codec_a_mu.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_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");