epan/dissectors/packet-h261.c

   1 /* packet-h261.c
   2  *
   3  * Routines for ITU-T Recommendation H.261 dissection
   4  *
   5  * $Id$
   6  *
   7  * Copyright 2000, Philips Electronics N.V.
   8  * Andreas Sikkema <h323@ramdyne.nl>
   9  *
  10  * Wireshark - Network traffic analyzer
  11  * By Gerald Combs <gerald@wireshark.org>
  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
  34
  35 #ifdef HAVE_CONFIG_H
  36 # include "config.h"
  37 #endif
  38
  39 #include <glib.h>
  40 #include <epan/packet.h>
  41
  42 #include <stdio.h>
  43 #include <string.h>
  44
  45 #include <epan/rtp_pt.h>
  46 #include <epan/iax2_codec_type.h>
  47
  48 /* H.261 header fields             */
  49 static int proto_h261          = -1;
  50 static int hf_h261_sbit        = -1;
  51 static int hf_h261_ebit        = -1;
  52 static int hf_h261_ibit        = -1;
  53 static int hf_h261_vbit        = -1;
  54 static int hf_h261_gobn        = -1;
  55 static int hf_h261_mbap        = -1;
  56 static int hf_h261_quant       = -1;
  57 static int hf_h261_hmvd        = -1; /* Mislabeled in a figure in section C.3.1 as HMDV */
  58 static int hf_h261_vmvd        = -1;
  59 static int hf_h261_data        = -1;
  60
  61 /* H.261 fields defining a sub tree */
  62 static gint ett_h261           = -1;
  63
  64 static void
  65 dissect_h261( tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree )
  66 {
  67         proto_item *ti            = NULL;
  68         proto_tree *h261_tree     = NULL;
  69         unsigned int offset       = 0;
  70
  71         col_set_str(pinfo->cinfo, COL_PROTOCOL, "H.261");
  72
  73         col_set_str(pinfo->cinfo, COL_INFO, "H.261 message");
  74
  75         if ( tree ) {
  76                 ti = proto_tree_add_item( tree, proto_h261, tvb, offset, -1, FALSE );
  77                 h261_tree = proto_item_add_subtree( ti, ett_h261 );
  78                 /* SBIT 1st octet, 3 bits */
  79                 proto_tree_add_uint( h261_tree, hf_h261_sbit, tvb, offset, 1, tvb_get_guint8( tvb, offset ) >> 5 );
  80                 /* EBIT 1st octet, 3 bits */
  81                 proto_tree_add_uint( h261_tree, hf_h261_ebit, tvb, offset, 1, ( tvb_get_guint8( tvb, offset )  >> 2 ) & 7 );
  82                 /* I flag, 1 bit */
  83                 proto_tree_add_boolean( h261_tree, hf_h261_ibit, tvb, offset, 1, tvb_get_guint8( tvb, offset ) & 2 );
  84                 /* V flag, 1 bit */
  85                 proto_tree_add_boolean( h261_tree, hf_h261_vbit, tvb, offset, 1, tvb_get_guint8( tvb, offset ) & 1 );
  86                 offset++;
  87
  88                 /* GOBN 2nd octet, 4 bits */
  89                 proto_tree_add_uint( h261_tree, hf_h261_gobn, tvb, offset, 1, tvb_get_guint8( tvb, offset ) >> 4 );
  90                 /* MBAP 2nd octet, 4 bits, 3rd octet 1 bit */
  91                 proto_tree_add_uint( h261_tree, hf_h261_mbap, tvb, offset, 1,
  92                     ( tvb_get_guint8( tvb, offset ) & 15 )
  93                     + ( tvb_get_guint8( tvb, offset + 1 ) >> 7 ) );
  94                 offset++;
  95
  96                 /* QUANT 3rd octet, 5 bits (starting at bit 2!) */
  97                 proto_tree_add_uint( h261_tree, hf_h261_quant, tvb, offset, 1, tvb_get_guint8( tvb, offset ) & 124 );
  98
  99                 /* HMVD 3rd octet 2 bits, 4th octet 3 bits */
 100                 proto_tree_add_uint( h261_tree, hf_h261_hmvd, tvb, offset, 2,
 101                     ( ( tvb_get_guint8( tvb, offset ) & 0x03 ) << 3 )
 102                      + ( tvb_get_guint8( tvb, offset+1 ) >> 5 ) );
 103                 offset++;
 104
 105                 /* VMVD 4th octet, last 5 bits */
 106                 proto_tree_add_uint( h261_tree, hf_h261_vmvd, tvb, offset, 1, tvb_get_guint8( tvb, offset ) & 31 );
 107                 offset++;
 108
 109                 /* The rest of the packet is the H.261 stream */
 110                 proto_tree_add_item( h261_tree, hf_h261_data, tvb, offset, -1, FALSE );
 111         }
 112 }
 113
 114 void
 115 proto_register_h261(void)
 116 {
 117         static hf_register_info hf[] =
 118         {
 119                 {
 120                         &hf_h261_sbit,
 121                         {
 122                                 "Start bit position",
 123                                 "h261.sbit",
 124                                 FT_UINT8,
 125                                 BASE_DEC,
 126                                 NULL,
 127                                 0x0,
 128                                 NULL, HFILL
 129                         }
 130                 },
 131                 {
 132                         &hf_h261_ebit,
 133                         {
 134                                 "End bit position",
 135                                 "h261.ebit",
 136                                 FT_UINT8,
