Asterisk - The Open Source Telephony Project GIT-master-2de1a68
res_remb_modifier.c
Go to the documentation of this file.
1/*
2 * Asterisk -- An open source telephony toolkit.
3 *
4 * Copyright (C) 2018, Digium, Inc.
5 *
6 * Joshua Colp <jcolp@digium.com>
7 *
8 * See http://www.asterisk.org for more information about
9 * the Asterisk project. Please do not directly contact
10 * any of the maintainers of this project for assistance;
11 * the project provides a web site, mailing lists and IRC
12 * channels for your use.
13 *
14 * This program is free software, distributed under the terms of
15 * the GNU General Public License Version 2. See the LICENSE file
16 * at the top of the source tree.
17 */
18
19/*!
20 * \file
21 *
22 * \brief REMB Modifier Module
23 *
24 * \author Joshua Colp <jcolp@digium.com>
25 */
26
27/*** MODULEINFO
28 <defaultenabled>no</defaultenabled>
29 <support_level>extended</support_level>
30 ***/
31
32#include "asterisk.h"
33
34#include <math.h>
35
36#include "asterisk/module.h"
37#include "asterisk/cli.h"
38#include "asterisk/channel.h"
39#include "asterisk/framehook.h"
40#include "asterisk/rtp_engine.h"
41
43 /*! \brief The amount of bitrate to use for REMB received from the channel */
45 /*! \brief The amount of bitrate to use for REMB sent to the channel */
47};
48
49static void remb_values_free(void *data)
50{
51 ast_free(data);
52}
53
54static const struct ast_datastore_info remb_info = {
55 .type = "REMB Values",
56 .destroy = remb_values_free,
57};
58
59static struct ast_frame *remb_hook_event_cb(struct ast_channel *chan, struct ast_frame *frame, enum ast_framehook_event event, void *data)
60{
61 struct ast_rtp_rtcp_feedback *feedback;
62 struct ast_datastore *remb_store;
64 int exp;
65 float bitrate = 0.0;
66
67 if (!frame) {
68 return NULL;
69 }
70
71 switch (event) {
74 break;
77 return frame;
78 }
79
80 /* We only care about REMB frames, all others will be unmodified */
81 if (frame->subclass.integer != AST_RTP_RTCP_PSFB) {
82 return frame;
83 }
84
85 feedback = frame->data.ptr;
86 if (feedback->fmt != AST_RTP_RTCP_FMT_REMB) {
87 return frame;
88 }
89
90 remb_store = ast_channel_datastore_find(chan, &remb_info, NULL);
91 if (!remb_store) {
92 return frame;
93 }
94 remb_values = remb_store->data;
95
96 /* If a bitrate override has been set apply it to the REMB Frame */
100 bitrate = remb_values->send_bitrate;
101 } else {
102 return frame;
103 }
104
105 /*
106 * The mantissa only has 18 bits available, so make sure it fits. Adjust the
107 * value and exponent for those values that don't.
108 *
109 * For example given the following:
110 *
111 * bitrate = 123456789.0
112 * frexp(bitrate, &exp);
113 *
114 * 'exp' should now equal 27 (number of bits needed to represent the value). Since
115 * the mantissa must fit into an 18-bit unsigned integer, and the given bitrate is
116 * too large to fit, we must subtract 18 from the exponent in order to get the
117 * number of times the bitrate will fit into that size integer.
118 *
119 * exp -= 18;
120 *
121 * 'exp' is now equal to 9. Now we can get the mantissa that fits into an 18-bit
122 * unsigned integer by dividing the bitrate by 2^exp:
123 *
124 * mantissa = 123456789.0 / 2^9
125 *
126 * This makes the final mantissa equal to 241126 (implicitly cast), which is less
127 * than 262143 (the max value that can be put into an unsigned 18-bit integer).
128 * So now we have the following:
129 *
130 * exp = 9;
131 * mantissa = 241126;
132 *
133 * If we multiply that back we should come up with something close to the original
134 * bit rate:
135 *
136 * 241126 * 2^9 = 123456512
137 *
138 * Precision is lost due to the nature of floating point values. Easier to why from
139 * the binary:
140 *
141 * 241126 * 2^9 = 241126 << 9 = 111010110111100110 << 9 = 111010110111100110000000000
142 *
143 * Precision on the "lower" end is lost due to zeros being shifted in. This loss is
144 * both expected and acceptable.
