packet-h261.c

   1 /* packet-h261.c
   2  *
   3  * Routines for ITU-T Recommendation H.261 dissection
   4  *
   5  * Copyright 2000, Philips Electronics N.V.
   6  * Andreas Sikkema <andreas.sikkema@philips.com>
   7  *
   8  * Ethereal - Network traffic analyzer
   9  * By Gerald Combs <gerald@zing.org>
  10  * Copyright 1998 Gerald Combs
  11  *
  12  *
  13  * This program is free software; you can redistribute it and/or
  14  * modify it under the terms of the GNU General Public License
  15  * as published by the Free Software Foundation; either version 2
  16  * of the License, or (at your option) any later version.
  17  *
  18  * This program is distributed in the hope that it will be useful,
  19  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  20  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  21  * GNU General Public License for more details.
  22  *
  23  * You should have received a copy of the GNU General Public License
  24  * along with this program; if not, write to the Free Software
  25  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
  26  */
  27
  28 /*
  29  * This dissector tries to dissect the H.261 protocol according to Annex C
  30  * of ITU-T Recommendation H.225.0 (02/98)
  31  *
  32  * This dissector is called by the RTP dissector
  33  */
  34
  35
  36 #ifdef HAVE_CONFIG_H
  37 # include "config.h"
  38 #endif
  39
  40 #include <glib.h>
  41 #include "packet.h"
  42
  43 #ifdef HAVE_SYS_TYPES_H
  44 #  include <sys/types.h>
  45 #endif
  46
  47 #ifdef HAVE_NETINET_IN_H
  48 #  include <netinet/in.h>
  49 #endif
  50
  51 #include <stdio.h>
  52 #include <string.h>
  53
  54 #include "packet-h261.h"
  55
  56 /* H.261 header fields             */
  57 static int proto_h261          = -1;
  58 static int hf_h261_sbit        = -1;
  59 static int hf_h261_ebit        = -1;
  60 static int hf_h261_ibit        = -1;
  61 static int hf_h261_vbit        = -1;
  62 static int hf_h261_gobn        = -1;
  63 static int hf_h261_mbap        = -1;
  64 static int hf_h261_quant       = -1;
  65 static int hf_h261_hmvd        = -1; /* Mislabeled in a figure in section C.3.1 as HMDV */
  66 static int hf_h261_vmvd        = -1;
  67 static int hf_h261_data        = -1;
  68
  69 /* H.261 fields defining a sub tree */
  70 static gint ett_h261           = -1;
  71
  72 void
  73 dissect_h261( tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree )
  74 {
  75         proto_item *ti            = NULL;
  76         proto_tree *h261_tree     = NULL;
  77         unsigned int offset       = 0;
  78
  79         if ( check_col( pinfo->fd, COL_PROTOCOL ) )   {
  80                 col_set_str( pinfo->fd, COL_PROTOCOL, "H.261" );
  81         }
  82
  83         if ( check_col( pinfo->fd, COL_INFO) ) {
  84                 col_set_str( pinfo->fd, COL_INFO, "H.261 message");
  85         }
  86
  87         if ( tree ) {
  88                 /* Using fd->pkt_len here instead of END_OF_FRAME. This variable is changed in dissect_rtp()! */
  89                 ti = proto_tree_add_item( tree, proto_h261, tvb, offset, tvb_length( tvb ), FALSE );
  90                 h261_tree = proto_item_add_subtree( ti, ett_h261 );
  91                 /* SBIT 1st octet, 3 bits */
  92                 proto_tree_add_uint( h261_tree, hf_h261_sbit, tvb, offset, 1, tvb_get_guint8( tvb, offset ) >> 5 );
  93                 /* EBIT 1st octet, 3 bits */
  94                 proto_tree_add_item( h261_tree, hf_h261_ebit, tvb, offset, 1, ( tvb_get_guint8( tvb, offset )  << 3 ) >> 5 );
  95                 /* I flag, 1 bit */
  96                 proto_tree_add_boolean( h261_tree, hf_h261_ibit, tvb, offset, 1, tvb_get_guint8( tvb, offset ) & 2 );
  97                 /* V flag, 1 bit */
  98                 proto_tree_add_boolean( h261_tree, hf_h261_vbit, tvb, offset, 1, tvb_get_guint8( tvb, offset ) & 1 );
  99                 offset++;
 100
 101                 /* GOBN 2nd octet, 4 bits */
 102                 proto_tree_add_uint( h261_tree, hf_h261_gobn, tvb, offset, 1, tvb_get_guint8( tvb, offset ) >> 4 );
 103                 /* MBAP 2nd octet, 4 bits, 3rd octet 1 bit */
 104                 proto_tree_add_uint( h261_tree, hf_h261_mbap, tvb, offset, 1,
 105                     ( tvb_get_guint8( tvb, offset ) & 15 )
 106                     + ( tvb_get_guint8( tvb, offset + 1 ) >> 7 ) );
 107                 offset++;
 108
 109                 /* QUANT 3rd octet, 5 bits (starting at bit 2!) */
 110                 proto_tree_add_uint( h261_tree, hf_h261_mbap, tvb, offset, 1, tvb_get_guint8( tvb, offset ) & 124 );
 111                 /* HMDV 3rd octet 2 bits, 4th octet 3 bits */
 112                 proto_tree_add_uint( h261_tree, hf_h261_mbap, tvb, offset, 1,
 113                     ( ( tvb_get_guint8( tvb, offset ) << 4) >> 4 )
 114                      + ( tvb_get_guint8( tvb, offset ) >> 5 ) );
 115                 offset++;
 116
 117                 /* VMVD 4th octet, last 5 bits */
 118                 proto_tree_add_uint( h261_tree, hf_h261_mbap, tvb, offset, 1, tvb_get_guint8( tvb, offset ) & 31 );
 119                 offset++;
 120
 121                 /* The rest of the packet is the H.261 stream */
 122                 proto_tree_add_bytes( h261_tree, hf_h261_data, tvb, offset, tvb_length_remaining( tvb, offset ), tvb_get_ptr( tvb, offset, tvb_length_remaining( tvb, offset ) ) );
