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/*
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* Copyright (c) 2021 The ZLMediaKit project authors. All Rights Reserved.
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*
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* This file is part of ZLMediaKit(https://github.com/ZLMediaKit/ZLMediaKit).
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*
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* Use of this source code is governed by MIT-like license that can be found in the
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* LICENSE file in the root of the source tree. All contributing project authors
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* may be found in the AUTHORS file in the root of the source tree.
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*/
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#include "TwccContext.h"
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#include "Rtcp/RtcpFCI.h"
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namespace mediakit {
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enum class ExtSeqStatus : int {
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normal = 0,
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looped,
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jumped,
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};
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void TwccContext::onRtp(uint32_t ssrc, uint16_t twcc_ext_seq, uint64_t stamp_ms) {
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switch ((ExtSeqStatus) checkSeqStatus(twcc_ext_seq)) {
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case ExtSeqStatus::jumped: /*seq异常,过滤掉*/ return;
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case ExtSeqStatus::looped: /*回环，触发发送twcc rtcp*/ onSendTwcc(ssrc); break;
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case ExtSeqStatus::normal: break;
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default: /*不可达*/assert(0); break;
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}
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auto result = _rtp_recv_status.emplace(twcc_ext_seq, stamp_ms);
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if (!result.second) {
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WarnL << "recv same twcc ext seq:" << twcc_ext_seq;
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return;
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}
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_max_stamp = result.first->second;
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if (!_min_stamp) {
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_min_stamp = _max_stamp;
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}
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if (needSendTwcc()) {
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//其他匹配条件立即发送twcc
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onSendTwcc(ssrc);
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}
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}
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bool TwccContext::needSendTwcc() const {
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if (_rtp_recv_status.empty()) {
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return false;
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}
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return (_rtp_recv_status.size() >= kMaxSeqSize) || (_max_stamp - _min_stamp >= kMaxTimeDelta);
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}
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int TwccContext::checkSeqStatus(uint16_t twcc_ext_seq) const {
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if (_rtp_recv_status.empty()) {
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return (int) ExtSeqStatus::normal;
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}
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auto max = _rtp_recv_status.rbegin()->first;
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auto delta = (int32_t) twcc_ext_seq - (int32_t) max;
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if (delta > 0 && delta < 0xFFFF / 2) {
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//正常增长
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return (int) ExtSeqStatus::normal;
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}
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if (delta < -0xFF00) {
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//回环
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TraceL << "rtp twcc ext seq looped:" << max << " -> " << twcc_ext_seq;
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return (int) ExtSeqStatus::looped;
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}
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if (delta > 0xFF00) {
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//回环后收到前面大的乱序的包，无法处理，丢弃
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TraceL << "rtp twcc ext seq jumped after looped:" << max << " -> " << twcc_ext_seq;
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return (int) ExtSeqStatus::jumped;
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}
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auto min = _rtp_recv_status.begin()->first;
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if (min <= twcc_ext_seq || twcc_ext_seq <= max) {
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//正常回退
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return (int) ExtSeqStatus::normal;
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}
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//seq莫名的大幅增加或减少，无法处理，丢弃
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TraceL << "rtp twcc ext seq jumped:" << max << " -> " << twcc_ext_seq;
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return (int) ExtSeqStatus::jumped;
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}
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void TwccContext::onSendTwcc(uint32_t ssrc) {
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auto max = _rtp_recv_status.rbegin()->first;
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auto begin = _rtp_recv_status.begin();
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auto min = begin->first;
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//参考时间戳的最小单位是64ms
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auto ref_time = begin->second >> 6;
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//还原基准时间戳
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auto last_time = ref_time << 6;
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FCI_TWCC::TwccPacketStatus status;
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for (auto seq = min; seq <= max; ++seq) {
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int16_t delta = 0;
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SymbolStatus symbol = SymbolStatus::not_received;
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auto it = _rtp_recv_status.find(seq);
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if (it != _rtp_recv_status.end()) {
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//recv delta,单位为250us,1ms等于4x250us
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delta = (int16_t) (4 * ((int64_t) it->second - (int64_t) last_time));
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if (delta < 0 || delta > 0xFF) {
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symbol = SymbolStatus::large_delta;
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} else {
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symbol = SymbolStatus::small_delta;
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}
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last_time = it->second;
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}
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status.emplace(seq, std::make_pair(symbol, delta));
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}
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auto fci = FCI_TWCC::create(ref_time, _twcc_pkt_count++, status);
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if (_cb) {
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_cb(ssrc, std::move(fci));
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}
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clearStatus();
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}
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void TwccContext::clearStatus() {
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_rtp_recv_status.clear();
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_min_stamp = 0;
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}
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void TwccContext::setOnSendTwccCB(TwccContext::onSendTwccCB cb) {
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_cb = std::move(cb);
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}
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}// namespace mediakit
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