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  * SPDX-License-Identifier: GPL-2.0-or-later
  13  */
  14
  15 /*
  16  * This dissector tries to dissect the H.261 protocol according to Annex C
  17  * of ITU-T Recommendation H.225.0 (02/98)
  18  */
  19
  20
  21 #include "config.h"
  22
  23 #include <epan/packet.h>
  24
  25 #include <epan/rtp_pt.h>
  26 #include <epan/iax2_codec_type.h>
  27
  28 void proto_register_h261(void);
  29 void proto_reg_handoff_h261(void);
  30
  31 /* H.261 header fields             */
  32 static int proto_h261          = -1;
  33 static int hf_h261_sbit        = -1;
  34 static int hf_h261_ebit        = -1;
  35 static int hf_h261_ibit        = -1;
  36 static int hf_h261_vbit        = -1;
  37 static int hf_h261_gobn        = -1;
  38 static int hf_h261_mbap        = -1;
  39 static int hf_h261_quant       = -1;
  40 static int hf_h261_hmvd        = -1; /* Mislabeled in a figure in section C.3.1 as HMDV */
  41 static int hf_h261_vmvd        = -1;
  42 static int hf_h261_data        = -1;
  43
  44 /* H.261 fields defining a sub tree */
  45 static gint ett_h261           = -1;
  46
  47 static int
  48 dissect_h261( tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data _U_ )
  49 {
  50         proto_item *ti            = NULL;
  51         proto_tree *h261_tree     = NULL;
  52         unsigned int offset       = 0;
  53         static const int * bits[] = {
  54                 /* SBIT 1st octet, 3 bits */
  55                 &hf_h261_sbit,
  56                 /* EBIT 1st octet, 3 bits */
  57                 &hf_h261_ebit,
  58                 /* I flag, 1 bit */
  59                 &hf_h261_ibit,
  60                 /* V flag, 1 bit */
  61                 &hf_h261_vbit,
  62                 NULL
  63         };
  64
  65         col_set_str(pinfo->cinfo, COL_PROTOCOL, "H.261");
  66
  67         col_set_str(pinfo->cinfo, COL_INFO, "H.261 message");
  68
  69         if ( tree ) {
  70                 ti = proto_tree_add_item( tree, proto_h261, tvb, offset, -1, ENC_NA );
  71                 h261_tree = proto_item_add_subtree( ti, ett_h261 );
  72
  73                 proto_tree_add_bitmask_list(h261_tree, tvb, offset, 1, bits, ENC_NA);
  74                 offset++;
  75
  76                 /* GOBN 2nd octet, 4 bits */
  77                 proto_tree_add_item( h261_tree, hf_h261_gobn, tvb, offset, 1, ENC_NA);
  78                 /* MBAP 2nd octet, 4 bits, 3rd octet 1 bit */
  79                 proto_tree_add_item( h261_tree, hf_h261_mbap, tvb, offset, 1, ENC_BIG_ENDIAN);
  80                 offset++;
  81
  82                 /* QUANT 3rd octet, 5 bits (starting at bit 2!) */
  83                 proto_tree_add_item( h261_tree, hf_h261_quant, tvb, offset, 1, ENC_NA );
  84
  85                 /* HMVD 3rd octet 2 bits, 4th octet 3 bits */
  86                 proto_tree_add_item( h261_tree, hf_h261_hmvd, tvb, offset, 2, ENC_BIG_ENDIAN);
  87                 offset++;
  88
  89                 /* VMVD 4th octet, last 5 bits */
  90                 proto_tree_add_item( h261_tree, hf_h261_vmvd, tvb, offset, 1, 0x1F );
  91                 offset++;
  92
  93                 /* The rest of the packet is the H.261 stream */
  94                 proto_tree_add_item( h261_tree, hf_h261_data, tvb, offset, -1, ENC_NA );
  95         }
  96         return tvb_captured_length(tvb);
  97 }
  98
  99 void
 100 proto_register_h261(void)
 101 {
 102         static hf_register_info hf[] =
 103         {
 104                 {
 105                         &hf_h261_sbit,
 106                         {
 107                                 "Start bit position",
 108                                 "h261.sbit",
 109                                 FT_UINT8,
 110                                 BASE_DEC,
 111                                 NULL,
 112                                 0xe0,
 113                                 NULL, HFILL
 114                         }
 115                 },
 116                 {
 117                         &hf_h261_ebit,
 118                         {
 119                                 "End bit position",
 120                                 "h261.ebit",
 121                                 FT_UINT8,
 122                                 BASE_DEC,
 123                                 NULL,
 124                                 0x1c,
 125                                 NULL, HFILL
 126                         }
 127                 },
 128                 {
 129                         &hf_h261_ibit,
 130                         {
 131                                 "Intra frame encoded data flag",
 132                                 "h261.i",
 133                                 FT_BOOLEAN,
