/*
* Copyright (c) 2016 The ZLMediaKit project authors. All Rights Reserved.
*
* This file is part of ZLMediaKit(https://github.com/xia-chu/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 "H264Rtp.h"
#include "Common/config.h"
namespace mediakit{
#if defined(_WIN32)
#pragma pack(push, 1)
#endif // defined(_WIN32)
class FuFlags {
public:
#if __BYTE_ORDER == __BIG_ENDIAN
unsigned start_bit: 1;
unsigned end_bit: 1;
unsigned reserved: 1;
unsigned nal_type: 5;
#else
unsigned nal_type: 5;
unsigned reserved: 1;
unsigned end_bit: 1;
unsigned start_bit: 1;
#endif
} PACKED;
#if defined(_WIN32)
#pragma pack(pop)
#endif // defined(_WIN32)
H264RtpDecoder::H264RtpDecoder() {
_frame = obtainFrame();
}
H264Frame::Ptr H264RtpDecoder::obtainFrame() {
auto frame = FrameImp::create<H264Frame>();
frame->_prefix_size = 4;
return frame;
}
bool H264RtpDecoder::inputRtp(const RtpPacket::Ptr &rtp, bool key_pos) {
auto seq = rtp->getSeq();
auto ret = decodeRtp(rtp);
if (!_gop_dropped && seq != (uint16_t) (_last_seq + 1) && _last_seq) {
_gop_dropped = true;
WarnL << "start drop h264 gop, last seq:" << _last_seq << ", rtp:\r\n" << rtp->dumpString();
}
_last_seq = seq;
return ret;
}
/*
RTF3984 5.2节 Common Structure of the RTP Payload Format
Table 1. Summary of NAL unit types and their payload structures
Type Packet Type name Section
---------------------------------------------------------
0 undefined -
1-23 NAL unit Single NAL unit packet per H.264 5.6
24 STAP-A Single-time aggregation packet 5.7.1
25 STAP-B Single-time aggregation packet 5.7.1
26 MTAP16 Multi-time aggregation packet 5.7.2
27 MTAP24 Multi-time aggregation packet 5.7.2
28 FU-A Fragmentation unit 5.8
29 FU-B Fragmentation unit 5.8
30-31 undefined -
*/
bool H264RtpDecoder::singleFrame(const RtpPacket::Ptr &rtp, const uint8_t *ptr, ssize_t size, uint64_t stamp){
_frame->_buffer.assign("\x00\x00\x00\x01", 4);
_frame->_buffer.append((char *) ptr, size);
_frame->_pts = stamp;
auto key = _frame->keyFrame();
outputFrame(rtp, _frame);
return key;
}
bool H264RtpDecoder::unpackStapA(const RtpPacket::Ptr &rtp, const uint8_t *ptr, ssize_t size, uint64_t stamp) {
//STAP-A 单一时间的组合包
auto have_key_frame = false;
auto end = ptr + size;
while (ptr + 2 < end) {
uint16_t len = (ptr[0] << 8) | ptr[1];
if (!len || ptr + len > end) {
WarnL << "invalid rtp data size:" << len << ",rtp:\r\n" << rtp->dumpString();
_gop_dropped = true;
break;
}
ptr += 2;
if (singleFrame(rtp, ptr, len, stamp)) {
have_key_frame = true;
}
ptr += len;
}
return have_key_frame;
}
bool H264RtpDecoder::mergeFu(const RtpPacket::Ptr &rtp, const uint8_t *ptr, ssize_t size, uint64_t stamp, uint16_t seq){
auto nal_suffix = *ptr & (~0x1F);
FuFlags *fu = (FuFlags *) (ptr + 1);
if (fu->start_bit) {
//该帧的第一个rtp包
_frame->_buffer.assign("\x00\x00\x00\x01", 4);
_frame->_buffer.push_back(nal_suffix | fu->nal_type);
_frame->_pts = stamp;
_fu_dropped = false;
}
if (_fu_dropped) {
//该帧不完整
return false;
}
if (!fu->start_bit && seq != (uint16_t) (_last_seq + 1)) {
//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
_fu_dropped = true;
_frame->_buffer.clear();
return false;
}
//后面追加数据
_frame->_buffer.append((char *) ptr + 2, size - 2);
if (!fu->end_bit) {
//非末尾包
return fu->start_bit ? _frame->keyFrame() : false;
}
//确保下一次fu必须收到第一个包
_fu_dropped = true;
//该帧最后一个rtp包,输出frame
outputFrame(rtp, _frame);
return false;
}
bool H264RtpDecoder::decodeRtp(const RtpPacket::Ptr &rtp) {
auto payload_size = rtp->getPayloadSize();
if (payload_size <= 0) {
//无实际负载
return false;
}
auto frame = rtp->getPayload();
auto stamp = rtp->getStampMS();
auto seq = rtp->getSeq();
int nal = H264_TYPE(frame[0]);
switch (nal) {
case 24:
// 24 STAP-A Single-time aggregation packet 5.7.1
return unpackStapA(rtp, frame + 1, payload_size - 1, stamp);
case 28:
// 28 FU-A Fragmentation unit
return mergeFu(rtp, frame, payload_size, stamp, seq);
default: {
if (nal < 24) {
//Single NAL Unit Packets
return singleFrame(rtp, frame, payload_size, stamp);
}
