res_remb_modifier.c File Reference

REMB Modifier Module. More...

#include "asterisk.h"
#include <math.h>
#include "asterisk/module.h"
#include "asterisk/cli.h"
#include "asterisk/channel.h"
#include "asterisk/framehook.h"
#include "asterisk/rtp_engine.h"

Include dependency graph for res_remb_modifier.c:

Go to the source code of this file.

Data Structures
struct	remb_values

Functions
static void	__reg_module (void)
static void	__unreg_module (void)
struct ast_module *	AST_MODULE_SELF_SYM (void)
static char *	handle_remb_set (struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
static int	load_module (void)
static struct ast_frame *	remb_hook_event_cb (struct ast_channel *chan, struct ast_frame *frame, enum ast_framehook_event event, void *data)
static void	remb_values_free (void *data)
static int	unload_module (void)

Variables
static struct ast_module_info	__mod_info = { .name = AST_MODULE, .flags = AST_MODFLAG_DEFAULT , .description = "REMB Modifier Module" , .key = "This paragraph is copyright (c) 2006 by Digium, Inc. \In order for your module to load, it must return this \key via a function called \"key\". Any code which \includes this paragraph must be licensed under the GNU \General Public License version 2 or later (at your \option). In addition to Digium's general reservations \of rights, Digium expressly reserves the right to \allow other parties to license this paragraph under \different terms. Any use of Digium, Inc. trademarks or \logos (including \"Asterisk\" or \"Digium\") without \express written permission of Digium, Inc. is prohibited.\n" , .buildopt_sum = AST_BUILDOPT_SUM, .support_level = AST_MODULE_SUPPORT_EXTENDED, .load = load_module, .unload = unload_module, }
static const struct ast_module_info *	ast_module_info = &__mod_info
static struct ast_cli_entry	remb_cli []
static const struct ast_datastore_info	remb_info

Detailed Description

REMB Modifier Module.

Author

Joshua Colp jcolp.nosp@m.@dig.nosp@m.ium.c.nosp@m.om

Definition in file res_remb_modifier.c.

Function Documentation

__reg_module()

static void __reg_module ( void  )

static

Definition at line 268 of file res_remb_modifier.c.

__unreg_module()

static void __unreg_module ( void  )

static

Definition at line 268 of file res_remb_modifier.c.

AST_MODULE_SELF_SYM()

struct ast_module * AST_MODULE_SELF_SYM

(

void

)

Definition at line 268 of file res_remb_modifier.c.

handle_remb_set()

static char * handle_remb_set ( struct ast_cli_entry *  e, int  cmd, struct ast_cli_args *  a  )

static

Definition at line 155 of file res_remb_modifier.c.

{
    struct ast_channel *chan;
    unsigned int bitrate;
    struct ast_datastore *remb_store;
    struct remb_values *remb_values;
    struct ast_framehook_interface interface = {
        .version = AST_FRAMEHOOK_INTERFACE_VERSION,
        .event_cb = remb_hook_event_cb,
    };
 
    switch(cmd) {
    case CLI_INIT:
        e->command = "remb set {send|receive}";
        e->usage =
            "Usage: remb set {send|receive} <channel> <bitrate in bits>\n"
            "       Set the REMB value which overwrites what we send or receive\n";
        return NULL;
    case CLI_GENERATE:
        return ast_complete_channels(a->line, a->word, a->pos, a->n, 3);
    }
 
    if (a->argc != 5) {
        return CLI_SHOWUSAGE;
    }
 
    if (sscanf(a->argv[4], "%30d", &bitrate) != 1) {
        ast_cli(a->fd, "%s is not a valid bitrate in bits\n", a->argv[4]);
        return CLI_SUCCESS;
    } else if (strcasecmp(a->argv[2], "send") && strcasecmp(a->argv[2], "receive")) {
        ast_cli(a->fd, "%s is not a valid direction for REMB\n", a->argv[2]);
        return CLI_SUCCESS;
    }
 
    chan = ast_channel_get_by_name(a->argv[3]);
    if (!chan) {
        ast_cli(a->fd, "%s is not a known channel\n", a->argv[3]);
        return CLI_SUCCESS;
    }
 
    ast_channel_lock(chan);
 
    remb_store = ast_channel_datastore_find(chan, &remb_info, NULL);
    if (!remb_store) {
        int framehook_id;
 
        framehook_id = ast_framehook_attach(chan, &interface);
        if (framehook_id < 0) {
            ast_cli(a->fd, "Could not attach framehook for modifying REMB\n");
            ast_channel_unlock(chan);
            ast_channel_unref(chan);
            return CLI_SUCCESS;
        }
 
