/*
* Copyright (c) 2016 The ZLMediaKit project authors. All Rights Reserved.
*
* This file is part of ZLMediaKit(https://github.com/xiongziliang/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{
typedef struct {
unsigned S :1;
unsigned E :1;
unsigned R :1;
unsigned type :5;
} FU;
static bool MakeFU(uint8_t in, FU &fu) {
fu.S = in >> 7;
fu.E = (in >> 6) & 0x01;
fu.R = (in >> 5) & 0x01;
fu.type = in & 0x1f;
if (fu.R != 0) {
return false;
}
return true;
}
H264RtpDecoder::H264RtpDecoder() {
_h264frame = obtainFrame();
}
H264Frame::Ptr H264RtpDecoder::obtainFrame() {
//从缓存池重新申请对象，防止覆盖已经写入环形缓存的对象
auto frame = ResourcePoolHelper<H264Frame>::obtainObj();
frame->_buffer.clear();
frame->_prefix_size = 4;
return frame;
}
bool H264RtpDecoder::inputRtp(const RtpPacket::Ptr &rtp, bool key_pos) {
return decodeRtp(rtp);
}
bool H264RtpDecoder::decodeRtp(const RtpPacket::Ptr &rtppack) {
/**
* h264帧类型
* Type==1:P/B frame
* Type==5:IDR frame
* Type==6:SEI frame
* Type==7:SPS frame
* Type==8:PPS frame
*/
/*
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 -
*/
const uint8_t *frame = (uint8_t *) rtppack->data() + rtppack->offset;
int length = rtppack->size() - rtppack->offset;
int nal_type = *frame & 0x1F;
int nal_suffix = *frame & (~0x1F);
if (nal_type >= 0 && nal_type < 24) {
//a full frame
_h264frame->_buffer.assign("\x0\x0\x0\x1", 4);
_h264frame->_buffer.append((char *) frame, length);
_h264frame->_pts = rtppack->timeStamp;
auto key = _h264frame->keyFrame();
onGetH264(_h264frame);
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) {
int 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
_h264frame->_buffer.assign("\x0\x0\x0\x1", 4);
_h264frame->_buffer.append((char *) ptr, len);
_h264frame->_pts = rtppack->timeStamp;
if ((ptr[0] & 0x1F) == H264Frame::NAL_IDR) {
haveIDR = true;
}
onGetH264(_h264frame);
}
ptr += len;
}
return haveIDR;
}
case 28:{
//FU-A
FU fu;
MakeFU(frame[1], fu);
if (fu.S) {
//该帧的第一个rtp包 FU-A start
_h264frame->_buffer.assign("\x0\x0\x0\x1", 4);
_h264frame->_buffer.push_back(nal_suffix | fu.type);
_h264frame->_buffer.append((char *) frame + 2, length - 2);
_h264frame->_pts = rtppack->timeStamp;
//该函数return时，保存下当前sequence,以便下次对比seq是否连续
_lastSeq = rtppack->sequence;
return _h264frame->keyFrame();
}
if (rtppack->sequence != _lastSeq + 1 && rtppack->sequence != 0) {
//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
_h264frame->_buffer.clear();
WarnL << "rtp丢包: " << rtppack->sequence << " != " << _lastSeq << " + 1,该帧被废弃";
return false;
}
if (!fu.E) {
//该帧的中间rtp包 FU-A mid
_h264frame->_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
_lastSeq = rtppack->sequence;
return false;
}
//该帧最后一个rtp包 FU-A end
_h264frame->_buffer.append((char *) frame + 2, length - 2);
_h264frame->_pts = rtppack->timeStamp;
onGetH264(_h264frame);
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
// 0 udef
// 30 udef
// 31 udef
WarnL << "不支持的rtp类型:" << (int) nal_type << " " << rtppack->sequence;
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);
//写入环形缓存
RtpCodec::inputFrame(frame);
_h264frame = obtainFrame();
}
////////////////////////////////////////////////////////////////////////
H264RtpEncoder::H264RtpEncoder(uint32_t ui32Ssrc,
uint32_t ui32MtuSize,
uint32_t ui32SampleRate,
uint8_t ui8PayloadType,
uint8_t ui8Interleaved) :
RtpInfo(ui32Ssrc,
ui32MtuSize,
ui32SampleRate,
ui8PayloadType,
ui8Interleaved) {
}
void H264RtpEncoder::inputFrame(const Frame::Ptr &frame) {
GET_CONFIG(uint32_t,cycleMS,Rtp::kCycleMS);
auto ptr = frame->data() + frame->prefixSize();
auto len = frame->size() - frame->prefixSize();
auto pts = frame->pts() % cycleMS;
auto nal_type = H264_TYPE(ptr[0]);
auto payload_size = _ui32MtuSize - 2;
//超过MTU则按照FU-A模式打包
if (len > payload_size + 1) {
//最高位bit为forbidden_zero_bit,
//后面2bit为nal_ref_idc(帧重要程度),00:可以丢,11:不能丢
//末尾5bit为nalu type，固定为28(FU-A)
unsigned char nal_fu_a = (*((unsigned char *) ptr) & (~0x1F)) | 28;
unsigned char s_e_r_flags;
bool fu_a_start = true;
bool mark_bit = false;
int offset = 1;
while (!mark_bit) {
if (len <= offset + payload_size) {
//FU-A end
mark_bit = true;
payload_size = len - offset;
s_e_r_flags = (1 << 6) | nal_type;
} else if (fu_a_start) {
//FU-A start
s_e_r_flags = (1 << 7) | nal_type;
} else {
//FU-A mid
s_e_r_flags = nal_type;
}
{
//传入nullptr先不做payload的内存拷贝
auto rtp = makeRtp(getTrackType(), nullptr, payload_size + 2, mark_bit, pts);
//rtp payload 负载部分
uint8_t *payload = (uint8_t*)rtp->data() + rtp->offset;
//FU-A 第1个字节
payload[0] = nal_fu_a;
//FU-A 第2个字节
payload[1] = s_e_r_flags;
//H264 数据
memcpy(payload + 2, (unsigned char *) ptr + offset, payload_size);
//输入到rtp环形缓存
RtpCodec::inputRtp(rtp, fu_a_start && nal_type == H264Frame::NAL_IDR);
}
offset += payload_size;
fu_a_start = false;
}
} 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, unsigned int len, bool mark, bool gop_pos, uint32_t uiStamp) {
RtpCodec::inputRtp(makeRtp(getTrackType(), data, len, mark, uiStamp), gop_pos);
}
}//namespace mediakit