packet-h261.c

   1 /* packet-h261.c
   2  *
   3  * Routines for ITU-T Recommendation H.261 dissection
   4  *
   5  * $Id: packet-h261.c,v 1.15 2002/02/01 07:37:20 guy Exp $
   6  *
   7  * Copyright 2000, Philips Electronics N.V.
   8  * Andreas Sikkema <andreas.sikkema@philips.com>
   9  *
  10  * Ethereal - Network traffic analyzer
  11  * By Gerald Combs <gerald@ethereal.com>
  12  * Copyright 1998 Gerald Combs
  13  *
  14  * This program is free software; you can redistribute it and/or
  15  * modify it under the terms of the GNU General Public License
  16  * as published by the Free Software Foundation; either version 2
  17  * of the License, or (at your option) any later version.
  18  *
  19  * This program is distributed in the hope that it will be useful,
  20  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  21  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  22  * GNU General Public License for more details.
  23  *
  24  * You should have received a copy of the GNU General Public License
  25  * along with this program; if not, write to the Free Software
  26  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
  27  */
  28
  29 /*
  30  * This dissector tries to dissect the H.261 protocol according to Annex C
  31  * of ITU-T Recommendation H.225.0 (02/98)
  32  *
  33  * This dissector is called by the RTP dissector
  34  */
  35
  36
  37 #ifdef HAVE_CONFIG_H
  38 # include "config.h"
  39 #endif
  40
  41 #include <glib.h>
  42 #include <epan/packet.h>
  43
  44 #ifdef HAVE_SYS_TYPES_H
  45 #  include <sys/types.h>
  46 #endif
  47
  48 #ifdef HAVE_NETINET_IN_H
  49 #  include <netinet/in.h>
  50 #endif
  51
  52 #include <stdio.h>
  53 #include <string.h>
  54
  55 /* H.261 header fields             */
  56 static int proto_h261          = -1;
  57 static int hf_h261_sbit        = -1;
  58 static int hf_h261_ebit        = -1;
  59 static int hf_h261_ibit        = -1;
  60 static int hf_h261_vbit        = -1;
  61 static int hf_h261_gobn        = -1;
  62 static int hf_h261_mbap        = -1;
  63 static int hf_h261_quant       = -1;
  64 static int hf_h261_hmvd        = -1; /* Mislabeled in a figure in section C.3.1 as HMDV */
  65 static int hf_h261_vmvd        = -1;
  66 static int hf_h261_data        = -1;
  67
  68 /* H.261 fields defining a sub tree */
  69 static gint ett_h261           = -1;
  70
  71 static void
  72 dissect_h261( tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree )
  73 {
  74         proto_item *ti            = NULL;
  75         proto_tree *h261_tree     = NULL;
  76         unsigned int offset       = 0;
  77
  78         if ( check_col( pinfo->cinfo, COL_PROTOCOL ) )   {
  79                 col_set_str( pinfo->cinfo, COL_PROTOCOL, "H.261" );
  80         }
  81
  82         if ( check_col( pinfo->cinfo, COL_INFO) ) {
  83                 col_set_str( pinfo->cinfo, COL_INFO, "H.261 message");
  84         }
  85
  86         if ( tree ) {
  87                 ti = proto_tree_add_item( tree, proto_h261, tvb, offset, -1, FALSE );
  88                 h261_tree = proto_item_add_subtree( ti, ett_h261 );
  89                 /* SBIT 1st octet, 3 bits */
  90                 proto_tree_add_uint( h261_tree, hf_h261_sbit, tvb, offset, 1, tvb_get_guint8( tvb, offset ) >> 5 );
  91                 /* EBIT 1st octet, 3 bits */
  92                 proto_tree_add_uint( h261_tree, hf_h261_ebit, tvb, offset, 1, ( tvb_get_guint8( tvb, offset )  << 3 ) >> 5 );
  93                 /* I flag, 1 bit */
  94                 proto_tree_add_boolean( h261_tree, hf_h261_ibit, tvb, offset, 1, tvb_get_guint8( tvb, offset ) & 2 );
  95                 /* V flag, 1 bit */
  96                 proto_tree_add_boolean( h261_tree, hf_h261_vbit, tvb, offset, 1, tvb_get_guint8( tvb, offset ) & 1 );
  97                 offset++;
  98
  99                 /* GOBN 2nd octet, 4 bits */
 100                 proto_tree_add_uint( h261_tree, hf_h261_gobn, tvb, offset, 1, tvb_get_guint8( tvb, offset ) >> 4 );
 101                 /* MBAP 2nd octet, 4 bits, 3rd octet 1 bit */
 102                 proto_tree_add_uint( h261_tree, hf_h261_mbap, tvb, offset, 1,
 103                     ( tvb_get_guint8( tvb, offset ) & 15 )
 104                     + ( tvb_get_guint8( tvb, offset + 1 ) >> 7 ) );
 105                 offset++;
 106
 107                 /* QUANT 3rd octet, 5 bits (starting at bit 2!) */
 108                 proto_tree_add_uint( h261_tree, hf_h261_quant, tvb, offset, 1, tvb_get_guint8( tvb, offset ) & 124 );
 109                 /* HMVD 3rd octet 2 bits, 4th octet 3 bits */
 110                 proto_tree_add_uint( h261_tree, hf_h261_hmvd, tvb, offset, 1,
 111                     ( ( tvb_get_guint8( tvb, offset ) << 4) >> 4 )
 112                      + ( tvb_get_guint8( tvb, offset ) >> 5 ) );
 113                 offset++;
 114
 115                 /* VMVD 4th octet, last 5 bits */
 116                 proto_tree_add_uint( h261_tree, hf_h261_vmvd, tvb, offset, 1, tvb_get_guint8( tvb, offset ) & 31 );
 117                 offset++;
 118
 119                 /* The rest of the packet is the H.261 stream */
 120                 proto_tree_add_item( h261_tree, hf_h261_data, tvb, offset, -1, FALSE );
 121         }
 122 }
 123
 124 void
 125 proto_register_h261(void)
 126 {
 127         static hf_register_info hf[] =
