ZLMediaKit/webrtc/Nack.cpp
2021-07-02 15:56:35 +08:00

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/*
* Copyright (c) 2016 The ZLMediaKit project authors. All Rights Reserved.
*
* This file is part of ZLMediaKit(https://github.com/ZLMediaKit/ZLMediaKit).
*
* Use of this source code is governed by MIT license that can be found in the
* LICENSE file in the root of the source tree. All contributing project authors
* may be found in the AUTHORS file in the root of the source tree.
*/
#include "Nack.h"
static constexpr uint32_t kMaxNackMS = 10 * 1000;
void NackList::push_back(RtpPacket::Ptr rtp) {
auto seq = rtp->getSeq();
_nack_cache_seq.emplace_back(seq);
_nack_cache_pkt.emplace(seq, std::move(rtp));
while (get_cache_ms() > kMaxNackMS) {
//需要清除部分nack缓存
pop_front();
}
}
void NackList::for_each_nack(const FCI_NACK &nack, const function<void(const RtpPacket::Ptr &rtp)> &func) {
auto seq = nack.getPid();
for (auto bit : nack.getBitArray()) {
if (bit) {
//丢包
RtpPacket::Ptr *ptr = get_rtp(seq);
if (ptr) {
func(*ptr);
}
}
++seq;
}
}
void NackList::pop_front() {
if (_nack_cache_seq.empty()) {
return;
}
_nack_cache_pkt.erase(_nack_cache_seq.front());
_nack_cache_seq.pop_front();
}
RtpPacket::Ptr *NackList::get_rtp(uint16_t seq) {
auto it = _nack_cache_pkt.find(seq);
if (it == _nack_cache_pkt.end()) {
return nullptr;
}
return &it->second;
}
uint32_t NackList::get_cache_ms() {
if (_nack_cache_seq.size() < 2) {
return 0;
}
uint32_t back = _nack_cache_pkt[_nack_cache_seq.back()]->getStampMS();
uint32_t front = _nack_cache_pkt[_nack_cache_seq.front()]->getStampMS();
if (back > front) {
return back - front;
}
//很有可能回环了
return back + (UINT32_MAX - front);
}
////////////////////////////////////////////////////////////////////////////////////////////////
void NackContext::received(uint16_t seq) {
if (!_last_max_seq && _seq.empty()) {
_last_max_seq = seq - 1;
}
_seq.emplace(seq);
auto max_seq = *_seq.rbegin();
auto min_seq = *_seq.begin();
auto diff = max_seq - min_seq;
if (!diff) {
return;
}
if (diff > UINT16_MAX / 2) {
//回环
_seq.clear();
_last_max_seq = min_seq;
return;
}
if (_seq.size() == diff + 1 && _last_max_seq + 1 == min_seq) {
//都是连续的seq未丢包
_seq.clear();
_last_max_seq = max_seq;
} else {
//seq不连续有丢包
if (min_seq == _last_max_seq + 1) {
//前面部分seq是连续的未丢包移除之
eraseFrontSeq();
}
//有丢包丢包从_last_max_seq开始
if (max_seq - _last_max_seq > FCI_NACK::kBitSize) {
vector<bool> vec;
vec.resize(FCI_NACK::kBitSize);
for (auto i = 0; i < FCI_NACK::kBitSize; ++i) {
vec[i] = _seq.find(_last_max_seq + i + 2) == _seq.end();
}
doNack(FCI_NACK(_last_max_seq + 1, vec));
_last_max_seq += FCI_NACK::kBitSize + 1;
if (_last_max_seq >= max_seq) {
_seq.clear();
} else {
auto it = _seq.emplace_hint(_seq.begin(), _last_max_seq);
_seq.erase(_seq.begin(), it);
}
}
}
}
void NackContext::setOnNack(onNack cb) {
_cb = std::move(cb);
}
void NackContext::doNack(const FCI_NACK &nack) {
if (_cb) {
_cb(nack);
}
}
void NackContext::eraseFrontSeq() {
//前面部分seq是连续的未丢包移除之
for (auto it = _seq.begin(); it != _seq.end();) {
if (*it != _last_max_seq + 1) {
//seq不连续丢包了
break;
}
_last_max_seq = *it;
it = _seq.erase(it);
}
}