codec_a_mu.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 1999 - 2005, Digium, Inc.
 *
 * Mark Spencer <[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 codec_a_mu.c - translate between alaw and ulaw directly
 *
 * \ingroup codecs
 */

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

#include "asterisk.h"

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

#define BUFFER_SAMPLES   8000 /* size for the translation buffers */

static unsigned char mu2a[256];
static unsigned char a2mu[256];

/* Sample frame data */
#include "ex_ulaw.h"
#include "ex_alaw.h"

/*! \brief convert frame data and store into the buffer */
static int alawtoulaw_framein(struct ast_trans_pvt *pvt, struct ast_frame *f)
{
   int x = f->samples;
   unsigned char *src = f->data.ptr;
   unsigned char *dst = pvt->outbuf.uc + pvt->samples;

   pvt->samples += x;
   pvt->datalen += x;

   while (x--)
      *dst++ = a2mu[*src++];

   return 0;
}

/*! \brief convert frame data and store into the buffer */
static int ulawtoalaw_framein(struct ast_trans_pvt *pvt, struct ast_frame *f)
{
   int x = f->samples;
   unsigned char *src = f->data.ptr;
   unsigned char *dst = pvt->outbuf.uc + pvt->samples;

   pvt->samples += x;
   pvt->datalen += x;

   while (x--)
      *dst++ = mu2a[*src++];

   return 0;
}

static struct ast_translator alawtoulaw = {
   .name = "alawtoulaw",
   .src_codec = {
      .name = "alaw",
      .type = AST_MEDIA_TYPE_AUDIO,
      .sample_rate = 8000,
   },
   .dst_codec = {
      .name = "ulaw",
      .type = AST_MEDIA_TYPE_AUDIO,
      .sample_rate = 8000,
   },
   .format = "ulaw",
   .framein = alawtoulaw_framein,
   .sample = alaw_sample,
   .buffer_samples = BUFFER_SAMPLES,
   .buf_size = BUFFER_SAMPLES,
};

static struct ast_translator ulawtoalaw = {
   .name = "ulawtoalaw",
   .src_codec = {
      .name = "ulaw",
      .type = AST_MEDIA_TYPE_AUDIO,
      .sample_rate = 8000,
   },
   .dst_codec = {
      .name = "alaw",
      .type = AST_MEDIA_TYPE_AUDIO,
      .sample_rate = 8000,
   },
   .format = "alaw",
   .framein = ulawtoalaw_framein,
   .sample = ulaw_sample,
   .buffer_samples = BUFFER_SAMPLES,
   .buf_size = BUFFER_SAMPLES,
};

/*! \brief standard module glue */

static int unload_module(void)
{
   int res;

   res = ast_unregister_translator(&ulawtoalaw);
   res |= ast_unregister_translator(&alawtoulaw);

   return res;
}

static int load_module(void)
{
   int res;
   int x;

   for (x=0;x<256;x++) {
      mu2a[x] = AST_LIN2A(AST_MULAW(x));
      a2mu[x] = AST_LIN2MU(AST_ALAW(x));
   }

   res = ast_register_translator(&alawtoulaw);
   res |= ast_register_translator(&ulawtoalaw);

   if (res) {
      unload_module();
      return AST_MODULE_LOAD_DECLINE;
   }

   return AST_MODULE_LOAD_SUCCESS;
}

AST_MODULE_INFO_STANDARD(ASTERISK_GPL_KEY, "A-law and Mulaw direct Coder/Decoder");