        remb_values = ast_calloc(1, sizeof(*remb_values));
        if (!remb_values) {
            ast_cli(a->fd, "Could not create a place to store provided REMB value\n");
            ast_framehook_detach(chan, framehook_id);
            ast_channel_unlock(chan);
            ast_channel_unref(chan);
            return CLI_SUCCESS;
        }
 
        remb_store = ast_datastore_alloc(&remb_info, NULL);
        if (!remb_store) {
            ast_cli(a->fd, "Could not create a place to store provided REMB value\n");
            ast_framehook_detach(chan, framehook_id);
            ast_channel_unlock(chan);
            ast_channel_unref(chan);
            ast_free(remb_values);
            return CLI_SUCCESS;
        }
 
        remb_store->data = remb_values;
        ast_channel_datastore_add(chan, remb_store);
    } else {
        remb_values = remb_store->data;
    }
 
    if (!strcasecmp(a->argv[2], "send")) {
        remb_values->send_bitrate = bitrate;
    } else if (!strcasecmp(a->argv[2], "receive")) {
        remb_values->receive_bitrate = bitrate;
    }
 
    ast_channel_unlock(chan);
    ast_channel_unref(chan);
 
    ast_cli(a->fd, "Set REMB %s override to a bitrate of %s on %s\n", a->argv[2], a->argv[3], a->argv[4]);
 
    return CLI_SUCCESS;
}

References a, ast_calloc, ast_channel_datastore_add(), ast_channel_datastore_find(), ast_channel_get_by_name(), ast_channel_lock, ast_channel_unlock, ast_channel_unref, ast_cli(), ast_complete_channels(), ast_datastore_alloc, ast_framehook_attach(), ast_framehook_detach(), AST_FRAMEHOOK_INTERFACE_VERSION, ast_free, CLI_GENERATE, CLI_INIT, CLI_SHOWUSAGE, CLI_SUCCESS, ast_cli_entry::command, ast_datastore::data, NULL, remb_values::receive_bitrate, remb_hook_event_cb(), remb_info, remb_values::send_bitrate, ast_cli_entry::usage, and ast_framehook_interface::version.

load_module()

static int load_module ( void  )

static

Definition at line 252 of file res_remb_modifier.c.

{
    ast_cli_register_multiple(remb_cli, ARRAY_LEN(remb_cli));
    return AST_MODULE_LOAD_SUCCESS;
}

References ARRAY_LEN, ast_cli_register_multiple, AST_MODULE_LOAD_SUCCESS, and remb_cli.

remb_hook_event_cb()

static struct ast_frame * remb_hook_event_cb ( struct ast_channel *  chan, struct ast_frame *  frame, enum ast_framehook_event  event, void *  data  )

static

Definition at line 59 of file res_remb_modifier.c.

{
    struct ast_rtp_rtcp_feedback *feedback;
    struct ast_datastore *remb_store;
    struct remb_values *remb_values;
    int exp;
    float bitrate = 0.0;
 
    if (!frame) {
        return NULL;
    }
 
    switch (event) {
    case AST_FRAMEHOOK_EVENT_READ:
    case AST_FRAMEHOOK_EVENT_WRITE:
        break;
    case AST_FRAMEHOOK_EVENT_ATTACHED:
    case AST_FRAMEHOOK_EVENT_DETACHED:
        return frame;
    }
 
    /* We only care about REMB frames, all others will be unmodified */
    if (frame->subclass.integer != AST_RTP_RTCP_PSFB) {
        return frame;
    }
 
    feedback = frame->data.ptr;
    if (feedback->fmt != AST_RTP_RTCP_FMT_REMB) {
        return frame;
    }
 
    remb_store = ast_channel_datastore_find(chan, &remb_info, NULL);
    if (!remb_store) {
        return frame;
    }
    remb_values = remb_store->data;
 
    /* If a bitrate override has been set apply it to the REMB Frame */
    if (event == AST_FRAMEHOOK_EVENT_READ && remb_values->receive_bitrate) {
        bitrate = remb_values->receive_bitrate;
    } else if (event == AST_FRAMEHOOK_EVENT_WRITE && remb_values->send_bitrate) {
        bitrate = remb_values->send_bitrate;
    } else {
        return frame;
    }
 
