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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 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 #include "config.h"
  36
  37 #include <glib.h>
  38 #include <epan/packet.h>
  39
  40 #include <epan/rtp_pt.h>
  41 #include <epan/iax2_codec_type.h>
  42
  43 /* H.261 header fields             */
  44 static int proto_h261          = -1;
  45 static int hf_h261_sbit        = -1;
  46 static int hf_h261_ebit        = -1;
  47 static int hf_h261_ibit        = -1;
  48 static int hf_h261_vbit        = -1;
  49 static int hf_h261_gobn        = -1;
  50 static int hf_h261_mbap        = -1;
  51 static int hf_h261_quant       = -1;
  52 static int hf_h261_hmvd        = -1; /* Mislabeled in a figure in section C.3.1 as HMDV */
  53 static int hf_h261_vmvd        = -1;
  54 static int hf_h261_data        = -1;
  55
  56 /* H.261 fields defining a sub tree */
  57 static gint ett_h261           = -1;
  58
  59 static void
  60 dissect_h261( tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree )
  61 {
  62         proto_item *ti            = NULL;
  63         proto_tree *h261_tree     = NULL;
  64         unsigned int offset       = 0;
  65
  66         col_set_str(pinfo->cinfo, COL_PROTOCOL, "H.261");
  67
  68         col_set_str(pinfo->cinfo, COL_INFO, "H.261 message");
  69
  70         if ( tree ) {
  71                 ti = proto_tree_add_item( tree, proto_h261, tvb, offset, -1, ENC_NA );
  72                 h261_tree = proto_item_add_subtree( ti, ett_h261 );
  73                 /* SBIT 1st octet, 3 bits */
  74                 proto_tree_add_uint( h261_tree, hf_h261_sbit, tvb, offset, 1, tvb_get_guint8( tvb, offset ) >> 5 );
  75                 /* EBIT 1st octet, 3 bits */
  76                 proto_tree_add_uint( h261_tree, hf_h261_ebit, tvb, offset, 1, ( tvb_get_guint8( tvb, offset )  >> 2 ) & 7 );
  77                 /* I flag, 1 bit */
  78                 proto_tree_add_boolean( h261_tree, hf_h261_ibit, tvb, offset, 1, tvb_get_guint8( tvb, offset ) & 2 );
  79                 /* V flag, 1 bit */
  80                 proto_tree_add_boolean( h261_tree, hf_h261_vbit, tvb, offset, 1, tvb_get_guint8( tvb, offset ) & 1 );
  81                 offset++;
  82
  83                 /* GOBN 2nd octet, 4 bits */
  84                 proto_tree_add_uint( h261_tree, hf_h261_gobn, tvb, offset, 1, tvb_get_guint8( tvb, offset ) >> 4 );
  85                 /* MBAP 2nd octet, 4 bits, 3rd octet 1 bit */
  86                 proto_tree_add_uint( h261_tree, hf_h261_mbap, tvb, offset, 1,
  87                     ( tvb_get_guint8( tvb, offset ) & 15 )
  88                     + ( tvb_get_guint8( tvb, offset + 1 ) >> 7 ) );
  89                 offset++;
  90
  91                 /* QUANT 3rd octet, 5 bits (starting at bit 2!) */
  92                 proto_tree_add_uint( h261_tree, hf_h261_quant, tvb, offset, 1, tvb_get_guint8( tvb, offset ) & 124 );
  93
  94                 /* HMVD 3rd octet 2 bits, 4th octet 3 bits */
  95                 proto_tree_add_uint( h261_tree, hf_h261_hmvd, tvb, offset, 2,
  96                     ( ( tvb_get_guint8( tvb, offset ) & 0x03 ) << 3 )
  97                      + ( tvb_get_guint8( tvb, offset+1 ) >> 5 ) );
  98                 offset++;
  99
 100                 /* VMVD 4th octet, last 5 bits */
 101                 proto_tree_add_uint( h261_tree, hf_h261_vmvd, tvb, offset, 1, tvb_get_guint8( tvb, offset ) & 31 );
 102                 offset++;
 103
 104                 /* The rest of the packet is the H.261 stream */
 105                 proto_tree_add_item( h261_tree, hf_h261_data, tvb, offset, -1, ENC_NA );
 106         }
 107 }
 108
 109 void
 110 proto_register_h261(void)
 111 {
 112         static hf_register_info hf[] =
 113         {
 114                 {
 115                         &hf_h261_sbit,
 116                         {
 117                                 "Start bit position",
 118                                 "h261.sbit",
 119                                 FT_UINT8,
 120                                 BASE_DEC,
 121                                 NULL,
 122                                 0x0,
 123                                 NULL, HFILL
 124                         }
 125                 },
 126                 {
 127                         &hf_h261_ebit,
 128                         {
 129                                 "End bit position",
 130                                 "h261.ebit",
 131                                 FT_UINT8,
 132                                 BASE_DEC,
 133                                 NULL,
 134                                 0x0,
 135                                 NULL, HFILL