 123         }
 124 }
 125
 126 void
 127 proto_register_h261(void)
 128 {
 129         static hf_register_info hf[] =
 130         {
 131                 {
 132                         &hf_h261_sbit,
 133                         {
 134                                 "Start bit position",
 135                                 "h261.sbit",
 136                                 FT_UINT8,
 137                                 BASE_DEC,
 138                                 NULL,
 139                                 0x0,
 140                                 ""
 141                         }
 142                 },
 143                 {
 144                         &hf_h261_ebit,
 145                         {
 146                                 "End bit position",
 147                                 "h261.ebit",
 148                                 FT_UINT8,
 149                                 BASE_DEC,
 150                                 NULL,
 151                                 0x0,
 152                                 ""
 153                         }
 154                 },
 155                 {
 156                         &hf_h261_ibit,
 157                         {
 158                                 "Intra frame encoded data flag",
 159                                 "h261.i",
 160                                 FT_BOOLEAN,
 161                                 BASE_NONE,
 162                                 NULL,
 163                                 0x0,
 164                                 ""
 165                         }
 166                 },
 167                 {
 168                         &hf_h261_vbit,
 169                         {
 170                                 "Motion vector flag",
 171                                 "h261.v",
 172                                 FT_BOOLEAN,
 173                                 BASE_NONE,
 174                                 NULL,
 175                                 0x0,
 176                                 ""
 177                         }
 178                 },
 179                 {
 180                         &hf_h261_gobn,
 181                         {
 182                                 "GOB Number",
 183                                 "h261.gobn",
 184                                 FT_UINT8,
 185                                 BASE_DEC,
 186                                 NULL,
 187                                 0x0,
 188                                 ""
 189                         }
 190                 },
 191                 {
 192                         &hf_h261_mbap,
 193                         {
 194                                 "Macroblock address predictor",
 195                                 "h261.mbap",
 196                                 FT_UINT8,
 197                                 BASE_DEC,
 198                                 NULL,
 199                                 0x0,
 200                                 ""
 201                         }
 202                 },
 203                 {
 204                         &hf_h261_quant,
 205                         {
 206                                 "Quantizer",
 207                                 "h261.quant",
 208                                 FT_UINT8,
 209                                 BASE_DEC,
 210                                 NULL,
 211                                 0x0,
 212                                 ""
 213                         }
 214                 },
 215                 {
 216                         &hf_h261_hmvd,
 217                         {
 218                                 "Horizontal motion vctor data",
 219                                 "h261.hmvd",
 220                                 FT_UINT8,
 221                                 BASE_DEC,
 222                                 NULL,
 223                                 0x0,
 224                                 ""
 225                         }
 226                 },
 227                 {
 228                         &hf_h261_vmvd,
 229                         {
 230                                 "Vertical motion vector data",
 231                                 "h261.vmvd",
 232                                 FT_UINT8,
 233                                 BASE_DEC,
 234                                 NULL,
 235                                 0x0,
 236                                 ""
 237                         }
 238                 },
 239                 {
 240                         &hf_h261_data,
 241                         {
 242                                 "H.261 stream",
 243                                 "h261.stream",
 244                                 FT_BYTES,
 245                                 BASE_NONE,
 246                                 NULL,
 247                                 0x0,
 248                                 ""
 249                         }
 250                 },
 251 };
 252
 253         static gint *ett[] =
 254         {
 255                 &ett_h261,
 256         };
 257
 258
 259         proto_h261 = proto_register_protocol("ITU-T Recommendation H.261",
 260             "H.261", "h261");
 261         proto_register_field_array(proto_h261, hf, array_length(hf));
 262         proto_register_subtree_array(ett, array_length(ett));
 263 }