mirror of
https://github.com/ZLMediaKit/ZLMediaKit.git
synced 2024-10-06 12:13:49 +08:00
329 lines
11 KiB
C++
329 lines
11 KiB
C++
/*
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* Copyright (c) 2016-present 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 "H264Rtp.h"
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#include "Common/config.h"
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namespace mediakit{
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#pragma pack(push, 1)
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class FuFlags {
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public:
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#if __BYTE_ORDER == __BIG_ENDIAN
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unsigned start_bit: 1;
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unsigned end_bit: 1;
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unsigned reserved: 1;
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unsigned nal_type: 5;
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#else
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unsigned nal_type: 5;
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unsigned reserved: 1;
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unsigned end_bit: 1;
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unsigned start_bit: 1;
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#endif
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};
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#pragma pack(pop)
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H264RtpDecoder::H264RtpDecoder() {
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_frame = obtainFrame();
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}
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H264Frame::Ptr H264RtpDecoder::obtainFrame() {
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auto frame = FrameImp::create<H264Frame>();
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frame->_prefix_size = 4;
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return frame;
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}
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bool H264RtpDecoder::inputRtp(const RtpPacket::Ptr &rtp, bool key_pos) {
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auto seq = rtp->getSeq();
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auto last_is_gop = _is_gop;
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_is_gop = decodeRtp(rtp);
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if (!_gop_dropped && seq != (uint16_t)(_last_seq + 1) && _last_seq) {
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_gop_dropped = true;
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WarnL << "start drop h264 gop, last seq:" << _last_seq << ", rtp:\r\n" << rtp->dumpString();
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}
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_last_seq = seq;
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// 确保有sps rtp的时候，gop从sps开始；否则从关键帧开始
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return _is_gop && !last_is_gop;
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}
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/*
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RTF3984 5.2节 Common Structure of the RTP Payload Format
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Table 1. Summary of NAL unit types and their payload structures
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Type Packet Type name Section
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---------------------------------------------------------
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0 undefined -
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1-23 NAL unit Single NAL unit packet per H.264 5.6
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24 STAP-A Single-time aggregation packet 5.7.1
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25 STAP-B Single-time aggregation packet 5.7.1
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26 MTAP16 Multi-time aggregation packet 5.7.2
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27 MTAP24 Multi-time aggregation packet 5.7.2
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28 FU-A Fragmentation unit 5.8
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29 FU-B Fragmentation unit 5.8
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30-31 undefined -
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*/
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bool H264RtpDecoder::singleFrame(const RtpPacket::Ptr &rtp, const uint8_t *ptr, ssize_t size, uint64_t stamp){
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_frame->_buffer.assign("\x00\x00\x00\x01", 4);
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_frame->_buffer.append((char *) ptr, size);
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_frame->_pts = stamp;
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auto key = _frame->keyFrame() || _frame->configFrame();
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outputFrame(rtp, _frame);
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return key;
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}
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bool H264RtpDecoder::unpackStapA(const RtpPacket::Ptr &rtp, const uint8_t *ptr, ssize_t size, uint64_t stamp) {
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//STAP-A 单一时间的组合包
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auto have_key_frame = false;
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auto end = ptr + size;
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while (ptr + 2 < end) {
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uint16_t len = (ptr[0] << 8) | ptr[1];
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if (!len || ptr + len > end) {
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WarnL << "invalid rtp data size:" << len << ",rtp:\r\n" << rtp->dumpString();
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_gop_dropped = true;
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break;
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}
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ptr += 2;
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if (singleFrame(rtp, ptr, len, stamp)) {
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have_key_frame = true;
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}
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ptr += len;
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}
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return have_key_frame;
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}
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bool H264RtpDecoder::mergeFu(const RtpPacket::Ptr &rtp, const uint8_t *ptr, ssize_t size, uint64_t stamp, uint16_t seq){
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auto nal_suffix = *ptr & (~0x1F);
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FuFlags *fu = (FuFlags *) (ptr + 1);
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if (fu->start_bit) {
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//该帧的第一个rtp包
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_frame->_buffer.assign("\x00\x00\x00\x01", 4);
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_frame->_buffer.push_back(nal_suffix | fu->nal_type);
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_frame->_pts = stamp;
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_fu_dropped = false;
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}