 136                         }
 137                 },
 138                 {
 139                         &hf_h261_ibit,
 140                         {
 141                                 "Intra frame encoded data flag",
 142                                 "h261.i",
 143                                 FT_BOOLEAN,
 144                                 BASE_NONE,
 145                                 NULL,
 146                                 0x0,
 147                                 NULL, HFILL
 148                         }
 149                 },
 150                 {
 151                         &hf_h261_vbit,
 152                         {
 153                                 "Motion vector flag",
 154                                 "h261.v",
 155                                 FT_BOOLEAN,
 156                                 BASE_NONE,
 157                                 NULL,
 158                                 0x0,
 159                                 NULL, HFILL
 160                         }
 161                 },
 162                 {
 163                         &hf_h261_gobn,
 164                         {
 165                                 "GOB Number",
 166                                 "h261.gobn",
 167                                 FT_UINT8,
 168                                 BASE_DEC,
 169                                 NULL,
 170                                 0x0,
 171                                 NULL, HFILL
 172                         }
 173                 },
 174                 {
 175                         &hf_h261_mbap,
 176                         {
 177                                 "Macroblock address predictor",
 178                                 "h261.mbap",
 179                                 FT_UINT8,
 180                                 BASE_DEC,
 181                                 NULL,
 182                                 0x0,
 183                                 NULL, HFILL
 184                         }
 185                 },
 186                 {
 187                         &hf_h261_quant,
 188                         {
 189                                 "Quantizer",
 190                                 "h261.quant",
 191                                 FT_UINT8,
 192                                 BASE_DEC,
 193                                 NULL,
 194                                 0x0,
 195                                 NULL, HFILL
 196                         }
 197                 },
 198                 {
 199                         &hf_h261_hmvd,
 200                         {
 201                                 "Horizontal motion vector data",
 202                                 "h261.hmvd",
 203                                 FT_UINT8,
 204                                 BASE_DEC,
 205                                 NULL,
 206                                 0x0,
 207                                 NULL, HFILL
 208                         }
 209                 },
 210                 {
 211                         &hf_h261_vmvd,
 212                         {
 213                                 "Vertical motion vector data",
 214                                 "h261.vmvd",
 215                                 FT_UINT8,
 216                                 BASE_DEC,
 217                                 NULL,
 218                                 0x0,
 219                                 NULL, HFILL
 220                         }
 221                 },
 222                 {
 223                         &hf_h261_data,
 224                         {
 225                                 "H.261 stream",
 226                                 "h261.stream",
 227                                 FT_BYTES,
 228                                 BASE_NONE,
 229                                 NULL,
 230                                 0x0,
 231                                 NULL, HFILL
 232                         }
 233                 },
 234 };
 235
 236         static gint *ett[] =
 237         {
 238                 &ett_h261,
 239         };
 240
 241
 242         proto_h261 = proto_register_protocol("ITU-T Recommendation H.261",
 243             "H.261", "h261");
 244         proto_register_field_array(proto_h261, hf, array_length(hf));
 245         proto_register_subtree_array(ett, array_length(ett));
 246 }
 247
 248 void
 249 proto_reg_handoff_h261(void)
 250 {
 251         dissector_handle_t h261_handle;
 252
 253         h261_handle = create_dissector_handle(dissect_h261, proto_h261);
 254         dissector_add_uint("rtp.pt", PT_H261, h261_handle);
 255         dissector_add_uint("iax2.codec", AST_FORMAT_H261, h261_handle);
 256 }