asterisk/codecs/codec_alaw.c

/*
 * 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
 */

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

#include "asterisk.h"

ASTERISK_FILE_VERSION(__FILE__, "$Revision$")

#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",
	.src_codec = {
		.name = "alaw",
		.type = AST_MEDIA_TYPE_AUDIO,
		.sample_rate = 8000,
	},
	.dst_codec = {
		.name = "slin",
		.type = AST_MEDIA_TYPE_AUDIO,
		.sample_rate = 8000,
	},
	.format = "slin",
	.framein = alawtolin_framein,
	.sample = alaw_sample,
	.buffer_samples = BUFFER_SAMPLES,
	.buf_size = BUFFER_SAMPLES * 2,
};

static struct ast_translator lintoalaw = {
	.name = "lintoalaw",
	.src_codec = {
		.name = "slin",
		.type = AST_MEDIA_TYPE_AUDIO,
		.sample_rate = 8000,
	},
	.dst_codec = {
		.name = "alaw",
		.type = AST_MEDIA_TYPE_AUDIO,
		.sample_rate = 8000,
	},
	.format = "alaw",
	.framein = lintoalaw_framein,
	.sample = slin8_sample,
	.buffer_samples = BUFFER_SAMPLES,
	.buf_size = BUFFER_SAMPLES,
};

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;

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

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

	return AST_MODULE_LOAD_SUCCESS;
}

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