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if (_fu_dropped) {
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//该帧不完整
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return false;
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}
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if (!fu->start_bit && seq != (uint16_t) (_last_seq + 1)) {
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//中间的或末尾的rtp包，其seq必须连续，否则说明rtp丢包，那么该帧不完整，必须得丢弃
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_fu_dropped = true;
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_frame->_buffer.clear();
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return false;
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}
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//后面追加数据
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_frame->_buffer.append((char *) ptr + 2, size - 2);
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if (!fu->end_bit) {
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//非末尾包
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return fu->start_bit ? (_frame->keyFrame() || _frame->configFrame()) : false;
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}
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//确保下一次fu必须收到第一个包
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_fu_dropped = true;
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//该帧最后一个rtp包,输出frame
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outputFrame(rtp, _frame);
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return false;
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}
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bool H264RtpDecoder::decodeRtp(const RtpPacket::Ptr &rtp) {
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auto payload_size = rtp->getPayloadSize();
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if (payload_size <= 0) {
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//无实际负载
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return false;
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}
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auto frame = rtp->getPayload();
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auto stamp = rtp->getStampMS();
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auto seq = rtp->getSeq();
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int nal = H264_TYPE(frame[0]);
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switch (nal) {
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case 24:
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// 24 STAP-A Single-time aggregation packet 5.7.1
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return unpackStapA(rtp, frame + 1, payload_size - 1, stamp);
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case 28:
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// 28 FU-A Fragmentation unit
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return mergeFu(rtp, frame, payload_size, stamp, seq);
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default: {
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if (nal < 24) {
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//Single NAL Unit Packets
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return singleFrame(rtp, frame, payload_size, stamp);
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}
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_gop_dropped = true;
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WarnL << "不支持该类型的264 RTP包, nal type:" << nal << ", rtp:\r\n" << rtp->dumpString();
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return false;
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}
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}
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}
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void H264RtpDecoder::outputFrame(const RtpPacket::Ptr &rtp, const H264Frame::Ptr &frame) {
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if (frame->dropAble()) {
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//不参与dts生成
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frame->_dts = frame->_pts;
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} else {
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//rtsp没有dts，那么根据pts排序算法生成dts
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_dts_generator.getDts(frame->_pts, frame->_dts);
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}
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if (frame->keyFrame() && _gop_dropped) {
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_gop_dropped = false;
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InfoL << "new gop received, rtp:\r\n" << rtp->dumpString();
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}
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if (!_gop_dropped) {
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RtpCodec::inputFrame(frame);
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}
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_frame = obtainFrame();
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}
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////////////////////////////////////////////////////////////////////////
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void H264RtpEncoder::insertConfigFrame(uint64_t pts){
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if (!_sps || !_pps) {
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return;
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}
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//gop缓存从sps开始，sps、pps后面还有时间戳相同的关键帧，所以mark bit为false
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packRtp(_sps->data() + _sps->prefixSize(), _sps->size() - _sps->prefixSize(), pts, false, true);
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packRtp(_pps->data() + _pps->prefixSize(), _pps->size() - _pps->prefixSize(), pts, false, false);
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}
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void H264RtpEncoder::packRtp(const char *ptr, size_t len, uint64_t pts, bool is_mark, bool gop_pos){
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if (len + 3 <= getRtpInfo().getMaxSize()) {
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// 采用STAP-A/Single NAL unit packet per H.264 模式
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packRtpSmallFrame(ptr, len, pts, is_mark, gop_pos);
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} else {
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//STAP-A模式打包会大于MTU,所以采用FU-A模式
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packRtpFu(ptr, len, pts, is_mark, gop_pos);
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}
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}
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void H264RtpEncoder::packRtpFu(const char *ptr, size_t len, uint64_t pts, bool is_mark, bool gop_pos){
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auto packet_size = getRtpInfo().getMaxSize() - 2;
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if (len <= packet_size + 1) {
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// 小于FU-A打包最小字节长度要求，采用STAP-A/Single NAL unit packet per H.264 模式
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packRtpSmallFrame(ptr, len, pts, is_mark, gop_pos);
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return;
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}
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//末尾5bit为nalu type，固定为28(FU-A)
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auto fu_char_0 = (ptr[0] & (~0x1F)) | 28;
