Thu Apr 28 2011 17:15:22

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 #include "asterisk.h"
00030 
00031 ASTERISK_FILE_VERSION(__FILE__, "$Revision: 233694 $")
00032 
00033 #include "asterisk/mod_format.h"
00034 #include "asterisk/module.h"
00035 #include "asterisk/endian.h"
00036 
00037 /* Some Ideas for this code came from makeg729e.c by Jeffrey Chilton */
00038 
00039 /* Portions of the conversion code are by guido@sienanet.it */
00040 
00041 #define  BUF_SIZE 20 /* two G729 frames */
00042 #define  G729A_SAMPLES  160
00043 
00044 static struct ast_frame *g729_read(struct ast_filestream *s, int *whennext)
00045 {
00046    int res;
00047    /* Send a frame from the file to the appropriate channel */
00048    s->fr.frametype = AST_FRAME_VOICE;
00049    s->fr.subclass = AST_FORMAT_G729A;
00050    s->fr.mallocd = 0;
00051    s->fr.samples = G729A_SAMPLES;
00052    AST_FRAME_SET_BUFFER(&s->fr, s->buf, AST_FRIENDLY_OFFSET, BUF_SIZE);
00053    if ((res = fread(s->fr.data.ptr, 1, s->fr.datalen, s->f)) != s->fr.datalen) {
00054       if (res && (res != 10)) /* XXX what for ? */
00055          ast_log(LOG_WARNING, "Short read (%d) (%s)!\n", res, strerror(errno));
00056       return NULL;
00057    }
00058    *whennext = s->fr.samples;
00059    return &s->fr;
00060 }
00061 
00062 static int g729_write(struct ast_filestream *fs, struct ast_frame *f)
00063 {
00064    int res;
00065    if (f->frametype != AST_FRAME_VOICE) {
00066       ast_log(LOG_WARNING, "Asked to write non-voice frame!\n");
00067       return -1;
00068    }
00069    if (f->subclass != AST_FORMAT_G729A) {
00070       ast_log(LOG_WARNING, "Asked to write non-G729 frame (%d)!\n", f->subclass);
00071       return -1;
00072    }
00073    if (f->datalen % 10) {
00074       ast_log(LOG_WARNING, "Invalid data length, %d, should be multiple of 10\n", f->datalen);
00075       return -1;
00076    }
00077    if ((res = fwrite(f->data.ptr, 1, f->datalen, fs->f)) != f->datalen) {
00078          ast_log(LOG_WARNING, "Bad write (%d/10): %s\n", res, strerror(errno));
00079          return -1;
00080    }
00081    return 0;
00082 }
00083 
00084 static int g729_seek(struct ast_filestream *fs, off_t sample_offset, int whence)
00085 {
00086    long bytes;
00087    off_t min,cur,max,offset=0;
00088    min = 0;
00089    cur = ftello(fs->f);
00090    fseeko(fs->f, 0, SEEK_END);
00091    max = ftello(fs->f);
00092    
00093    bytes = BUF_SIZE * (sample_offset / G729A_SAMPLES);
00094    if (whence == SEEK_SET)
00095       offset = bytes;
00096    else if (whence == SEEK_CUR || whence == SEEK_FORCECUR)
00097       offset = cur + bytes;
00098    else if (whence == SEEK_END)
00099       offset = max - bytes;
00100    if (whence != SEEK_FORCECUR) {
00101       offset = (offset > max)?max:offset;
00102    }
00103    /* protect against seeking beyond begining. */
00104    offset = (offset < min)?min:offset;
00105    if (fseeko(fs->f, offset, SEEK_SET) < 0)
00106       return -1;
00107    return 0;
00108 }
00109 
00110 static int g729_trunc(struct ast_filestream *fs)
00111 {
00112    /* Truncate file to current length */
00113    if (ftruncate(fileno(fs->f), ftello(fs->f)) < 0)
00114       return -1;
00115    return 0;
00116 }
00117 
00118 static off_t g729_tell(struct ast_filestream *fs)
00119 {
00120    off_t offset = ftello(fs->f);
00121    return (offset/BUF_SIZE)*G729A_SAMPLES;
00122 }
00123 
00124 static const struct ast_format g729_f = {
00125    .name = "g729",
00126    .exts = "g729",
00127    .format = AST_FORMAT_G729A,
00128    .write = g729_write,
00129    .seek = g729_seek,
00130    .trunc = g729_trunc,
00131    .tell = g729_tell,
00132    .read = g729_read,
00133    .buf_size = BUF_SIZE + AST_FRIENDLY_OFFSET,
00134 };
00135 
00136 static int load_module(void)
00137 {
00138    if (ast_format_register(&g729_f))
00139       return AST_MODULE_LOAD_FAILURE;
00140    return AST_MODULE_LOAD_SUCCESS;
00141 }
00142 
00143 static int unload_module(void)
00144 {
00145    return ast_format_unregister(g729_f.name);
00146 }  
00147 
00148 AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_LOAD_ORDER, "Raw G729 data",
00149    .load = load_module,
00150    .unload = unload_module,
00151    .load_pri = 10,
00152 );