c_rtp.h

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/*
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

/**
 * @file c_rtp.h
 * @brief ROHC compression context for the RTP profile.
 * @author David Moreau from TAS
 * @author Didier Barvaux <didier.barvaux@toulouse.viveris.com>
 */

#ifndef C_RTP_H
#define C_RTP_H

#include "c_generic.h"
#include "ts_sc_comp.h"
#include "protocols/udp.h"
#include "protocols/rtp.h"


/**
 * @brief Define the RTP and UDP specific temporary variables in the profile
 *        compression context.
 *
 * This object must be used by the RTP-specific decompression context
 * sc_rtp_context.
 *
 * @see sc_rtp_context
 */
struct rtp_tmp_vars
{
        /// The number of UDP/RTP fields that changed in the UDP/RTP headers
        int send_rtp_dynamic;

        /// The number of bits needed to encode ts_send
        size_t nr_ts_bits;

        /// The number of bits of TS to place in the extension 3 header
        size_t nr_ts_bits_ext3;

        /// The real timestamp of the last RTP message
        uint32_t timestamp;

        /// The TS field to send (ts_scaled or ts)
        uint32_t ts_send;

        /// Whether the M bit is set in the RTP header or not
        int m_set;

        /// Whether the Payload Type (PT) field changed or not
        int rtp_pt_changed;
};


/**
 * @brief Define the RTP part of the profile decompression context.
 *
 * This object must be used with the generic part of the decompression
 * context c_generic_context.
 *
 * @warning The 2 first fields MUST stay at the beginning of the structure
 *          to be compatible with \ref sc_udp_context
 *
 * @see c_generic_context
 */
struct sc_rtp_context
{
        /// @brief The number of times the UDP checksum field was added to the
        ///        compressed header
        int udp_checksum_change_count;

        /// The previous UDP header
        struct udphdr old_udp;

        /// @brief The number of times the RTP Payload Type (PT) field was added to
        ///        the compressed header
        int rtp_pt_change_count;

        /// The previous RTP header
        struct rtphdr old_rtp;

        /// @brief RTP-specific temporary variables that are used during one single
        ///        compression of packet
        struct rtp_tmp_vars tmp;

        /// Scaled RTP Time Stamp
        int tss;

        /// Whether the Time Stride field is present or not
        int tis;

        /// Structure to encode the TS field
        struct ts_sc_comp ts_sc;
};


/*
 * Function prototypes.
 */

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

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

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

void rtp_decide_state(struct c_context *const context);

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

#endif