    /*
     * The mantissa only has 18 bits available, so make sure it fits. Adjust the
     * value and exponent for those values that don't.
     *
     * For example given the following:
     *
     * bitrate = 123456789.0
     * frexp(bitrate, &exp);
     *
     * 'exp' should now equal 27 (number of bits needed to represent the value). Since
     * the mantissa must fit into an 18-bit unsigned integer, and the given bitrate is
     * too large to fit, we must subtract 18 from the exponent in order to get the
     * number of times the bitrate will fit into that size integer.
     *
     * exp -= 18;
     *
     * 'exp' is now equal to 9. Now we can get the mantissa that fits into an 18-bit
     * unsigned integer by dividing the bitrate by 2^exp:
     *
     * mantissa = 123456789.0 / 2^9
     *
     * This makes the final mantissa equal to 241126 (implicitly cast), which is less
     * than 262143 (the max value that can be put into an unsigned 18-bit integer).
     * So now we have the following:
     *
     * exp = 9;
     * mantissa = 241126;
     *
     * If we multiply that back we should come up with something close to the original
     * bit rate:
     *
     * 241126 * 2^9 = 123456512
     *
     * Precision is lost due to the nature of floating point values. Easier to why from
     * the binary:
     *
     * 241126 * 2^9 = 241126 << 9 = 111010110111100110 << 9 = 111010110111100110000000000
     *
     * Precision on the "lower" end is lost due to zeros being shifted in. This loss is
     * both expected and acceptable.
     */
    frexp(bitrate, &exp);
    exp = exp > 18 ? exp - 18 : 0;
 
    feedback->remb.br_mantissa = bitrate / (1 << exp);
    feedback->remb.br_exp = exp;
 
    return frame;
}

References ast_channel_datastore_find(), AST_FRAMEHOOK_EVENT_ATTACHED, AST_FRAMEHOOK_EVENT_DETACHED, AST_FRAMEHOOK_EVENT_READ, AST_FRAMEHOOK_EVENT_WRITE, AST_RTP_RTCP_FMT_REMB, AST_RTP_RTCP_PSFB, ast_rtp_rtcp_feedback_remb::br_exp, ast_rtp_rtcp_feedback_remb::br_mantissa, ast_datastore::data, ast_frame::data, ast_rtp_rtcp_feedback::fmt, ast_frame_subclass::integer, NULL, ast_frame::ptr, remb_values::receive_bitrate, ast_rtp_rtcp_feedback::remb, remb_info, remb_values::send_bitrate, and ast_frame::subclass.

Referenced by handle_remb_set().

remb_values_free()

static void remb_values_free ( void *  data )

static

Definition at line 49 of file res_remb_modifier.c.

{
    ast_free(data);
}

References ast_free.

unload_module()

static int unload_module ( void  )

static

Definition at line 258 of file res_remb_modifier.c.

{
    ast_cli_unregister_multiple(remb_cli, ARRAY_LEN(remb_cli));
    return 0;
}

References ARRAY_LEN, ast_cli_unregister_multiple(), and remb_cli.

Variable Documentation

__mod_info

struct ast_module_info __mod_info = { .name = AST_MODULE, .flags = AST_MODFLAG_DEFAULT , .description = "REMB Modifier Module" , .key = "This paragraph is copyright (c) 2006 by Digium, Inc. \In order for your module to load, it must return this \key via a function called \"key\". Any code which \includes this paragraph must be licensed under the GNU \General Public License version 2 or later (at your \option). In addition to Digium's general reservations \of rights, Digium expressly reserves the right to \allow other parties to license this paragraph under \different terms. Any use of Digium, Inc. trademarks or \logos (including \"Asterisk\" or \"Digium\") without \express written permission of Digium, Inc. is prohibited.\n" , .buildopt_sum = AST_BUILDOPT_SUM, .support_level = AST_MODULE_SUPPORT_EXTENDED, .load = load_module, .unload = unload_module, }

static

Definition at line 268 of file res_remb_modifier.c.

ast_module_info

const struct ast_module_info* ast_module_info = &__mod_info

static

Definition at line 268 of file res_remb_modifier.c.

remb_cli

struct ast_cli_entry remb_cli[]

static

Initial value:

= {
    { .handler =  handle_remb_set , .summary =  "Set the REMB value which overwrites what is sent or received" ,},
}

Definition at line 248 of file res_remb_modifier.c.

Referenced by load_module(), and unload_module().

remb_info

const struct ast_datastore_info remb_info

static

Initial value:

= {
    .type = "REMB Values",
    .destroy = remb_values_free,
}

Definition at line 54 of file res_remb_modifier.c.

Referenced by handle_remb_set(), and remb_hook_event_cb().