Thu Oct 11 06:47:15 2012

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: 233694 $")
00030 
00031 #include "asterisk/mod_format.h"
00032 #include "asterisk/module.h"
00033 #include "asterisk/endian.h"
00034 
00035 /* Some Ideas for this code came from makeh263e.c by Jeffrey Chilton */
00036 
00037 /* Portions of the conversion code are by guido@sienanet.it */
00038 
00039 /* According to:
00040  * http://lists.mpegif.org/pipermail/mp4-tech/2005-July/005741.html
00041  * the maximum actual frame size is not 2048, but 8192.  Since the maximum
00042  * theoretical limit is not much larger (32k = 15bits), we'll go for that
00043  * size to ensure we don't corrupt frames sent to us (unless they're
00044  * ridiculously large). */
00045 #define  BUF_SIZE 32768 /* Four real h.263 Frames */
00046 
00047 struct h263_desc {
00048    unsigned int lastts;
00049 };
00050 
00051 
00052 static int h263_open(struct ast_filestream *s)
00053 {
00054    unsigned int ts;
00055    int res;
00056 
00057    if ((res = fread(&ts, 1, sizeof(ts), s->f)) < sizeof(ts)) {
00058       ast_log(LOG_WARNING, "Empty file!\n");
00059       return -1;
00060    }
00061    return 0;
00062 }
00063 
00064 static struct ast_frame *h263_read(struct ast_filestream *s, int *whennext)
00065 {
00066    int res;
00067    int mark;
00068    unsigned short len;
00069    unsigned int ts;
00070    struct h263_desc *fs = (struct h263_desc *)s->_private;
00071 
00072    /* Send a frame from the file to the appropriate channel */
00073    if ((res = fread(&len, 1, sizeof(len), s->f)) < 1)
00074       return NULL;
00075    len = ntohs(len);
00076    mark = (len & 0x8000) ? 1 : 0;
00077    len &= 0x7fff;
00078    if (len > BUF_SIZE) {
00079       ast_log(LOG_WARNING, "Length %d is too long\n", len);
00080       return NULL;
00081    }
00082    s->fr.frametype = AST_FRAME_VIDEO;
00083    s->fr.subclass = AST_FORMAT_H263;
00084    s->fr.mallocd = 0;
00085    AST_FRAME_SET_BUFFER(&s->fr, s->buf, AST_FRIENDLY_OFFSET, len);
00086    if ((res = fread(s->fr.data.ptr, 1, s->fr.datalen, s->f)) != s->fr.datalen) {
00087       if (res)
00088          ast_log(LOG_WARNING, "Short read (%d) (%s)!\n", res, strerror(errno));
00089       return NULL;
00090    }
00091    s->fr.samples = fs->lastts;   /* XXX what ? */
00092    s->fr.datalen = len;
00093    s->fr.subclass |= mark;
00094    s->fr.delivery.tv_sec = 0;
00095    s->fr.delivery.tv_usec = 0;
00096    if ((res = fread(&ts, 1, sizeof(ts), s->f)) == sizeof(ts)) {
00097       fs->lastts = ntohl(ts);
00098       *whennext = fs->lastts * 4/45;
00099    } else
00100       *whennext = 0;
00101    return &s->fr;
00102 }
00103 
00104 static int h263_write(struct ast_filestream *fs, struct ast_frame *f)
00105 {
00106    int res;
00107    unsigned int ts;
00108    unsigned short len;
00109    int subclass;
00110    int mark=0;
00111    if (f->frametype != AST_FRAME_VIDEO) {
00112       ast_log(LOG_WARNING, "Asked to write non-video frame!\n");
00113       return -1;
00114    }
00115    subclass = f->subclass;
00116    if (subclass & 0x1)
00117       mark=0x8000;
00118    subclass &= ~0x1;
00119    if (subclass != AST_FORMAT_H263) {
00120       ast_log(LOG_WARNING, "Asked to write non-h263 frame (%d)!\n", f->subclass);
00121       return -1;
00122    }
00123    ts = htonl(f->samples);
00124    if ((res = fwrite(&ts, 1, sizeof(ts), fs->f)) != sizeof(ts)) {
00125          ast_log(LOG_WARNING, "Bad write (%d/4): %s\n", res, strerror(errno));
00126          return -1;
00127    }
00128    len = htons(f->datalen | mark);
00129    if ((res = fwrite(&len, 1, sizeof(len), fs->f)) != sizeof(len)) {
00130          ast_log(LOG_WARNING, "Bad write (%d/2): %s\n", res, strerror(errno));
00131          return -1;
00132    }
00133    if ((res = fwrite(f->data.ptr, 1, f->datalen, fs->f)) != f->datalen) {
00134          ast_log(LOG_WARNING, "Bad write (%d/%d): %s\n", res, f->datalen, strerror(errno));
00135          return -1;
00136    }
00137    return 0;
00138 }
00139 
00140 static int h263_seek(struct ast_filestream *fs, off_t sample_offset, int whence)
00141 {
00142    /* No way Jose */
00143    return -1;
00144 }
00145 
00146 static int h263_trunc(struct ast_filestream *fs)
00147 {
00148    /* Truncate file to current length */
00149    if (ftruncate(fileno(fs->f), ftello(fs->f)) < 0)
00150       return -1;
00151    return 0;
00152 }
00153 
00154 static off_t h263_tell(struct ast_filestream *fs)
00155 {
00156    off_t offset = ftello(fs->f);
00157    return offset; /* XXX totally bogus, needs fixing */
00158 }
00159 
00160 static const struct ast_format h263_f = {
00161    .name = "h263",
00162    .exts = "h263",
00163    .format = AST_FORMAT_H263,
00164    .open = h263_open,
00165    .write = h263_write,
00166    .seek = h263_seek,
00167    .trunc = h263_trunc,
00168    .tell = h263_tell,
00169    .read = h263_read,
00170    .buf_size = BUF_SIZE + AST_FRIENDLY_OFFSET,
00171    .desc_size = sizeof(struct h263_desc),
00172 };
00173 
00174 static int load_module(void)
00175 {
00176    if (ast_format_register(&h263_f))
00177       return AST_MODULE_LOAD_FAILURE;
00178    return AST_MODULE_LOAD_SUCCESS;
00179 }
00180 
00181 static int unload_module(void)
00182 {
00183    return ast_format_unregister(h263_f.name);
00184 }  
00185 
00186 AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_LOAD_ORDER, "Raw H.263 data",
00187    .load = load_module,
00188    .unload = unload_module,
00189    .load_pri = 10,
00190 );

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