res_format_attr_celt.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 2011, Digium, Inc.
 *
 * David Vossel <[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 CELT format attribute interface
 *
 * \author David Vossel <[email protected]>
 */

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

#include "asterisk.h"

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

#include "asterisk/module.h"
#include "asterisk/format.h"
#include "asterisk/astobj2.h"           /* for ao2_ref */
#include "asterisk/logger.h"            /* for ast_log, LOG_WARNING */
#include "asterisk/strings.h"           /* for ast_str_append */
#include "asterisk/utils.h"             /* for MIN */

/*!
 * \brief CELT attribute structure.
 *
 * \note The only attribute that affects compatibility here is the sample rate.
 */
struct celt_attr {
   unsigned int samplerate;
   unsigned int maxbitrate;
   unsigned int framesize;
};

static void celt_destroy(struct ast_format *format)
{
   struct celt_attr *attr = ast_format_get_attribute_data(format);

   ast_free(attr);
}

static int celt_clone(const struct ast_format *src, struct ast_format *dst)
{
   struct celt_attr *original = ast_format_get_attribute_data(src);
   struct celt_attr *attr = ast_calloc(1, sizeof(*attr));

   if (!attr) {
      return -1;
   }

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

   ast_format_set_attribute_data(dst, attr);

   return 0;
}

static struct ast_format *celt_parse_sdp_fmtp(const struct ast_format *format, const char *attributes)
{
   char *attribs = ast_strdupa(attributes), *attrib;
   struct ast_format *cloned;
   struct celt_attr *attr;
   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 (sscanf(attribs, "framesize=%30u", &val) == 1) {
      attr->framesize = val;
   }

   return cloned;
}

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

   if (!attr || !attr->framesize) {
      return;
   }

   ast_str_append(str, 0, "a=fmtp:%u framesize=%u\r\n", payload, attr->framesize);
}

static enum ast_format_cmp_res celt_cmp(const struct ast_format *format1, const struct ast_format *format2)
{
   struct celt_attr *attr1 = ast_format_get_attribute_data(format1);
   struct celt_attr *attr2 = ast_format_get_attribute_data(format2);

   if (((!attr1 || !attr1->samplerate) && (!attr2 || !attr2->samplerate)) ||
      (attr1->samplerate == attr2->samplerate)) {
      return AST_FORMAT_CMP_EQUAL;
   }

   return AST_FORMAT_CMP_NOT_EQUAL;
}

static struct ast_format *celt_getjoint(const struct ast_format *format1, const struct ast_format *format2)
{
   struct celt_attr *attr1 = ast_format_get_attribute_data(format1);
   struct celt_attr *attr2 = ast_format_get_attribute_data(format2);
   struct ast_format *jointformat;
   struct celt_attr *jointattr;

   if (attr1 && attr2 && (attr1->samplerate != attr2->samplerate)) {
      return NULL;
   }

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

   /* either would work, they are guaranteed the same at this point. */
   jointattr->samplerate = attr1->samplerate;
   /* Take the lowest max bitrate */
   jointattr->maxbitrate = MIN(attr1->maxbitrate, attr2->maxbitrate);

   jointattr->framesize = attr2->framesize; /* TODO figure out what joint framesize means */

   return jointformat;
}

static struct ast_format *celt_set(const struct ast_format *format, const char *name, const char *value)
{
   struct ast_format *cloned;
   struct celt_attr *attr;
   unsigned int val;

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

   if (sscanf(value, "%30u", &val) != 1) {
      ast_log(LOG_WARNING, "Unknown value '%s' for attribute type '%s'\n",
         value, name);
      ao2_ref(cloned, -1);
      return NULL;
   }

   if (!strcasecmp(name, "sample_rate")) {
      attr->samplerate = val;
   } else if (!strcasecmp(name, "max_bitrate")) {
      attr->maxbitrate = val;
   } else if (!strcasecmp(name, "frame_size")) {
      attr->framesize = val;
   } else {
      ast_log(LOG_WARNING, "Unknown attribute type '%s'\n", name);
      ao2_ref(cloned, -1);
      return NULL;
   }

   return cloned;
}

static struct ast_format_interface celt_interface = {
   .format_destroy = celt_destroy,
   .format_clone = celt_clone,
   .format_cmp = celt_cmp,
   .format_get_joint = celt_getjoint,
   .format_attribute_set = celt_set,
   .format_parse_sdp_fmtp = celt_parse_sdp_fmtp,
   .format_generate_sdp_fmtp = celt_generate_sdp_fmtp,
};

static int load_module(void)
{
   if (ast_format_interface_register("celt", &celt_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, "CELT Format Attribute Module",
   .support_level = AST_MODULE_SUPPORT_CORE,
   .load = load_module,
   .unload = unload_module,
   .load_pri = AST_MODPRI_CHANNEL_DEPEND,
);