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  * $Id$
   8  *
   9  * Wiretap Library
  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.
  14  *
  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.
  19  *
  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.
  23  */
  24
  25 #include "config.h"
  26
  27 #ifdef HAVE_SYS_TYPES_H
  28 #include <sys/types.h>
  29 #endif
  30
  31 #ifdef HAVE_UNISTD_H
  32 #include <unistd.h>
  33 #endif
  34
  35 #include "mpeg.h"
  36 #include "wsutil/mpeg-audio.h"
  37
  38 #include "wtap-int.h"
  39 #include "buffer.h"
  40 #include "file_wrappers.h"
  41 #include <errno.h>
  42 #include <stdlib.h>
  43 #include <string.h>
  44 #include <time.h>
  45
  46 #define PES_PREFIX 1
  47 #define PES_VALID(n) (((n) >> 8 & 0xffffff) == PES_PREFIX)
  48
  49 typedef struct {
  50         nstime_t now;
  51         time_t t0;
  52 } mpeg_t;
  53
  54 static int
  55 mpeg_resync(wtap *wth, int *err, gchar **err_info _U_)
  56 {
  57         gint64 offset = file_tell(wth->fh);
  58         int count = 0;
  59         int byte = file_getc(wth->fh);
  60
  61         while (byte != EOF) {
  62                 if (byte == 0xff && count > 0) {
  63                         byte = file_getc(wth->fh);
  64                         if (byte != EOF && (byte & 0xe0) == 0xe0)
  65                                 break;
  66                 } else
  67                         byte = file_getc(wth->fh);
  68                 count++;
  69         }
  70         if (file_seek(wth->fh, offset, SEEK_SET, err) == -1)
  71                 return 0;
  72         return count;
  73 }
  74
  75 static int
  76 mpeg_read_header(wtap *wth, int *err, gchar **err_info, guint32 *n)
  77 {
  78         int bytes_read;
  79
  80         errno = WTAP_ERR_CANT_READ;
  81         bytes_read = file_read(n, sizeof *n, wth->fh);
  82         if (bytes_read != sizeof *n) {
  83                 *err = file_error(wth->fh, err_info);
  84                 if (*err == 0 && bytes_read != 0)
  85                         *err = WTAP_ERR_SHORT_READ;
  86                 return -1;
  87         }
  88         *n = g_ntohl(*n);
  89         if (file_seek(wth->fh, -(gint64)(sizeof *n), SEEK_CUR, err) == -1)
  90                 return -1;
  91         return bytes_read;
  92 }
  93
  94 #define SCRHZ 27000000
  95
  96 static gboolean
  97 mpeg_read(wtap *wth, int *err, gchar **err_info, gint64 *data_offset)
  98 {
  99         mpeg_t *mpeg = (mpeg_t *)wth->priv;
 100         guint32 n;
 101         int bytes_read = mpeg_read_header(wth, err, err_info, &n);
 102         unsigned int packet_size;
 103         nstime_t ts = mpeg->now;
 104
 105         if (bytes_read == -1)
 106                 return FALSE;
 107         if (PES_VALID(n)) {
 108                 gint64 offset = file_tell(wth->fh);
 109                 guint8 stream;
 110
 111                 if (offset == -1)
 112                         return -1;
 113                 if (file_seek(wth->fh, 3, SEEK_CUR, err) == -1)
 114                         return FALSE;
 115
 116                 bytes_read = file_read(&stream, sizeof stream, wth->fh);
 117                 if (bytes_read != sizeof stream) {
 118                         *err = file_error(wth->fh, err_info);
 119                         return FALSE;
 120                 }
 121
 122                 if (stream == 0xba) {
 123                         guint32 pack1;
 124                         guint32 pack0;
 125                         guint64 pack;
 126                         guint8 stuffing;
 127
 128                         bytes_read = file_read(&pack1, sizeof pack1, wth->fh);
 129                         if (bytes_read != sizeof pack1) {
 130                                 *err = file_error(wth->fh, err_info);
 131                                 if (*err == 0 && bytes_read != 0)
 132                                         *err = WTAP_ERR_SHORT_READ;
 133                                 return FALSE;
 134                         }
 135                         bytes_read = file_read(&pack0, sizeof pack0, wth->fh);
 136                         if (bytes_read != sizeof pack0) {
 137                                 *err = file_error(wth->fh, err_info);
 138                                 if (*err == 0 && bytes_read != 0)
 139                                         *err = WTAP_ERR_SHORT_READ;
 140                                 return FALSE;
 141                         }
 142                         pack = (guint64)g_ntohl(pack1) << 32 | g_ntohl(pack0);
 143
 144                         switch (pack >> 62) {
 145                                 case 1:
 146                                         if (file_seek(wth->fh, 1, SEEK_CUR, err) == -1)
 147                                                 return FALSE;
 148                                         bytes_read = file_read(&stuffing,
 149                                                         sizeof stuffing, wth->fh);
 150                                         if (bytes_read != sizeof stuffing) {
 151                                                 *err = file_error(wth->fh, err_info);
 152                                                 return FALSE;
 153                                         }
 154                                         stuffing &= 0x07;
 155                                         packet_size = 14 + stuffing;
 156
 157                                         {
 158                                                 guint64 bytes = pack >> 16;
