epan/dissectors/packet-g723.c

   1 /* packet-g723.c
   2  * Routines for G.723 dissection
   3  * Copyright 2005, Anders Broman <anders.broman[at]ericsson.com>
   4  *
   5  * $Id$
   6  *
   7  * Wireshark - Network traffic analyzer
   8  * By Gerald Combs <gerald@wireshark.org>
   9  * Copyright 1998 Gerald Combs
  10  *
  11  * This program is free software; you can redistribute it and/or
  12  * modify it under the terms of the GNU General Public License
  13  * as published by the Free Software Foundation; either version 2
  14  * of the License, or (at your option) any later version.
  15  *
  16  * This program is distributed in the hope that it will be useful,
  17  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  18  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19  * GNU General Public License for more details.
  20  *
  21  * You should have received a copy of the GNU General Public License
  22  * along with this program; if not, write to the Free Software
  23  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  24  *
  25  * References:
  26  */
  27
  28 #include "config.h"
  29
  30 #include <glib.h>
  31
  32 #include <epan/packet.h>
  33 #include <epan/rtp_pt.h>
  34
  35
  36 /* Initialize the protocol and registered fields */
  37 static int proto_g723                                   = -1;
  38 static int hf_g723_frame_size_and_codec = -1;
  39 static int hf_g723_lpc_B5_B0                    = -1;
  40
  41 /* Initialize the subtree pointers */
  42 static int ett_g723 = -1;
  43
  44
  45 /*               RFC 3551
  46         The least significant two bits of the first
  47         octet in the frame determine the frame size and codec type:
  48          bits  content                      octets/frame
  49          00    high-rate speech (6.3 kb/s)            24
  50          01    low-rate speech  (5.3 kb/s)            20
  51          10    SID frame                               4
  52          11    reserved
  53
  54  */
  55 static const value_string g723_frame_size_and_codec_type_value[] = {
  56         {0,                     "High-rate speech (6.3 kb/s)"},
  57         {1,                     "Low-rate speech  (5.3 kb/s)"}, /* Not coded */
  58         {2,                     "SID frame"},
  59         {3,                     "Reserved"},
  60         { 0,    NULL }
  61 };
  62
  63
  64 /* Code to actually dissect the packets */
  65 static void
  66 dissect_g723(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
  67 {
  68         int offset = 0;
  69         guint octet;
  70
  71 /* Set up structures needed to add the protocol subtree and manage it */
  72         proto_item *ti;
  73         proto_tree *g723_tree;
  74
  75 /* Make entries in Protocol column and Info column on summary display */
  76         col_set_str(pinfo->cinfo, COL_PROTOCOL, "G.723.1");
  77         if (tree) {
  78                 ti = proto_tree_add_item(tree, proto_g723, tvb, 0, -1, ENC_NA);
  79
  80                 g723_tree = proto_item_add_subtree(ti, ett_g723);
  81
  82                 octet = tvb_get_guint8(tvb,offset);
  83                 proto_tree_add_item(g723_tree, hf_g723_frame_size_and_codec, tvb, offset, 1, ENC_BIG_ENDIAN);
  84                 proto_tree_add_item(g723_tree, hf_g723_lpc_B5_B0, tvb, offset, 1, ENC_BIG_ENDIAN);
  85
  86                 if ((octet & 0x1) == 1 ) /* Low rate */
  87                         return;
  88         }/* if tree */
  89
  90 }
  91
  92
  93 /* Register the protocol with Wireshark */
  94 /* If this dissector uses sub-dissector registration add a registration routine.
  95    This format is required because a script is used to find these routines and
  96    create the code that calls these routines.
  97 */
  98 void
  99 proto_reg_handoff_g723(void)
 100 {
 101         dissector_handle_t g723_handle;
 102
 103         g723_handle = create_dissector_handle(dissect_g723, proto_g723);
 104
 105         dissector_add_uint("rtp.pt", PT_G723, g723_handle);
 106
 107 }
 108
 109 /* this format is require because a script is used to build the C function
 110    that calls all the protocol registration.
 111 */
 112
 113 void
 114 proto_register_g723(void)
 115 {
 116
 117
 118 /* Setup list of header fields  See Section 1.6.1 for details*/
 119         static hf_register_info hf[] = {
 120                 { &hf_g723_frame_size_and_codec,
 121                         { "Frame size and codec type", "g723.frame_size_and_codec",
 122                         FT_UINT8, BASE_HEX, VALS(g723_frame_size_and_codec_type_value), 0x03,
 123                         "RATEFLAG_B0", HFILL }
 124                 },
 125                 { &hf_g723_lpc_B5_B0,
 126                         { "LPC_B5...LPC_B0",           "g723.lpc.b5b0",
 127                         FT_UINT8, BASE_HEX, NULL, 0xfc,
 128                         NULL, HFILL }
 129                 },
 130
 131         };
 132
 133 /* Setup protocol subtree array */
 134         static gint *ett[] = {
 135                 &ett_g723,
 136         };
 137
 138 /* Register the protocol name and description */
 139         proto_g723 = proto_register_protocol("G.723","G.723", "g723");
 140
 141 /* Required function calls to register the header fields and subtrees used */
 142         proto_register_field_array(proto_g723, hf, array_length(hf));
 143         proto_register_subtree_array(ett, array_length(ett));
 144
 145 }
 146
 147