559 lines
20 KiB
C++
559 lines
20 KiB
C++
#include "defines.h"
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#include "rtp.h"
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#include "rtp_fec.h"
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namespace RTP{
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/// Based on the `block PT` value, we can either find the
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/// contents of the codec payload (e.g. H264, VP8) or a ULPFEC header
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/// (RFC 5109). The structure of the ULPFEC data is as follows.
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///
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/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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/// | RTP Header (12 octets or more) |
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/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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/// | FEC Header (10 octets) |
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/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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/// | FEC Level 0 Header |
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/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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/// | FEC Level 0 Payload |
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/// | |
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/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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/// | FEC Level 1 Header |
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/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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/// | FEC Level 1 Payload |
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/// | |
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/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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/// | Cont. |
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/// | |
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/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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///
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/// FEC HEADER:
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///
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/// 0 1 2 3
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/// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
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/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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/// |E|L|P|X| CC |M| PT recovery | SN base |
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/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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/// | TS recovery |
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/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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/// | length recovery |
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/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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///
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///
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/// FEC LEVEL HEADER
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///
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/// 0 1 2 3
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/// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
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/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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/// | Protection Length | mask |
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/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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/// | mask cont. (present only when L = 1) |
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/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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///
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PacketFEC::PacketFEC(){}
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PacketFEC::~PacketFEC(){
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receivedSeqNums.clear();
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coveredSeqNums.clear();
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}
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bool PacketFEC::initWithREDPacket(const char *data, size_t nbytes){
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if (!data){
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FAIL_MSG("Given fecData pointer is NULL.");
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return false;
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}
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if (nbytes < 23){
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FAIL_MSG("Given fecData is too small. Should be at least: 12 (RTP) + 1 (RED) + 10 (FEC) 23 "
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"bytes.");
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return false;
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}
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if (coveredSeqNums.size() != 0){
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FAIL_MSG("It seems we're already initialized; coveredSeqNums already set.");
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return false;
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}
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if (receivedSeqNums.size() != 0){
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FAIL_MSG("It seems we're already initialized; receivedSeqNums is not empty.");
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return false;
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}
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// Decode RED header.
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RTP::Packet rtpPkt(data, nbytes);
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uint8_t *redHeader = (uint8_t *)(data + rtpPkt.getHsize());
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uint8_t moreBlocks = redHeader[0] & 0x80;
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if (moreBlocks == 1){
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FAIL_MSG("RED header indicates there are multiple blocks. Haven't seen this before (@todo "
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"implement, exiting now).");
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// \todo do not EXIT!
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return false;
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}
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// Copy the data, starting at the FEC header (skip RTP + RED header)
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size_t numHeaderBytes = rtpPkt.getHsize() + 1;
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if (numHeaderBytes > nbytes){
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FAIL_MSG("Invalid FEC packet; too small to contain FEC data.");
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return false;
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}
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fecPacketData.assign(NULL, 0);
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fecPacketData.append(data + numHeaderBytes, nbytes - numHeaderBytes);
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// Extract the sequence numbers this packet protects.
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if (!extractCoveringSequenceNumbers()){
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FAIL_MSG("Failed to extract the protected sequence numbers for this FEC.");
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// @todo we probably want to reset our set.
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return false;
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}
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return true;
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}
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uint8_t PacketFEC::getExtensionFlag(){
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if (fecPacketData.size() == 0){
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FAIL_MSG("Cannot get extension-flag from the FEC header; fecPacketData member is not set. "
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"Not initialized?");
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return 0;
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}
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return ((fecPacketData[0] & 0x80) >> 7);
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}
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uint8_t PacketFEC::getLongMaskFlag(){
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if (fecPacketData.size() == 0){
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FAIL_MSG("Cannot get the long-mask-flag from the FEC header. fecPacketData member is not "
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"set. Not initialized?");
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return 0;
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}
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return ((fecPacketData[0] & 0x40) >> 6);
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}
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// Returns 0 (error), 2 or 6, wich are the valid sizes of the mask.