 159                                                 guint64 ts_val =
 160                                                         (bytes >> 43 & 0x0007) << 30 |
 161                                                         (bytes >> 27 & 0x7fff) << 15 |
 162                                                         (bytes >> 11 & 0x7fff) << 0;
 163                                                 guint ext = (guint)((bytes >> 1) & 0x1ff);
 164                                                 guint64 cr = 300 * ts_val + ext;
 165                                                 guint rem = (guint)(cr % SCRHZ);
 166                                                 mpeg->now.secs
 167                                                         = mpeg->t0 + (time_t)(cr / SCRHZ);
 168                                                 mpeg->now.nsecs
 169                                                         = (int)(G_GINT64_CONSTANT(1000000000) * rem / SCRHZ);
 170                                         }
 171                                         ts = mpeg->now;
 172                                         break;
 173                                 default:
 174                                         packet_size = 12;
 175                         }
 176                 } else {
 177                         guint16 length;
 178                         bytes_read = file_read(&length, sizeof length, wth->fh);
 179                         if (bytes_read != sizeof length) {
 180                                 *err = file_error(wth->fh, err_info);
 181                                 if (*err == 0 && bytes_read != 0)
 182                                         *err = WTAP_ERR_SHORT_READ;
 183                                 return FALSE;
 184                         }
 185                         length = g_ntohs(length);
 186                         packet_size = 6 + length;
 187                 }
 188
 189                 if (file_seek(wth->fh, offset, SEEK_SET, err) == -1)
 190                         return FALSE;
 191         } else {
 192                 struct mpa mpa;
 193
 194                 MPA_UNMARSHAL(&mpa, n);
 195                 if (MPA_VALID(&mpa)) {
 196                         packet_size = MPA_BYTES(&mpa);
 197                         mpeg->now.nsecs += MPA_DURATION_NS(&mpa);
 198                         if (mpeg->now.nsecs >= 1000000000) {
 199                                 mpeg->now.secs++;
 200                                 mpeg->now.nsecs -= 1000000000;
 201                         }
 202                 } else {
 203                         packet_size = mpeg_resync(wth, err, err_info);
 204                         if (packet_size == 0)
 205                                 return FALSE;
 206                 }
 207         }
 208         *data_offset = file_tell(wth->fh);
 209
 210         if (!wtap_read_packet_bytes(wth->fh, wth->frame_buffer,
 211                                 packet_size, err, err_info))
 212                 return FALSE;
 213         /* XXX - relative, not absolute, time stamps */
 214         wth->phdr.presence_flags = WTAP_HAS_TS;
 215         wth->phdr.ts = ts;
 216         wth->phdr.caplen = packet_size;
 217         wth->phdr.len = packet_size;
 218         return TRUE;
 219 }
 220
 221 static gboolean
 222 mpeg_seek_read(wtap *wth, gint64 seek_off,
 223                 struct wtap_pkthdr *phdr _U_, Buffer *buf, int length,
 224                 int *err, gchar **err_info)
 225 {
 226         if (file_seek(wth->random_fh, seek_off, SEEK_SET, err) == -1)
 227                 return FALSE;
 228         return wtap_read_packet_bytes(wth->random_fh, buf, length, err, err_info);
 229 }
 230
 231 struct _mpeg_magic {
 232         size_t len;
 233         const gchar* match;
 234 } magic[] = {
 235         { 3, "TAG" }, /* ID3v1 */
 236         { 3, "ID3" }, /* ID3v2 */
 237         { 3, "\0\0\1" }, /* MPEG PES */
 238         { 2, "\xff\xfb" }, /* MP3, taken from http://en.wikipedia.org/wiki/MP3#File_structure */
 239         { 0, NULL }
 240 };
 241
 242 int
 243 mpeg_open(wtap *wth, int *err, gchar **err_info)
 244 {
 245         int bytes_read;
 246         char magic_buf[16];
 247         struct _mpeg_magic* m;
 248         mpeg_t *mpeg;
 249
 250         errno = WTAP_ERR_CANT_READ;
 251         bytes_read = file_read(magic_buf, sizeof magic_buf, wth->fh);
 252         if (bytes_read != (int) sizeof magic_buf) {
 253                 *err = file_error(wth->fh, err_info);
 254                 if (*err != 0 && *err != WTAP_ERR_SHORT_READ)
 255                         return -1;
 256                 return 0;
 257         }
 258
 259         for (m=magic; m->match; m++) {
 260                 if (memcmp(magic_buf, m->match, m->len) == 0)
 261                         goto good_magic;
 262         }
 263
 264         return 0;
 265
 266 good_magic:
 267         /* This appears to be a file with MPEG data. */
 268         if (file_seek(wth->fh, 0, SEEK_SET, err) == -1)
 269                 return -1;
 270
 271         wth->file_type_subtype = WTAP_FILE_TYPE_SUBTYPE_MPEG;
 272         wth->file_encap = WTAP_ENCAP_MPEG;
 273         wth->tsprecision = WTAP_FILE_TSPREC_NSEC;
 274         wth->subtype_read = mpeg_read;
 275         wth->subtype_seek_read = mpeg_seek_read;
 276         wth->snapshot_length = 0;
 277
 278         mpeg = (mpeg_t *)g_malloc(sizeof(mpeg_t));
 279         wth->priv = (void *)mpeg;
 280         mpeg->now.secs = 0;
 281         mpeg->now.nsecs = 0;
 282         mpeg->t0 = mpeg->now.secs;
 283
 284         return 1;
 285 }