如何使用OpenCV+MMPEAG開啟攝像頭，顯示的同時推播RTMP流。

注意，設定中：

程式碼詳解：

1、    char* outUrl = "rtmp://localhost/live/livestream";
這個地址，是AMS(Adeobe Media Server)的預設地址。
2、
    //註冊所有的編解碼器
    avcodec_register_all();
    //註冊所有的封裝器
    av_register_all();
    //註冊所有網路協定
    avformat_network_init();
    //開啟攝像頭
    VideoCapture cam;
    namedWindow("video");
    Mat frame;
 
    //畫素格式轉換上下文
    SwsContext*  vsc = NULL;
    //輸出的資料結構
    AVFrame* yuv = NULL;
    //編碼器上下文
    AVCodecContext* vc = NULL;
    //rtmp flv 封裝器
    AVFormatContext* ic = NULL;   
宣告好多變數，是OpenCV & MMPEAG 正常執行所需要的。
3、
    try {
        /// 1. Open Cam
        //  這裡預設開啟的是攝像頭0，並獲得攝像頭引數
        cam.open(0);
        if (!cam.isOpened()) {
            throw exception("cam open failed");
        }
        cout << "cam open sucess"<< endl;
 
        int inWidth = cam.get(CAP_PROP_FRAME_WIDTH);
        int inHeight = cam.get(CAP_PROP_FRAME_HEIGHT);
        int fps = cam.get(CAP_PROP_FPS);
        if (fps == 0) {
            fps = 25;
        }
        cout << fps<< endl;
 
        /// 2. 初始化 SwsContext(轉換格式上下文)
        vsc = sws_getCachedContext(vsc,
            inWidth, inHeight, AV_PIX_FMT_BGR24, 
            inWidth, inHeight, AV_PIX_FMT_YUV420P, 
            SWS_BICUBIC, 
            0, 0, 0
            );
        if (!vsc) {
            throw exception("sws_getCachedContext failed");
        }
 
        ///3.初始化輸出的資料結構
        yuv = av_frame_alloc();
        yuv->format = AV_PIX_FMT_YUV420P;
        yuv->width = inWidth;
        yuv->height = inHeight;
        yuv->pts = 0;
        //分配 YUV 空間
        int ret = av_frame_get_buffer(yuv, 32);
        if (ret != 0) {
            char buf[1024] = { 0 };
            av_strerror(ret, buf, sizeof(buf) - 1);
            throw exception(buf);
        }
 
        ///4. 初始化編碼器上下文
        //a. 找到編碼器,這裡全部基於MMPEAG
        AVCodec* codec = avcodec_find_encoder(AV_CODEC_ID_H264);
        if (!codec) {
            throw exception("Can't find H.264 encoder");
        }
        //b. 建立編碼器上下文
        vc = avcodec_alloc_context3(codec);
        if (!vc) {
            throw exception("avcodec_alloc_context3 failed");
        }
        //c. 設定編碼器引數
        vc->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
        vc->codec_id = codec->id;
        vc->thread_count = 8;
        vc->bit_rate = 50 * 1024 * 8; //video size(bits) per second: 50kByte
        vc->width = inWidth;
        vc->height = inHeight;
        
        vc->time_base = { 1,fps };//used to calculate pts: pts*time_base = second
        vc->framerate = { fps,1 };
 
        vc->gop_size = 50;// for how many frames there is a I frame（關鍵幀）
        vc->max_b_frames = 0;//if these is no B frames, the orders of both decoding and presentation will be the same
        vc->pix_fmt = AV_PIX_FMT_YUV420P;
        
        //d. 開啟編碼器上下文（Open encodder context）
        ret = avcodec_open2(vc, 0, 0);
        if (ret != 0) {
            char buf[1024] = { 0 };
            av_strerror(ret, buf, sizeof(buf) - 1);
            throw exception(buf);
        }
        cout << "avcodec_open2 successed!"<< endl;
        