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uint8_t PacketFEC::getNumBytesUsedForMask(){
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if (fecPacketData.size() == 0){
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FAIL_MSG("Cannot get the number of bytes used by the mask. fecPacketData member is not set. "
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"Not initialized?");
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return 0;
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}
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if (getLongMaskFlag() == 0){return 2;}
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return 6;
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}
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uint16_t PacketFEC::getSequenceBaseNumber(){
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if (fecPacketData.size() == 0){
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FAIL_MSG(
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"Cannot get the sequence base number. fecPacketData member is not set. Not initialized?");
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return 0;
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}
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return (uint16_t)(fecPacketData[2] << 8) | fecPacketData[3];
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}
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char *PacketFEC::getFECHeader(){
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if (fecPacketData.size() == 0){
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FAIL_MSG("Cannot get fec header. fecPacketData member is not set. Not initialized?");
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}
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return fecPacketData;
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}
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char *PacketFEC::getLevel0Header(){
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if (fecPacketData.size() == 0){
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FAIL_MSG("Cannot get the level 0 header. fecPacketData member is not set. Not initialized?");
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return NULL;
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}
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return (char *)(fecPacketData + 10);
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}
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char *PacketFEC::getLevel0Payload(){
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if (fecPacketData.size() == 0){
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FAIL_MSG("Cannot get the level 0 payload. fecPacketData member is not set. Not initialized?");
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return NULL;
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}
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// 10 bytes for FEC header
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// 2 bytes for `Protection Length`
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// 2 or 6 bytes for `mask`.
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return (char *)(fecPacketData + 10 + 2 + getNumBytesUsedForMask());
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}
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uint16_t PacketFEC::getLevel0ProtectionLength(){
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if (fecPacketData.size() == 0){
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FAIL_MSG("Cannot get the level 0 protection length. fecPacketData member is not set. Not "
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"initialized?");
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return 0;
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}
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char *level0Header = getLevel0Header();
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if (!level0Header){
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FAIL_MSG("Failed to get the level 0 header, cannot get protection length.");
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return 0;
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}
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uint16_t protectionLength = (level0Header[0] << 8) | level0Header[1];
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return protectionLength;
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}
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uint16_t PacketFEC::getLengthRecovery(){
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char *fecHeader = getFECHeader();
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if (!fecHeader){
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FAIL_MSG("Cannot get the FEC header which we need to get the `length recovery` field. Not "
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"initialized?");
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return 0;
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}
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uint16_t lengthRecovery = (fecHeader[8] << 8) | fecHeader[9];
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return lengthRecovery;
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}
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// Based on InsertFecPacket of forward_error_correction.cc from
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// Chromium. (used as reference). The `mask` from the
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// FEC-level-header can be 2 or 6 bytes long. Whenever a bit is
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// set to 1 it means that we have to calculate the sequence
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// number for that bit. To calculate the sequence number we
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// start with the `SN base` value (base sequence number) and
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// use the bit offset to increment the SN-base value. E.g.
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// when it's bit 4 and SN-base is 230, it meas that this FEC
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// packet protects the media packet with sequence number
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// 230. We have to start counting the bit numbers from the
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// most-significant-bit (e.g. 1 << 7).
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bool PacketFEC::extractCoveringSequenceNumbers(){
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if (coveredSeqNums.size() != 0){
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FAIL_MSG("Cannot extract protected sequence numbers; looks like we already did that.");
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return false;
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}
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size_t maskNumBytes = getNumBytesUsedForMask();
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if (maskNumBytes != 2 && maskNumBytes != 6){
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FAIL_MSG("Invalid mask size (%zu) cannot extract sequence numbers.", maskNumBytes);
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return false;
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}
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char *maskPtr = getLevel0Header();
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if (!maskPtr){
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FAIL_MSG("Failed to get the level-0 header ptr. Cannot extract protected sequence numbers.");
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return false;
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}
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uint16_t seqNumBase = getSequenceBaseNumber();
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if (seqNumBase == 0){WARN_MSG("Base sequence number is 0; it's possible but unlikely.");}
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// Skip the `Protection Length`
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maskPtr = maskPtr + 2;
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for (uint16_t byteDX = 0; byteDX < maskNumBytes; ++byteDX){
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uint8_t maskByte = maskPtr[byteDX];
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for (uint16_t bitDX = 0; bitDX < 8; ++bitDX){
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if (maskByte & ((1 << 7) - bitDX)){
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uint16_t seqNum = seqNumBase + (byteDX << 3) + bitDX;
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coveredSeqNums.insert(seqNum);
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}
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}
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}
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return true;
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}
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// \todo rename coversSequenceNumber
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bool PacketFEC::coversSequenceNumber(uint16_t sn){
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return (coveredSeqNums.count(sn) == 0) ? false : true;
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}
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void PacketFEC::addReceivedSequenceNumber(uint16_t sn){
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if (false == coversSequenceNumber(sn)){
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FAIL_MSG("Trying to add a received sequence number this instance is not handling (%u).", sn);
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return;
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}
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receivedSeqNums.insert(sn);
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}
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/// This function can be called to recover a missing packet. A
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/// FEC packet is received with a list of media packets it
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/// might be able to recover; this PacketFEC is received after
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/// we should have received the media packets it's protecting.
