 0;
00283 }
00284 
00285 static struct ast_bridge_technology softmix_bridge = {
00286    .name = "softmix",
00287    .capabilities = AST_BRIDGE_CAPABILITY_MULTIMIX | AST_BRIDGE_CAPABILITY_THREAD | AST_BRIDGE_CAPABILITY_MULTITHREADED,
00288    .preference = AST_BRIDGE_PREFERENCE_LOW,
00289 #ifdef SOFTMIX_16_SUPPORT
00290    .formats = AST_FORMAT_SLINEAR16,
00291 #else
00292    .formats = AST_FORMAT_SLINEAR,
00293 #endif
00294    .create = softmix_bridge_create,
00295    .destroy = softmix_bridge_destroy,
00296    .join = softmix_bridge_join,
00297    .leave = softmix_bridge_leave,
00298    .write = softmix_bridge_write,
00299    .thread = softmix_bridge_thread,
00300    .poke = softmix_bridge_poke,
00301 };
00302 
00303 static int unload_module(void)
00304 {
00305    return ast_bridge_technology_unregister(&softmix_bridge);
00306 }
00307 
00308 static int load_module(void)
00309 {
00310    return ast_bridge_technology_register(&softmix_bridge);
00311 }
00312 
00313 AST_MODULE_INFO_STANDARD(ASTERISK_GPL_KEY, "Multi-party software based channel mixing");

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