        ///5. 輸出封裝器和頻流設定
        //a. Create context for MUX
        ret = avformat_alloc_output_context2(&ic, 0, "flv", outUrl);
        if (ret != 0) {
            char buf[1024] = { 0 };
            av_strerror(ret, buf, sizeof(buf) - 1);
            throw exception(buf);
        }
        //b. Add video stream
        AVStream* vs = avformat_new_stream(ic, NULL);
        if (!vs) {
            throw exception("avformat_new_stream failed");
        }
        vs->codecpar->codec_tag = 0;
        // copy  parameter from Encoder to MUX
        avcodec_parameters_from_context(vs->codecpar, vc);
        av_dump_format(ic, 0, outUrl, 1);
 
        ///6. Open rtmp output IO（開啟輸出IO)
        ret = avio_open(&ic->pb, outUrl, AVIO_FLAG_WRITE);
        if (ret != 0) {
            char buf[1024] = { 0 };
            av_strerror(ret, buf, sizeof(buf) - 1);
            throw exception(buf);
        }
        //write mux header
        ret = avformat_write_header(ic, NULL); // after this operation the stream's time_base will also be changed, not vc->time_base anymore
        if (ret != 0) {
            char buf[1024] = { 0 };
            av_strerror(ret, buf, sizeof(buf) - 1);
            throw exception(buf);
        }
 
        AVPacket pack;
        memset(&pack, 0, sizeof(pack));
        int vpts = 0;
 
        //住迴圈，讀入->顯示->轉碼
        for (;;) {
            ///從cam中讀取書
            if (!cam.grab()) {
                continue;
            }
            if (!cam.retrieve(frame)) {
                continue;
            }
            imshow("video", frame);
            waitKey(1);
 
            /// convert RGB to YUV 
            // Input data structure--RGB
            uint8_t* indata[AV_NUM_DATA_POINTERS] = { 0 };//srcStride
            indata[0] = frame.data;
            int inlinesize[AV_NUM_DATA_POINTERS] = { 0 };//srcSlice
            //一行（寬）資料的位元組數
            inlinesize[0] = frame.cols * frame.elemSize();
 
            int h = sws_scale(vsc, indata, inlinesize, 0, frame.rows,
                yuv->data, yuv->linesize);
            if (h <= 0) {
                continue;
            }
 
            ///Mux YUV to flv h.264
            yuv->pts = vpts;
            vpts++;
            ret = avcodec_send_frame(vc, yuv);
            if (ret != 0) {
                continue;
            }
            ret = avcodec_receive_packet(vc, &pack);
            if (ret != 0 || pack.size > 0) {
                cout << '*' <<pack.size<< flush;
            }
            else {
                continue;
            }
            
            ///推流
            pack.pts = av_rescale_q(pack.pts, vc->time_base, vs->time_base);
            pack.dts = av_rescale_q(pack.dts, vc->time_base, vs->time_base);
            ret = av_interleaved_write_frame(ic, &pack);
            if (ret == 0) {
                cout << '#'<< flush;
            }
 
        }
    }
    catch (exception &ex) {
        
        if (cam.isOpened())
            cam.release();
        if (vsc) {
            sws_freeContext(vsc);
            vsc = NULL;
        }
        if (vc) {
            avio_closep(&ic->pb);
            avcodec_free_context(&vc);
        }
        cerr << ex.what() << endl;
    }
    getchar();

在一段程式碼中解決所有問題，可能不是一個很好的習慣，我需要做一些改變。

這裡對程式碼進行了封裝，使得可以簡化成目前情況：

#include <opencv2/core.hpp>
#include <opencv2/imgcodecs.hpp>
#include <opencv2/highgui.hpp>
#include <iostream>
#include "XMediaEncode.h"
#include "XRtmp.h"
extern "C"
{
#include <libswscale/swscale.h>
#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
}
using namespace cv;
using namespace std;
 
 
 
//初始化畫素格式上下文
void test004()
{
    //相機的rtsp url
    char *inUrl = "rtsp://admin:@192.168.10.30:554/ch0_0.264";
    VideoCapture cam;
    namedWindow("video");
 
