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  * 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
  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 "rtp_pt.h"
  46
  47 /* H.261 header fields             */
  48 static int proto_h261          = -1;
  49 static int hf_h261_sbit        = -1;
  50 static int hf_h261_ebit        = -1;
  51 static int hf_h261_ibit        = -1;
  52 static int hf_h261_vbit        = -1;
  53 static int hf_h261_gobn        = -1;
  54 static int hf_h261_mbap        = -1;
  55 static int hf_h261_quant       = -1;
  56 static int hf_h261_hmvd        = -1; /* Mislabeled in a figure in section C.3.1 as HMDV */
  57 static int hf_h261_vmvd        = -1;
  58 static int hf_h261_data        = -1;
  59
  60 /* H.261 fields defining a sub tree */
  61 static gint ett_h261           = -1;
  62
  63 static void
  64 dissect_h261( tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree )
  65 {
  66         proto_item *ti            = NULL;
  67         proto_tree *h261_tree     = NULL;
  68         unsigned int offset       = 0;
  69
  70         if ( check_col( pinfo->cinfo, COL_PROTOCOL ) )   {
  71                 col_set_str( pinfo->cinfo, COL_PROTOCOL, "H.261" );
  72         }
  73
  74         if ( check_col( pinfo->cinfo, COL_INFO) ) {
  75                 col_set_str( pinfo->cinfo, COL_INFO, "H.261 message");
  76         }
  77
  78         if ( tree ) {
  79                 ti = proto_tree_add_item( tree, proto_h261, tvb, offset, -1, FALSE );
  80                 h261_tree = proto_item_add_subtree( ti, ett_h261 );
  81                 /* SBIT 1st octet, 3 bits */
  82                 proto_tree_add_uint( h261_tree, hf_h261_sbit, tvb, offset, 1, tvb_get_guint8( tvb, offset ) >> 5 );
  83                 /* EBIT 1st octet, 3 bits */
  84                 proto_tree_add_uint( h261_tree, hf_h261_ebit, tvb, offset, 1, ( tvb_get_guint8( tvb, offset )  << 3 ) >> 5 );
  85                 /* I flag, 1 bit */
  86                 proto_tree_add_boolean( h261_tree, hf_h261_ibit, tvb, offset, 1, tvb_get_guint8( tvb, offset ) & 2 );
  87                 /* V flag, 1 bit */
  88                 proto_tree_add_boolean( h261_tree, hf_h261_vbit, tvb, offset, 1, tvb_get_guint8( tvb, offset ) & 1 );
  89                 offset++;
  90
  91                 /* GOBN 2nd octet, 4 bits */
  92                 proto_tree_add_uint( h261_tree, hf_h261_gobn, tvb, offset, 1, tvb_get_guint8( tvb, offset ) >> 4 );
  93                 /* MBAP 2nd octet, 4 bits, 3rd octet 1 bit */
  94                 proto_tree_add_uint( h261_tree, hf_h261_mbap, tvb, offset, 1,
  95                     ( tvb_get_guint8( tvb, offset ) & 15 )
  96                     + ( tvb_get_guint8( tvb, offset + 1 ) >> 7 ) );
  97                 offset++;
  98
  99                 /* QUANT 3rd octet, 5 bits (starting at bit 2!) */
 100                 proto_tree_add_uint( h261_tree, hf_h261_quant, tvb, offset, 1, tvb_get_guint8( tvb, offset ) & 124 );
 101
 102                 /* HMVD 3rd octet 2 bits, 4th octet 3 bits */
 103                 proto_tree_add_uint( h261_tree, hf_h261_hmvd, tvb, offset, 2,
 104                     ( ( tvb_get_guint8( tvb, offset ) & 0x03 ) << 3 )
 105                      + ( tvb_get_guint8( tvb, offset+1 ) >> 5 ) );
 106                 offset++;
 107
 108                 /* VMVD 4th octet, last 5 bits */
 109                 proto_tree_add_uint( h261_tree, hf_h261_vmvd, tvb, offset, 1, tvb_get_guint8( tvb, offset ) & 31 );
 110                 offset++;
 111
 112                 /* The rest of the packet is the H.261 stream */
 113                 proto_tree_add_item( h261_tree, hf_h261_data, tvb, offset, -1, FALSE );
 114         }
 115 }
 116
 117 void
 118 proto_register_h261(void)
 119 {
 120         static hf_register_info hf[] =
 121         {
 122                 {
 123                         &hf_h261_sbit,
 124                         {
 125                                 "Start bit position",
 126                                 "h261.sbit",
 127                                 FT_UINT8,
 128                                 BASE_DEC,
 129                                 NULL,
 130                                 0x0,
 131                                 "", HFILL
 132                         }
 133                 },
 134                 {
 135                         &hf_h261_ebit,
 136                         {
 137                                 "End bit position",
 138                                 "h261.ebit",
 139                                 FT_UINT8,
 140                                 BASE_DEC,
 141                                 NULL,
