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/* packet-h261.c
*
* Routines for ITU-T Recommendation H.261 dissection
*
* Copyright 2000, Philips Electronics N.V.
* Andreas Sikkema <h323@ramdyne.nl>
*
* Wireshark - Network traffic analyzer
* By Gerald Combs <gerald@wireshark.org>
* Copyright 1998 Gerald Combs
*
* SPDX-License-Identifier: GPL-2.0-or-later
*/
/*
* This dissector tries to dissect the H.261 protocol according to Annex C
* of ITU-T Recommendation H.225.0 (02/98)
*/
#include "config.h"
#include <epan/packet.h>
#include <epan/rtp_pt.h>
#include <epan/iax2_codec_type.h>
void proto_register_h261(void);
void proto_reg_handoff_h261(void);
static dissector_handle_t h261_handle;
/* H.261 header fields */
static int proto_h261 = -1;
static int hf_h261_sbit = -1;
static int hf_h261_ebit = -1;
static int hf_h261_ibit = -1;
static int hf_h261_vbit = -1;
static int hf_h261_gobn = -1;
static int hf_h261_mbap = -1;
static int hf_h261_quant = -1;
static int hf_h261_hmvd = -1; /* Mislabeled in a figure in section C.3.1 as HMDV */
static int hf_h261_vmvd = -1;
static int hf_h261_data = -1;
/* H.261 fields defining a sub tree */
static gint ett_h261 = -1;
static int
dissect_h261( tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data _U_ )
{
proto_item *ti = NULL;
proto_tree *h261_tree = NULL;
unsigned int offset = 0;
static int * const bits[] = {
/* SBIT 1st octet, 3 bits */
&hf_h261_sbit,
/* EBIT 1st octet, 3 bits */
&hf_h261_ebit,
/* I flag, 1 bit */
&hf_h261_ibit,
/* V flag, 1 bit */
&hf_h261_vbit,
NULL
};
col_set_str(pinfo->cinfo, COL_PROTOCOL, "H.261");
col_set_str(pinfo->cinfo, COL_INFO, "H.261 message");
ti = proto_tree_add_item( tree, proto_h261, tvb, offset, -1, ENC_NA);
h261_tree = proto_item_add_subtree( ti, ett_h261 );
proto_tree_add_bitmask_list(h261_tree, tvb, offset, 1, bits, ENC_NA);
offset++;
/* GOBN 2nd octet, 4 bits */
proto_tree_add_item( h261_tree, hf_h261_gobn, tvb, offset, 1, ENC_NA);
/* MBAP 2nd octet, 4 bits, 3rd octet 1 bit */
proto_tree_add_item( h261_tree, hf_h261_mbap, tvb, offset, 2, ENC_BIG_ENDIAN);
offset++;
/* QUANT 3rd octet, 5 bits (starting at bit 2!) */
proto_tree_add_item( h261_tree, hf_h261_quant, tvb, offset, 1, ENC_NA);
/* HMVD 3rd octet 2 bits, 4th octet 3 bits */
proto_tree_add_item( h261_tree, hf_h261_hmvd, tvb, offset, 2, ENC_BIG_ENDIAN);
offset++;
/* VMVD 4th octet, last 5 bits */
proto_tree_add_item( h261_tree, hf_h261_vmvd, tvb, offset, 1, ENC_NA);
offset++;
/* The rest of the packet is the H.261 stream */
proto_tree_add_item( h261_tree, hf_h261_data, tvb, offset, -1, ENC_NA);
return tvb_captured_length(tvb);
}
void
proto_register_h261(void)
{
static hf_register_info hf[] =
{
{
&hf_h261_sbit,
{
"Start bit position",
"h261.sbit",
FT_UINT8,
BASE_DEC,
NULL,
0xe0,
NULL, HFILL
}
},
{
&hf_h261_ebit,
{
"End bit position",
"h261.ebit",
FT_UINT8,
BASE_DEC,
NULL,
0x1c,
NULL, HFILL
}
},
{
&hf_h261_ibit,
{
"Intra frame encoded data flag",
"h261.i",
FT_BOOLEAN,
8,
NULL,
0x02,
NULL, HFILL
}
},
{
&hf_h261_vbit,
{
"Motion vector flag",
"h261.v",
FT_BOOLEAN,
8,
NULL,
0x01,
NULL, HFILL
}
},
{
&hf_h261_gobn,
{
"GOB Number",
"h261.gobn",
FT_UINT8,
BASE_DEC,
NULL,
0xF0,
NULL, HFILL
}
},
{
&hf_h261_mbap,
{
"Macroblock address predictor",
"h261.mbap",
FT_UINT16,
BASE_DEC,
NULL,
0x0F80,
NULL, HFILL
}
},
{
&hf_h261_quant,
{
"Quantizer",
"h261.quant",
FT_UINT8,
BASE_DEC,
NULL,
0x7C,
NULL, HFILL
}
},
{
&hf_h261_hmvd,
{
"Horizontal motion vector data",
"h261.hmvd",
FT_UINT16,
BASE_DEC,
NULL,
0x03E0,
NULL, HFILL
}
},
{
&hf_h261_vmvd,
{
"Vertical motion vector data",
"h261.vmvd",
FT_UINT8,
BASE_DEC,
NULL,
0x0,
NULL, HFILL
}
},
{
&hf_h261_data,
{
"H.261 stream",
"h261.stream",
FT_BYTES,
BASE_NONE,
NULL,
0x0,
NULL, HFILL
}
},
};
static gint *ett[] =
{
&ett_h261,
};
proto_h261 = proto_register_protocol("ITU-T Recommendation H.261",
"H.261", "h261");
proto_register_field_array(proto_h261, hf, array_length(hf));
proto_register_subtree_array(ett, array_length(ett));
h261_handle = register_dissector("h261", dissect_h261, proto_h261);
}
void
proto_reg_handoff_h261(void)
{
dissector_add_uint("rtp.pt", PT_H261, h261_handle);
dissector_add_uint("iax2.codec", AST_FORMAT_H261, h261_handle);
}
/*
* Editor modelines - https://www.wireshark.org/tools/modelines.html
*
* Local variables:
* c-basic-offset: 8
* tab-width: 8
* indent-tabs-mode: t
* End:
*
* vi: set shiftwidth=8 tabstop=8 noexpandtab:
* :indentSize=8:tabSize=8:noTabs=false:
*/
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