res_format_attr_silk.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 2011, Digium, Inc.
 *
 * David Vossel <dvossel@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 SILK format attribute interface
 *
 * \author David Vossel <dvossel@digium.com>
 */

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

#include "asterisk.h"

ASTERISK_FILE_VERSION(__FILE__, "$Revision: 370055 $")

#include "asterisk/module.h"
#include "asterisk/format.h"

/*!
 * \brief SILK attribute structure.
 *
 * \note The only attribute that affects compatibility here is the sample rate.
 */
struct silk_attr {
   unsigned int samplerate;
   unsigned int maxbitrate;
   unsigned int dtx;
   unsigned int fec;
   unsigned int packetloss_percentage;
};

static int silk_sdp_parse(struct ast_format_attr *format_attr, const char *attributes)
{
   struct silk_attr *attr = (struct silk_attr *) format_attr;
   unsigned int val;

   if (sscanf(attributes, "maxaveragebitrate=%30u", &val) == 1) {
      attr->maxbitrate = val;
   }
   if (sscanf(attributes, "usedtx=%30u", &val) == 1) {
      attr->dtx = val;
   }
   if (sscanf(attributes, "useinbandfec=%30u", &val) == 1) {
      attr->fec = val;
   }

   return 0;
}

static void silk_sdp_generate(const struct ast_format_attr *format_attr, unsigned int payload, struct ast_str **str)
{
   struct silk_attr *attr = (struct silk_attr *) format_attr;

   if ((attr->maxbitrate > 5000) && (attr->maxbitrate < 40000)) { 
      ast_str_append(str, 0, "a=fmtp:%d maxaveragebitrate=%d\r\n", payload, attr->maxbitrate);
   }

   ast_str_append(str, 0, "a=fmtp:%d usedtx=%d\r\n", payload, attr->dtx);
   ast_str_append(str, 0, "a=fmtp:%d useinbandfec=%d\r\n", payload, attr->fec);
}

static enum ast_format_cmp_res silk_cmp(const struct ast_format_attr *fattr1, const struct ast_format_attr *fattr2)
{
   struct silk_attr *attr1 = (struct silk_attr *) fattr1;
   struct silk_attr *attr2 = (struct silk_attr *) fattr2;

   if (attr1->samplerate == attr2->samplerate) {
      return AST_FORMAT_CMP_EQUAL;
   }
   return AST_FORMAT_CMP_NOT_EQUAL;
}

static int silk_get_val(const struct ast_format_attr *fattr, int key, void *result)
{
   const struct silk_attr *attr = (struct silk_attr *) fattr;
   int *val = result;

   switch (key) {
   case SILK_ATTR_KEY_SAMP_RATE:
      *val = attr->samplerate;
      break;
   case SILK_ATTR_KEY_MAX_BITRATE:
      *val = attr->maxbitrate;
      break;
   case SILK_ATTR_KEY_DTX:
      *val = attr->dtx;
      break;
   case SILK_ATTR_KEY_FEC:
      *val = attr->fec;
      break;
   case SILK_ATTR_KEY_PACKETLOSS_PERCENTAGE:
      *val = attr->packetloss_percentage;
      break;
   default:
      ast_log(LOG_WARNING, "unknown attribute type %d\n", key);
      return -1;
   }
   return 0;
}

static int silk_isset(const struct ast_format_attr *fattr, va_list ap)
{
   enum silk_attr_keys key;
   const struct silk_attr *attr = (struct silk_attr *) fattr;