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///
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/// Here we first fill al list with the received sequence
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/// numbers that we're protecting; when we're missing one
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/// packet this function will try to recover it.
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///
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/// The `receivedMediaPackets` is the history of media packets
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/// that you received and keep in a memory. These are used
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/// when XORing when we reconstruct a packet.
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void PacketFEC::tryToRecoverMissingPacket(std::map<uint16_t, Packet> &receivedMediaPackets,
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Packet &reconstructedPacket){
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// Mark all the media packets that we protect and which have
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// been received as "received" in our internal list.
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std::set<uint16_t>::iterator protIt = coveredSeqNums.begin();
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while (protIt != coveredSeqNums.end()){
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if (receivedMediaPackets.count(*protIt) == 1){addReceivedSequenceNumber(*protIt);}
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protIt++;
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}
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// We have received all media packets that we could recover;
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// so there is no need for this FEC packet.
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// @todo Jaron shall we reuse allocs/PacketFECs?
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if (receivedSeqNums.size() == coveredSeqNums.size()){return;}
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if (coveredSeqNums.size() != (receivedSeqNums.size() + 1)){
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// missing more then 1 packet. we can only recover when
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// one packet is lost.
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return;
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}
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// Find missing sequence number.
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uint16_t missingSeqNum = 0;
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protIt = coveredSeqNums.begin();
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while (protIt != coveredSeqNums.end()){
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if (receivedSeqNums.count(*protIt) == 0){
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missingSeqNum = *protIt;
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break;
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}
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++protIt;
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}
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if (!coversSequenceNumber(missingSeqNum)){
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WARN_MSG("We cannot recover %u.", missingSeqNum);
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return;
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}
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// Copy FEC into new RTP-header
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char *fecHeader = getFECHeader();
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if (!fecHeader){
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FAIL_MSG("Failed to get the fec header. Cannot recover.");
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return;
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}
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recoverData.assign(NULL, 0);
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recoverData.append(fecHeader, 12);
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// Copy FEC into new RTP-payload
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char *level0Payload = getLevel0Payload();
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if (!level0Payload){
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FAIL_MSG("Failed to get the level-0 payload data (XOR'd media data from FEC packet).");
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return;
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}
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uint16_t level0ProtLen = getLevel0ProtectionLength();
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if (level0ProtLen == 0){
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FAIL_MSG("Failed to get the level-0 protection length.");
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return;
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}
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recoverData.append(level0Payload, level0ProtLen);
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uint8_t recoverLength[2] ={fecHeader[8], fecHeader[9]};
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// XOR headers
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protIt = coveredSeqNums.begin();
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while (protIt != coveredSeqNums.end()){
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uint16_t seqNum = *protIt;
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if (seqNum == missingSeqNum){
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++protIt;
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continue;
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}
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Packet &mediaPacket = receivedMediaPackets[seqNum];
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char *mediaData = mediaPacket.ptr();
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uint16_t mediaSize = mediaPacket.getPayloadSize();
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uint8_t *mediaSizePtr = (uint8_t *)&mediaSize;
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WARN_MSG(" => XOR header with %u, size: %u.", seqNum, mediaSize);
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// V, P, X, CC, M, PT
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recoverData[0] ^= mediaData[0];
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recoverData[1] ^= mediaData[1];
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// Timestamp
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recoverData[4] ^= mediaData[4];
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recoverData[5] ^= mediaData[5];
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recoverData[6] ^= mediaData[6];
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recoverData[7] ^= mediaData[7];
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// Length of recovered media packet
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recoverLength[0] ^= mediaSizePtr[1];
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recoverLength[1] ^= mediaSizePtr[0];
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++protIt;
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}
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uint16_t recoverPayloadSize = ntohs(*(uint16_t *)recoverLength);
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// XOR payloads
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protIt = coveredSeqNums.begin();
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while (protIt != coveredSeqNums.end()){
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uint16_t seqNum = *protIt;
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if (seqNum == missingSeqNum){
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++protIt;
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continue;
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}
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Packet &mediaPacket = receivedMediaPackets[seqNum];
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char *mediaData = mediaPacket.ptr() + mediaPacket.getHsize();
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for (size_t i = 0; i < recoverPayloadSize; ++i){recoverData[12 + i] ^= mediaData[i];}
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++protIt;
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}
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// And setup the reconstructed packet.
