wireshark/epan/dissectors/packet-h263p.c

/* packet-h263p.c
 *
 * Routines for RFC-4629-encapsulated H.263 dissection
 *
 * Copyright 2003 Niklas Ogren <niklas.ogren@7l.se>
 * Seven Levels Consultants AB
 *
 * Copyright 2008 Richard van der Hoff, MX Telecom
 * <richardv@mxtelecom.com>
 *
 * Wireshark - Network traffic analyzer
 * By Gerald Combs <gerald@wireshark.org>
 * Copyright 1998 Gerald Combs
 *
 * SPDX-License-Identifier: GPL-2.0-or-later
 */

#include "config.h"

#include <epan/packet.h>

#include <epan/prefs.h>

#include "packet-h263.h"

void proto_reg_handoff_h263P(void);
void proto_register_h263P(void);

static int proto_h263P = -1;

/* H.263 RFC 4629 fields */
static int hf_h263P_payload = -1;
static int hf_h263P_rr = -1;
static int hf_h263P_pbit = -1;
static int hf_h263P_vbit = -1;
static int hf_h263P_plen = -1;
static int hf_h263P_pebit = -1;
static int hf_h263P_tid = -1;
static int hf_h263P_trun = -1;
static int hf_h263P_s = -1;
static int hf_h263P_extra_hdr = -1;
/* static int hf_h263P_PSC = -1; */
/* static int hf_h263P_TR = -1; */


/* H.263-1998 fields defining a sub tree */
static gint ett_h263P = -1;
static gint ett_h263P_extra_hdr = -1;
static gint ett_h263P_payload   = -1;
static gint ett_h263P_data = -1;

static dissector_handle_t h263P_handle;

/* RFC 4629 */
static int
dissect_h263P( tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data _U_ )
{
    proto_item *ti                  = NULL;
    proto_item *data_item           = NULL;
    proto_item *extra_hdr_item      = NULL;
    proto_tree *h263P_tree          = NULL;
    proto_tree *h263P_extr_hdr_tree = NULL;
    proto_tree *h263P_data_tree     = NULL;
    unsigned int offset             = 0;
    guint16 data16, plen;
    guint8 startcode;

    /*
    tvbuff_t *next_tvb;
    */

    col_set_str(pinfo->cinfo, COL_PROTOCOL, "H.263 RFC4629 ");

    if ( tree ) {
      ti = proto_tree_add_item( tree, proto_h263P, tvb, offset, -1, ENC_NA );
      h263P_tree = proto_item_add_subtree( ti, ett_h263P );

      data16 = tvb_get_ntohs(tvb,offset);
      proto_tree_add_item( h263P_tree, hf_h263P_rr, tvb, offset, 2, ENC_BIG_ENDIAN );
      proto_tree_add_item( h263P_tree, hf_h263P_pbit, tvb, offset, 2, ENC_BIG_ENDIAN );
      proto_tree_add_item( h263P_tree, hf_h263P_vbit, tvb, offset, 2, ENC_BIG_ENDIAN );
      proto_tree_add_item( h263P_tree, hf_h263P_plen, tvb, offset, 2, ENC_BIG_ENDIAN );
      proto_tree_add_item( h263P_tree, hf_h263P_pebit, tvb, offset, 2, ENC_BIG_ENDIAN );
      offset = offset +2;
      /*
       *   V: 1 bit
       *
       *      Indicates the presence of an 8-bit field containing information
       *      for Video Redundancy Coding (VRC), which follows immediately after
       *      the initial 16 bits of the payload header, if present.  For syntax
       *      and semantics of that 8-bit VRC field, see Section 5.2.
       */

