1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
|
/* mp2t.c
*
* ISO/IEC 13818-1 MPEG2-TS file format decoder for the Wiretap library.
* Written by Weston Schmidt <weston_schmidt@alumni.purdue.edu>
* Copyright 2012 Weston Schmidt
*
* $Id$
*
* Wiretap Library
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#ifdef HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#include "mp2t.h"
#include "wtap-int.h"
#include "buffer.h"
#include "file_wrappers.h"
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#define MP2T_SYNC_BYTE 0x47
#define MP2T_SIZE 188
#define MP2T_QAM256_BITRATE 38810700 /* bits per second */
#define MP2T_QAM64_BITRATE 26970350 /* bits per second */
/* we try to detect trailing data up to 40 bytes after each packet */
#define TRAILER_LEN_MAX 40
/* number of consecutive packets we must read to decide that a file
is actually an mpeg2 ts */
#define SYNC_STEPS 10
typedef struct {
int start_offset;
/* length of trailing data (e.g. FEC) that's appended after each packet */
guint8 trailer_len;
} mp2t_filetype_t;
static gboolean
mp2t_read_data(guint8 *dest, int length, int *err, gchar **err_info, FILE_T fh)
{
int bytes_read;
bytes_read = file_read(dest, length, fh);
if (length != bytes_read) {
*err = file_error(fh, err_info);
/* bytes_read==0 is end of file, not a short read */
if (bytes_read>0 && *err == 0) {
*err = WTAP_ERR_SHORT_READ;
}
return FALSE;
}
return TRUE;
}
static gboolean
mp2t_read(wtap *wth, int *err, gchar **err_info, gint64 *data_offset)
{
mp2t_filetype_t *mp2t;
guint64 tmp;
mp2t = (mp2t_filetype_t*) wth->priv;
*data_offset = file_tell(wth->fh);
/* read only the actual mpeg2 ts packet, not including a trailer */
buffer_assure_space(wth->frame_buffer, MP2T_SIZE);
if (FALSE == mp2t_read_data(buffer_start_ptr(wth->frame_buffer),
MP2T_SIZE, err, err_info, wth->fh))
{
return FALSE;
}
/* if there's a trailer, skip it and go to the start of the next packet */
if (mp2t->trailer_len!=0 &&
(-1 == file_seek(wth->fh, mp2t->trailer_len, SEEK_CUR, err))) {
return FALSE;
}
/* XXX - relative, not absolute, time stamps */
wth->phdr.presence_flags = WTAP_HAS_TS;
/*
* Every packet in an MPEG2-TS stream is has a fixed size of
* MP2T_SIZE plus the number of trailer bytes.
*
* The bitrate is constant, so the time offset, from the beginning
* of the stream, of a given packet is the packet offset, in bits,
* divided by the bitrate.
*
* It would be really cool to be able to configure the bitrate...
*/
tmp = ((guint64)(*data_offset - mp2t->start_offset) * 8); /* offset, in bits */
wth->phdr.ts.secs = tmp / MP2T_QAM256_BITRATE;
wth->phdr.ts.nsecs = (tmp % MP2T_QAM256_BITRATE) * 1000000000 / MP2T_QAM256_BITRATE;
wth->phdr.caplen = MP2T_SIZE;
wth->phdr.len = MP2T_SIZE;
return TRUE;
}
static gboolean
mp2t_seek_read(wtap *wth, gint64 seek_off,
union wtap_pseudo_header *pseudo_header _U_, guint8 *pd, int length,
int *err, gchar **err_info)
{
if (-1 == file_seek(wth->random_fh, seek_off, SEEK_SET, err)) {
return FALSE;
}
return mp2t_read_data(pd, length, err, err_info, wth->random_fh);
}
int
mp2t_open(wtap *wth, int *err, gchar **err_info)
{
int bytes_read;
guint8 buffer[MP2T_SIZE+TRAILER_LEN_MAX];
guint8 trailer_len = 0;
guint sync_steps = 0;
int i;
int first;
mp2t_filetype_t *mp2t;
errno = WTAP_ERR_CANT_READ;
bytes_read = file_read(buffer, MP2T_SIZE, wth->fh);
if (MP2T_SIZE != bytes_read) {
*err = file_error(wth->fh, err_info);
return (*err == 0) ? 0 : -1;
}
first = -1;
for (i = 0; i < MP2T_SIZE; i++) {
if (MP2T_SYNC_BYTE == buffer[i]) {
first = i;
break;
}
}
if (-1 == first) {
return 0; /* wrong file type - not an mpeg2 ts file */
}
if (-1 == file_seek(wth->fh, first, SEEK_SET, err)) {
return -1;
}
/* read some packets and make sure they all start with a sync byte */
do {
bytes_read = file_read(buffer, MP2T_SIZE+trailer_len, wth->fh);
if (bytes_read < 0)
return -1; /* read error */
if (bytes_read < MP2T_SIZE+trailer_len) {
if(sync_steps<2) return 0; /* wrong file type - not an mpeg2 ts file */
break; /* end of file, that's ok if we're still in sync */
}
if (buffer[0] == MP2T_SYNC_BYTE) {
sync_steps++;
}
else {
/* no sync byte found, check if trailing data is appended
and we have to increase the packet size */
/* if we've already detected a trailer field, we must remain in sync
another mismatch means we have no mpeg2 ts file */
if (trailer_len>0)
return 0;
/* check if a trailer is appended to the packet */
for (i=0; i<TRAILER_LEN_MAX; i++) {
if (buffer[i] == MP2T_SYNC_BYTE) {
trailer_len = i;
if (-1 == file_seek(wth->fh, first, SEEK_SET, err)) {
return -1;
}
sync_steps = 0;
break;
}
}
/* no sync byte found in the vicinity, this is no mpeg2 ts file */
if (i==TRAILER_LEN_MAX)
return 0;
}
} while (sync_steps < SYNC_STEPS);
if (-1 == file_seek(wth->fh, first, SEEK_SET, err)) {
return -1;
}
wth->file_type = WTAP_FILE_MPEG_2_TS;
wth->file_encap = WTAP_ENCAP_MPEG_2_TS;
wth->tsprecision = WTAP_FILE_TSPREC_NSEC;
wth->subtype_read = mp2t_read;
wth->subtype_seek_read = mp2t_seek_read;
wth->snapshot_length = 0;
mp2t = (mp2t_filetype_t*) g_malloc(sizeof(mp2t_filetype_t));
if (NULL == mp2t) {
return -1;
}
wth->priv = mp2t;
mp2t->start_offset = first;
mp2t->trailer_len = trailer_len;
return 1;
}
|
