FEC

FEC is defined by RFC5109 and is used to perform forward error correction on RTP packets.

This article does not give an example, and the use is relatively simple. The basic process is: initialize the fec structure -> generate/repair FEC packets -> custom processing -> release the generated/repaired FEC packets -> release the fec structure.

Header file

#include "mln_fec.h"

Module

fec

Functions/Macros

mln_fec_new

mln_fec_t *mln_fec_new(void);

Description: Create the mln_fec_t structure.

Return value: return the structure pointer successfully, otherwise return NULL

mln_fec_free

void mln_fec_free(mln_fec_t *fec);

Description: Free the mln_fec_t structure.

Return value: none

mln_fec_encode

mln_fec_result_t *mln_fec_encode(mln_fec_t *fec, uint8_t *packets[], uint16_t packlen[], size_t n, uint16_t group_size);

Description: Generate a corresponding FEC message for a given RTP message, where:

• packets RTP packet array, each element is an RTP packet. Note: Here is the complete RTP message (including header and body).
• packlen RTP packet length array, each element corresponds to an element in packets.
• n is the number of RTP packets.
• group_size indicates that one FEC packet is generated for every group_size RTP packet, that is, this function may generate multiple FEC packets at a time.

Return value: return mln_fec_result_t structure pointer if successful, otherwise return NULL

mln_fec_result_free

void mln_fec_result_free(mln_fec_result_t *fr);

Description: Free the mln_fec_result_t structure memory.

Return value: none

mln_fec_decode

mln_fec_result_t *mln_fec_decode(mln_fec_t *fec, uint8_t *packets[], uint16_t *packLen, size_t n);

Description: Repair RTP packets. FEC uses XOR to repair, so it can only accept the case where only one RTP packet is lost. If more than one RTP packet is lost, it cannot be repaired.

• packets An array of FEC packets and RTP packets, each element is an RTP or FEC packet. Note: Here is the complete RTP message (including header and body).
• packlen An array of packet lengths, each element corresponds to an element in packets.
• n is the number of packets.

Return value: return mln_fec_result_t structure pointer if successful, otherwise return NULL

mln_fec_set_pt

mln_fec_set_pt(fec,_pt)

Description: Set the PT field in the RTP header.

Return value: none

mln_fec_get_result

mln_fec_get_result(_result,index,_len)

Description: Get the index-th packet in _result of class behavior mln_fec_result_t, index starts from 0. _len is the length of the obtained packet.

Return value: the memory address of the obtained message content

mln_fec_get_result_num

mln_fec_get_result_num(_result)

Description: Get the number of results in _result of class behavior mln_fec_result_t.

Return value: the number of results