    //畫素格式轉換上下文
    SwsContext *vsc = NULL;
 
    try
    {
        ////////////////////////////////////////////////////////////////
        /// 1 使用opencv開啟rtsp相機
        cam.open(inUrl);
        if (!cam.isOpened())
        {
            throw exception("cam open failed!");
        }
        cout << inUrl << " cam open success" << endl;
        int inWidth = (int)cam.get(CAP_PROP_FRAME_WIDTH);
        int inHeight = (int)cam.get(CAP_PROP_FRAME_HEIGHT);
        int fps = (int)cam.get(CAP_PROP_FPS);
 
        ///2 初始化格式轉換上下文
        vsc = sws_getCachedContext(vsc,
            inWidth, inHeight, AV_PIX_FMT_BGR24,     //源寬、高、畫素格式
            inWidth, inHeight, AV_PIX_FMT_YUV420P,//目標寬、高、畫素格式
            SWS_BICUBIC,  // 尺寸變化使用演演算法
            0, 0, 0
        );
        if (!vsc)
        {
            throw exception("sws_getCachedContext failed!");
        }
        Mat frame;
        for (;;)
        {
            ///讀取rtsp視訊幀，解碼視訊幀
            if (!cam.grab())
            {
                continue;
            }
            ///yuv轉換為rgb
            if (!cam.retrieve(frame))
            {
                continue;
            }
            imshow("video", frame);
            waitKey(1);
        }
    }
    catch (exception &ex)
    {
        if (cam.isOpened())
            cam.release();
        if (vsc)
        {
            sws_freeContext(vsc);
            vsc = NULL;
        }
        cerr << ex.what() << endl;
    }
    getchar();
}
 
//rtsp資料來源到rtmp推流      要重點複習 
void test005()
{
    cout << "void test005()!" << endl;
    //相機的rtsp url
    char *inUrl = "rtsp://admin:@192.168.10.30:554/ch0_0.264";
    //nginx-rtmp 直播伺服器rtmp推流URL
    char *outUrl = "rtmp://192.168.10.181/live";
 
    //註冊所有的編解碼器
    avcodec_register_all();
 
    //註冊所有的封裝器
    av_register_all();
 
    //註冊所有網路協定
    avformat_network_init();
 
 
    VideoCapture cam;
    Mat frame;
    namedWindow("video");
 
    //畫素格式轉換上下文
    SwsContext *vsc = NULL;
 
    //輸出的資料結構
    AVFrame *yuv = NULL;
 
    //編碼器上下文
    AVCodecContext *vc = NULL;
 
    //rtmp flv 封裝器
    AVFormatContext *ic = NULL;
 
 
    try
    {    ////////////////////////////////////////////////////////////////
        /// 1 使用opencv開啟rtsp相機
        cam.open(inUrl);
        if (!cam.isOpened())
        {
            throw exception("cam open failed!");
        }
        cout << inUrl << " cam open success" << endl;
        int inWidth = (int)cam.get(CAP_PROP_FRAME_WIDTH);
        int inHeight = (int)cam.get(CAP_PROP_FRAME_HEIGHT);
        int fps = (int)cam.get(CAP_PROP_FPS);
 
        ///2 初始化格式轉換上下文
        vsc = sws_getCachedContext(vsc,
            inWidth, inHeight, AV_PIX_FMT_BGR24,     //源寬、高、畫素格式
            inWidth, inHeight, AV_PIX_FMT_YUV420P,//目標寬、高、畫素格式
            SWS_BICUBIC,  // 尺寸變化使用演演算法
            0, 0, 0
        );
        if (!vsc)
        {
            throw exception("sws_getCachedContext failed!");
        }
 
        ///3 初始化輸出的資料結構
        yuv = av_frame_alloc();
        yuv->format = AV_PIX_FMT_YUV420P;
        yuv->width = inWidth;
        yuv->height = inHeight;
        yuv->pts = 0;
        //分配yuv空間
        int ret = av_frame_get_buffer(yuv, 32);
        if (ret != 0)
        {
            char buf[1024] = { 0 };
            av_strerror(ret, buf, sizeof(buf) - 1);
            throw exception(buf);
        }
 
