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 static dissector_handle_t h261_handle;
  32
  33 /* H.261 header fields             */
  34 static int proto_h261;
  35 static int hf_h261_sbit;
  36 static int hf_h261_ebit;
  37 static int hf_h261_ibit;
  38 static int hf_h261_vbit;
  39 static int hf_h261_gobn;
  40 static int hf_h261_mbap;
  41 static int hf_h261_quant;
  42 static int hf_h261_hmvd; /* Mislabeled in a figure in section C.3.1 as HMDV */
  43 static int hf_h261_vmvd;
  44 static int hf_h261_data;
  45
  46 /* H.261 fields defining a sub tree */
  47 static int ett_h261;
  48
  49 static int
  50 dissect_h261( tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data _U_ )
  51 {
  52         proto_item *ti            = NULL;
  53         proto_tree *h261_tree     = NULL;
  54         unsigned int offset       = 0;
  55         static int * const bits[] = {
  56                 /* SBIT 1st octet, 3 bits */
  57                 &hf_h261_sbit,
  58                 /* EBIT 1st octet, 3 bits */
  59                 &hf_h261_ebit,
  60                 /* I flag, 1 bit */
  61                 &hf_h261_ibit,
  62                 /* V flag, 1 bit */
  63                 &hf_h261_vbit,
  64                 NULL
  65         };
  66
  67         col_set_str(pinfo->cinfo, COL_PROTOCOL, "H.261");
  68
  69         col_set_str(pinfo->cinfo, COL_INFO, "H.261 message");
  70
  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
  74         proto_tree_add_bitmask_list(h261_tree, tvb, offset, 1, bits, ENC_NA);
  75         offset++;
  76
  77         /* GOBN 2nd octet, 4 bits */
  78         proto_tree_add_item( h261_tree, hf_h261_gobn, tvb, offset, 1, ENC_NA);
  79         /* MBAP 2nd octet, 4 bits, 3rd octet 1 bit */
  80         proto_tree_add_item( h261_tree, hf_h261_mbap, tvb, offset, 2, ENC_BIG_ENDIAN);
  81         offset++;
  82
  83         /* QUANT 3rd octet, 5 bits (starting at bit 2!) */
  84         proto_tree_add_item( h261_tree, hf_h261_quant, tvb, offset, 1, ENC_NA);
  85
  86         /* HMVD 3rd octet 2 bits, 4th octet 3 bits */
  87         proto_tree_add_item( h261_tree, hf_h261_hmvd, tvb, offset, 2, ENC_BIG_ENDIAN);
  88         offset++;
  89
  90         /* VMVD 4th octet, last 5 bits */
  91         proto_tree_add_item( h261_tree, hf_h261_vmvd, tvb, offset, 1, ENC_NA);
  92         offset++;
  93
  94         /* The rest of the packet is the H.261 stream */
  95         proto_tree_add_item( h261_tree, hf_h261_data, tvb, offset, -1, ENC_NA);
  96
  97         return tvb_captured_length(tvb);
  98 }
  99
 100 void
 101 proto_register_h261(void)
 102 {
 103         static hf_register_info hf[] =
 104         {
 105                 {
 106                         &hf_h261_sbit,
 107                         {
 108                                 "Start bit position",
 109                                 "h261.sbit",
 110                                 FT_UINT8,
 111                                 BASE_DEC,
 112                                 NULL,
 113                                 0xe0,
 114                                 NULL, HFILL
 115                         }
 116                 },
 117                 {
 118                         &hf_h261_ebit,
 119                         {
 120                                 "End bit position",
 121                                 "h261.ebit",
 122                                 FT_UINT8,
 123                                 BASE_DEC,
 124                                 NULL,
 125                                 0x1c,
 126                                 NULL, HFILL
 127                         }
 128                 },
 129                 {
 130                         &hf_h261_ibit,
 131                         {
 132                                 "Intra frame encoded data flag",
 133                                 "h261.i",
 134                                 FT_BOOLEAN,
 135                                 8,
 136                                 NULL,
 137                                 0x02,
 138                                 NULL, HFILL
 139                         }
 140                 },
 141                 {
 142                         &hf_h261_vbit,
 143                         {
 144                                 "Motion vector flag",
 145                                 "h261.v",
 146                                 FT_BOOLEAN,
 147                                 8,
 148                                 NULL,
 149                                 0x01,
 150                                 NULL, HFILL
 151                         }
 152                 },
 153                 {
 154                         &hf_h261_gobn,
 155                         {
 156                                 "GOB Number",
 157                                 "h261.gobn",
 158                                 FT_UINT8,
 159                                 BASE_DEC,
 160                                 NULL,
 161                                 0xF0,
 162                                 NULL, HFILL
 163                         }
 164                 },
 165                 {
 166                         &hf_h261_mbap,
 167                         {
 168                                 "Macroblock address predictor",
 169                                 "h261.mbap",
 170                                 FT_UINT16,
 171                                 BASE_DEC,
 172                                 NULL,
 173                                 0x0F80,
 174                                 NULL, HFILL
 175                         }
 176                 },
 177                 {
 178                         &hf_h261_quant,
 179                         {
 180                                 "Quantizer",
 181                                 "h261.quant",
 182                                 FT_UINT8,
 183                                 BASE_DEC,
 184                                 NULL,
 185                                 0x7C,
 186                                 NULL, HFILL
 187                         }
 188                 },
 189                 {
 190                         &hf_h261_hmvd,
 191                         {
 192                                 "Horizontal motion vector data",
 193                                 "h261.hmvd",
 194                                 FT_UINT16,
 195                                 BASE_DEC,
 196                                 NULL,
 197                                 0x03E0,
 198                                 NULL, HFILL
 199                         }
 200                 },
 201                 {
 202                         &hf_h261_vmvd,
 203                         {
 204                                 "Vertical motion vector data",
 205                                 "h261.vmvd",
 206                                 FT_UINT8,
 207                                 BASE_DEC,
 208                                 NULL,
 209                                 0x0,
 210                                 NULL, HFILL
 211                         }
 212                 },
 213                 {
 214                         &hf_h261_data,
 215                         {
 216                                 "H.261 stream",
 217                                 "h261.stream",
 218                                 FT_BYTES,
 219                                 BASE_NONE,
 220                                 NULL,
 221                                 0x0,
 222                                 NULL, HFILL
 223                         }
 224                 },
 225 };
 226
 227         static int *ett[] =
 228         {
 229                 &ett_h261,
 230         };
 231
 232
 233         proto_h261 = proto_register_protocol("ITU-T Recommendation H.261",
 234             "H.261", "h261");
 235         proto_register_field_array(proto_h261, hf, array_length(hf));
 236         proto_register_subtree_array(ett, array_length(ett));
 237
 238         h261_handle = register_dissector("h261", dissect_h261, proto_h261);
 239 }
 240
 241 void
 242 proto_reg_handoff_h261(void)
 243 {
 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  -  https://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  */