ROHC compression context for the RTP profile. More...

#include <netinet/ip.h>
#include <netinet/udp.h>
#include "c_generic.h"
#include "c_udp.h"
#include "ts_sc_comp.h"

Include dependency graph for c_rtp.h:

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Classes
struct	rtp_tmp_variables
	Define the RTP and UDP specific temporary variables in the profile compression context. More...
struct	sc_rtp_context
	Define the RTP part of the profile decompression context. More...
Functions
int	c_rtp_create (struct c_context *context, const struct ip_packet ip)
	Create a new RTP context and initialize it thanks to the given IP/UDP/RTP packet.
void	c_rtp_destroy (struct c_context *context)
	Destroy the RTP context.
int	c_rtp_check_context (struct c_context *context, const struct ip_packet ip)
	Check if the IP/UDP/RTP packet belongs to the context.
int	c_rtp_encode (struct c_context context, const struct ip_packet ip, int packet_size, unsigned char dest, int dest_size, int *payload_offset)
	Encode an IP/UDP/RTP packet according to a pattern decided by several different factors.
void	rtp_decide_state (struct c_context *context)
	Decide the state that should be used for the next packet compressed with the ROHC RTP profile.
int	rtp_code_UO_packet_tail (struct c_context context, const unsigned char next_header, unsigned char *dest, int counter)
int	rtp_code_static_rtp_part (struct c_context context, const unsigned char next_header, unsigned char *dest, int counter)
	Build the static part of the UDP/RTP headers.
int	rtp_code_dynamic_rtp_part (struct c_context context, const unsigned char next_header, unsigned char *dest, int counter)
	Build the dynamic part of the UDP/RTP headers.
int	rtp_changed_rtp_dynamic (struct c_context context, const struct udphdr udp)
	Check if the dynamic part of the UDP/RTP headers changed.

Detailed Description

ROHC compression context for the RTP profile.

Author:: David Moreau from TAS; Didier Barvaux <didier.barvaux@toulouse.viveris.com>

Function Documentation

int c_rtp_check_context	(	struct c_context *	context,
		struct ip_packet	ip
	)

Check if the IP/UDP/RTP packet belongs to the context.

Conditions are:

the number of IP headers must be the same as in context
IP version of the two IP headers must be the same as in context
IP packets must not be fragmented
the source and destination addresses of the two IP headers must match the ones in the context
the transport protocol must be UDP
the source and destination ports of the UDP header must match the ones in the context
IPv6 only: the Flow Label of the two IP headers must match the ones the context
the SSRC field of the RTP header must match the one in the context

All the context but the last one are done by the c_udp_check_context() function.

This function is one of the functions that must exist in one profile for the framework to work.

Parameters:

context	The compression context
ip	The IP/UDP/RTP packet to check

Returns:: 1 if the IP/UDP/RTP packet belongs to the context, 0 if it does not belong to the context and -1 if an error occurs

See also:: c_udp_check_context

References c_udp_check_context(), ip_get_inner_packet(), ip_get_next_layer(), ip_get_protocol(), sc_rtp_context::old_rtp, rohc_debugf, c_context::specific, c_generic_context::specific, and rtphdr::ssrc.

int c_rtp_create	(	struct c_context *	context,
		const struct ip_packet	ip
	)

Create a new RTP context and initialize it thanks to the given IP/UDP/RTP packet.

This function is one of the functions that must exist in one profile for the framework to work.

