Sat Aug 6 00:39:28 2011

Asterisk developer's documentation


codec_alaw.c

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00001 /*
00002  * Asterisk -- An open source telephony toolkit.
00003  *
00004  * Copyright (C) 1999 - 2005, Digium, Inc.
00005  *
00006  * Mark Spencer <markster@digium.com>
00007  *
00008  * See http://www.asterisk.org for more information about
00009  * the Asterisk project. Please do not directly contact
00010  * any of the maintainers of this project for assistance;
00011  * the project provides a web site, mailing lists and IRC
00012  * channels for your use.
00013  *
00014  * This program is free software, distributed under the terms of
00015  * the GNU General Public License Version 2. See the LICENSE file
00016  * at the top of the source tree.
00017  */
00018 
00019 /*! \file
00020  *
00021  * \brief codec_alaw.c - translate between signed linear and alaw
00022  * 
00023  * \ingroup codecs
00024  */
00025 
00026 #include "asterisk.h"
00027 
00028 ASTERISK_FILE_VERSION(__FILE__, "$Revision: 267539 $")
00029 
00030 #include <fcntl.h>
00031 #include <netinet/in.h>
00032 #include <stdio.h>
00033 #include <stdlib.h>
00034 #include <string.h>
00035 #include <unistd.h>
00036 
00037 #include "asterisk/lock.h"
00038 #include "asterisk/logger.h"
00039 #include "asterisk/module.h"
00040 #include "asterisk/config.h"
00041 #include "asterisk/options.h"
00042 #include "asterisk/translate.h"
00043 #include "asterisk/channel.h"
00044 #include "asterisk/alaw.h"
00045 #include "asterisk/utils.h"
00046 
00047 #define BUFFER_SAMPLES   8096 /* size for the translation buffers */
00048 
00049 /* Sample frame data (Mu data is okay) */
00050 
00051 #include "slin_ulaw_ex.h"
00052 #include "ulaw_slin_ex.h"
00053 
00054 /*! \brief decode frame into lin and fill output buffer. */
00055 static int alawtolin_framein(struct ast_trans_pvt *pvt, struct ast_frame *f)
00056 {
00057    int i = f->samples;
00058    unsigned char *src = f->data;
00059    int16_t *dst = (int16_t *)pvt->outbuf + pvt->samples;
00060 
00061    pvt->samples += i;
00062    pvt->datalen += i * 2;  /* 2 bytes/sample */
00063    
00064    while (i--)
00065       *dst++ = AST_ALAW(*src++);
00066 
00067    return 0;
00068 }
00069 
00070 /*! \brief convert and store input samples in output buffer */
00071 static int lintoalaw_framein(struct ast_trans_pvt *pvt, struct ast_frame *f)
00072 {
00073    int i = f->samples;
00074    char *dst = pvt->outbuf + pvt->samples;
00075    int16_t *src = f->data;
00076 
00077    pvt->samples += i;
00078    pvt->datalen += i;   /* 1 byte/sample */
00079 
00080    while (i--) 
00081       *dst++ = AST_LIN2A(*src++);
00082 
00083    return 0;
00084 }
00085 
00086 /*! \brief alawToLin_Sample */
00087 static struct ast_frame *alawtolin_sample(void)
00088 {
00089    static struct ast_frame f;
00090    f.frametype = AST_FRAME_VOICE;
00091    f.subclass = AST_FORMAT_ALAW;
00092    f.datalen = sizeof(ulaw_slin_ex);
00093    f.samples = sizeof(ulaw_slin_ex);
00094    f.mallocd = 0;
00095    f.offset = 0;
00096    f.src = __PRETTY_FUNCTION__;
00097    f.data = ulaw_slin_ex;
00098    return &f;
00099 }
00100 
00101 /*! \brief LinToalaw_Sample */
00102 static struct ast_frame *lintoalaw_sample(void)
00103 {
00104    static struct ast_frame f;
00105    f.frametype = AST_FRAME_VOICE;
00106    f.subclass = AST_FORMAT_SLINEAR;
00107    f.datalen = sizeof(slin_ulaw_ex);
00108    f.samples = sizeof(slin_ulaw_ex) / 2;
00109    f.mallocd = 0;
00110    f.offset = 0;
00111    f.src = __PRETTY_FUNCTION__;
00112    f.data = slin_ulaw_ex;
00113    return &f;
00114 }
00115 
00116 static struct ast_translator alawtolin = {
00117    .name = "alawtolin",
00118    .srcfmt = AST_FORMAT_ALAW,
00119    .dstfmt = AST_FORMAT_SLINEAR,
00120    .framein = alawtolin_framein,
00121    .sample = alawtolin_sample,
00122    .buffer_samples = BUFFER_SAMPLES,
00123    .buf_size = BUFFER_SAMPLES * 2,
00124 };
00125 
00126 static struct ast_translator lintoalaw = {
00127    "lintoalaw",
00128    .srcfmt = AST_FORMAT_SLINEAR,
00129    .dstfmt = AST_FORMAT_ALAW,
00130    .framein = lintoalaw_framein,
00131    .sample = lintoalaw_sample,
00132    .buffer_samples = BUFFER_SAMPLES,
00133    .buf_size = BUFFER_SAMPLES,
00134 };
00135 
00136 /*! \brief standard module stuff */
00137 
00138 static int reload(void)
00139 {
00140    return 0;
00141 }
00142 
00143 static int unload_module(void)
00144 {
00145    int res;
00146 
00147    res = ast_unregister_translator(&lintoalaw);
00148    res |= ast_unregister_translator(&alawtolin);
00149 
00150    return res;
00151 }
00152 
00153 static int load_module(void)
00154 {
00155    int res;
00156 
00157    res = ast_register_translator(&alawtolin);
00158    if (!res)
00159       res = ast_register_translator(&lintoalaw);
00160    else
00161       ast_unregister_translator(&alawtolin);
00162 
00163    return res;
00164 }
00165 
00166 AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_DEFAULT, "A-law Coder/Decoder",
00167       .load = load_module,
00168       .unload = unload_module,
00169       .reload = reload,
00170           );

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