/*
5.1.1 Picture Start Code (PSC) (22 bits)
PSC is a word of 22 bits. Its value is 0000 0000 0000 0000 1 00000. All picture start codes shall be
byte aligned.
( 1000 00xx)
End Of Sequence (EOS) (22 bits)
A codeword of 22 bits. Its value is 0000 0000 0000 0000 1 11111.
( 1111 11xx )
Group of Block Start Code (GBSC) (17 bits)
A word of 17 bits. Its value is 0000 0000 0000 0000 1.
( 1xxx xxxx )
End Of Sub-Bitstream code (EOSBS) (23 bits)
The EOSBS code is a codeword of 23 bits. Its value is 0000 0000 0000 0000 1 11110 0.
( 1111 100x )
Slice Start Code (SSC) (17 bits)
A word of 17 bits. Its value is 0000 0000 0000 0000 1.
( 1xxx xxxx )
*/
static void dissect_h263_data( tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree )
{
guint offset = 0;
proto_item *h263_payload_item = NULL;
proto_tree *h263_payload_tree = NULL;
guint32 data;
guint8 startcode;
col_append_str( pinfo->cinfo, COL_INFO, "H263 payload ");
if( tree ) {
h263_payload_item = proto_tree_add_item( tree, proto_h263_data, tvb, offset, -1, FALSE );
h263_payload_tree = proto_item_add_subtree( h263_payload_item, ett_h263_payload );
}
/* Check for PSC, PSC is a word of 22 bits. Its value is 0000 0000 0000 0000' 1000 00xx xxxx xxxx. */
data = tvb_get_ntohl(tvb, offset);
if (( data & 0xffff8000) == 0x00008000 ) {
/* Start Code found
*
* Startc code holds bit 17 -23 of the codeword
*/
startcode = tvb_get_guint8(tvb,offset+2)&0xfe;
if (startcode & 0x80){
switch(startcode){
case 0xf8:
/* End Of Sub-Bitstream code (EOSBS)
* ( 1111 100. )
*/
break;
case 0x80:
case 0x82:
/* Picture Start Code (PSC)
* ( 1000 00x.)
*/
col_append_str( pinfo->cinfo, COL_INFO, "(PSC) ");
offset = dissect_h263_picture_layer( tvb, pinfo, h263_payload_tree, offset, -1, FALSE);
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) ");
offset = dissect_h263_group_of_blocks_layer( tvb, h263_payload_tree, offset,FALSE);
break;
}
}else{
/* Error */
}
}
if( tree )
proto_tree_add_item( h263_payload_tree, hf_h263_data, tvb, offset, -1, FALSE );
}
/* RFC 4629 */
static void
dissect_h263P( tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree )
{
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;
}
proto_tree_add_item( h263P_tree, hf_h263P_payload, tvb, offset, -1, ENC_NA );
}
}