   for (key = va_arg(ap, int);
      key != AST_FORMAT_ATTR_END;
      key = va_arg(ap, int))
   {
      switch (key) {
      case SILK_ATTR_KEY_SAMP_RATE:
         if (attr->samplerate != (va_arg(ap, int))) {
            return -1;
         }
         break;
      case SILK_ATTR_KEY_MAX_BITRATE:
         if (attr->maxbitrate != (va_arg(ap, int))) {
            return -1;
         }
         break;
      case SILK_ATTR_KEY_DTX:
         if (attr->dtx != (va_arg(ap, int))) {
            return -1;
         }
         break;
      case SILK_ATTR_KEY_FEC:
         if (attr->fec != (va_arg(ap, int))) {
            return -1;
         }
         break;
      case SILK_ATTR_KEY_PACKETLOSS_PERCENTAGE:
         if (attr->packetloss_percentage != (va_arg(ap, int))) {
            return -1;
         }
         break;
      default:
         ast_log(LOG_WARNING, "unknown attribute type %d\n", key);
         return -1;
      }
   }
   return 0;
}
static int silk_getjoint(const struct ast_format_attr *fattr1, const struct ast_format_attr *fattr2, struct ast_format_attr *result)
{
   struct silk_attr *attr1 = (struct silk_attr *) fattr1;
   struct silk_attr *attr2 = (struct silk_attr *) fattr2;
   struct silk_attr *attr_res = (struct silk_attr *) result;
   int joint = -1;

   attr_res->samplerate = attr1->samplerate & attr2->samplerate;
   /* sample rate is the only attribute that has any bearing on if joint capabilities exist or not */
   if (attr_res->samplerate) {
      joint = 0;
   }
   /* Take the lowest max bitrate */
   attr_res->maxbitrate = MIN(attr1->maxbitrate, attr2->maxbitrate);

   /* Only do dtx if both sides want it. DTX is a trade off between
    * computational complexity and bandwidth. */
   attr_res->dtx = attr1->dtx && attr2->dtx ? 1 : 0;

   /* Only do FEC if both sides want it.  If a peer specifically requests not
    * to receive with FEC, it may be a waste of bandwidth. */
   attr_res->fec = attr1->fec && attr2->fec ? 1 : 0;

   /* Use the maximum packetloss percentage between the two attributes. This affects how
    * much redundancy is used in the FEC. */
   attr_res->packetloss_percentage = MAX(attr1->packetloss_percentage, attr2->packetloss_percentage);
   return joint;
}

static void silk_set(struct ast_format_attr *fattr, va_list ap)
{
   enum silk_attr_keys key;
   struct silk_attr *attr = (struct silk_attr *) fattr;

   for (key = va_arg(ap, int);
      key != AST_FORMAT_ATTR_END;
      key = va_arg(ap, int))
   {
      switch (key) {
      case SILK_ATTR_KEY_SAMP_RATE:
         attr->samplerate = (va_arg(ap, int));
         break;
      case SILK_ATTR_KEY_MAX_BITRATE:
         attr->maxbitrate = (va_arg(ap, int));
         break;
      case SILK_ATTR_KEY_DTX:
         attr->dtx = (va_arg(ap, int));
         break;
      case SILK_ATTR_KEY_FEC:
         attr->fec = (va_arg(ap, int));
         break;
      case SILK_ATTR_KEY_PACKETLOSS_PERCENTAGE:
         attr->packetloss_percentage = (va_arg(ap, int));
         break;
      default:
         ast_log(LOG_WARNING, "unknown attribute type %d\n", key);
      }
   }
}

static struct ast_format_attr_interface silk_interface = {
   .id = AST_FORMAT_SILK,
   .format_attr_cmp = silk_cmp,
   .format_attr_get_joint = silk_getjoint,
   .format_attr_set = silk_set,
   .format_attr_isset = silk_isset,
   .format_attr_get_val = silk_get_val,
   .format_attr_sdp_parse = silk_sdp_parse,
   .format_attr_sdp_generate = silk_sdp_generate,
};

static int load_module(void)
{
   if (ast_format_attr_reg_interface(&silk_interface)) {
      return AST_MODULE_LOAD_DECLINE;
   }

   return AST_MODULE_LOAD_SUCCESS;
}

static int unload_module(void)
{
   ast_format_attr_unreg_interface(&silk_interface);
   return 0;
}

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