FLV文件推流到Nginx(C++实现)

本文将介绍如何通过librtmp将flv文件推送到Nginx。首先我们明确文件flv和rtmp flv的文件格式是不一样的，具体参考RTMP FLV和FLV文件的区别。文章结构：首先进行解析flv文件，然后从解析后的文件中，读取音频/视频文件，最后将音视频文件利用librtmp推送到Nginx服务器中。Nginx 支持RTMP就不在此赘述。该过程的实现放在下文。

解析FLV

首先我们要了解FLV文件的格式

图片来源于网络。这张图片清楚地展示了FLV的文件结构，首先是FLV Header，一般是9个字节，然后就是一系列的pre tagsize 和 tag。我们需要的是tag中的Tag Data，将它发送到服务端。FLV协议详解

获取音/视频数据

获取所谓的音视频数据就是将FLV Header，preTagSize和Body的头（tagheader）去掉，剩下的就是音视频数据了。tag header 是，1byte TT（Tag Type ），0x08音频，0x09视频，0x12 script， 2-4byte，Tag body的长度， PreTagSize - Tag Header Size = Tag body size， 5-7byte,时间戳，单位：毫秒，script它的时间戳是0，第8个字节，扩展时间戳，真正的时间戳格式[扩展，时间戳]，一共是4字节
， 9-11，StreamId 0。
好了剩下的工作就是解析这些头了，使用fread读取二进制文件。

推流到Nginx

要推流，肯定先要连接到RTMP server的。

创建RTMP，使用RTMP_Alloc()函数。
初始化RTMP，RTMP_Init(rtmp);
设置RTMP连接地址，RTMP_SetupURL(rtmp, addr);
连接，RTMP_Connect(rtmp, NULL)

librtmp的基本步骤

initialize RTMP Object
configure RTMP URL
connect Nginx（Media Stream Server）
send data packet

源代码

//
// Created by wenfan on 2021/8/10.
//#ifndef PLAY_FLVUPSTREAM_H
#define PLAY_FLVUPSTREAM_H#include <cstdio>
#include <string>
#include <librtmp/rtmp.h>using namespace std;class FLVUpStream {public:FILE* openFLV(string flvaddr);void publish_stream();RTMP* connect_rtmp_server(string rtmpaddr);void send_data(FILE* fp, RTMP* rtmp);RTMPPacket *alloc_packet();void free_packet(RTMPPacket* rtmpPacket);
};
#endif //PLAY_FLVUPSTREAM_H

