epan/dissectors/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 <h323@ramdyne.nl>
   7  *
   8  * Wireshark - Network traffic analyzer
   9  * By Gerald Combs <gerald@wireshark.org>
  10  * Copyright 1998 Gerald Combs
  11  *
  12  * This program is free software; you can redistribute it and/or
  13  * modify it under the terms of the GNU General Public License
  14  * as published by the Free Software Foundation; either version 2
  15  * of the License, or (at your option) any later version.
  16  *
  17  * This program is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20  * GNU General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU General Public License
  23  * along with this program; if not, write to the Free Software
  24  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  25  */
  26
  27 /*
  28  * This dissector tries to dissect the H.261 protocol according to Annex C
  29  * of ITU-T Recommendation H.225.0 (02/98)
  30  */
  31
  32
  33 #include "config.h"
  34
  35 #include <epan/packet.h>
  36
  37 #include <epan/rtp_pt.h>
  38 #include <epan/iax2_codec_type.h>
  39
  40 void proto_register_h261(void);
  41 void proto_reg_handoff_h261(void);
  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         static const int * bits[] = {
  66                 /* SBIT 1st octet, 3 bits */
  67                 &hf_h261_sbit,
  68                 /* EBIT 1st octet, 3 bits */
  69                 &hf_h261_ebit,
  70                 /* I flag, 1 bit */
  71                 &hf_h261_ibit,
  72                 /* V flag, 1 bit */
  73                 &hf_h261_vbit,
  74                 NULL
  75         };
  76
  77         col_set_str(pinfo->cinfo, COL_PROTOCOL, "H.261");
  78
  79         col_set_str(pinfo->cinfo, COL_INFO, "H.261 message");
  80
  81         if ( tree ) {
  82                 ti = proto_tree_add_item( tree, proto_h261, tvb, offset, -1, ENC_NA );
  83                 h261_tree = proto_item_add_subtree( ti, ett_h261 );
  84
  85                 proto_tree_add_bitmask_list(h261_tree, tvb, offset, 1, bits, ENC_NA);
  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, ENC_NA );
 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                                 0xe0,
 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                                 0x1c,
 140                                 NULL, HFILL
 141                         }
 142                 },
 143                 {
 144                         &hf_h261_ibit,
 145                         {
 146                                 "Intra frame encoded data flag",
 147                                 "h261.i",
 148                                 FT_BOOLEAN,
 149                                 8,
 150                                 NULL,
 151                                 0x02,
 152                                 NULL, HFILL
 153                         }
 154                 },
 155                 {
 156                         &hf_h261_vbit,
 157                         {
 158                                 "Motion vector flag",
 159                                 "h261.v",
 160                                 FT_BOOLEAN,
 161                                 8,
 162                                 NULL,
 163                                 0x01,
 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_uint("rtp.pt", PT_H261, h261_handle);
 260         dissector_add_uint("iax2.codec", AST_FORMAT_H261, h261_handle);
 261 }
 262
 263 /*
 264  * Editor modelines  -  http://www.wireshark.org/tools/modelines.html
 265  *
 266  * Local variables:
 267  * c-basic-offset: 8
 268  * tab-width: 8
 269  * indent-tabs-mode: t
 270  * End:
 271  *
 272  * vi: set shiftwidth=8 tabstop=8 noexpandtab:
 273  * :indentSize=8:tabSize=8:noTabs=false:
 274  */