Wed Oct 28 11:45:37 2009

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 #include "asterisk.h"
00029 
00030 ASTERISK_FILE_VERSION(__FILE__, "$Revision: 89515 $")
00031 
00032 #include "asterisk/mod_format.h"
00033 #include "asterisk/module.h"
00034 
00035 #define G723_MAX_SIZE 1024
00036 
00037 static struct ast_frame *g723_read(struct ast_filestream *s, int *whennext)
00038 {
00039    unsigned short size;
00040    int res;
00041    int delay;
00042    /* Read the delay for the next packet, and schedule again if necessary */
00043    /* XXX is this ignored ? */
00044    if (fread(&delay, 1, 4, s->f) == 4) 
00045       delay = ntohl(delay);
00046    else
00047       delay = -1;
00048    if (fread(&size, 1, 2, s->f) != 2) {
00049       /* Out of data, or the file is no longer valid.  In any case
00050          go ahead and stop the stream */
00051       return NULL;
00052    }
00053    /* Looks like we have a frame to read from here */
00054    size = ntohs(size);
00055    if (size > G723_MAX_SIZE) {
00056       ast_log(LOG_WARNING, "Size %d is invalid\n", size);
00057       /* The file is apparently no longer any good, as we
00058          shouldn't ever get frames even close to this 
00059          size.  */
00060       return NULL;
00061    }
00062    /* Read the data into the buffer */
00063    s->fr.frametype = AST_FRAME_VOICE;
00064    s->fr.subclass = AST_FORMAT_G723_1;
00065    s->fr.mallocd = 0;
00066    AST_FRAME_SET_BUFFER(&s->fr, s->buf, AST_FRIENDLY_OFFSET, size);
00067    if ((res = fread(s->fr.data, 1, s->fr.datalen, s->f)) != size) {
00068       ast_log(LOG_WARNING, "Short read (%d of %d bytes) (%s)!\n", res, size, strerror(errno));
00069       return NULL;
00070    }
00071    *whennext = s->fr.samples = 240;
00072    return &s->fr;
00073 }
00074 
00075 static int g723_write(struct ast_filestream *s, struct ast_frame *f)
00076 {
00077    uint32_t delay;
00078    uint16_t size;
00079    int res;
00080    /* XXX there used to be a check s->fr means a read stream */
00081    if (f->frametype != AST_FRAME_VOICE) {
00082       ast_log(LOG_WARNING, "Asked to write non-voice frame!\n");
00083       return -1;
00084    }
00085    if (f->subclass != AST_FORMAT_G723_1) {
00086       ast_log(LOG_WARNING, "Asked to write non-g723 frame!\n");
00087       return -1;
00088    }
00089    delay = 0;
00090    if (f->datalen <= 0) {
00091       ast_log(LOG_WARNING, "Short frame ignored (%d bytes long?)\n", f->datalen);
00092       return 0;
00093    }
00094    if ((res = fwrite(&delay, 1, 4, s->f)) != 4) {
00095       ast_log(LOG_WARNING, "Unable to write delay: res=%d (%s)\n", res, strerror(errno));
00096       return -1;
00097    }
00098    size = htons(f->datalen);
00099    if ((res = fwrite(&size, 1, 2, s->f)) != 2) {
00100       ast_log(LOG_WARNING, "Unable to write size: res=%d (%s)\n", res, strerror(errno));
00101       return -1;
00102    }
00103    if ((res = fwrite(f->data, 1, f->datalen, s->f)) != f->datalen) {
00104       ast_log(LOG_WARNING, "Unable to write frame: res=%d (%s)\n", res, strerror(errno));
00105       return -1;
00106    }  
00107    return 0;
00108 }
00109 
00110 static int g723_seek(struct ast_filestream *fs, off_t sample_offset, int whence)
00111 {
00112    return -1;
00113 }
00114 
00115 static int g723_trunc(struct ast_filestream *fs)
00116 {
00117    /* Truncate file to current length */
00118    if (ftruncate(fileno(fs->f), ftello(fs->f)) < 0)
00119       return -1;
00120    return 0;
00121 }
00122 
00123 static off_t g723_tell(struct ast_filestream *fs)
00124 {
00125    return -1;
00126 }
00127 
00128 static const struct ast_format g723_1_f = {
00129    .name = "g723sf",
00130    .exts = "g723|g723sf",
00131    .format = AST_FORMAT_G723_1,
00132    .write = g723_write,
00133    .seek =  g723_seek,
00134    .trunc = g723_trunc,
00135    .tell =  g723_tell,
00136    .read =  g723_read,
00137    .buf_size = G723_MAX_SIZE + AST_FRIENDLY_OFFSET,
00138 };
00139 
00140 static int load_module(void)
00141 {
00142    if (ast_format_register(&g723_1_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(g723_1_f.name);
00150 }  
00151 
00152 AST_MODULE_INFO_STANDARD(ASTERISK_GPL_KEY, "G.723.1 Simple Timestamp File Format");

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