/*
* 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"
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) {
return decodeRtp(rtp);
}
/*
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::decodeRtp(const RtpPacket::Ptr &rtp) {
auto frame = rtp->getPayload();
auto length = rtp->getPayloadSize();
auto stamp = rtp->getStampMS();
auto seq = rtp->getSeq();
auto nal_type = *frame & 0x1F;
auto nal_suffix = *frame & (~0x1F);
if (nal_type >= 0 && nal_type < 24) {
//a full frame
_frame->_buffer.assign("\x00\x00\x00\x01", 4);
_frame->_buffer.append((char *) frame, length);
_frame->_pts = stamp;
auto key = _frame->keyFrame();
onGetH264(_frame);
return (key); //i frame
}
switch (nal_type) {
case 24: {
// 24 STAP-A 单一时间的组合包
bool haveIDR = false;
auto ptr = frame + 1;
while (true) {
size_t off = ptr - frame;
if (off >= length) {
break;
}
//获取当前nalu的大小
uint16_t len = *ptr++;
len <<= 8;
len |= *ptr++;
if (off + len > length) {
break;
}
if (len > 0) {
//有有效数据
_frame->_buffer.assign("\x00\x00\x00\x01", 4);
_frame->_buffer.append((char *) ptr, len);
_frame->_pts = stamp;
if ((ptr[0] & 0x1F) == H264Frame::NAL_IDR) {
haveIDR = true;
}
onGetH264(_frame);
}
ptr += len;
}
return haveIDR;
}
case 28: {
//FU-A
FuFlags *fu = (FuFlags *) (frame + 1);
if (fu->start_bit) {
//该帧的第一个rtp包 FU-A start
//预留空间，防止频繁扩容拷贝
_frame->_buffer.reserve(_max_frame_size);
_frame->_buffer.assign("\x00\x00\x00\x01", 4);
_frame->_buffer.push_back(nal_suffix | fu->nal_type);
_frame->_buffer.append((char *) frame + 2, length - 2);
_frame->_pts = stamp;
//该函数return时，保存下当前sequence,以便下次对比seq是否连续
_last_seq = seq;
return _frame->keyFrame();
}
if (seq != (uint16_t) (_last_seq + 1)) {
//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
_frame->_buffer.clear();
WarnL << "rtp丢包: " << seq << " != " << _last_seq << " + 1,该帧被废弃";
return false;
}
if (!fu->end_bit) {
//该帧的中间rtp包 FU-A mid
_frame->_buffer.append((char *) frame + 2, length - 2);
//该函数return时，保存下当前sequence,以便下次对比seq是否连续
_last_seq = seq;
return false;
}
//该帧最后一个rtp包 FU-A end
_frame->_buffer.append((char *) frame + 2, length - 2);
_frame->_pts = stamp;
//计算最大的帧
auto frame_size = _frame->size();
if (frame_size > _max_frame_size) {
_max_frame_size = frame_size;
}
onGetH264(_frame);
return false;
}
default: {
// 29 FU-B 单NAL单元B模式
// 25 STAP-B 单一时间的组合包
// 26 MTAP16 多个时间的组合包
// 27 MTAP24 多个时间的组合包
WarnL << "不支持的rtp类型:" << (int) nal_type << " " << seq;
return false;
}
}
}
void H264RtpDecoder::onGetH264(const H264Frame::Ptr &frame) {
//rtsp没有dts，那么根据pts排序算法生成dts
_dts_generator.getDts(frame->_pts,frame->_dts);
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::inputFrame(const Frame::Ptr &frame) {
auto ptr = frame->data() + frame->prefixSize();
auto len = frame->size() - frame->prefixSize();
auto pts = frame->pts();
auto nal_type = H264_TYPE(ptr[0]);
auto packet_size = getMaxSize() - 2;
//末尾5bit为nalu type，固定为28(FU-A)
auto fu_char_0 = (ptr[0] & (~0x1F)) | 28;
auto fu_char_1 = nal_type;
FuFlags *fu_flags = (FuFlags *) (&fu_char_1);
fu_flags->start_bit = 1;
//超过MTU则按照FU-A模式打包
if (len > packet_size + 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, 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, fu_flags->start_bit && nal_type == H264Frame::NAL_IDR);
offset += packet_size;
fu_flags->start_bit = 0;
}
} else {
//如果帧长度不超过mtu, 则按照Single NAL unit packet per H.264 方式打包
makeH264Rtp(ptr, len, false, false, pts);
}
}
void H264RtpEncoder::makeH264Rtp(const void* data, size_t len, bool mark, bool gop_pos, uint32_t uiStamp) {
RtpCodec::inputRtp(makeRtp(getTrackType(), data, len, mark, uiStamp), gop_pos);
}
}//namespace mediakit