ROHC compression/decompression library
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00001 /* 00002 * This program is free software; you can redistribute it and/or modify 00003 * it under the terms of the GNU General Public License as published by 00004 * the Free Software Foundation; either version 2 of the License, or 00005 * (at your option) any later version. 00006 * 00007 * This program is distributed in the hope that it will be useful, 00008 * but WITHOUT ANY WARRANTY; without even the implied warranty of 00009 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 00010 * GNU General Public License for more details. 00011 * 00012 * You should have received a copy of the GNU General Public License 00013 * along with this program; if not, write to the Free Software 00014 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA 00015 */ 00016 00017 /** 00018 * @file c_rtp.h 00019 * @brief ROHC compression context for the RTP profile. 00020 * @author David Moreau from TAS 00021 * @author Didier Barvaux <didier.barvaux@toulouse.viveris.com> 00022 */ 00023 00024 #ifndef C_RTP_H 00025 #define C_RTP_H 00026 00027 #include "c_generic.h" 00028 #include "ts_sc_comp.h" 00029 #include "rtp.h" 00030 00031 #include <netinet/ip.h> 00032 #include <netinet/udp.h> 00033 00034 00035 /** 00036 * @brief Define the RTP and UDP specific temporary variables in the profile 00037 * compression context. 00038 * 00039 * This object must be used by the RTP-specific decompression context 00040 * sc_rtp_context. 00041 * 00042 * @see sc_rtp_context 00043 */ 00044 struct rtp_tmp_vars 00045 { 00046 /// The number of UDP/RTP fields that changed in the UDP/RTP headers 00047 int send_rtp_dynamic; 00048 00049 /// The number of bits needed to encode ts_send 00050 size_t nr_ts_bits; 00051 00052 /// The number of bits of TS to place in the extension 3 header 00053 size_t nr_ts_bits_ext3; 00054 00055 /// The real timestamp of the last RTP message 00056 uint32_t timestamp; 00057 00058 /// The TS field to send (ts_scaled or ts) 00059 uint32_t ts_send; 00060 00061 /// Whether the M bit is set in the RTP header or not 00062 int m_set; 00063 00064 /// Whether the Payload Type (PT) field changed or not 00065 int rtp_pt_changed; 00066 }; 00067 00068 00069 /** 00070 * @brief Define the RTP part of the profile decompression context. 00071 * 00072 * This object must be used with the generic part of the decompression 00073 * context c_generic_context. 00074 * 00075 * @warning The 2 first fields MUST stay at the beginning of the structure 00076 * to be compatible with \ref sc_udp_context 00077 * 00078 * @see c_generic_context 00079 */ 00080 struct sc_rtp_context 00081 { 00082 /// @brief The number of times the UDP checksum field was added to the 00083 /// compressed header 00084 int udp_checksum_change_count; 00085 00086 /// The previous UDP header 00087 struct udphdr old_udp; 00088 00089 /// @brief The number of times the RTP Payload Type (PT) field was added to 00090 /// the compressed header 00091 int rtp_pt_change_count; 00092 00093 /// The previous RTP header 00094 struct rtphdr old_rtp; 00095 00096 /// @brief RTP-specific temporary variables that are used during one single 00097 /// compression of packet 00098 struct rtp_tmp_vars tmp; 00099 00100 /// A window used to encode the TS field 00101 struct c_wlsb *ts_window; 00102 00103 /// Scaled RTP Time Stamp 00104 int tss; 00105 00106 /// Whether the Time Stride field is present or not 00107 int tis; 00108 00109 /// Structure to encode the TS field 00110 struct ts_sc_comp ts_sc; 00111 }; 00112 00113 00114 /* 00115 * Function prototypes. 00116 */ 00117 00118 int c_rtp_create(struct c_context *const context, const struct ip_packet *ip); 00119 void c_rtp_destroy(struct c_context *const context); 00120 00121 int c_rtp_check_context(const struct c_context *context, 00122 const struct ip_packet *ip); 00123 00124 int c_rtp_encode(struct c_context *const context, 00125 const struct ip_packet *ip, 00126 const int packet_size, 00127 unsigned char *const dest, 00128 const int dest_size, 00129 rohc_packet_t *const packet_type, 00130 int *const payload_offset); 00131 00132 void rtp_decide_state(struct c_context *const context); 00133 00134 int rtp_code_UO_packet_tail(struct c_context *context, 00135 const unsigned char *next_header, 00136 unsigned char *dest, 00137 int counter); 00138 00139 00140 #endif 00141