_gop_dropped = true;
WarnL << "不支持该类型的264 RTP包, nal type:" << nal << ", rtp:\r\n" << rtp->dumpString();
return false;
}
}
}
void H264RtpDecoder::outputFrame(const RtpPacket::Ptr &rtp, const H264Frame::Ptr &frame) {
if (frame->dropAble()) {
//不参与dts生成
frame->_dts = frame->_pts;
} else {
//rtsp没有dts，那么根据pts排序算法生成dts
_dts_generator.getDts(frame->_pts, frame->_dts);
}
if (frame->keyFrame() && _gop_dropped) {
_gop_dropped = false;
InfoL << "new gop received, rtp:\r\n" << rtp->dumpString();
}
if (!_gop_dropped) {
RtpCodec::inputFrame(frame);
}
_frame = obtainFrame();
}
////////////////////////////////////////////////////////////////////////
H264RtpEncoder::H264RtpEncoder(uint32_t ssrc, uint32_t mtu, uint32_t sample_rate, uint8_t pt, uint8_t interleaved)
: RtpInfo(ssrc, mtu, sample_rate, pt, interleaved) {
}
void H264RtpEncoder::insertConfigFrame(uint64_t pts){
if (!_sps || !_pps) {
return;
}
//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
packRtp(_sps->data() + _sps->prefixSize(), _sps->size() - _sps->prefixSize(), pts, false, true);
packRtp(_pps->data() + _pps->prefixSize(), _pps->size() - _pps->prefixSize(), pts, false, false);
}
void H264RtpEncoder::packRtp(const char *ptr, size_t len, uint64_t pts, bool is_mark, bool gop_pos){
if (len + 3 <= getMaxSize()) {
//STAP-A模式打包小于MTU
packRtpStapA(ptr, len, pts, is_mark, gop_pos);
} else {
//STAP-A模式打包会大于MTU,所以采用FU-A模式
packRtpFu(ptr, len, pts, is_mark, gop_pos);
}
}
void H264RtpEncoder::packRtpFu(const char *ptr, size_t len, uint64_t pts, bool is_mark, bool gop_pos){
auto packet_size = getMaxSize() - 2;
if (len <= packet_size + 1) {
//小于FU-A打包最小字节长度要求，采用STAP-A模式
packRtpStapA(ptr, len, pts, is_mark, gop_pos);
return;
}
//末尾5bit为nalu type，固定为28(FU-A)
auto fu_char_0 = (ptr[0] & (~0x1F)) | 28;
auto fu_char_1 = H264_TYPE(ptr[0]);
FuFlags *fu_flags = (FuFlags *) (&fu_char_1);
fu_flags->start_bit = 1;
size_t offset = 1;
while (!fu_flags->end_bit) {
if (!fu_flags->start_bit && len <= offset + packet_size) {
//FU-A end
packet_size = len - offset;
fu_flags->end_bit = 1;
}
//传入nullptr先不做payload的内存拷贝
auto rtp = makeRtp(getTrackType(), nullptr, packet_size + 2, fu_flags->end_bit && is_mark, pts);
//rtp payload 负载部分
uint8_t *payload = rtp->getPayload();
//FU-A 第1个字节
payload[0] = fu_char_0;
//FU-A 第2个字节
payload[1] = fu_char_1;
//H264 数据
memcpy(payload + 2, (uint8_t *) ptr + offset, packet_size);
//输入到rtp环形缓存
RtpCodec::inputRtp(rtp, gop_pos);
offset += packet_size;
fu_flags->start_bit = 0;
}
}
void H264RtpEncoder::packRtpStapA(const char *ptr, size_t len, uint64_t pts, bool is_mark, bool gop_pos){
//如果帧长度不超过mtu,为了兼容性 webrtc，采用STAP-A模式打包
auto rtp = makeRtp(getTrackType(), nullptr, len + 3, is_mark, pts);
uint8_t *payload = rtp->getPayload();
//STAP-A
payload[0] = (ptr[0] & (~0x1F)) | 24;
payload[1] = (len >> 8) & 0xFF;
payload[2] = len & 0xff;
memcpy(payload + 3, (uint8_t *) ptr, len);
RtpCodec::inputRtp(rtp, gop_pos);
}
bool H264RtpEncoder::inputFrame(const Frame::Ptr &frame) {
auto ptr = frame->data() + frame->prefixSize();
switch (H264_TYPE(ptr[0])) {
case H264Frame::NAL_SPS: {
_sps = Frame::getCacheAbleFrame(frame);
return true;
}
case H264Frame::NAL_PPS: {
_pps = Frame::getCacheAbleFrame(frame);
return true;
}
default: break;
}
GET_CONFIG(int,lowLatency,Rtp::kLowLatency);
if (lowLatency) { // 低延迟模式
if (_last_frame) {
flush();
}
inputFrame_l(frame, true);
} else {
if (_last_frame) {
//如果时间戳发生了变化，那么markbit才置true
inputFrame_l(_last_frame, _last_frame->pts() != frame->pts());
}
_last_frame = Frame::getCacheAbleFrame(frame);
}
return true;
}
void H264RtpEncoder::flush() {
if (_last_frame) {
// 如果时间戳发生了变化，那么markbit才置true
inputFrame_l(_last_frame, true);
_last_frame = nullptr;
}
}
bool H264RtpEncoder::inputFrame_l(const Frame::Ptr &frame, bool is_mark){
if (frame->keyFrame()) {
//保证每一个关键帧前都有SPS与PPS
insertConfigFrame(frame->pts());
}
packRtp(frame->data() + frame->prefixSize(), frame->size() - frame->prefixSize(), frame->pts(), is_mark, false);
return true;
}
}//namespace mediakit