wiretap/mpeg.c

   1 /* mpeg.c
   2  *
   3  * MPEG file format decoder for the Wiretap library.
   4  * Written by Shaun Jackman <sjackman@gmail.com>
   5  * Copyright 2007 Shaun Jackman
   6  *
   7  * Wiretap Library
   8  * This program is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU General Public License
  10  * as published by the Free Software Foundation; either version 2
  11  * of the License, or (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * along with this program; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  21  */
  22
  23 #include "config.h"
  24
  25 #ifdef HAVE_SYS_TYPES_H
  26 #include <sys/types.h>
  27 #endif
  28
  29 #ifdef HAVE_UNISTD_H
  30 #include <unistd.h>
  31 #endif
  32
  33 #include "mpeg.h"
  34 #include "wsutil/mpeg-audio.h"
  35
  36 #include "wtap-int.h"
  37 #include <wsutil/buffer.h>
  38 #include "file_wrappers.h"
  39 #include <errno.h>
  40 #include <stdlib.h>
  41 #include <string.h>
  42 #include <time.h>
  43
  44 #define PES_PREFIX 1
  45 #define PES_VALID(n) (((n) >> 8 & 0xffffff) == PES_PREFIX)
  46
  47 typedef struct {
  48         nstime_t now;
  49         time_t t0;
  50 } mpeg_t;
  51
  52 static int
  53 mpeg_resync(FILE_T fh, int *err)
  54 {
  55         gint64 offset = file_tell(fh);
  56         int count = 0;
  57         int byte = file_getc(fh);
  58
  59         while (byte != EOF) {
  60                 if (byte == 0xff && count > 0) {
  61                         byte = file_getc(fh);
  62                         if (byte != EOF && (byte & 0xe0) == 0xe0)
  63                                 break;
  64                 } else
  65                         byte = file_getc(fh);
  66                 count++;
  67         }
  68         if (file_seek(fh, offset, SEEK_SET, err) == -1)
  69                 return 0;
  70         return count;
  71 }
  72
  73 #define SCRHZ 27000000
  74
  75 static gboolean
  76 mpeg_read_packet(wtap *wth, FILE_T fh, struct wtap_pkthdr *phdr, Buffer *buf,
  77     gboolean is_random, int *err, gchar **err_info)
  78 {
  79         mpeg_t *mpeg = (mpeg_t *)wth->priv;
  80         guint32 n;
  81         unsigned int packet_size;
  82         nstime_t ts = mpeg->now;
  83
  84         /*
  85          * All packets have at least 4 bytes in them.  Read the first
  86          * 4 bytes and determine whether it's a PES packet or not
  87          * based on that.
  88          *
  89          * XXX - can an MPEG file contain a mixture of PES and non-PES
  90          * packets?  If not, can we determine whether the packets will
  91          * be PES packets or not based on the magic number (i.e., if the
  92          * file begins with 0x00 0x00 0x01, it contains PES packets,
  93          * otherwise it doesn't)?
  94          */
  95         if (!wtap_read_bytes_or_eof(fh, &n, sizeof n, err, err_info))
  96                 return FALSE;
  97         if (file_seek(fh, -(gint64)(sizeof n), SEEK_CUR, err) == -1)
  98                 return FALSE;
  99         n = g_ntohl(n);
 100         if (PES_VALID(n)) {
 101                 gint64 offset = file_tell(fh);
 102                 guint8 stream;
 103
 104                 if (!file_skip(fh, 3, err))
 105                         return FALSE;
 106
 107                 if (!wtap_read_bytes(fh, &stream, sizeof stream, err, err_info))
 108                         return FALSE;
 109
 110                 if (stream == 0xba) {
 111                         guint32 pack1;
 112                         guint32 pack0;
 113                         guint64 pack;
 114                         guint8 stuffing;
 115
 116                         if (!wtap_read_bytes(fh, &pack1, sizeof pack1, err, err_info))
 117                                 return FALSE;
 118                         if (!wtap_read_bytes(fh, &pack0, sizeof pack0, err, err_info))
 119                                 return FALSE;
 120                         pack = (guint64)g_ntohl(pack1) << 32 | g_ntohl(pack0);
 121
 122                         switch (pack >> 62) {
 123                                 case 1:
 124                                         if (!file_skip(fh, 1, err))
 125                                                 return FALSE;
 126                                         if (!wtap_read_bytes(fh, &stuffing,
 127                                             sizeof stuffing, err, err_info))
 128                                                 return FALSE;
 129                                         stuffing &= 0x07;
 130                                         packet_size = 14 + stuffing;
 131
 132                                         if (!is_random) {
 133                                                 guint64 bytes = pack >> 16;
 134                                                 guint64 ts_val =
 135                                                         (bytes >> 43 & 0x0007) << 30 |
 136                                                         (bytes >> 27 & 0x7fff) << 15 |
 137                                                         (bytes >> 11 & 0x7fff) << 0;
 138                                                 guint ext = (guint)((bytes >> 1) & 0x1ff);
 139                                                 guint64 cr = 300 * ts_val + ext;
 140                                                 guint rem = (guint)(cr % SCRHZ);
 141                                                 mpeg->now.secs
