Sat Aug 6 00:39:28 2011

Asterisk developer's documentation


format_h263.c

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00001 /*
00002  * Asterisk -- An open source telephony toolkit.
00003  *
00004  * Copyright (C) 1999 - 2006, 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 h263 data.
00022  * \arg File name extension: h263
00023  * \ingroup formats
00024  * \arg See \ref AstVideo
00025  */
00026  
00027 #include "asterisk.h"
00028 
00029 ASTERISK_FILE_VERSION(__FILE__, "$Revision: 233782 $")
00030 
00031 #include <unistd.h>
00032 #include <netinet/in.h>
00033 #include <arpa/inet.h>
00034 #include <stdlib.h>
00035 #include <sys/time.h>
00036 #include <stdio.h>
00037 #include <errno.h>
00038 #include <string.h>
00039 
00040 #include "asterisk/lock.h"
00041 #include "asterisk/channel.h"
00042 #include "asterisk/file.h"
00043 #include "asterisk/logger.h"
00044 #include "asterisk/sched.h"
00045 #include "asterisk/module.h"
00046 #include "asterisk/endian.h"
00047 
00048 /* Some Ideas for this code came from makeh263e.c by Jeffrey Chilton */
00049 
00050 /* Portions of the conversion code are by guido@sienanet.it */
00051 
00052 /* According to:
00053  * http://lists.mpegif.org/pipermail/mp4-tech/2005-July/005741.html
00054  * the maximum actual frame size is not 2048, but 8192.  Since the maximum
00055  * theoretical limit is not much larger (32k = 15bits), we'll go for that
00056  * size to ensure we don't corrupt frames sent to us (unless they're
00057  * ridiculously large). */
00058 #define  BUF_SIZE 32768 /* Four real h.263 Frames */
00059 
00060 struct h263_desc {
00061    unsigned int lastts;
00062 };
00063 
00064 
00065 static int h263_open(struct ast_filestream *s)
00066 {
00067    unsigned int ts;
00068    int res;
00069 
00070    if ((res = fread(&ts, 1, sizeof(ts), s->f)) < sizeof(ts)) {
00071       ast_log(LOG_WARNING, "Empty file!\n");
00072       return -1;
00073    }
00074    return 0;
00075 }
00076 
00077 static struct ast_frame *h263_read(struct ast_filestream *s, int *whennext)
00078 {
00079    int res;
00080    int mark;
00081    unsigned short len;
00082    unsigned int ts;
00083    struct h263_desc *fs = (struct h263_desc *)s->_private;
00084 
00085    /* Send a frame from the file to the appropriate channel */
00086    if ((res = fread(&len, 1, sizeof(len), s->f)) < 1)
00087       return NULL;
00088    len = ntohs(len);
00089    mark = (len & 0x8000) ? 1 : 0;
00090    len &= 0x7fff;
00091    if (len > BUF_SIZE) {
00092       ast_log(LOG_WARNING, "Length %d is too long\n", len);
00093       return NULL;
00094    }
00095    s->fr.frametype = AST_FRAME_VIDEO;
00096    s->fr.subclass = AST_FORMAT_H263;
00097    s->fr.mallocd = 0;
00098    AST_FRAME_SET_BUFFER(&s->fr, s->buf, AST_FRIENDLY_OFFSET, len);
00099    if ((res = fread(s->fr.data, 1, s->fr.datalen, s->f)) != s->fr.datalen) {
00100       if (res)
00101          ast_log(LOG_WARNING, "Short read (%d) (%s)!\n", res, strerror(errno));
00102       return NULL;
00103    }
00104    s->fr.samples = fs->lastts;   /* XXX what ? */
00105    s->fr.datalen = len;
00106    s->fr.subclass |= mark;
00107    s->fr.delivery.tv_sec = 0;
00108    s->fr.delivery.tv_usec = 0;
00109    if ((res = fread(&ts, 1, sizeof(ts), s->f)) == sizeof(ts)) {
00110       fs->lastts = ntohl(ts);
00111       *whennext = fs->lastts * 4/45;
00112    } else
00113       *whennext = 0;
00114    return &s->fr;
00115 }
00116 
00117 static int h263_write(struct ast_filestream *fs, struct ast_frame *f)
00118 {
00119    int res;
00120    unsigned int ts;
00121    unsigned short len;
00122    int subclass;
00123    int mark=0;
00124    if (f->frametype != AST_FRAME_VIDEO) {
00125       ast_log(LOG_WARNING, "Asked to write non-video frame!\n");
00126       return -1;
00127    }
00128    subclass = f->subclass;
00129    if (subclass & 0x1)
00130       mark=0x8000;
00131    subclass &= ~0x1;
00132    if (subclass != AST_FORMAT_H263) {
00133       ast_log(LOG_WARNING, "Asked to write non-h263 frame (%d)!\n", f->subclass);
00134       return -1;
00135    }
00136    ts = htonl(f->samples);
00137    if ((res = fwrite(&ts, 1, sizeof(ts), fs->f)) != sizeof(ts)) {
00138          ast_log(LOG_WARNING, "Bad write (%d/4): %s\n", res, strerror(errno));
00139          return -1;
00140    }
00141    len = htons(f->datalen | mark);
00142    if ((res = fwrite(&len, 1, sizeof(len), fs->f)) != sizeof(len)) {
00143          ast_log(LOG_WARNING, "Bad write (%d/2): %s\n", res, strerror(errno));
00144          return -1;
00145    }
00146    if ((res = fwrite(f->data, 1, f->datalen, fs->f)) != f->datalen) {
00147          ast_log(LOG_WARNING, "Bad write (%d/%d): %s\n", res, f->datalen, strerror(errno));
00148          return -1;
00149    }
00150    return 0;
00151 }
00152 
00153 static int h263_seek(struct ast_filestream *fs, off_t sample_offset, int whence)
00154 {
00155    /* No way Jose */
00156    return -1;
00157 }
00158 
00159 static int h263_trunc(struct ast_filestream *fs)
00160 {
00161    /* Truncate file to current length */
00162    if (ftruncate(fileno(fs->f), ftello(fs->f)) < 0)
00163       return -1;
00164    return 0;
00165 }
00166 
00167 static off_t h263_tell(struct ast_filestream *fs)
00168 {
00169    off_t offset = ftello(fs->f);
00170    return offset; /* XXX totally bogus, needs fixing */
00171 }
00172 
00173 static const struct ast_format h263_f = {
00174    .name = "h263",
00175    .exts = "h263",
00176    .format = AST_FORMAT_H263,
00177    .open = h263_open,
00178    .write = h263_write,
00179    .seek = h263_seek,
00180    .trunc = h263_trunc,
00181    .tell = h263_tell,
00182    .read = h263_read,
00183    .buf_size = BUF_SIZE + AST_FRIENDLY_OFFSET,
00184    .desc_size = sizeof(struct h263_desc),
00185 };
00186 
00187 static int load_module(void)
00188 {
00189    return ast_format_register(&h263_f);
00190 }
00191 
00192 static int unload_module(void)
00193 {
00194    return ast_format_unregister(h263_f.name);
00195 }  
00196 
00197 AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_LOAD_FIRST, "Raw H.263 data",
00198    .load = load_module,
00199    .unload = unload_module,
00200 );

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