 134                                 8,
 135                                 NULL,
 136                                 0x02,
 137                                 NULL, HFILL
 138                         }
 139                 },
 140                 {
 141                         &hf_h261_vbit,
 142                         {
 143                                 "Motion vector flag",
 144                                 "h261.v",
 145                                 FT_BOOLEAN,
 146                                 8,
 147                                 NULL,
 148                                 0x01,
 149                                 NULL, HFILL
 150                         }
 151                 },
 152                 {
 153                         &hf_h261_gobn,
 154                         {
 155                                 "GOB Number",
 156                                 "h261.gobn",
 157                                 FT_UINT8,
 158                                 BASE_DEC,
 159                                 NULL,
 160                                 0xF0,
 161                                 NULL, HFILL
 162                         }
 163                 },
 164                 {
 165                         &hf_h261_mbap,
 166                         {
 167                                 "Macroblock address predictor",
 168                                 "h261.mbap",
 169                                 FT_UINT8,
 170                                 BASE_DEC,
 171                                 NULL,
 172                                 0x0E80,
 173                                 NULL, HFILL
 174                         }
 175                 },
 176                 {
 177                         &hf_h261_quant,
 178                         {
 179                                 "Quantizer",
 180                                 "h261.quant",
 181                                 FT_UINT8,
 182                                 BASE_DEC,
 183                                 NULL,
 184                                 0x7C,
 185                                 NULL, HFILL
 186                         }
 187                 },
 188                 {
 189                         &hf_h261_hmvd,
 190                         {
 191                                 "Horizontal motion vector data",
 192                                 "h261.hmvd",
 193                                 FT_UINT8,
 194                                 BASE_DEC,
 195                                 NULL,
 196                                 0x03E0,
 197                                 NULL, HFILL
 198                         }
 199                 },
 200                 {
 201                         &hf_h261_vmvd,
 202                         {
 203                                 "Vertical motion vector data",
 204                                 "h261.vmvd",
 205                                 FT_UINT8,
 206                                 BASE_DEC,
 207                                 NULL,
 208                                 0x0,
 209                                 NULL, HFILL
 210                         }
 211                 },
 212                 {
 213                         &hf_h261_data,
 214                         {
 215                                 "H.261 stream",
 216                                 "h261.stream",
 217                                 FT_BYTES,
 218                                 BASE_NONE,
 219                                 NULL,
 220                                 0x0,
 221                                 NULL, HFILL
 222                         }
 223                 },
 224 };
 225
 226         static gint *ett[] =
 227         {
 228                 &ett_h261,
 229         };
 230
 231
 232         proto_h261 = proto_register_protocol("ITU-T Recommendation H.261",
 233             "H.261", "h261");
 234         proto_register_field_array(proto_h261, hf, array_length(hf));
 235         proto_register_subtree_array(ett, array_length(ett));
 236 }
 237
 238 void
 239 proto_reg_handoff_h261(void)
 240 {
 241         dissector_handle_t h261_handle;
 242
 243         h261_handle = create_dissector_handle(dissect_h261, proto_h261);
 244         dissector_add_uint("rtp.pt", PT_H261, h261_handle);
 245         dissector_add_uint("iax2.codec", AST_FORMAT_H261, h261_handle);
 246 }
 247
 248 /*
 249  * Editor modelines  -  http://www.wireshark.org/tools/modelines.html
 250  *
 251  * Local variables:
 252  * c-basic-offset: 8
 253  * tab-width: 8
 254  * indent-tabs-mode: t
 255  * End:
 256  *
 257  * vi: set shiftwidth=8 tabstop=8 noexpandtab:
 258  * :indentSize=8:tabSize=8:noTabs=false:
 259  */