 142                                                         = mpeg->t0 + (time_t)(cr / SCRHZ);
 143                                                 mpeg->now.nsecs
 144                                                         = (int)(G_GINT64_CONSTANT(1000000000) * rem / SCRHZ);
 145                                         }
 146                                         ts = mpeg->now;
 147                                         break;
 148                                 default:
 149                                         packet_size = 12;
 150                         }
 151                 } else {
 152                         guint16 length;
 153                         if (!wtap_read_bytes(fh, &length, sizeof length, err, err_info))
 154                                 return FALSE;
 155                         length = g_ntohs(length);
 156                         packet_size = 6 + length;
 157                 }
 158
 159                 if (file_seek(fh, offset, SEEK_SET, err) == -1)
 160                         return FALSE;
 161         } else {
 162                 struct mpa mpa;
 163
 164                 MPA_UNMARSHAL(&mpa, n);
 165                 if (MPA_VALID(&mpa)) {
 166                         packet_size = MPA_BYTES(&mpa);
 167                         if (!is_random) {
 168                                 mpeg->now.nsecs += MPA_DURATION_NS(&mpa);
 169                                 if (mpeg->now.nsecs >= 1000000000) {
 170                                         mpeg->now.secs++;
 171                                         mpeg->now.nsecs -= 1000000000;
 172                                 }
 173                         }
 174                 } else {
 175                         packet_size = mpeg_resync(fh, err);
 176                         if (packet_size == 0)
 177                                 return FALSE;
 178                 }
 179         }
 180
 181         if (!wtap_read_packet_bytes(fh, buf, packet_size, err, err_info))
 182                 return FALSE;
 183
 184         phdr->rec_type = REC_TYPE_PACKET;
 185
 186         /* XXX - relative, not absolute, time stamps */
 187         if (!is_random) {
 188                 phdr->presence_flags = WTAP_HAS_TS;
 189                 phdr->ts = ts;
 190         }
 191         phdr->caplen = packet_size;
 192         phdr->len = packet_size;
 193
 194         return TRUE;
 195 }
 196
 197 static gboolean
 198 mpeg_read(wtap *wth, int *err, gchar **err_info, gint64 *data_offset)
 199 {
 200         *data_offset = file_tell(wth->fh);
 201
 202         return mpeg_read_packet(wth, wth->fh, &wth->phdr, wth->frame_buffer,
 203             FALSE, err, err_info);
 204 }
 205
 206 static gboolean
 207 mpeg_seek_read(wtap *wth, gint64 seek_off,
 208                 struct wtap_pkthdr *phdr, Buffer *buf,
 209                 int *err, gchar **err_info)
 210 {
 211         if (file_seek(wth->random_fh, seek_off, SEEK_SET, err) == -1)
 212                 return FALSE;
 213
 214         if (!mpeg_read_packet(wth, wth->random_fh, phdr, buf, TRUE, err,
 215             err_info)) {
 216                 if (*err == 0)
 217                         *err = WTAP_ERR_SHORT_READ;
 218                 return FALSE;
 219         }
 220         return TRUE;
 221 }
 222
 223 struct _mpeg_magic {
 224         size_t len;
 225         const gchar* match;
 226 } magic[] = {
 227         { 3, "TAG" }, /* ID3v1 */
 228         { 3, "ID3" }, /* ID3v2 */
 229         { 3, "\0\0\1" }, /* MPEG PES */
 230         { 2, "\xff\xfb" }, /* MP3, taken from http://en.wikipedia.org/wiki/MP3#File_structure */
 231         { 0, NULL }
 232 };
 233
 234 wtap_open_return_val
 235 mpeg_open(wtap *wth, int *err, gchar **err_info)
 236 {
 237         char magic_buf[16];
 238         struct _mpeg_magic* m;
 239         mpeg_t *mpeg;
 240
 241         if (!wtap_read_bytes(wth->fh, magic_buf, sizeof magic_buf,
 242             err, err_info)) {
 243                 if (*err != WTAP_ERR_SHORT_READ)
 244                         return WTAP_OPEN_ERROR;
 245                 return WTAP_OPEN_NOT_MINE;
 246         }
 247
 248         for (m=magic; m->match; m++) {
 249                 if (memcmp(magic_buf, m->match, m->len) == 0)
 250                         goto good_magic;
 251         }
 252
 253         return WTAP_OPEN_NOT_MINE;
 254
 255 good_magic:
 256         /* This appears to be a file with MPEG data. */
 257         if (file_seek(wth->fh, 0, SEEK_SET, err) == -1)
 258                 return WTAP_OPEN_ERROR;
 259
 260         wth->file_type_subtype = WTAP_FILE_TYPE_SUBTYPE_MPEG;
 261         wth->file_encap = WTAP_ENCAP_MPEG;
 262         wth->file_tsprec = WTAP_TSPREC_NSEC;
 263         wth->subtype_read = mpeg_read;
 264         wth->subtype_seek_read = mpeg_seek_read;
 265         wth->snapshot_length = 0;
 266
 267         mpeg = (mpeg_t *)g_malloc(sizeof(mpeg_t));
 268         wth->priv = (void *)mpeg;
 269         mpeg->now.secs = 0;
 270         mpeg->now.nsecs = 0;
 271         mpeg->t0 = mpeg->now.secs;
 272
 273         return WTAP_OPEN_MINE;
 274 }
 275
 276 /*
 277  * Editor modelines  -  http://www.wireshark.org/tools/modelines.html
 278  *
 279  * Local variables:
 280  * c-basic-offset: 8
 281  * tab-width: 8
 282  * indent-tabs-mode: t
 283  * End:
 284  *
 285  * vi: set shiftwidth=8 tabstop=8 noexpandtab:
 286  * :indentSize=8:tabSize=8:noTabs=false:
 287  */