Sat Mar 10 01:54:17 2012

Asterisk developer's documentation


format_g723.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 /*! 
00020  * \file
00021  *
00022  * \brief Old-style G.723.1 frame/timestamp format.
00023  * 
00024  * \arg Extensions: g723, g723sf
00025  * \ingroup formats
00026  */
00027 
00028 /*** MODULEINFO
00029    <support_level>core</support_level>
00030  ***/
00031  
00032 #include "asterisk.h"
00033 
00034 ASTERISK_FILE_VERSION(__FILE__, "$Revision: 328209 $")
00035 
00036 #include "asterisk/mod_format.h"
00037 #include "asterisk/module.h"
00038 
00039 #define G723_MAX_SIZE 1024
00040 
00041 static struct ast_frame *g723_read(struct ast_filestream *s, int *whennext)
00042 {
00043    unsigned short size;
00044    int res;
00045    int delay;
00046    /* Read the delay for the next packet, and schedule again if necessary */
00047    /* XXX is this ignored ? */
00048    if (fread(&delay, 1, 4, s->f) == 4) 
00049       delay = ntohl(delay);
00050    else
00051       delay = -1;
00052    if (fread(&size, 1, 2, s->f) != 2) {
00053       /* Out of data, or the file is no longer valid.  In any case
00054          go ahead and stop the stream */
00055       return NULL;
00056    }
00057    /* Looks like we have a frame to read from here */
00058    size = ntohs(size);
00059    if (size > G723_MAX_SIZE) {
00060       ast_log(LOG_WARNING, "Size %d is invalid\n", size);
00061       /* The file is apparently no longer any good, as we
00062          shouldn't ever get frames even close to this 
00063          size.  */
00064       return NULL;
00065    }
00066    /* Read the data into the buffer */
00067    s->fr.frametype = AST_FRAME_VOICE;
00068    s->fr.subclass.codec = AST_FORMAT_G723_1;
00069    s->fr.mallocd = 0;
00070    AST_FRAME_SET_BUFFER(&s->fr, s->buf, AST_FRIENDLY_OFFSET, size);
00071    if ((res = fread(s->fr.data.ptr, 1, s->fr.datalen, s->f)) != size) {
00072       ast_log(LOG_WARNING, "Short read (%d of %d bytes) (%s)!\n", res, size, strerror(errno));
00073       return NULL;
00074    }
00075    *whennext = s->fr.samples = 240;
00076    return &s->fr;
00077 }
00078 
00079 static int g723_write(struct ast_filestream *s, struct ast_frame *f)
00080 {
00081    uint32_t delay;
00082    uint16_t size;
00083    int res;
00084    /* XXX there used to be a check s->fr means a read stream */
00085    if (f->frametype != AST_FRAME_VOICE) {
00086       ast_log(LOG_WARNING, "Asked to write non-voice frame!\n");
00087       return -1;
00088    }
00089    if (f->subclass.codec != AST_FORMAT_G723_1) {
00090       ast_log(LOG_WARNING, "Asked to write non-g723 frame!\n");
00091       return -1;
00092    }
00093    delay = 0;
00094    if (f->datalen <= 0) {
00095       ast_log(LOG_WARNING, "Short frame ignored (%d bytes long?)\n", f->datalen);
00096       return 0;
00097    }
00098    if ((res = fwrite(&delay, 1, 4, s->f)) != 4) {
00099       ast_log(LOG_WARNING, "Unable to write delay: res=%d (%s)\n", res, strerror(errno));
00100       return -1;
00101    }
00102    size = htons(f->datalen);
00103    if ((res = fwrite(&size, 1, 2, s->f)) != 2) {
00104       ast_log(LOG_WARNING, "Unable to write size: res=%d (%s)\n", res, strerror(errno));
00105       return -1;
00106    }
00107    if ((res = fwrite(f->data.ptr, 1, f->datalen, s->f)) != f->datalen) {
00108       ast_log(LOG_WARNING, "Unable to write frame: res=%d (%s)\n", res, strerror(errno));
00109       return -1;
00110    }  
00111    return 0;
00112 }
00113 
00114 static int g723_seek(struct ast_filestream *fs, off_t sample_offset, int whence)
00115 {
00116    return -1;
00117 }
00118 
00119 static int g723_trunc(struct ast_filestream *fs)
00120 {
00121    /* Truncate file to current length */
00122    if (ftruncate(fileno(fs->f), ftello(fs->f)) < 0)
00123       return -1;
00124    return 0;
00125 }
00126 
00127 static off_t g723_tell(struct ast_filestream *fs)
00128 {
00129    return -1;
00130 }
00131 
00132 static const struct ast_format g723_1_f = {
00133    .name = "g723sf",
00134    .exts = "g723|g723sf",
00135    .format = AST_FORMAT_G723_1,
00136    .write = g723_write,
00137    .seek =  g723_seek,
00138    .trunc = g723_trunc,
00139    .tell =  g723_tell,
00140    .read =  g723_read,
00141    .buf_size = G723_MAX_SIZE + AST_FRIENDLY_OFFSET,
00142 };
00143 
00144 static int load_module(void)
00145 {
00146    if (ast_format_register(&g723_1_f))
00147       return AST_MODULE_LOAD_FAILURE;
00148    return AST_MODULE_LOAD_SUCCESS;
00149 }
00150 
00151 static int unload_module(void)
00152 {
00153    return ast_format_unregister(g723_1_f.name);
00154 }
00155 
00156 AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_LOAD_ORDER, "G.723.1 Simple Timestamp File Format",
00157    .load = load_module,
00158    .unload = unload_module,
00159    .load_pri = AST_MODPRI_APP_DEPEND
00160 );

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