 128         {
 129                 {
 130                         &hf_h261_sbit,
 131                         {
 132                                 "Start bit position",
 133                                 "h261.sbit",
 134                                 FT_UINT8,
 135                                 BASE_DEC,
 136                                 NULL,
 137                                 0x0,
 138                                 "", HFILL
 139                         }
 140                 },
 141                 {
 142                         &hf_h261_ebit,
 143                         {
 144                                 "End bit position",
 145                                 "h261.ebit",
 146                                 FT_UINT8,
 147                                 BASE_DEC,
 148                                 NULL,
 149                                 0x0,
 150                                 "", HFILL
 151                         }
 152                 },
 153                 {
 154                         &hf_h261_ibit,
 155                         {
 156                                 "Intra frame encoded data flag",
 157                                 "h261.i",
 158                                 FT_BOOLEAN,
 159                                 BASE_NONE,
 160                                 NULL,
 161                                 0x0,
 162                                 "", HFILL
 163                         }
 164                 },
 165                 {
 166                         &hf_h261_vbit,
 167                         {
 168                                 "Motion vector flag",
 169                                 "h261.v",
 170                                 FT_BOOLEAN,
 171                                 BASE_NONE,
 172                                 NULL,
 173                                 0x0,
 174                                 "", HFILL
 175                         }
 176                 },
 177                 {
 178                         &hf_h261_gobn,
 179                         {
 180                                 "GOB Number",
 181                                 "h261.gobn",
 182                                 FT_UINT8,
 183                                 BASE_DEC,
 184                                 NULL,
 185                                 0x0,
 186                                 "", HFILL
 187                         }
 188                 },
 189                 {
 190                         &hf_h261_mbap,
 191                         {
 192                                 "Macroblock address predictor",
 193                                 "h261.mbap",
 194                                 FT_UINT8,
 195                                 BASE_DEC,
 196                                 NULL,
 197                                 0x0,
 198                                 "", HFILL
 199                         }
 200                 },
 201                 {
 202                         &hf_h261_quant,
 203                         {
 204                                 "Quantizer",
 205                                 "h261.quant",
 206                                 FT_UINT8,
 207                                 BASE_DEC,
 208                                 NULL,
 209                                 0x0,
 210                                 "", HFILL
 211                         }
 212                 },
 213                 {
 214                         &hf_h261_hmvd,
 215                         {
 216                                 "Horizontal motion vector data",
 217                                 "h261.hmvd",
 218                                 FT_UINT8,
 219                                 BASE_DEC,
 220                                 NULL,
 221                                 0x0,
 222                                 "", HFILL
 223                         }
 224                 },
 225                 {
 226                         &hf_h261_vmvd,
 227                         {
 228                                 "Vertical motion vector data",
 229                                 "h261.vmvd",
 230                                 FT_UINT8,
 231                                 BASE_DEC,
 232                                 NULL,
 233                                 0x0,
 234                                 "", HFILL
 235                         }
 236                 },
 237                 {
 238                         &hf_h261_data,
 239                         {
 240                                 "H.261 stream",
 241                                 "h261.stream",
 242                                 FT_BYTES,
 243                                 BASE_NONE,
 244                                 NULL,
 245                                 0x0,
 246                                 "", HFILL
 247                         }
 248                 },
 249 };
 250
 251         static gint *ett[] =
 252         {
 253                 &ett_h261,
 254         };
 255
 256
 257         proto_h261 = proto_register_protocol("ITU-T Recommendation H.261",
 258             "H.261", "h261");
 259         proto_register_field_array(proto_h261, hf, array_length(hf));
 260         proto_register_subtree_array(ett, array_length(ett));
 261
 262         register_dissector("h261", dissect_h261, proto_h261);
 263 }