Parameters:

context	The compression context
ip	The IP/UDP/RTP packet given to initialize the new context

Returns:: 1 if successful, 0 otherwise

References c_create_sc(), c_create_wlsb(), c_generic_create(), c_generic_destroy(), C_WINDOW_WIDTH, c_generic_context::code_dynamic_part, c_generic_context::code_static_part, c_generic_context::code_UO_packet_head, c_generic_context::code_UO_packet_tail, c_generic_context::compute_crc_dynamic, c_generic_context::compute_crc_static, c_generic_context::decide_state, c_generic_context::init_at_IR, ip_get_inner_packet(), ip_get_next_layer(), ip_get_protocol(), rtp_tmp_variables::m_set, c_generic_context::next_header_len, c_generic_context::next_header_proto, rtp_tmp_variables::nr_ts_bits, sc_rtp_context::old_rtp, sc_rtp_context::old_udp, rohc_debugf, rtp_code_dynamic_rtp_part(), rtp_code_static_rtp_part(), rtp_compute_crc_dynamic(), rtp_compute_crc_static(), rtp_decide_state(), sc_rtp_context::rtp_pt_change_count, rtp_tmp_variables::rtp_pt_changed, rtp_tmp_variables::send_rtp_dynamic, c_context::specific, c_generic_context::specific, rtp_tmp_variables::timestamp, sc_rtp_context::tmp_variables, sc_rtp_context::ts_sc, rtp_tmp_variables::ts_send, sc_rtp_context::ts_window, sc_rtp_context::udp_checksum_change_count, and udp_code_UO_packet_tail().

void c_rtp_destroy ( struct c_context * context )

Destroy the RTP context.

This function is one of the functions that must exist in one profile for the framework to work.

Parameters:

context The RTP compression context to destroy

References c_destroy_sc(), c_generic_destroy(), c_context::specific, c_generic_context::specific, and sc_rtp_context::ts_sc.

int c_rtp_encode	(	struct c_context *	context,
		const struct ip_packet	ip,
		int	packet_size,
		unsigned char *	dest,
		int	dest_size,
		int *	payload_offset
	)

Encode an IP/UDP/RTP packet according to a pattern decided by several different factors.

Parameters:

context	The compression context
ip	The IP packet to encode
packet_size	The length of the IP packet to encode
dest	The rohc-packet-under-build buffer
dest_size	The length of the rohc-packet-under-build buffer
payload_offset	The offset for the payload in the IP packet

Returns:: The length of the created ROHC packet

References c_generic_encode(), ip_get_inner_packet(), ip_get_next_layer(), ip_get_protocol(), sc_rtp_context::old_rtp, sc_rtp_context::old_udp, PACKET_IR, PACKET_IR_DYN, generic_tmp_variables::packet_type, rohc_debugf, rtp_changed_rtp_dynamic(), rtp_tmp_variables::send_rtp_dynamic, c_context::specific, c_generic_context::specific, rtp_tmp_variables::timestamp, rtphdr::timestamp, sc_rtp_context::tmp_variables, and c_generic_context::tmp_variables.

int rtp_changed_rtp_dynamic	(	struct c_context *	context,
		const struct udphdr *	udp
	)

Check if the dynamic part of the UDP/RTP headers changed.

Parameters:

context	The compression context
udp	The UDP/RTP headers

Returns:: The number of UDP/RTP fields that changed

References rtphdr::cc, rtphdr::m, rtp_tmp_variables::m_set, MAX_IR_COUNT, sc_rtp_context::old_rtp, sc_rtp_context::old_udp, rtphdr::pt, rohc_debugf, sc_rtp_context::rtp_pt_change_count, rtp_tmp_variables::rtp_pt_changed, c_context::specific, c_generic_context::specific, rtphdr::ssrc, rtphdr::timestamp, rtp_tmp_variables::timestamp, sc_rtp_context::tmp_variables, and sc_rtp_context::udp_checksum_change_count.

Referenced by c_rtp_encode().

int rtp_code_dynamic_rtp_part	(	struct c_context *	context,
		const unsigned char *	next_header,
		unsigned char *	dest,
		int	counter
	)

Build the dynamic part of the UDP/RTP headers.


