293 lines
9.8 KiB
C++
293 lines
9.8 KiB
C++
/*
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* Copyright (c) 2016 The ZLMediaKit project authors. All Rights Reserved.
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*
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* This file is part of ZLMediaKit(https://github.com/xia-chu/ZLMediaKit).
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*
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* Use of this source code is governed by MIT 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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namespace mediakit{
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#if defined(_WIN32)
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#pragma pack(push, 1)
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#endif // defined(_WIN32)
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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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} PACKED;
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#if defined(_WIN32)
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#pragma pack(pop)
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#endif // defined(_WIN32)
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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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return decodeRtp(rtp);
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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::decodeRtp(const RtpPacket::Ptr &rtp) {
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auto frame = rtp->getPayload();
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auto length = rtp->getPayloadSize();
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auto stamp = rtp->getStampMS();
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auto seq = rtp->getSeq();
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auto nal_type = *frame & 0x1F;
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auto nal_suffix = *frame & (~0x1F);
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if (nal_type >= 0 && nal_type < 24) {
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//a full frame
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_frame->_buffer.assign("\x00\x00\x00\x01", 4);
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_frame->_buffer.append((char *) frame, length);
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_frame->_pts = stamp;
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auto key = _frame->keyFrame();
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onGetH264(_frame);
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return (key); //i frame
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}
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switch (nal_type) {
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case 24: {
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// 24 STAP-A 单一时间的组合包
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bool haveIDR = false;
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auto ptr = frame + 1;
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while (true) {
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size_t off = ptr - frame;
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if (off >= length) {
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break;
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}
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//获取当前nalu的大小
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uint16_t len = *ptr++;
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len <<= 8;
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len |= *ptr++;
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if (off + len > length) {
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break;
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}
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if (len > 0) {
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//有有效数据
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_frame->_buffer.assign("\x00\x00\x00\x01", 4);
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_frame->_buffer.append((char *) ptr, len);
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_frame->_pts = stamp;
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if ((ptr[0] & 0x1F) == H264Frame::NAL_IDR) {
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haveIDR = true;
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}
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onGetH264(_frame);
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}
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ptr += len;
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}
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return haveIDR;
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}
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case 28: {
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//FU-A
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FuFlags *fu = (FuFlags *) (frame + 1);
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if (fu->start_bit) {
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//该帧的第一个rtp包 FU-A start
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//预留空间，防止频繁扩容拷贝
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_frame->_buffer.reserve(_max_frame_size);
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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->_buffer.append((char *) frame + 2, length - 2);
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_frame->_pts = stamp;
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//该函数return时，保存下当前sequence,以便下次对比seq是否连续
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_last_seq = seq;
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return _frame->keyFrame();
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}
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if (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(如果回环了则判定为连续)，否则说明rtp丢包，那么该帧不完整，必须得丢弃
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_frame->_buffer.clear();
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WarnL << "rtp丢包: " << seq << " != " << _last_seq << " + 1,该帧被废弃";
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return false;
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}
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if (!fu->end_bit) {
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//该帧的中间rtp包 FU-A mid
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_frame->_buffer.append((char *) frame + 2, length - 2);
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//该函数return时，保存下当前sequence,以便下次对比seq是否连续
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_last_seq = seq;
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return false;
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}
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//该帧最后一个rtp包 FU-A end
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_frame->_buffer.append((char *) frame + 2, length - 2);
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_frame->_pts = stamp;
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//计算最大的帧
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auto frame_size = _frame->size();
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if (frame_size > _max_frame_size) {
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_max_frame_size = frame_size;
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}
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onGetH264(_frame);
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return false;
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}
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default: {
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// 29 FU-B 单NAL单元B模式
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// 25 STAP-B 单一时间的组合包
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// 26 MTAP16 多个时间的组合包
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// 27 MTAP24 多个时间的组合包
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WarnL << "不支持的rtp类型:" << (int) nal_type << " " << seq;
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return false;
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}
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}
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}
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void H264RtpDecoder::onGetH264(const H264Frame::Ptr &frame) {
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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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RtpCodec::inputFrame(frame);
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_frame = obtainFrame();
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}
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////////////////////////////////////////////////////////////////////////
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H264RtpEncoder::H264RtpEncoder(uint32_t ssrc, uint32_t mtu, uint32_t sample_rate, uint8_t pt, uint8_t interleaved)
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: RtpInfo(ssrc, mtu, sample_rate, pt, interleaved) {
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}
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void H264RtpEncoder::insertConfigFrame(uint32_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, uint32_t pts, bool is_mark, bool gop_pos){
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if (len + 3 <= getMaxSize()) {
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//STAP-A模式打包小于MTU
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packRtpStapA(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, uint32_t pts, bool is_mark, bool gop_pos){
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auto packet_size = 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模式
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packRtpStapA(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 = makeRtp(getTrackType(), 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::packRtpStapA(const char *ptr, size_t len, uint32_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 = makeRtp(getTrackType(), 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::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_AUD:
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case H264Frame::NAL_SEI : {
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return;
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}
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case H264Frame::NAL_SPS: {
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_sps = Frame::getCacheAbleFrame(frame);
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return;
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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;
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}
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default: break;
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}
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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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void 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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}
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}//namespace mediakit
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