Thu Jul 9 13:40:34 2009

Asterisk developer's documentation


format_ilbc.c

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00001 /*
00002  * Asterisk -- An open source telephony toolkit.
00003  *
00004  * Brian K. West <brian@bkw.org>
00005  * 
00006  * Copyright (C) 1999 - 2005, Digium, Inc.
00007  *
00008  * Mark Spencer <markster@digium.com>
00009  *
00010  * See http://www.asterisk.org for more information about
00011  * the Asterisk project. Please do not directly contact
00012  * any of the maintainers of this project for assistance;
00013  * the project provides a web site, mailing lists and IRC
00014  * channels for your use.
00015  *
00016  * This program is free software, distributed under the terms of
00017  * the GNU General Public License Version 2. See the LICENSE file
00018  * at the top of the source tree.
00019  */
00020 
00021 /*! \file
00022  *
00023  * \brief Save to raw, headerless iLBC data.
00024  * \arg File name extension: ilbc
00025  * \ingroup formats
00026  */
00027 
00028 #include "asterisk.h"
00029 
00030 ASTERISK_FILE_VERSION(__FILE__, "$Revision: 175828 $")
00031 
00032 #include "asterisk/mod_format.h"
00033 #include "asterisk/module.h"
00034 #include "asterisk/endian.h"
00035 
00036 /* Some Ideas for this code came from makeg729e.c by Jeffrey Chilton */
00037 
00038 /* Portions of the conversion code are by guido@sienanet.it */
00039 
00040 #define  ILBC_BUF_SIZE  50 /* One Real iLBC Frame */
00041 #define  ILBC_SAMPLES   240
00042 
00043 static struct ast_frame *ilbc_read(struct ast_filestream *s, int *whennext)
00044 {
00045    int res;
00046    /* Send a frame from the file to the appropriate channel */
00047    s->fr.frametype = AST_FRAME_VOICE;
00048    s->fr.subclass = AST_FORMAT_ILBC;
00049    s->fr.mallocd = 0;
00050    AST_FRAME_SET_BUFFER(&s->fr, s->buf, AST_FRIENDLY_OFFSET, ILBC_BUF_SIZE);
00051    if ((res = fread(s->fr.data, 1, s->fr.datalen, s->f)) != s->fr.datalen) {
00052       if (res)
00053          ast_log(LOG_WARNING, "Short read (%d) (%s)!\n", res, strerror(errno));
00054       return NULL;
00055    }
00056    *whennext = s->fr.samples = ILBC_SAMPLES;
00057    return &s->fr;
00058 }
00059 
00060 static int ilbc_write(struct ast_filestream *fs, struct ast_frame *f)
00061 {
00062    int res;
00063    if (f->frametype != AST_FRAME_VOICE) {
00064       ast_log(LOG_WARNING, "Asked to write non-voice frame!\n");
00065       return -1;
00066    }
00067    if (f->subclass != AST_FORMAT_ILBC) {
00068       ast_log(LOG_WARNING, "Asked to write non-iLBC frame (%d)!\n", f->subclass);
00069       return -1;
00070    }
00071    if (f->datalen % 50) {
00072       ast_log(LOG_WARNING, "Invalid data length, %d, should be multiple of 50\n", f->datalen);
00073       return -1;
00074    }
00075    if ((res = fwrite(f->data, 1, f->datalen, fs->f)) != f->datalen) {
00076          ast_log(LOG_WARNING, "Bad write (%d/50): %s\n", res, strerror(errno));
00077          return -1;
00078    }
00079    return 0;
00080 }
00081 
00082 static int ilbc_seek(struct ast_filestream *fs, off_t sample_offset, int whence)
00083 {
00084    long bytes;
00085    off_t min,cur,max,offset=0;
00086    min = 0;
00087    cur = ftello(fs->f);
00088    fseeko(fs->f, 0, SEEK_END);
00089    max = ftello(fs->f);
00090    
00091    bytes = ILBC_BUF_SIZE * (sample_offset / ILBC_SAMPLES);
00092    if (whence == SEEK_SET)
00093       offset = bytes;
00094    else if (whence == SEEK_CUR || whence == SEEK_FORCECUR)
00095       offset = cur + bytes;
00096    else if (whence == SEEK_END)
00097       offset = max - bytes;
00098    if (whence != SEEK_FORCECUR) {
00099       offset = (offset > max)?max:offset;
00100    }
00101    /* protect against seeking beyond begining. */
00102    offset = (offset < min)?min:offset;
00103    if (fseeko(fs->f, offset, SEEK_SET) < 0)
00104       return -1;
00105    return 0;
00106 }
00107 
00108 static int ilbc_trunc(struct ast_filestream *fs)
00109 {
00110    /* Truncate file to current length */
00111    if (ftruncate(fileno(fs->f), ftello(fs->f)) < 0)
00112       return -1;
00113    return 0;
00114 }
00115 
00116 static off_t ilbc_tell(struct ast_filestream *fs)
00117 {
00118    off_t offset = ftello(fs->f);
00119    return (offset/ILBC_BUF_SIZE)*ILBC_SAMPLES;
00120 }
00121 
00122 static const struct ast_format ilbc_f = {
00123    .name = "iLBC",
00124    .exts = "ilbc",
00125    .format = AST_FORMAT_ILBC,
00126    .write = ilbc_write,
00127    .seek = ilbc_seek,
00128    .trunc = ilbc_trunc,
00129    .tell = ilbc_tell,
00130    .read = ilbc_read,
00131    .buf_size = ILBC_BUF_SIZE + AST_FRIENDLY_OFFSET,
00132 };
00133 
00134 static int load_module(void)
00135 {
00136    if (ast_format_register(&ilbc_f))
00137       return AST_MODULE_LOAD_FAILURE;
00138    return AST_MODULE_LOAD_SUCCESS;
00139 }
00140 
00141 static int unload_module(void)
00142 {
00143    return ast_format_unregister(ilbc_f.name);
00144 }  
00145 
00146 AST_MODULE_INFO_STANDARD(ASTERISK_GPL_KEY, "Raw iLBC data");

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