From b9874da790bda9aa54d9c6d06d41b935d6f7b243 Mon Sep 17 00:00:00 2001
From: Joshua Colp <jcolp@digium.com>
Date: Thu, 20 Sep 2018 09:48:38 +0000
Subject: [PATCH] res_remb_modifier: Add module for controlling REMB from CLI.
This adds a module which registers a CLI command that can set the
REMB bitrate value for REMB as it enters or exits Asterisk. This
allows you to ignore what Asterisk or a client produces and is
useful for demonstrations.
This does not generate REMB frames, however, but just modifies
them as they flow to or from a channel.
Change-Id: Ib089427c46a4a36d645cecfe02406adb38c17bec
---
res/res_remb_modifier.c | 225 ++++++++++++++++++++++++++++++++++++++++
1 file changed, 225 insertions(+)
create mode 100644 res/res_remb_modifier.c
diff --git a/res/res_remb_modifier.c b/res/res_remb_modifier.c
new file mode 100644
index 0000000000..1e79b83d1c
--- /dev/null
+++ b/res/res_remb_modifier.c
@@ -0,0 +1,225 @@
+/*
+ * Asterisk -- An open source telephony toolkit.
+ *
+ * Copyright (C) 2018, 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 REMB Modifier Module
+ *
+ * \author Joshua Colp <jcolp@digium.com>
+ */
+
+/*** MODULEINFO
+ <support_level>extended</support_level>
+ <defaultenabled>no</defaultenabled>
+ ***/
+
+#include "asterisk.h"
+
+#include "asterisk/module.h"
+#include "asterisk/cli.h"
+#include "asterisk/channel.h"
+#include "asterisk/framehook.h"
+#include "asterisk/rtp_engine.h"
+
+struct remb_values {
+ /*! \brief The amount of bitrate to use for REMB received from the channel */
+ unsigned int receive_bitrate;
+ /*! \brief The amount of bitrate to use for REMB sent to the channel */
+ unsigned int send_bitrate;
+};
+
+static void remb_values_free(void *data)
+{
+ ast_free(data);
+}
+
+static const struct ast_datastore_info remb_info = {
+ .type = "REMB Values",
+ .destroy = remb_values_free,
+};
+
+static struct ast_frame *remb_hook_event_cb(struct ast_channel *chan, struct ast_frame *frame, enum ast_framehook_event event, void *data)
+{
+ struct ast_rtp_rtcp_feedback *feedback;
+ struct ast_datastore *remb_store;
+ struct remb_values *remb_values;
+
+ 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) {
+ feedback->remb.br_mantissa = remb_values->receive_bitrate;
+ feedback->remb.br_exp = 0;
+ } else if (event == AST_FRAMEHOOK_EVENT_WRITE && remb_values->send_bitrate) {
+ feedback->remb.br_mantissa = remb_values->send_bitrate;
+ feedback->remb.br_exp = 0;
+ }
+
+ /* The mantissa only has 18 bits available, so while it exceeds them we bump
+ * up the exp.
+ */
+ while (feedback->remb.br_mantissa > 0x3ffff) {
+ feedback->remb.br_mantissa = feedback->remb.br_mantissa >> 1;
+ feedback->remb.br_exp++;
+ }
+
+ return frame;
+}
+
+static char *handle_remb_set(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
+{
+ 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;
+}
+
+static struct ast_cli_entry remb_cli[] = {
+ AST_CLI_DEFINE(handle_remb_set, "Set the REMB value which overwrites what is sent or received"),
+};
+
+static int load_module(void)
+{
+ ast_cli_register_multiple(remb_cli, ARRAY_LEN(remb_cli));
+ return AST_MODULE_LOAD_SUCCESS;
+}
+
+static int unload_module(void)
+{
+ ast_cli_unregister_multiple(remb_cli, ARRAY_LEN(remb_cli));
+ return 0;
+}
+
+AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_DEFAULT, "REMB Modifier Module",
+ .support_level = AST_MODULE_SUPPORT_EXTENDED,
+ .load = load_module,
+ .unload = unload_module,
+);
--
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