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reconstructedPacket = Packet(recoverData, recoverPayloadSize);
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reconstructedPacket.setSequence(missingSeqNum);
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// @todo check what other header fields we need to fix.
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}
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void FECSorter::addPacket(const Packet &pack){
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if (tmpVideoLossPrevention & SDP_LOSS_PREVENTION_ULPFEC){
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packetHistory[pack.getSequence()] = pack;
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while (packetHistory.begin()->first < pack.getSequence() - 500){
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packetHistory.erase(packetHistory.begin());
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}
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}
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Sorter::addPacket(pack);
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}
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/// This function will handle RED packets that may be used to
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/// encapsulate ULPFEC or simply the codec payload (e.g. H264,
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/// VP8). This function is created to handle FEC with
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/// WebRTC. When we want to use FEC with WebRTC we have to add
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/// both the `a=rtpmap:<ulp-fmt> ulpfec/90000` and
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/// `a=rtpmap<red-fmt> red/90000` lines to the SDP. FEC is
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/// always used together with RED (RFC 1298). It turns out
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/// that with WebRTC the RED only adds one byte after the RTP
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/// header (only the `F` and `block PT`, see below)`. The
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/// `block PT` is the payload type of the data that
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/// follows. This would be `<ulp-fmt>` for FEC data. Though
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/// these RED packets may contain FEC or just the media:
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/// H264/VP8.
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///
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/// RED HEADER:
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///
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/// 0 1 2 3
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/// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
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/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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/// |F| block PT | timestamp offset | block length |
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/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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///
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void FECSorter::addREDPacket(char *dat, unsigned int len, uint8_t codecPayloadType,
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uint8_t REDPayloadType, uint8_t ULPFECPayloadType){
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RTP::Packet pkt(dat, len);
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if (pkt.getPayloadType() != REDPayloadType){
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FAIL_MSG("Requested to add a RED packet, but it has an invalid payload type.");
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return;
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}
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// Check if the `F` flag is set. Chromium will always set
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// this to 0 (at time of writing, check: https://goo.gl/y1eJ6k
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uint8_t *REDHeader = (uint8_t *)(dat + pkt.getHsize());
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uint8_t moreBlocksAvailable = REDHeader[0] & 0x80;
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if (moreBlocksAvailable == 1){
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FAIL_MSG("Not yet received a RED packet that had it's F bit set; @todo implement.");
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exit(EXIT_FAILURE);
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return;
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}
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// Extract the `block PT` field which can be the media-pt,
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// fec-pt. When it's just media that follows, we move all
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// data one byte up and reconstruct a normal media packet.
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uint8_t blockPayloadType = REDHeader[0] & 0x7F;
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if (blockPayloadType == codecPayloadType){
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memmove(dat + pkt.getHsize(), dat + pkt.getHsize() + 1, len - pkt.getHsize() - 1);
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dat[1] &= 0x80;
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dat[1] |= codecPayloadType;
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RTP::Packet mediaPacket((const char *)dat, len - 1);
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addPacket(mediaPacket);
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return;
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}
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// When the payloadType equals our ULP/FEC payload type, we
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// received a REC packet (RFC 5109) that contains FEC data
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// and a list of sequence number that it covers and can
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// reconstruct.
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//
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// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
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//
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// \todo Jaron, I'm now just generating a `PacketFEC` on the heap
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// and we're not managing destruction anywhere atm; I guess
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// re-use or destruction needs to be part of the algo that
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// is going to deal with FEC.