 142                                 0x0,
 143                                 "", HFILL
 144                         }
 145                 },
 146                 {
 147                         &hf_h261_ibit,
 148                         {
 149                                 "Intra frame encoded data flag",
 150                                 "h261.i",
 151                                 FT_BOOLEAN,
 152                                 BASE_NONE,
 153                                 NULL,
 154                                 0x0,
 155                                 "", HFILL
 156                         }
 157                 },
 158                 {
 159                         &hf_h261_vbit,
 160                         {
 161                                 "Motion vector flag",
 162                                 "h261.v",
 163                                 FT_BOOLEAN,
 164                                 BASE_NONE,
 165                                 NULL,
 166                                 0x0,
 167                                 "", HFILL
 168                         }
 169                 },
 170                 {
 171                         &hf_h261_gobn,
 172                         {
 173                                 "GOB Number",
 174                                 "h261.gobn",
 175                                 FT_UINT8,
 176                                 BASE_DEC,
 177                                 NULL,
 178                                 0x0,
 179                                 "", HFILL
 180                         }
 181                 },
 182                 {
 183                         &hf_h261_mbap,
 184                         {
 185                                 "Macroblock address predictor",
 186                                 "h261.mbap",
 187                                 FT_UINT8,
 188                                 BASE_DEC,
 189                                 NULL,
 190                                 0x0,
 191                                 "", HFILL
 192                         }
 193                 },
 194                 {
 195                         &hf_h261_quant,
 196                         {
 197                                 "Quantizer",
 198                                 "h261.quant",
 199                                 FT_UINT8,
 200                                 BASE_DEC,
 201                                 NULL,
 202                                 0x0,
 203                                 "", HFILL
 204                         }
 205                 },
 206                 {
 207                         &hf_h261_hmvd,
 208                         {
 209                                 "Horizontal motion vector data",
 210                                 "h261.hmvd",
 211                                 FT_UINT8,
 212                                 BASE_DEC,
 213                                 NULL,
 214                                 0x0,
 215                                 "", HFILL
 216                         }
 217                 },
 218                 {
 219                         &hf_h261_vmvd,
 220                         {
 221                                 "Vertical motion vector data",
 222                                 "h261.vmvd",
 223                                 FT_UINT8,
 224                                 BASE_DEC,
 225                                 NULL,
 226                                 0x0,
 227                                 "", HFILL
 228                         }
 229                 },
 230                 {
 231                         &hf_h261_data,
 232                         {
 233                                 "H.261 stream",
 234                                 "h261.stream",
 235                                 FT_BYTES,
 236                                 BASE_NONE,
 237                                 NULL,
 238                                 0x0,
 239                                 "", HFILL
 240                         }
 241                 },
 242 };
 243
 244         static gint *ett[] =
 245         {
 246                 &ett_h261,
 247         };
 248
 249
 250         proto_h261 = proto_register_protocol("ITU-T Recommendation H.261",
 251             "H.261", "h261");
 252         proto_register_field_array(proto_h261, hf, array_length(hf));
 253         proto_register_subtree_array(ett, array_length(ett));
 254 }
 255
 256 void
 257 proto_reg_handoff_h261(void)
 258 {
 259         dissector_handle_t h261_handle;
 260
 261         h261_handle = create_dissector_handle(dissect_h261, proto_h261);
 262         dissector_add("rtp.pt", PT_H261, h261_handle);
 263 }