 137                                 BASE_DEC,
 138                                 NULL,
 139                                 0x0,
 140                                 NULL, HFILL
 141                         }
 142                 },
 143                 {
 144                         &hf_h261_ibit,
 145                         {
 146                                 "Intra frame encoded data flag",
 147                                 "h261.i",
 148                                 FT_BOOLEAN,
 149                                 BASE_NONE,
 150                                 NULL,
 151                                 0x0,
 152                                 NULL, HFILL
 153                         }
 154                 },
 155                 {
 156                         &hf_h261_vbit,
 157                         {
 158                                 "Motion vector flag",
 159                                 "h261.v",
 160                                 FT_BOOLEAN,
 161                                 BASE_NONE,
 162                                 NULL,
 163                                 0x0,
 164                                 NULL, HFILL
 165                         }
 166                 },
 167                 {
 168                         &hf_h261_gobn,
 169                         {
 170                                 "GOB Number",
 171                                 "h261.gobn",
 172                                 FT_UINT8,
 173                                 BASE_DEC,
 174                                 NULL,
 175                                 0x0,
 176                                 NULL, HFILL
 177                         }
 178                 },
 179                 {
 180                         &hf_h261_mbap,
 181                         {
 182                                 "Macroblock address predictor",
 183                                 "h261.mbap",
 184                                 FT_UINT8,
 185                                 BASE_DEC,
 186                                 NULL,
 187                                 0x0,
 188                                 NULL, HFILL
 189                         }
 190                 },
 191                 {
 192                         &hf_h261_quant,
 193                         {
 194                                 "Quantizer",
 195                                 "h261.quant",
 196                                 FT_UINT8,
 197                                 BASE_DEC,
 198                                 NULL,
 199                                 0x0,
 200                                 NULL, HFILL
 201                         }
 202                 },
 203                 {
 204                         &hf_h261_hmvd,
 205                         {
 206                                 "Horizontal motion vector data",
 207                                 "h261.hmvd",
 208                                 FT_UINT8,
 209                                 BASE_DEC,
 210                                 NULL,
 211                                 0x0,
 212                                 NULL, HFILL
 213                         }
 214                 },
 215                 {
 216                         &hf_h261_vmvd,
 217                         {
 218                                 "Vertical motion vector data",
 219                                 "h261.vmvd",
 220                                 FT_UINT8,
 221                                 BASE_DEC,
 222                                 NULL,
 223                                 0x0,
 224                                 NULL, HFILL
 225                         }
 226                 },
 227                 {
 228                         &hf_h261_data,
 229                         {
 230                                 "H.261 stream",
 231                                 "h261.stream",
 232                                 FT_BYTES,
 233                                 BASE_NONE,
 234                                 NULL,
 235                                 0x0,
 236                                 NULL, HFILL
 237                         }
 238                 },
 239 };
 240
 241         static gint *ett[] =
 242         {
 243                 &ett_h261,
 244         };
 245
 246
 247         proto_h261 = proto_register_protocol("ITU-T Recommendation H.261",
 248             "H.261", "h261");
 249         proto_register_field_array(proto_h261, hf, array_length(hf));
 250         proto_register_subtree_array(ett, array_length(ett));
 251 }
 252
 253 void
 254 proto_reg_handoff_h261(void)
 255 {
 256         dissector_handle_t h261_handle;
 257
 258         h261_handle = create_dissector_handle(dissect_h261, proto_h261);
 259         dissector_add("rtp.pt", PT_H261, h261_handle);
 260         dissector_add("iax2.codec", AST_FORMAT_H261, h261_handle);
 261 }