前言

• 上一篇文章我们介绍了如何使用FFMpeg工具进行推流。但如果要在我们的代码工程中，实现推流。就要下载FFMpegSDK包，调用相关API，在我们自己的程序中实现推流。

FFMpegSDK下载

• 下载动态库文件
  
• 选择这个下载
  

使用FFMpegSDK推流

• 下载FFMpegSDK后，拷贝到我们的工程下
• 目录结构如下

•   ├─ bin
    ├─ doc
    ├─ include
    		├─ libavcodec
    		├─ libavdevice
    		├─ libavfilter
    		├─ libavformat
    		├─ libavutil
    		├─ libpostproc
    		├─ libswresample
    		└─ libswscale
    ├─ lib
    		└─pkgconfig
    ├─ src
    		└─ main.cpp
    ├─ build_x64
    └─ CMakeLists.txt
  

• bin，doc，include，lib目录都是FFMpegSDK包中的内容，直接拷贝过来
• src 在这个目录下创建一个源文件 main.cpp，在代码中调用FFMpeg提供的API，实现推流，内容如下

•   extern "C"{
    #include "libavformat/avformat.h"
    #include "libavcodec/avcodec.h"
    #include "libavutil/time.h"
    };
    #include <iostream>
    
    
    void printErr(int errNum);
    
    static double r2d(AVRational r){
        return (r.num == 0 || r.den == 0) ? 0.0 : (double)r.num / (double)r.den;
    }
    
    int main(){
        //初始化网络库以及网络加密协议相关的库
        avformat_network_init();
    
        //打开文件, 解封文件头
        AVFormatContext *inContext = NULL;
        char *inFile = "001.mp4";
        int ret = avformat_open_input(&inContext, inFile, 0, 0);
        if(ret != 0){
            printErr(ret);
            return -1;
        }
    
        std::cout<<"avformat_open_input success"<<std::endl;
    
        //获取音视频流信息
        ret = avformat_find_stream_info(inContext, 0);
        if(ret != 0){
            printErr(ret);
            return -1;
        }
    
        std::cout<<"avformat_find_stream_info success"<<std::endl;
    
        //打印信息
        av_dump_format(inContext, 0, inFile, 0);
    
        //输出流
        AVFormatContext *outContext;
        char *outFile = "rtmp://192.168.206.131:10088/live";
        ret = avformat_alloc_output_context2(&outContext, 0, "flv", outFile);
        if(outContext == 0){
            printErr(ret);
            return -1;
        }
    
        std::cout<<"avformat_alloc_output_context2 success"<<std::endl;
    
        //配置输出流
        //遍历输入的AVStream
        for(int i = 0; i < inContext->nb_streams; i++){
            AVStream *outStream = avformat_new_stream(outContext, NULL);
            if(outStream == NULL){
                printErr(-1);
                return -1;
            }
    
            //复制配置信息
            ret = avcodec_parameters_copy(outStream->codecpar, inContext->streams[i]->codecpar);
            if(ret < 0){
                printErr(ret);
                return -1;
            }
    
            outStream->codecpar->codec_tag = 0;
        }
    
        //输出
        av_dump_format(outContext, 0, outFile, 1);
    
        //rtmp推流
        
        //打开io
        ret = avio_open(&outContext->pb, outFile, AVIO_FLAG_WRITE);
        if(ret != 0){
            printErr(ret);
            return -1;
        }
        std::cout<<"avio_open success"<<std::endl;
    
        //写入头信息
        ret = avformat_write_header(outContext, NULL);
        if(ret < 0){
            printErr(ret);
            return -1;
        }
        std::cout<<"avformat_write_header success"<<std::endl;
    
        //推流帧数据
        AVPacket avpkt;
        long long startTime = av_gettime();
        while(1){
            //读帧数据
            ret = av_read_frame(inContext, &avpkt);
            if(ret != 0){
                break;
            }
    
            std::cout << avpkt.pts << std::endl;
    
            //计算转换pts dts
            AVRational inTime = inContext->streams[avpkt.stream_index]->time_base;
            AVRational outTime = outContext->streams[avpkt.stream_index]->time_base;
            avpkt.pts = av_rescale_q_rnd(avpkt.pts, inTime, outTime, (AVRounding)(AV_ROUND_NEAR_INF | AV_ROUND_PASS_MINMAX));
            avpkt.dts = av_rescale_q_rnd(avpkt.dts, inTime, outTime, (AVRounding)(AV_ROUND_NEAR_INF | AV_ROUND_PASS_MINMAX));
            avpkt.duration = av_rescale_q_rnd(avpkt.duration, inTime, outTime, (AVRounding)(AV_ROUND_NEAR_INF | AV_ROUND_PASS_MINMAX));
            avpkt.pos = -1;
    
             //处理视频帧,控制推流速度
            if(inContext->streams[avpkt.stream_index]->codecpar->codec_type = AVMEDIA_TYPE_VIDEO){
                //时间基数
                AVRational tb = inContext->streams[avpkt.stream_index]->time_base;
                
                long long nowTime = av_gettime() - startTime;
                long long dtsTime = avpkt.dts * (1000 * 1000 * r2d(tb));
                if(dtsTime > nowTime){
                    av_usleep(dtsTime - nowTime);
                }
                
            }
    
    
            //发送数据
            ret = av_interleaved_write_frame(outContext, &avpkt);
            if(ret < 0){
                printErr(ret);
                return -1;
            }
    
            //释放
            av_packet_unref(&avpkt);
        }
    
        system("pause");
        return 0;
    }
    
    void printErr(int errNum){
        char errBuf[1024] = {0};
        av_strerror(errNum, errBuf, sizeof(errBuf));
        system("pause");
    }
  

• CMakeLists.txt文件，实现编译，内容如下

•   cmake_minimum_required (VERSION 3.5)
    project (FFmpegSDK)
    
    MESSAGE(STATUS "PROJECT_SOURCE_DIR" ${PROJECT_SOURCE_DIR})
    SET(SRC_LISTS ${PROJECT_SOURCE_DIR}/src/main.cpp)
       
    
    # 配置工程需要的头文件目录 
    include_directories(${PROJECT_SOURCE_DIR}/include)
    
    
    IF(WIN32)
    	set(CMAKE_C_FLAGS_RELEASE "/MD /MP /Od /Zi /EHsc")
    ENDIF()
    
    
    set(PRO_AVCODEC_LIB ${PROJECT_SOURCE_DIR}/lib/avcodec.lib)
    set(PRO_AVFORMAT_LIB ${PROJECT_SOURCE_DIR}/lib/avformat.lib)
    set(PRO_AVUTIL_LIB ${PROJECT_SOURCE_DIR}/lib/avutil.lib)
    
    
    ADD_EXECUTABLE(FFmpegSDK ${SRC_LISTS})
    TARGET_LINK_LIBRARIES(FFmpegSDK ${PRO_AVCODEC_LIB} ${PRO_AVFORMAT_LIB} ${PRO_AVUTIL_LIB})
  

• 在build_x64目录下执行以下编译命令
  • cmake -G “Visual Studio 14 2015 Win64” …
  • cmake --build ./ --config Release
• 编译成功后，在build_x86\Release目录下就会生成可执行程序FFmpegSDK.exe
• 再把对应的库avcodec-60.dll、avformat-60.dll、avutil-58.dll、swresample-4.dll和要推送的视频文件001.mp4拷贝到build_x86\Release下。运行FFmpegSDK.exe就可以实现推流
• 可以使用VLC工具来播放推送流