res_format_attr_ilbc.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 2016, Alexander Traud
 *
 * Alexander Traud <pabstraud@compuserve.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 iLBC format attribute interface
 *
 * \author Alexander Traud <pabstraud@compuserve.com>
 *
 * \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,
);