145 */
146 frexp(bitrate, &exp);
147 exp = exp > 18 ? exp - 18 : 0;
148
149 feedback->remb.br_mantissa = bitrate / (1 << exp);
150 feedback->remb.br_exp = exp;
151
152 return frame;
153}
154
155static char *handle_remb_set(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
156{
157 struct ast_channel *chan;
158 unsigned int bitrate;
159 struct ast_datastore *remb_store;
160 struct remb_values *remb_values;
161 struct ast_framehook_interface interface = {
163 .event_cb = remb_hook_event_cb,
164 };
165
166 switch(cmd) {
167 case CLI_INIT:
168 e->command = "remb set {send|receive}";
169 e->usage =
170 "Usage: remb set {send|receive} <channel> <bitrate in bits>\n"
171 " Set the REMB value which overwrites what we send or receive\n";
172 return NULL;
173 case CLI_GENERATE:
174 return ast_complete_channels(a->line, a->word, a->pos, a->n, 3);
175 }
176
177 if (a->argc != 5) {
178 return CLI_SHOWUSAGE;
179 }
180
181 if (sscanf(a->argv[4], "%30d", &bitrate) != 1) {
182 ast_cli(a->fd, "%s is not a valid bitrate in bits\n", a->argv[4]);
183 return CLI_SUCCESS;
184 } else if (strcasecmp(a->argv[2], "send") && strcasecmp(a->argv[2], "receive")) {
185 ast_cli(a->fd, "%s is not a valid direction for REMB\n", a->argv[2]);
186 return CLI_SUCCESS;
187 }
188
189 chan = ast_channel_get_by_name(a->argv[3]);
190 if (!chan) {
191 ast_cli(a->fd, "%s is not a known channel\n", a->argv[3]);
192 return CLI_SUCCESS;
193 }
194
195 ast_channel_lock(chan);
196
197 remb_store = ast_channel_datastore_find(chan, &remb_info, NULL);
198 if (!remb_store) {
199 int framehook_id;
200
201 framehook_id = ast_framehook_attach(chan, &interface);
202 if (framehook_id < 0) {
203 ast_cli(a->fd, "Could not attach framehook for modifying REMB\n");
204 ast_channel_unlock(chan);
205 ast_channel_unref(chan);
206 return CLI_SUCCESS;
207 }
208
209 remb_values = ast_calloc(1, sizeof(*remb_values));
210 if (!remb_values) {
211 ast_cli(a->fd, "Could not create a place to store provided REMB value\n");
212 ast_framehook_detach(chan, framehook_id);
213 ast_channel_unlock(chan);
214 ast_channel_unref(chan);
215 return CLI_SUCCESS;
216 }
217
218 remb_store = ast_datastore_alloc(&remb_info, NULL);
219 if (!remb_store) {
220 ast_cli(a->fd, "Could not create a place to store provided REMB value\n");
221 ast_framehook_detach(chan, framehook_id);
222 ast_channel_unlock(chan);
223 ast_channel_unref(chan);
225 return CLI_SUCCESS;
226 }
227
228 remb_store->data = remb_values;
229 ast_channel_datastore_add(chan, remb_store);
230 } else {
231 remb_values = remb_store->data;
232 }
233
234 if (!strcasecmp(a->argv[2], "send")) {
235 remb_values->send_bitrate = bitrate;
236 } else if (!strcasecmp(a->argv[2], "receive")) {
237 remb_values->receive_bitrate = bitrate;
238 }
239
240 ast_channel_unlock(chan);
241 ast_channel_unref(chan);
242
243 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]);
244
245 return CLI_SUCCESS;
246}
247
248static struct ast_cli_entry remb_cli[] = {
249 AST_CLI_DEFINE(handle_remb_set, "Set the REMB value which overwrites what is sent or received"),
250};
251
252static int load_module(void)
253{
256}
257
258static int unload_module(void)
259{
261 return 0;
262}
263
265 .support_level = AST_MODULE_SUPPORT_EXTENDED,
266 .load = load_module,
267 .unload = unload_module,
Asterisk main include file. File version handling, generic pbx functions.
#define ast_free(a)
Definition: astmm.h:180
#define ast_calloc(num, len)
A wrapper for calloc()
Definition: astmm.h:202
General Asterisk PBX channel definitions.
int ast_channel_datastore_add(struct ast_channel *chan, struct ast_datastore *datastore)
Add a datastore to a channel.
