Sat Aug 6 00:39:28 2011

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: 233782 $")
00031 
00032 #include <unistd.h>
00033 #include <netinet/in.h>
00034 #include <arpa/inet.h>
00035 #include <stdlib.h>
00036 #include <stdio.h>
00037 #include <errno.h>
00038 #include <string.h>
00039 #include <sys/time.h>
00040 
00041 #include "asterisk/lock.h"
00042 #include "asterisk/channel.h"
00043 #include "asterisk/file.h"
00044 #include "asterisk/logger.h"
00045 #include "asterisk/sched.h"
00046 #include "asterisk/module.h"
00047 
00048 #define G723_MAX_SIZE 1024
00049 
00050 static struct ast_frame *g723_read(struct ast_filestream *s, int *whennext)
00051 {
00052    unsigned short size;
00053    int res;
00054    int delay;
00055    /* Read the delay for the next packet, and schedule again if necessary */
00056    /* XXX is this ignored ? */
00057    if (fread(&delay, 1, 4, s->f) == 4) 
00058       delay = ntohl(delay);
00059    else
00060       delay = -1;
00061    if (fread(&size, 1, 2, s->f) != 2) {
00062       /* Out of data, or the file is no longer valid.  In any case
00063          go ahead and stop the stream */
00064       return NULL;
00065    }
00066    /* Looks like we have a frame to read from here */
00067    size = ntohs(size);
00068    if (size > G723_MAX_SIZE) {
00069       ast_log(LOG_WARNING, "Size %d is invalid\n", size);
00070       /* The file is apparently no longer any good, as we
00071          shouldn't ever get frames even close to this 
00072          size.  */
00073       return NULL;
00074    }
00075    /* Read the data into the buffer */
00076    s->fr.frametype = AST_FRAME_VOICE;
00077    s->fr.subclass = AST_FORMAT_G723_1;
00078    s->fr.mallocd = 0;
00079    AST_FRAME_SET_BUFFER(&s->fr, s->buf, AST_FRIENDLY_OFFSET, size);
00080    if ((res = fread(s->fr.data, 1, s->fr.datalen, s->f)) != size) {
00081       ast_log(LOG_WARNING, "Short read (%d of %d bytes) (%s)!\n", res, size, strerror(errno));
00082       return NULL;
00083    }
00084    *whennext = s->fr.samples = 240;
00085    return &s->fr;
00086 }
00087 
00088 static int g723_write(struct ast_filestream *s, struct ast_frame *f)
00089 {
00090    uint32_t delay;
00091    uint16_t size;
00092    int res;
00093    /* XXX there used to be a check s->fr means a read stream */
00094    if (f->frametype != AST_FRAME_VOICE) {
00095       ast_log(LOG_WARNING, "Asked to write non-voice frame!\n");
00096       return -1;
00097    }
00098    if (f->subclass != AST_FORMAT_G723_1) {
00099       ast_log(LOG_WARNING, "Asked to write non-g723 frame!\n");
00100       return -1;
00101    }
00102    delay = 0;
00103    if (f->datalen <= 0) {
00104       ast_log(LOG_WARNING, "Short frame ignored (%d bytes long?)\n", f->datalen);
00105       return 0;
00106    }
00107    if ((res = fwrite(&delay, 1, 4, s->f)) != 4) {
00108       ast_log(LOG_WARNING, "Unable to write delay: res=%d (%s)\n", res, strerror(errno));
00109       return -1;
00110    }
00111    size = htons(f->datalen);
00112    if ((res = fwrite(&size, 1, 2, s->f)) != 2) {
00113       ast_log(LOG_WARNING, "Unable to write size: res=%d (%s)\n", res, strerror(errno));
00114       return -1;
00115    }
00116    if ((res = fwrite(f->data, 1, f->datalen, s->f)) != f->datalen) {
00117       ast_log(LOG_WARNING, "Unable to write frame: res=%d (%s)\n", res, strerror(errno));
00118       return -1;
00119    }  
00120    return 0;
00121 }
00122 
00123 static int g723_seek(struct ast_filestream *fs, off_t sample_offset, int whence)
00124 {
00125    return -1;
00126 }
00127 
00128 static int g723_trunc(struct ast_filestream *fs)
00129 {
00130    /* Truncate file to current length */
00131    if (ftruncate(fileno(fs->f), ftello(fs->f)) < 0)
00132       return -1;
00133    return 0;
00134 }
00135 
00136 static off_t g723_tell(struct ast_filestream *fs)
00137 {
00138    return -1;
00139 }
00140 
00141 static const struct ast_format g723_1_f = {
00142    .name = "g723sf",
00143    .exts = "g723|g723sf",
00144    .format = AST_FORMAT_G723_1,
00145    .write = g723_write,
00146    .seek =  g723_seek,
00147    .trunc = g723_trunc,
00148    .tell =  g723_tell,
00149    .read =  g723_read,
00150    .buf_size = G723_MAX_SIZE + AST_FRIENDLY_OFFSET,
00151 };
00152 
00153 static int load_module(void)
00154 {
00155    return ast_format_register(&g723_1_f);
00156 }
00157 
00158 static int unload_module(void)
00159 {
00160    return ast_format_unregister(g723_1_f.name);
00161 }  
00162 
00163 AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_LOAD_FIRST, "G.723.1 Simple Timestamp File Format",
00164    .load = load_module,
00165    .unload = unload_module,
00166 );

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