3 * ISO/IEC 13818-1 MPEG2-TS file format decoder for the Wiretap library.
4 * Written by Weston Schmidt <weston_schmidt@alumni.purdue.edu>
5 * Copyright 2012 Weston Schmidt
10 * This program is free software; you can redistribute it and/or
11 * modify it under the terms of the GNU General Public License
12 * as published by the Free Software Foundation; either version 2
13 * of the License, or (at your option) any later version.
15 * This program is distributed in the hope that it will be useful,
16 * but WITHOUT ANY WARRANTY; without even the implied warranty of
17 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
18 * GNU General Public License for more details.
20 * You should have received a copy of the GNU General Public License
21 * along with this program; if not, write to the Free Software
22 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
27 #ifdef HAVE_SYS_TYPES_H
28 #include <sys/types.h>
39 #include "file_wrappers.h"
45 #define MP2T_SYNC_BYTE 0x47
47 #define MP2T_QAM256_BITRATE 38810700 /* bits per second */
48 #define MP2T_QAM64_BITRATE 26970350 /* bits per second */
50 /* we try to detect trailing data up to 40 bytes after each packet */
51 #define TRAILER_LEN_MAX 40
53 /* number of consecutive packets we must read to decide that a file
54 is actually an mpeg2 ts */
60 /* length of trailing data (e.g. FEC) that's appended after each packet */
65 mp2t_read_packet(mp2t_filetype_t *mp2t, FILE_T fh, gint64 offset,
66 struct wtap_pkthdr *phdr, Buffer *buf, int *err,
72 buffer_assure_space(buf, MP2T_SIZE);
73 errno = WTAP_ERR_CANT_READ;
74 bytes_read = file_read(buffer_start_ptr(buf), MP2T_SIZE, fh);
75 if (MP2T_SIZE != bytes_read) {
76 *err = file_error(fh, err_info);
77 /* bytes_read==0 is end of file, not a short read */
78 if (bytes_read>0 && *err == 0) {
79 *err = WTAP_ERR_SHORT_READ;
84 /* XXX - relative, not absolute, time stamps */
85 phdr->presence_flags = WTAP_HAS_TS;
88 * Every packet in an MPEG2-TS stream is has a fixed size of
89 * MP2T_SIZE plus the number of trailer bytes.
91 * The bitrate is constant, so the time offset, from the beginning
92 * of the stream, of a given packet is the packet offset, in bits,
93 * divided by the bitrate.
95 * It would be really cool to be able to configure the bitrate...
97 tmp = ((guint64)(offset - mp2t->start_offset) * 8); /* offset, in bits */
98 phdr->ts.secs = (time_t)(tmp / MP2T_QAM256_BITRATE);
99 phdr->ts.nsecs = (int)((tmp % MP2T_QAM256_BITRATE) * 1000000000 / MP2T_QAM256_BITRATE);
101 phdr->caplen = MP2T_SIZE;
102 phdr->len = MP2T_SIZE;
108 mp2t_read(wtap *wth, int *err, gchar **err_info, gint64 *data_offset)
110 mp2t_filetype_t *mp2t;
112 mp2t = (mp2t_filetype_t*) wth->priv;
114 *data_offset = file_tell(wth->fh);
116 if (!mp2t_read_packet(mp2t, wth->fh, *data_offset, &wth->phdr,
117 wth->frame_buffer, err, err_info)) {
121 /* if there's a trailer, skip it and go to the start of the next packet */
122 if (mp2t->trailer_len!=0) {
123 if (-1 == file_seek(wth->fh, mp2t->trailer_len, SEEK_CUR, err)) {
132 mp2t_seek_read(wtap *wth, gint64 seek_off, struct wtap_pkthdr *phdr,
133 Buffer *buf, int *err, gchar **err_info)
135 mp2t_filetype_t *mp2t;
137 if (-1 == file_seek(wth->random_fh, seek_off, SEEK_SET, err)) {
141 mp2t = (mp2t_filetype_t*) wth->priv;
143 if (!mp2t_read_packet(mp2t, wth->random_fh, seek_off, phdr, buf,
146 *err = WTAP_ERR_SHORT_READ;
153 mp2t_open(wtap *wth, int *err, gchar **err_info)
156 guint8 buffer[MP2T_SIZE+TRAILER_LEN_MAX];
157 guint8 trailer_len = 0;
158 guint sync_steps = 0;
161 mp2t_filetype_t *mp2t;
164 errno = WTAP_ERR_CANT_READ;
165 bytes_read = file_read(buffer, MP2T_SIZE, wth->fh);
167 if (MP2T_SIZE != bytes_read) {
168 *err = file_error(wth->fh, err_info);
169 if (*err != 0 && *err != WTAP_ERR_SHORT_READ)
175 for (i = 0; i < MP2T_SIZE; i++) {
176 if (MP2T_SYNC_BYTE == buffer[i]) {
182 return 0; /* wrong file type - not an mpeg2 ts file */
185 if (-1 == file_seek(wth->fh, first, SEEK_SET, err)) {
188 /* read some packets and make sure they all start with a sync byte */
190 bytes_read = file_read(buffer, MP2T_SIZE+trailer_len, wth->fh);
191 if (bytes_read < 0) {
192 *err = file_error(wth->fh, err_info);
193 return -1; /* read error */
195 if (bytes_read < MP2T_SIZE+trailer_len) {
196 if(sync_steps<2) return 0; /* wrong file type - not an mpeg2 ts file */
197 break; /* end of file, that's ok if we're still in sync */
199 if (buffer[0] == MP2T_SYNC_BYTE) {
203 /* no sync byte found, check if trailing data is appended
204 and we have to increase the packet size */
206 /* if we've already detected a trailer field, we must remain in sync
207 another mismatch means we have no mpeg2 ts file */
211 /* check if a trailer is appended to the packet */
212 for (i=0; i<TRAILER_LEN_MAX; i++) {
213 if (buffer[i] == MP2T_SYNC_BYTE) {
215 if (-1 == file_seek(wth->fh, first, SEEK_SET, err)) {
222 /* no sync byte found in the vicinity, this is no mpeg2 ts file */
223 if (i==TRAILER_LEN_MAX)
226 } while (sync_steps < SYNC_STEPS);
228 if (-1 == file_seek(wth->fh, first, SEEK_SET, err)) {
232 wth->file_type_subtype = WTAP_FILE_TYPE_SUBTYPE_MPEG_2_TS;
233 wth->file_encap = WTAP_ENCAP_MPEG_2_TS;
234 wth->tsprecision = WTAP_FILE_TSPREC_NSEC;
235 wth->subtype_read = mp2t_read;
236 wth->subtype_seek_read = mp2t_seek_read;
237 wth->snapshot_length = 0;
239 mp2t = (mp2t_filetype_t*) g_malloc(sizeof(mp2t_filetype_t));
245 mp2t->start_offset = first;
246 mp2t->trailer_len = trailer_len;