 Dynamic part of UDP header (5.7.7.5):

    +---+---+---+---+---+---+---+---+
 1  /           Checksum            /   2 octets
    +---+---+---+---+---+---+---+---+

 Dynamic part of RTP header (5.7.7.6):

    +---+---+---+---+---+---+---+---+
 2  |  V=2  | P | RX|      CC       |  (RX is NOT the RTP X bit)
    +---+---+---+---+---+---+---+---+
 3  | M |            PT             |
    +---+---+---+---+---+---+---+---+
 4  /      RTP Sequence Number      /  2 octets
    +---+---+---+---+---+---+---+---+
 5  /   RTP Timestamp (absolute)    /  4 octets
    +---+---+---+---+---+---+---+---+
 6  /      Generic CSRC list        /  variable length
    +---+---+---+---+---+---+---+---+
 7  : Reserved  | X |  Mode |TIS|TSS:  if RX = 1
    +---+---+---+---+---+---+---+---+
 8  :         TS_Stride             :  1-4 octets, if TSS = 1
    +---+---+---+---+---+---+---+---+
 9  :         Time_Stride           :  1-4 octets, if TIS = 1
    +---+---+---+---+---+---+---+---+

Parts 6 & 9 are not supported yet. The TIS flag in part 7 is not supported.

Parameters:

context	The compression context
next_header	The UDP/RTP headers
dest	The rohc-packet-under-build buffer
counter	The current position in the rohc-packet-under-build buffer

Returns:: The new position in the rohc-packet-under-build buffer

References c_bytesSdvl(), c_encodeSdvl(), rtphdr::cc, rtphdr::extension, get_ts_stride(), INIT_STRIDE, INIT_TS, is_ts_constant(), rtphdr::m, c_context::mode, PACKET_IR, generic_tmp_variables::packet_type, rtphdr::padding, rtphdr::pt, rohc_debugf, ROHC_TRUE, sc_rtp_context::rtp_pt_change_count, SEND_SCALED, rtphdr::sn, c_context::specific, c_generic_context::specific, ts_sc_comp::state, rtphdr::timestamp, c_generic_context::tmp_variables, sc_rtp_context::ts_sc, sc_rtp_context::udp_checksum_change_count, and rtphdr::version.

Referenced by c_rtp_create().

int rtp_code_static_rtp_part	(	struct c_context *	context,
		const unsigned char *	next_header,
		unsigned char *	dest,
		int	counter
	)

Build the static part of the UDP/RTP headers.


 Static part of UDP header (5.7.7.5):

    +---+---+---+---+---+---+---+---+
 1  /          Source Port          /   2 octets
    +---+---+---+---+---+---+---+---+
 2  /       Destination Port        /   2 octets
    +---+---+---+---+---+---+---+---+

 Static part of RTP header (5.7.7.6):

    +---+---+---+---+---+---+---+---+
 3  /             SSRC              /   4 octets
    +---+---+---+---+---+---+---+---+

Parts 1 & 2 are done by the udp_code_static_udp_part() function. Part 3 is done by this function.

Parameters:

context	The compression context
next_header	The UDP/RTP headers
dest	The rohc-packet-under-build buffer
counter	The current position in the rohc-packet-under-build buffer

Returns:: The new position in the rohc-packet-under-build buffer

See also:: udp_code_static_udp_part

References rohc_debugf, rtphdr::ssrc, and udp_code_static_udp_part().

Referenced by c_rtp_create().

int rtp_code_UO_packet_tail	(	struct c_context *	context,
		const unsigned char *	next_header,
		unsigned char *	dest,
		int	counter
	)

void rtp_decide_state ( struct c_context * context )

Decide the state that should be used for the next packet compressed with the ROHC RTP profile.

The three states are:

Initialization and Refresh (IR),
First Order (FO),
Second Order (SO).

Parameters:

context The compression context

References change_state(), decide_state(), FO, INIT_STRIDE, INIT_TS, IR, is_ts_constant(), MAX_IR_COUNT, rohc_debugf, rtp_tmp_variables::send_rtp_dynamic, c_context::specific, c_generic_context::specific, ts_sc_comp::state, c_context::state, sc_rtp_context::tmp_variables, sc_rtp_context::ts_sc, and sc_rtp_context::udp_checksum_change_count.

Referenced by c_rtp_create().

Classes

Functions

Detailed Description

Function Documentation