Definition: channel.c:2385
#define ast_channel_lock(chan)
Definition: channel.h:2922
#define ast_channel_unref(c)
Decrease channel reference count.
Definition: channel.h:2958
struct ast_channel * ast_channel_get_by_name(const char *name)
Find a channel by name.
Definition: channel.c:1454
#define ast_channel_unlock(chan)
Definition: channel.h:2923
struct ast_datastore * ast_channel_datastore_find(struct ast_channel *chan, const struct ast_datastore_info *info, const char *uid)
Find a datastore on a channel.
Definition: channel.c:2399
Standard Command Line Interface.
#define CLI_SHOWUSAGE
Definition: cli.h:45
#define CLI_SUCCESS
Definition: cli.h:44
int ast_cli_unregister_multiple(struct ast_cli_entry *e, int len)
Unregister multiple commands.
Definition: clicompat.c:30
#define AST_CLI_DEFINE(fn, txt,...)
Definition: cli.h:197
void ast_cli(int fd, const char *fmt,...)
Definition: clicompat.c:6
char * ast_complete_channels(const char *line, const char *word, int pos, int state, int rpos)
Command completion for the list of active channels.
Definition: main/cli.c:1862
@ CLI_INIT
Definition: cli.h:152
@ CLI_GENERATE
Definition: cli.h:153
#define ast_cli_register_multiple(e, len)
Register multiple commands.
Definition: cli.h:265
#define ast_datastore_alloc(info, uid)
Definition: datastore.h:85
FrameHook Architecture.
int ast_framehook_attach(struct ast_channel *chan, struct ast_framehook_interface *i)
Attach an framehook onto a channel for frame interception.
Definition: framehook.c:132
ast_framehook_event
These are the types of events that the framehook's event callback can receive.
Definition: framehook.h:151
@ AST_FRAMEHOOK_EVENT_ATTACHED
Definition: framehook.h:154
@ AST_FRAMEHOOK_EVENT_DETACHED
Definition: framehook.h:155
@ AST_FRAMEHOOK_EVENT_WRITE
Definition: framehook.h:153
@ AST_FRAMEHOOK_EVENT_READ
Definition: framehook.h:152
int ast_framehook_detach(struct ast_channel *chan, int framehook_id)
Detach an framehook from a channel.
Definition: framehook.c:177
#define AST_FRAMEHOOK_INTERFACE_VERSION
Definition: framehook.h:227
Asterisk module definitions.
@ AST_MODFLAG_DEFAULT
Definition: module.h:315
#define AST_MODULE_INFO(keystr, flags_to_set, desc, fields...)
Definition: module.h:543
@ AST_MODULE_SUPPORT_EXTENDED
Definition: module.h:122
#define ASTERISK_GPL_KEY
The text the key() function should return.
Definition: module.h:46
@ AST_MODULE_LOAD_SUCCESS
Definition: module.h:70
static void remb_values_free(void *data)
static struct ast_cli_entry remb_cli[]
static const struct ast_datastore_info remb_info
static char * handle_remb_set(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
static struct ast_frame * remb_hook_event_cb(struct ast_channel *chan, struct ast_frame *frame, enum ast_framehook_event event, void *data)
static int load_module(void)
static int unload_module(void)
#define NULL
Definition: resample.c:96
Pluggable RTP Architecture.
#define AST_RTP_RTCP_PSFB
Definition: rtp_engine.h:324
#define AST_RTP_RTCP_FMT_REMB
Definition: rtp_engine.h:334
Main Channel structure associated with a channel.
descriptor for a cli entry.
Definition: cli.h:171
char * command
Definition: cli.h:186
const char * usage
Definition: cli.h:177
Structure for a data store type.
Definition: datastore.h:31
const char * type
Definition: datastore.h:32
Structure for a data store object.
Definition: datastore.h:64
void * data
Definition: datastore.h:66
Data structure associated with a single frame of data.
struct ast_frame_subclass subclass
union ast_frame::@226 data
An object that represents data received in a feedback report.
Definition: rtp_engine.h:383
unsigned int fmt
Definition: rtp_engine.h:384
struct ast_rtp_rtcp_feedback_remb remb
Definition: rtp_engine.h:386
Definition: astman.c:222
float receive_bitrate
The amount of bitrate to use for REMB received from the channel.
float send_bitrate
The amount of bitrate to use for REMB sent to the channel.
static struct test_val a
#define ARRAY_LEN(a)
Definition: utils.h:666