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//
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// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
|
|
if (blockPayloadType == ULPFECPayloadType){
|
|
WARN_MSG(" => got fec packet: %u", pkt.getSequence());
|
|
PacketFEC *fec = new PacketFEC();
|
|
if (!fec->initWithREDPacket(dat, len)){
|
|
delete fec;
|
|
fec = NULL;
|
|
FAIL_MSG("Failed to initialize a `PacketFEC`");
|
|
}
|
|
fecPackets.push_back(fec);
|
|
|
|
Packet recreatedPacket;
|
|
fec->tryToRecoverMissingPacket(packetHistory, recreatedPacket);
|
|
if (recreatedPacket.ptr() != NULL){
|
|
char *pl = (char *)recreatedPacket.getPayload();
|
|
WARN_MSG(" => reconstructed %u, %02X %02X %02X %02X | %02X %02X %02X %02X",
|
|
recreatedPacket.getSequence(), pl[0], pl[1], pl[2], pl[3], pl[4], pl[5], pl[6], pl[7]);
|
|
addPacket(recreatedPacket);
|
|
}
|
|
return;
|
|
}
|
|
|
|
FAIL_MSG("Unhandled RED block payload type %u. Check the answer SDP.", blockPayloadType);
|
|
}
|
|
|
|
/// Each FEC packet is capable of recovering a limited amount
|
|
/// of media packets. Some experimentation showed that most
|
|
/// often one FEC is used to protect somewhere between 2-10
|
|
/// media packets. Each FEC packet has a list of sequence
|
|
/// number that it can recover when all other media packets
|
|
/// have been received except the one that we want to
|
|
/// recover. This function returns the FEC packet might be able
|
|
/// to recover the given sequence number.
|
|
PacketFEC *FECSorter::getFECPacketWhichCoversSequenceNumber(uint16_t sn){
|
|
size_t nfecs = fecPackets.size();
|
|
for (size_t i = 0; i < nfecs; ++i){
|
|
PacketFEC *fec = fecPackets[i];
|
|
if (fec->coversSequenceNumber(sn)){return fec;}
|
|
}
|
|
return NULL;
|
|
}
|
|
|
|
void FECPacket::sendRTCP_RR(RTP::FECSorter &sorter, uint32_t mySSRC, uint32_t theirSSRC, void *userData,
|
|
void callBack(void *userData, const char *payload, size_t nbytes, uint8_t channel)){
|
|
char *rtcpData = (char *)malloc(32);
|
|
if (!rtcpData){
|
|
FAIL_MSG("Could not allocate 32 bytes. Something is seriously messed up.");
|
|
return;
|
|
}
|
|
if (!(sorter.lostCurrent + sorter.packCurrent)){sorter.packCurrent++;}
|
|
rtcpData[0] = 0x81; // version 2, no padding, one receiver report
|
|
rtcpData[1] = 201; // receiver report
|
|
Bit::htobs(rtcpData + 2, 7); // 7 4-byte words follow the header
|
|
Bit::htobl(rtcpData + 4, mySSRC); // set receiver identifier
|
|
Bit::htobl(rtcpData + 8, theirSSRC); // set source identifier
|
|
rtcpData[12] = (sorter.lostCurrent * 255) / (sorter.lostCurrent + sorter.packCurrent); // fraction lost since prev RR
|
|
Bit::htob24(rtcpData + 13, sorter.lostTotal); // cumulative packets lost since start
|
|
Bit::htobl(rtcpData + 16,
|
|
sorter.rtpSeq | (sorter.packTotal & 0xFFFF0000ul)); // highest sequence received
|
|
Bit::htobl(rtcpData + 20, 0); /// \TODO jitter (diff in timestamp vs packet arrival)
|
|
Bit::htobl(rtcpData + 24, 0); /// \TODO last SR (middle 32 bits of last SR or zero)
|
|
Bit::htobl(rtcpData + 28, 0); /// \TODO delay since last SR in 2b seconds + 2b fraction
|
|
callBack(userData, rtcpData, 32, 0);
|
|
sorter.lostCurrent = 0;
|
|
sorter.packCurrent = 0;
|
|
free(rtcpData);
|
|
}
|
|
|
|
}// namespace RTP
|