        ///4 初始化編碼上下文，分為以下三步
        //a 找到編碼器
        AVCodec *codec = avcodec_find_encoder(AV_CODEC_ID_H264);
        if (!codec)
        {
            throw exception("Can`t find h264 encoder!");
        }
        //b 建立編碼器上下文
        vc = avcodec_alloc_context3(codec);
        if (!vc)
        {
            throw exception("avcodec_alloc_context3 failed!");
        }
        //c 設定編碼器引數
        vc->flags |= AV_CODEC_FLAG_GLOBAL_HEADER; //全域性引數
        vc->codec_id = codec->id;
        vc->thread_count = 8;
 
        vc->bit_rate = 50 * 1024 * 8;//壓縮後每秒視訊的bit位大小 50kB
        vc->width = inWidth;
        vc->height = inHeight;
        vc->time_base = { 1,fps };
        vc->framerate = { fps,1 };
 
        //畫面組的大小，多少幀一個關鍵幀
        vc->gop_size = 50;
        vc->max_b_frames = 0;
        vc->pix_fmt = AV_PIX_FMT_YUV420P;
        //d 開啟編碼器上下文
        ret = avcodec_open2(vc, 0, 0);
 
        if (ret != 0)
        {
            char buf[1024] = { 0 };
            av_strerror(ret, buf, sizeof(buf) - 1);
            throw exception(buf);
        }
        cout << "avcodec_open2 success!" << endl;
 
        ///5 輸出封裝器和視訊流設定
        //a 建立輸出封裝器上下文
        ret = avformat_alloc_output_context2(&ic, 0, "flv", outUrl);
        if (ret != 0)
        {
            char buf[1024] = { 0 };
            av_strerror(ret, buf, sizeof(buf) - 1);
            throw exception(buf);
        }
 
        //b 新增視訊流 
        AVStream *vs = avformat_new_stream(ic, NULL);
        if (!vs)
        {
            throw exception("avformat_new_stream failed");
        }
        vs->codecpar->codec_tag = 0;
        //從編碼器複製引數
        avcodec_parameters_from_context(vs->codecpar, vc);
        av_dump_format(ic, 0, outUrl, 1);
 
 
        ///開啟rtmp 的網路輸出IO
        ret = avio_open(&ic->pb, outUrl, AVIO_FLAG_WRITE);
        if (ret != 0)
        {
            char buf[1024] = { 0 };
            av_strerror(ret, buf, sizeof(buf) - 1);
            throw exception(buf);
        }
 
        //寫入封裝頭
        ret = avformat_write_header(ic, NULL);
        if (ret != 0)
        {
            char buf[1024] = { 0 };
            av_strerror(ret, buf, sizeof(buf) - 1);
            throw exception(buf);
        }
 
        AVPacket pack;
        memset(&pack, 0, sizeof(pack));
        int vpts = 0;
        
        //死迴圈
        for (;;)
        {
            ///讀取rtsp視訊幀，解碼視訊幀
            if (!cam.grab())
            {
                continue;
            }
            ///yuv轉換為rgb
            if (!cam.retrieve(frame))
            {
                continue;
            }
            imshow("video", frame);
            waitKey(1);
 
 
            ///rgb to yuv
            //輸入的資料結構
            uint8_t *indata[AV_NUM_DATA_POINTERS] = { 0 };
            //indata[0] bgrbgrbgr
            //plane indata[0] bbbbb indata[1]ggggg indata[2]rrrrr 
            indata[0] = frame.data;
            int insize[AV_NUM_DATA_POINTERS] = { 0 };
            //一行（寬）資料的位元組數
            insize[0] = frame.cols * frame.elemSize();
            int h = sws_scale(vsc, indata, insize, 0, frame.rows, //源資料
                yuv->data, yuv->linesize);
            if (h <= 0)
            {
                continue;
            }
            cout << h << " " << flush;
 