实现

//
// Created by wenfan on 2021/8/10.
//#include "FLVUpStream.h"
#include <librtmp/rtmp.h>
#include <thread>/*** 这里涉及到大小端的问题* @param fp* @param u24*/
static void read_u24(FILE* fp, unsigned int* u24 ){unsigned int tmp = 0;fread(&tmp, 1, 3 , fp);*u24 = ((tmp >> 16) & 0xFF) | ((tmp << 16) & 0xFF0000) |  ((tmp) & 0xFF00);
}/*** FLV的Header一共9字节* 第1-3 byte 固定：'F' 'L' 'V'* 第4byte ，version* 第5字节的0～5位必须是0，进行保留* 第5字节的6位，是否有音频Tag* 第5字节的7位，保留，为0* 第5字节的8位，表示是否有音频Tag* 第6-9位是Header的大小，必须是9* @param flvaddr* @return*/
FILE* FLVUpStream::openFLV(string flvaddr){FILE* fp = NULL;fp = fopen(flvaddr.c_str(), "r+b");if(!fp){printf("Failed to open flv file: %s", flvaddr.c_str());return NULL;}//jump 9 byte FLV Headerfseek(fp, 13, SEEK_SET);//jump 4 byte PreTagSize//fseek(fp, 4, SEEK_CUR);return fp;
}/*** 经历5个步骤，创建好RTMP Stream* @param rtmpaddr* @return*/
RTMP* FLVUpStream::connect_rtmp_server(string rtmpaddr){RTMP* rtmp = nullptr;char* addr = new char[rtmpaddr.length()];strcpy(addr, rtmpaddr.c_str());// 1.create RTMP Object and init it;rtmp = RTMP_Alloc();if(!rtmp){printf("Failed to alloc RTMP Memory\n");goto __ERROR ;}RTMP_Init(rtmp);//2. set rtmp server address and set connection timeoutrtmp->Link.timeout = 10;RTMP_SetupURL(rtmp, addr);//3.Setup connectionif(!RTMP_Connect(rtmp, NULL)){printf("Failed to connect RTMP Server\n");goto __ERROR;}//4.The option is publish, not set the option is playRTMP_EnableWrite(rtmp);//5.create StreamRTMP_ConnectStream(rtmp, 0);return rtmp;__ERROR:if(rtmp){RTMP_Close(rtmp);RTMP_Free(rtmp);}return NULL;
}/*** 释放RTMPPacket内存* @param rtmpPacket*/
void FLVUpStream::free_packet(RTMPPacket* rtmpPacket){if(rtmpPacket){//释放分配的Packet包内内存RTMPPacket_Free(rtmpPacket);//释放包装结构体free(rtmpPacket);}
}/**** @return*/
RTMPPacket* FLVUpStream::alloc_packet(){RTMPPacket* packet;packet = (RTMPPacket*) malloc(sizeof(RTMPPacket));if(!packet){printf("Failed to alloc RTMPPacket, No Memory!\n");return NULL;}if(!RTMPPacket_Alloc(packet, 64*1024*1024*1024)) {printf("Failed to alloc RTMPPacket content, No Memory!\n");return NULL;}RTMPPacket_Reset(packet);packet->m_hasAbsTimestamp = 0;packet->m_nChannel = 0x4;return packet;
}/*** tag header* 1byte TT（Tag Type ），0x08音频，0x09视频，0x12 script* 2-4byte，Tag body的长度， PreTagSize - Tag Header Size = Tag body size* 5-7byte,时间戳，单位：毫秒，script它的时间戳是0* 第8个字节，扩展时间戳， 真正的时间戳格式[扩展，时间戳]，一共是4字节* 9-11，StreamId 0** @param fp* @param pPacket*/
static int  read_data(FILE *fp, RTMPPacket** pPacket){int ret = 0;size_t data_size;char tt;unsigned int tag_data_size;unsigned  int ts;char extend_ts;unsigned int streamId;unsigned int preTagSize ;/*** 去读body*///read_u8(fp,&tt);fread(&tt, 1,1, fp);read_u24(fp, &tag_data_size);read_u24(fp, &ts);fread(&extend_ts, 1, 1, fp);read_u24(fp, &streamId);printf("tag header :tt : %d, ts = %d, data_size = %d, streamId = %d\n", tt, ts , tag_data_size,streamId);//读取音视频数据data_size = fread((*pPacket)->m_body, 1, tag_data_size,fp);//读取preTagSize，4个字节fread(&preTagSize, 1, 4, fp);if(data_size != tag_data_size){printf("Failed to read tag body from flv ,(data_size = %zu, tag_data_size = %d)\n", data_size, tag_data_size);return ret;}//设置packet data(*pPacket)->m_headerType = RTMP_PACKET_SIZE_LARGE;(*pPacket)->m_nTimeStamp = ts;(*pPacket)->m_packetType = tt;(*pPacket)->m_nBodySize = tag_data_size;return 1;
}/*** 推流* @param fp* @param rtmp*/
void FLVUpStream::send_data(FILE *fp, RTMP *rtmp) {//1.create  RTMP_Packet ObjectRTMPPacket* packet = NULL;packet = alloc_packet();packet->m_nInfoField2 = rtmp->m_stream_id;while (1){//2.read data from flvif(!read_data(fp, &packet)){printf("over!\n");break;}//3.judge connection is nornalif(!RTMP_IsConnected(rtmp)){printf("Disconnect with the RTMP server!\n");return;}//4.send dataRTMP_SendPacket(rtmp,packet, 0);this_thread::sleep_for(std::chrono::milliseconds(10));}// realse packetfree_packet(packet);return;
}/*** 进行推流* 进行三个步骤：* 1.读取flv文件* 2.连接RTMP服务器* 3.推送音频/视频数据* @return*/
void FLVUpStream::publish_stream(){string flvaddr = "/Users/fengjianqiang/Movies/1.flv";string rtmpaddr = "rtmp://localhost:1935/rtmplive/room";//1.读取flv文件FILE* fp = openFLV(flvaddr);//2.连接RTMP服务器RTMP* rtmp = connect_rtmp_server(rtmpaddr);//3.publish audio /video datasend_data(fp, rtmp);
}