codec_alaw.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 1999 - 2005, Digium, Inc.
 *
 * Mark Spencer <markster@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 codec_alaw.c - translate between signed linear and alaw
 * 
 * \ingroup codecs
 */

#include "asterisk.h"

ASTERISK_FILE_VERSION(__FILE__, "$Revision: 150729 $")

#include "asterisk/module.h"
#include "asterisk/config.h"
#include "asterisk/translate.h"
#include "asterisk/alaw.h"
#include "asterisk/utils.h"

#define BUFFER_SAMPLES   8096 /* size for the translation buffers */

/* Sample frame data */
#include "asterisk/slin.h"
#include "ex_alaw.h"

/*! \brief decode frame into lin and fill output buffer. */
static int alawtolin_framein(struct ast_trans_pvt *pvt, struct ast_frame *f)
{
   int i = f->samples;
   unsigned char *src = f->data.ptr;
   int16_t *dst = pvt->outbuf.i16 + pvt->samples;

   pvt->samples += i;
   pvt->datalen += i * 2;  /* 2 bytes/sample */
   
   while (i--)
      *dst++ = AST_ALAW(*src++);

   return 0;
}

/*! \brief convert and store input samples in output buffer */
static int lintoalaw_framein(struct ast_trans_pvt *pvt, struct ast_frame *f)
{
   int i = f->samples;
   char *dst = pvt->outbuf.c + pvt->samples;
   int16_t *src = f->data.ptr;

   pvt->samples += i;
   pvt->datalen += i;   /* 1 byte/sample */

   while (i--) 
      *dst++ = AST_LIN2A(*src++);

   return 0;
}

static struct ast_translator alawtolin = {
   .name = "alawtolin",
   .srcfmt = AST_FORMAT_ALAW,
   .dstfmt = AST_FORMAT_SLINEAR,
   .framein = alawtolin_framein,
   .sample = alaw_sample,
   .buffer_samples = BUFFER_SAMPLES,
   .buf_size = BUFFER_SAMPLES * 2,
   .plc_samples = 160,
};

static struct ast_translator lintoalaw = {
   "lintoalaw",
   .srcfmt = AST_FORMAT_SLINEAR,
   .dstfmt = AST_FORMAT_ALAW,
   .framein = lintoalaw_framein,
   .sample = slin8_sample,
   .buffer_samples = BUFFER_SAMPLES,
   .buf_size = BUFFER_SAMPLES,
};

static int parse_config(int reload)
{
   struct ast_variable *var;
   struct ast_flags config_flags = { reload ? CONFIG_FLAG_FILEUNCHANGED : 0 };
   struct ast_config *cfg = ast_config_load("codecs.conf", config_flags);
   if (cfg == CONFIG_STATUS_FILEMISSING || cfg == CONFIG_STATUS_FILEUNCHANGED || cfg == CONFIG_STATUS_FILEINVALID)
      return 0;
   for (var = ast_variable_browse(cfg, "plc"); var; var = var->next) {
      if (!strcasecmp(var->name, "genericplc")) {
         alawtolin.useplc = ast_true(var->value) ? 1 : 0;
         ast_verb(3, "codec_alaw: %susing generic PLC\n", alawtolin.useplc ? "" : "not ");
      }
   }
   ast_config_destroy(cfg);
   return 0;
}

/*! \brief standard module stuff */

static int reload(void)
{
   if (parse_config(1))
      return AST_MODULE_LOAD_DECLINE;
   return AST_MODULE_LOAD_SUCCESS;
}

static int unload_module(void)
{
   int res;

   res = ast_unregister_translator(&lintoalaw);
   res |= ast_unregister_translator(&alawtolin);

   return res;
}

static int load_module(void)
{
   int res;

   if (parse_config(0))
      return AST_MODULE_LOAD_DECLINE;
   res = ast_register_translator(&alawtolin);
   if (!res)
      res = ast_register_translator(&lintoalaw);
   else
      ast_unregister_translator(&alawtolin);
   if (res)
      return AST_MODULE_LOAD_FAILURE;
   return AST_MODULE_LOAD_SUCCESS;
}

AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_DEFAULT, "A-law Coder/Decoder",
      .load = load_module,
      .unload = unload_module,
      .reload = reload,
          );