            ///h264編碼
            yuv->pts = vpts;
            vpts++;
            ret = avcodec_send_frame(vc, yuv);
            if (ret != 0)
                continue;
 
            ret = avcodec_receive_packet(vc, &pack);
            if (ret != 0 || pack.size > 0)
            {
                cout << "*" << pack.size << flush;
            }
            else
            {
                continue;
            }
            //推流
            pack.pts = av_rescale_q(pack.pts, vc->time_base, vs->time_base);
            pack.dts = av_rescale_q(pack.dts, vc->time_base, vs->time_base);
            pack.duration = av_rescale_q(pack.duration, vc->time_base, vs->time_base);
            ret = av_interleaved_write_frame(ic, &pack);
            if (ret == 0)
            {
                cout << "#" << flush;
            }
        }
 
    }
    catch (exception &ex)
    {
        if (cam.isOpened())
            cam.release();
        if (vsc)
        {
            sws_freeContext(vsc);
            vsc = NULL;
        }
 
        if (vc)
        {
            avio_closep(&ic->pb);
            avcodec_free_context(&vc);
        }
 
        cerr << ex.what() << endl;
    }
    getchar();
}
 
//opencv_rtsp_to_rtmp_class封裝重構程式碼    要重點複習
void test006()
{
    cout << "void test006()!" << endl;
    //相機的rtsp url
    char *inUrl = "rtsp://admin:@192.168.10.30:554/ch0_0.264";
    //nginx-rtmp 直播伺服器rtmp推流URL
    char *outUrl = "rtmp://192.168.10.181/live";
 
 
    //編碼器和畫素格式轉換
    XMediaEncode *me = XMediaEncode::Get(0);
 
    //封裝和推流物件
    XRtmp *xr = XRtmp::Get(0);
 
    VideoCapture cam;
    Mat frame;
    namedWindow("video");
 
    int ret = 0;
    try
    {    ////////////////////////////////////////////////////////////////
        /// 1 使用opencv開啟rtsp相機
        cam.open(inUrl);
        if (!cam.isOpened())
        {
            throw exception("cam open failed!");
        }
        cout << inUrl << " cam open success" << endl;
        int inWidth = (int)cam.get(CAP_PROP_FRAME_WIDTH);
        int inHeight = (int)cam.get(CAP_PROP_FRAME_HEIGHT);
        int fps = (int)cam.get(CAP_PROP_FPS);
 
        ///2 初始化格式轉換上下文
        ///3 初始化輸出的資料結構
        me->inWidth = inWidth;
        me->inHeight = inHeight;
        me->outWidth = inWidth;
        me->outHeight = inHeight;
        me->InitScale();
 
        ///4 初始化編碼上下文
        //a 找到編碼器
        if (!me->InitVideoCodec())
        {
            throw exception("InitVideoCodec failed!");
        }
 
        ///5 輸出封裝器和視訊流設定
        xr->Init(outUrl);
 
        //新增視訊流 
        xr->AddStream(me->vc);
        xr->SendHead();
 
        for (;;)
        {
            ///讀取rtsp視訊幀，解碼視訊幀
            if (!cam.grab())
            {
                continue;
            }
            ///yuv轉換為rgb
            if (!cam.retrieve(frame))
            {
                continue;
            }
            //imshow("video", frame);
            //waitKey(1);
 
 
            ///rgb to yuv
            me->inPixSize = frame.elemSize();
            AVFrame *yuv = me->RGBToYUV((char*)frame.data);
            if (!yuv) continue;
 
            ///h264編碼
            AVPacket *pack = me->EncodeVideo(yuv);
            if (!pack) continue;
 
            xr->SendFrame(pack);
 
 
        }
 
    }
    catch (exception &ex)
    {
        if (cam.isOpened())
            cam.release();
        cerr << ex.what() << endl;
    }
    getchar();
}
 
int main(int argc, char *argv[])
{
    //test000();
    //test001();
    //test002();
    //test003();
    //test004();
    //test005();
    test006();
    return 0;
}

具體操作：

——————————————————————————————————————

選擇攝像頭並且開啟攝像頭；

vlc開啟網路串流

輸入：

rtmp://localhost/live/livestream

串流攝像頭內容：

參考資料《利用ffmpeg和opencv進行視訊的解碼播放》

文中程式碼：

https://files.cnblogs.com/files/blogs/758212/opencv_rtsp2rtmp-master.rar
https://files.cnblogs.com/files/blogs/758212/main.js