      if ((data16&0x0200)==0x0200){
          /* V bit = 1
           *   The format of the VRC header extension is as follows:
           *
           *         0 1 2 3 4 5 6 7
           *        +-+-+-+-+-+-+-+-+
           *        | TID | Trun  |S|
           *        +-+-+-+-+-+-+-+-+
           *
           *   TID: 3 bits
           *
           *   Thread ID.  Up to 7 threads are allowed.  Each frame of H.263+ VRC
           *   data will use as reference information only sync frames or frames
           *   within the same thread.  By convention, thread 0 is expected to be
           *   the "canonical" thread, which is the thread from which the sync frame
           *   should ideally be used.  In the case of corruption or loss of the
           *   thread 0 representation, a representation of the sync frame with a
           *   higher thread number can be used by the decoder.  Lower thread
           *   numbers are expected to contain representations of the sync frames
           *   equal to or better than higher thread numbers in the absence of data
           *   corruption or loss.  See [Vredun] for a detailed discussion of VRC.
           *
           *   Trun: 4 bits
           *
           *   Monotonically increasing (modulo 16) 4-bit number counting the packet
           *   number within each thread.
           *
           *   S: 1 bit
           *
           *   A bit that indicates that the packet content is for a sync frame.
           *   :
           */
          proto_tree_add_item( h263P_tree, hf_h263P_tid, tvb, offset, 1, ENC_BIG_ENDIAN );
          proto_tree_add_item( h263P_tree, hf_h263P_trun, tvb, offset, 1, ENC_BIG_ENDIAN );
          proto_tree_add_item( h263P_tree, hf_h263P_s, tvb, offset, 1, ENC_BIG_ENDIAN );
          offset++;
      }

      /* Length, in bytes, of the extra picture header. */
      plen = (data16 & 0x01f8) >> 3;
      if (plen != 0){
          extra_hdr_item = proto_tree_add_item( h263P_tree, hf_h263P_extra_hdr, tvb, offset, plen, ENC_NA );
          h263P_extr_hdr_tree = proto_item_add_subtree( extra_hdr_item, ett_h263P_extra_hdr );
          dissect_h263_picture_layer( tvb, pinfo, h263P_extr_hdr_tree, offset, plen, TRUE);
          offset += plen;
      }
      if ((data16&0x0400)!=0){
          /* P bit = 1 */
          data_item = proto_tree_add_item( h263P_tree, hf_h263P_payload, tvb, offset, -1, ENC_NA );
          h263P_data_tree = proto_item_add_subtree( data_item, ett_h263P_data );
          /* Startc code holds bit 17 -23 of the codeword */
          startcode = tvb_get_guint8(tvb,offset)&0xfe;
          if (startcode & 0x80){
              /* All picture, slice, and EOSBS start codes
               * shall be byte aligned, and GOB and EOS start codes may be byte aligned.
               */
              switch(startcode){
              case 0xf8:
                  /* End Of Sub-Bitstream code (EOSBS)
                   * EOSBS codes shall be byte aligned
                   * ( 1111 100. )
                   */
                  break;
              case 0x80:
              case 0x82:
                  /* Picture Start Code (PSC)
                   * ( 1000 00x.)
                   */
                  col_append_str( pinfo->cinfo, COL_INFO, "(PSC) ");
                  dissect_h263_picture_layer( tvb, pinfo, h263P_data_tree, offset, -1, TRUE);
                  break;
              case 0xfc:
              case 0xfe:
                  /* End Of Sequence (EOS)
                   * ( 1111 11x. )
                   */
              default:
                  /* Group of Block Start Code (GBSC) or
                   * Slice Start Code (SSC)
                   */
                  col_append_str( pinfo->cinfo, COL_INFO, "(GBSC) ");
                  dissect_h263_group_of_blocks_layer( tvb, h263P_data_tree, offset,TRUE);
                  break;
              }
          }else{
              /* Error */
          }
          return tvb_captured_length(tvb);
      }
      proto_tree_add_item( h263P_tree, hf_h263P_payload, tvb, offset, -1, ENC_NA );
    }
    return tvb_captured_length(tvb);
}

void
proto_reg_handoff_h263P(void)
{
    dissector_add_string("rtp_dyn_payload_type","H263-1998", h263P_handle);
    dissector_add_string("rtp_dyn_payload_type","H263-2000", h263P_handle);
    dissector_add_uint_range_with_preference("rtp.pt", "", h263P_handle);
}


void
proto_register_h263P(void)
{
    module_t *h263P_module;

