res_format_attr_ilbc.c

Go to the documentation of this file.

/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 2016, Alexander Traud
 *
 * Alexander Traud <[email protected]>
 *
 * 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 iLBC format attribute interface
 *
 * \author Alexander Traud <[email protected]>
 *
 * \note http://tools.ietf.org/html/rfc3952
 */

/*** MODULEINFO
 <support_level>core</support_level>
 ***/

#include "asterisk.h"

#include <ctype.h> /* for tolower */

#include "asterisk/module.h"
#include "asterisk/format.h"
#include "asterisk/strings.h" /* for ast_str_append */
#include "asterisk/utils.h" /* for ast_free */

#include "asterisk/ilbc.h"

static struct ilbc_attr default_ilbc_attr = {
 .mode = 20,
};

static void ilbc_destroy(struct ast_format *format)
{
 struct ilbc_attr *attr = ast_format_get_attribute_data(format);

 ast_free(attr);
}

static int ilbc_clone(const struct ast_format *src, struct ast_format *dst)
{
 struct ilbc_attr *original = ast_format_get_attribute_data(src);
 struct ilbc_attr *attr = ast_malloc(sizeof(*attr));

 if (!attr) {
 return -1;
 }

 if (original) {
 *attr = *original;
 } else {
 *attr = default_ilbc_attr;
 }

 ast_format_set_attribute_data(dst, attr);

 return 0;
}

static struct ast_format *ilbc_parse_sdp_fmtp(const struct ast_format *format, const char *attributes)
{
 char *attribs = ast_strdupa(attributes), *attrib;
 struct ast_format *cloned;
 struct ilbc_attr *attr;
 const char *kvp;
 unsigned int val;

 cloned = ast_format_clone(format);
 if (!cloned) {
 return NULL;
 }
 attr = ast_format_get_attribute_data(cloned);

 /* lower-case everything, so we are case-insensitive */
 for (attrib = attribs; *attrib; ++attrib) {
 *attrib = tolower(*attrib);
 } /* based on channels/chan_sip.c:process_a_sdp_image() */

 if ((kvp = strstr(attribs, "mode")) && sscanf(kvp, "mode=%30u", &val) == 1) {
 attr->mode = val;
 } else {
 attr->mode = 30; /* optional attribute; 30 is default value */
 }

 return cloned;
}

static void ilbc_generate_sdp_fmtp(const struct ast_format *format, unsigned int payload, struct ast_str **str)
{
 struct ilbc_attr *attr = ast_format_get_attribute_data(format);

 if (!attr) {
 attr = &default_ilbc_attr;
 }

 /* When the VoIP/SIP client Zoiper calls Asterisk and its
 * iLBC 20 is disabled but iLBC 30 enabled, Zoiper still
 * falls back to iLBC 20, when there is no mode=30 in the
 * answer. Consequently, Zoiper defaults to iLBC 20. To
 * make that client happy, Asterisk sends mode always.
 * tested in June 2016, Zoiper Premium 1.13.2 for iPhone
 */
 /* if (attr->mode != 30) */ {
 ast_str_append(str, 0, "a=fmtp:%u mode=%u\r\n", payload, attr->mode);
 }
}

static struct ast_format *ilbc_getjoint(const struct ast_format *format1, const struct ast_format *format2)
{
 struct ast_format *jointformat;
 struct ilbc_attr *attr1 = ast_format_get_attribute_data(format1);
 struct ilbc_attr *attr2 = ast_format_get_attribute_data(format2);
 struct ilbc_attr *attr_res;

 if (!attr1) {
 attr1 = &default_ilbc_attr;
 }

 if (!attr2) {
 attr2 = &default_ilbc_attr;
 }

 jointformat = ast_format_clone(format1);
 if (!jointformat) {
 return NULL;
 }
 attr_res = ast_format_get_attribute_data(jointformat);

 if (attr1->mode != attr2->mode) {
 attr_res->mode = 30;
 }

 return jointformat;
}

static struct ast_format_interface ilbc_interface = {
 .format_destroy = ilbc_destroy,
 .format_clone = ilbc_clone,
 .format_cmp = NULL,
 .format_get_joint = ilbc_getjoint,
 .format_attribute_set = NULL,
 .format_parse_sdp_fmtp = ilbc_parse_sdp_fmtp,
 .format_generate_sdp_fmtp = ilbc_generate_sdp_fmtp,
};

static int load_module(void)
{
 if (ast_format_interface_register("ilbc", &ilbc_interface)) {
 return AST_MODULE_LOAD_DECLINE;
 }

 return AST_MODULE_LOAD_SUCCESS;
}

static int unload_module(void)
{
 return 0;
}

AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_LOAD_ORDER, "iLBC Format Attribute Module",
 .support_level = AST_MODULE_SUPPORT_CORE,
 .load = load_module,
 .unload = unload_module,
 .load_pri = AST_MODPRI_CHANNEL_DEPEND,
);