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auto fu_char_1 = H264_TYPE(ptr[0]);
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FuFlags *fu_flags = (FuFlags *) (&fu_char_1);
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fu_flags->start_bit = 1;
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size_t offset = 1;
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while (!fu_flags->end_bit) {
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if (!fu_flags->start_bit && len <= offset + packet_size) {
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//FU-A end
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packet_size = len - offset;
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fu_flags->end_bit = 1;
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}
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//传入nullptr先不做payload的内存拷贝
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auto rtp = getRtpInfo().makeRtp(TrackVideo, nullptr, packet_size + 2, fu_flags->end_bit && is_mark, pts);
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//rtp payload 负载部分
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uint8_t *payload = rtp->getPayload();
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//FU-A 第1个字节
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payload[0] = fu_char_0;
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//FU-A 第2个字节
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payload[1] = fu_char_1;
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//H264 数据
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memcpy(payload + 2, (uint8_t *) ptr + offset, packet_size);
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//输入到rtp环形缓存
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RtpCodec::inputRtp(rtp, gop_pos);
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offset += packet_size;
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fu_flags->start_bit = 0;
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}
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}
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void H264RtpEncoder::packRtpSmallFrame(const char *data, size_t len, uint64_t pts, bool is_mark, bool gop_pos) {
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GET_CONFIG(bool, h264_stap_a, Rtp::kH264StapA);
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if (h264_stap_a) {
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packRtpStapA(data, len, pts, is_mark, gop_pos);
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} else {
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packRtpSingleNalu(data, len, pts, is_mark, gop_pos);
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}
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}
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void H264RtpEncoder::packRtpStapA(const char *ptr, size_t len, uint64_t pts, bool is_mark, bool gop_pos){
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// 如果帧长度不超过mtu,为了兼容性 webrtc，采用STAP-A模式打包
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auto rtp = getRtpInfo().makeRtp(TrackVideo, nullptr, len + 3, is_mark, pts);
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uint8_t *payload = rtp->getPayload();
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//STAP-A
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payload[0] = (ptr[0] & (~0x1F)) | 24;
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payload[1] = (len >> 8) & 0xFF;
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payload[2] = len & 0xff;
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memcpy(payload + 3, (uint8_t *) ptr, len);
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RtpCodec::inputRtp(rtp, gop_pos);
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}
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void H264RtpEncoder::packRtpSingleNalu(const char *data, size_t len, uint64_t pts, bool is_mark, bool gop_pos) {
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// Single NAL unit packet per H.264 模式
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RtpCodec::inputRtp(getRtpInfo().makeRtp(TrackVideo, data, len, is_mark, pts), gop_pos);
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}
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bool H264RtpEncoder::inputFrame(const Frame::Ptr &frame) {
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auto ptr = frame->data() + frame->prefixSize();
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switch (H264_TYPE(ptr[0])) {
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case H264Frame::NAL_SPS: {
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_sps = Frame::getCacheAbleFrame(frame);
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return true;
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}
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case H264Frame::NAL_PPS: {
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_pps = Frame::getCacheAbleFrame(frame);
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return true;
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}
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default: break;
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}
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GET_CONFIG(int,lowLatency,Rtp::kLowLatency);
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if (lowLatency) { // 低延迟模式
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if (_last_frame) {
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flush();
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}
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inputFrame_l(frame, true);
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} else {
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if (_last_frame) {
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//如果时间戳发生了变化，那么markbit才置true
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inputFrame_l(_last_frame, _last_frame->pts() != frame->pts());
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}
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_last_frame = Frame::getCacheAbleFrame(frame);
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}
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return true;
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}
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void H264RtpEncoder::flush() {
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if (_last_frame) {
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// 如果时间戳发生了变化，那么markbit才置true
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inputFrame_l(_last_frame, true);
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_last_frame = nullptr;
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}
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}
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bool H264RtpEncoder::inputFrame_l(const Frame::Ptr &frame, bool is_mark){
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if (frame->keyFrame()) {
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//保证每一个关键帧前都有SPS与PPS
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insertConfigFrame(frame->pts());
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}
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packRtp(frame->data() + frame->prefixSize(), frame->size() - frame->prefixSize(), frame->pts(), is_mark, false);
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return true;
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}
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}//namespace mediakit
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