    static hf_register_info hf[] =
    {
        {
            &hf_h263P_payload,
            {
                "H.263 RFC4629 payload",
                "h263p.payload",
                FT_NONE,
                BASE_NONE,
                NULL,
                0x0,
                "The actual H.263 RFC4629 data", HFILL
            }
        },
        {
            &hf_h263P_rr,
            {
                "Reserved",
                "h263p.rr",
                FT_UINT16,
                BASE_DEC,
                NULL,
                0xf800,
                "Reserved SHALL be zero", HFILL
            }
        },
        {
            &hf_h263P_pbit,
            {
                "P",
                "h263p.p",
                FT_BOOLEAN,
                16,
                NULL,
                0x0400,
                "Indicates (GOB/Slice) start or (EOS or EOSBS)", HFILL
            }
        },
        {
            &hf_h263P_vbit,
            {
                "V",
                "h263p.v",
                FT_BOOLEAN,
                16,
                NULL,
                0x0200,
                "presence of Video Redundancy Coding (VRC) field", HFILL
            }
        },
        {
            &hf_h263P_plen,
            {
                "PLEN",
                "h263p.plen",
                FT_UINT16,
                BASE_DEC,
                NULL,
                0x01f8,
                "Length, in bytes, of the extra picture header", HFILL
            }
        },
        {
            &hf_h263P_pebit,
            {
                "PEBIT",
                "h263p.pebit",
                FT_UINT16,
                BASE_DEC,
                NULL,
                0x0003,
                "number of bits that shall be ignored in the last byte of the picture header", HFILL
            }
        },


        {
            &hf_h263P_tid,
            {
                "Thread ID",
                "h263p.tid",
                FT_UINT8,
                BASE_DEC,
                NULL,
                0xe0,
                NULL, HFILL
            }
        },
        {
            &hf_h263P_trun,
            {
                "Trun",
                "h263p.trun",
                FT_UINT8,
                BASE_DEC,
                NULL,
                0x1e,
                "Monotonically increasing (modulo 16) 4-bit number counting the packet number within each thread", HFILL
            }
        },
        {
            &hf_h263P_s,
            {
                "S",
                "h263p.s",
                FT_UINT8,
                BASE_DEC,
                NULL,
                0x01,
                "Indicates that the packet content is for a sync frame", HFILL
            }
        },
        {
            &hf_h263P_extra_hdr,
            {
                "Extra picture header",
                "h263p.extra_hdr",
                FT_BYTES,
                BASE_NONE,
                NULL,
                0x0,
                NULL, HFILL
            }
        },
#if 0
        {
            &hf_h263P_PSC,
            {
                "H.263 PSC",
                "h263p.PSC",
                FT_UINT16,
                BASE_HEX,
                NULL,
                0xfc00,
                "Picture Start Code(PSC)", HFILL
            }
        },
#endif
#if 0
        {
            &hf_h263P_TR,
            {
                "H.263 Temporal Reference",
                "h263p.tr",
                FT_UINT16,
                BASE_HEX,
                NULL,
                0x03fc,
                "Temporal Reference, TR", HFILL
            }
        },
#endif

    };

    static gint *ett[] =
    {
        &ett_h263P,
        &ett_h263P_extra_hdr,
        &ett_h263P_payload,
        &ett_h263P_data,
    };


    proto_h263P = proto_register_protocol("ITU-T Recommendation H.263 RTP Payload header (RFC4629)",
        "H.263P", "h263p");

    proto_register_field_array(proto_h263P, hf, array_length(hf));
    proto_register_subtree_array(ett, array_length(ett));

    h263P_module = prefs_register_protocol(proto_h263P, NULL);

    prefs_register_obsolete_preference(h263P_module, "dynamic.payload.type");

    h263P_handle = register_dissector("h263P", dissect_h263P, proto_h263P);
}

/*
 * Editor modelines  -  https://www.wireshark.org/tools/modelines.html
 *
 * Local variables:
 * c-basic-offset: 4
 * tab-width: 8
 * indent-tabs-mode: nil
 * End:
 *
 * vi: set shiftwidth=4 tabstop=8 expandtab:
 * :indentSize=4:tabSize=8:noTabs=true:
 */