Sat Mar 10 01:54:17 2012

Asterisk developer's documentation


format_g729.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 Save to raw, headerless G729 data.
00022  * \note This is not an encoder/decoder. The codec fo g729 is only
00023  * available with a commercial license from Digium, due to patent
00024  * restrictions. Check http://www.digium.com for information.
00025  * \arg Extensions: g729 
00026  * \ingroup formats
00027  */
00028 
00029 /*** MODULEINFO
00030    <support_level>core</support_level>
00031  ***/
00032  
00033 #include "asterisk.h"
00034 
00035 ASTERISK_FILE_VERSION(__FILE__, "$Revision: 328209 $")
00036 
00037 #include "asterisk/mod_format.h"
00038 #include "asterisk/module.h"
00039 #include "asterisk/endian.h"
00040 
00041 /* Some Ideas for this code came from makeg729e.c by Jeffrey Chilton */
00042 
00043 /* Portions of the conversion code are by guido@sienanet.it */
00044 
00045 #define  BUF_SIZE 20 /* two G729 frames */
00046 #define  G729A_SAMPLES  160
00047 
00048 static struct ast_frame *g729_read(struct ast_filestream *s, int *whennext)
00049 {
00050    int res;
00051    /* Send a frame from the file to the appropriate channel */
00052    s->fr.frametype = AST_FRAME_VOICE;
00053    s->fr.subclass.codec = AST_FORMAT_G729A;
00054    s->fr.mallocd = 0;
00055    s->fr.samples = G729A_SAMPLES;
00056    AST_FRAME_SET_BUFFER(&s->fr, s->buf, AST_FRIENDLY_OFFSET, BUF_SIZE);
00057    if ((res = fread(s->fr.data.ptr, 1, s->fr.datalen, s->f)) != s->fr.datalen) {
00058       if (res && (res != 10)) /* XXX what for ? */
00059          ast_log(LOG_WARNING, "Short read (%d) (%s)!\n", res, strerror(errno));
00060       return NULL;
00061    }
00062    *whennext = s->fr.samples;
00063    return &s->fr;
00064 }
00065 
00066 static int g729_write(struct ast_filestream *fs, struct ast_frame *f)
00067 {
00068    int res;
00069    if (f->frametype != AST_FRAME_VOICE) {
00070       ast_log(LOG_WARNING, "Asked to write non-voice frame!\n");
00071       return -1;
00072    }
00073    if (f->subclass.codec != AST_FORMAT_G729A) {
00074       ast_log(LOG_WARNING, "Asked to write non-G729 frame (%s)!\n", ast_getformatname(f->subclass.codec));
00075       return -1;
00076    }
00077    if (f->datalen % 10) {
00078       ast_log(LOG_WARNING, "Invalid data length, %d, should be multiple of 10\n", f->datalen);
00079       return -1;
00080    }
00081    if ((res = fwrite(f->data.ptr, 1, f->datalen, fs->f)) != f->datalen) {
00082          ast_log(LOG_WARNING, "Bad write (%d/10): %s\n", res, strerror(errno));
00083          return -1;
00084    }
00085    return 0;
00086 }
00087 
00088 static int g729_seek(struct ast_filestream *fs, off_t sample_offset, int whence)
00089 {
00090    long bytes;
00091    off_t min,cur,max,offset=0;
00092    min = 0;
00093    cur = ftello(fs->f);
00094    fseeko(fs->f, 0, SEEK_END);
00095    max = ftello(fs->f);
00096    
00097    bytes = BUF_SIZE * (sample_offset / G729A_SAMPLES);
00098    if (whence == SEEK_SET)
00099       offset = bytes;
00100    else if (whence == SEEK_CUR || whence == SEEK_FORCECUR)
00101       offset = cur + bytes;
00102    else if (whence == SEEK_END)
00103       offset = max - bytes;
00104    if (whence != SEEK_FORCECUR) {
00105       offset = (offset > max)?max:offset;
00106    }
00107    /* protect against seeking beyond begining. */
00108    offset = (offset < min)?min:offset;
00109    if (fseeko(fs->f, offset, SEEK_SET) < 0)
00110       return -1;
00111    return 0;
00112 }
00113 
00114 static int g729_trunc(struct ast_filestream *fs)
00115 {
00116    /* Truncate file to current length */
00117    if (ftruncate(fileno(fs->f), ftello(fs->f)) < 0)
00118       return -1;
00119    return 0;
00120 }
00121 
00122 static off_t g729_tell(struct ast_filestream *fs)
00123 {
00124    off_t offset = ftello(fs->f);
00125    return (offset/BUF_SIZE)*G729A_SAMPLES;
00126 }
00127 
00128 static const struct ast_format g729_f = {
00129    .name = "g729",
00130    .exts = "g729",
00131    .format = AST_FORMAT_G729A,
00132    .write = g729_write,
00133    .seek = g729_seek,
00134    .trunc = g729_trunc,
00135    .tell = g729_tell,
00136    .read = g729_read,
00137    .buf_size = BUF_SIZE + AST_FRIENDLY_OFFSET,
00138 };
00139 
00140 static int load_module(void)
00141 {
00142    if (ast_format_register(&g729_f))
00143       return AST_MODULE_LOAD_FAILURE;
00144    return AST_MODULE_LOAD_SUCCESS;
00145 }
00146 
00147 static int unload_module(void)
00148 {
00149    return ast_format_unregister(g729_f.name);
00150 }
00151 
00152 AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_LOAD_ORDER, "Raw G.729 data",
00153    .load = load_module,
00154    .unload = unload_module,
00155    .load_pri = AST_MODPRI_APP_DEPEND
00156 );

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