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