1 将Opencv中的BGR视频流使用FFmpge编码为H264视频流

本文主要介绍如何将OpenCV从视频文件或者摄像头读取的BGR视频流通过FFmpeg编码为H264视频流，并将编码的H264视频流再解码为OpenCV的BGR视频流。

本文将上述需求封装为两个类，一个为OpenCVH264Encoder类，主要负责将OpenCV的BGR视频流编码为H264视频流，另一个为OpenCVH264Decoder类，主要负责将编码后的H264视频流解码为OpenCV的BGR视频流。

本文中提到的功能主要依赖于三个第三方库：OpenCV、FFmpeg、easylogging++，其中easylogging++用于日志输出，可使用其他日志库进行替换。

其中全局的头文件为OpenCVToFFmpegH264Header.h，内容如下

#ifndef OPENCV_TO_FFMPEG_H264_HEADER_H_
#define OPENCV_TO_FFMPEG_H264_HEADER_H_

// ffmpeg
extern "C" {
    #include <libavcodec\avcodec.h>
    #include <libavformat\avformat.h>
    #include <libavutil\channel_layout.h>
    #include <libavutil\common.h>
    #include <libavutil\imgutils.h>
    #include <libswscale\swscale.h>
    #include <libavutil\imgutils.h>
    #include <libavutil\opt.h>
    #include <libavutil\mathematics.h>
    #include <libavutil\samplefmt.h>
    #include <libswresample\swresample.h>
}

// opencv
#include "opencv/cv.h"
#include "opencv2/opencv.hpp"

// easylogging++
#include "easylogging++.h"
#define ELPP_THREAD_SAFE

#endif // !OPENCV_TO_FFMPEG_H264_HEADER_H_

1.1 OpenCVH264Encoder编码类、OpenCVH264Decoder解码类使用示例

#include <iostream>
#include "OpenCVToFFmpegH264Header.h"
#include "OpenCVH264Encoder.h"
#include "OpenCVH264Decoder.h"

INITIALIZE_EASYLOGGINGPP

void InitEasyLoggintPP()
{
    el::Configurations defaultConf;
    defaultConf.setToDefault();
    //设置最大文件大小
    defaultConf.setGlobally(el::ConfigurationType::MaxLogFileSize, "104857600");
    //是否写入文件
    defaultConf.setGlobally(el::ConfigurationType::ToFile, "true");
    //是否输出控制台
    defaultConf.setGlobally(el::ConfigurationType::ToStandardOutput, "true");

    defaultConf.setGlobally(el::ConfigurationType::Format, "[%datetime]  [%function]   [%loc]   [%level] : %msg");
    //设置配置文件
    el::Loggers::reconfigureLogger("default", defaultConf);
}


int main()
{
    cv::VideoCapture videoReader("C:/Users/Administrator/Desktop/1.mp4");

    if (!videoReader.isOpened())
    {
        return 0;
    }

    const int width = (int)videoReader.get(cv::CAP_PROP_FRAME_WIDTH);
    const int height = (int)videoReader.get(cv::CAP_PROP_FRAME_HEIGHT);
    const int frameRate = (int)videoReader.get(cv::CAP_PROP_FPS);
    const int totalFrames = (int)videoReader.get(cv::CAP_PROP_FRAME_COUNT);
    //const int bitrate = 1000000;
    const int bitrate = 400000;

    std::vector<cv::Mat> cvMatVec;
    cvMatVec.clear();

    while (true)
    {
        cv::Mat image;
        videoReader >> image;
        if (image.empty())
            break;
        cvMatVec.push_back(image);
    }
    videoReader.release();


    for (int i = 0; i < 2; ++i)
    {
        auto encode_start = std::chrono::system_clock::now();

        OpenCVH264Encoder openCVH264Encoder;

        openCVH264Encoder.Init(width, height, bitrate, frameRate);

        for (int j = 0; j < cvMatVec.size(); ++j)
        {
            if (!openCVH264Encoder.EncodeCVMatToH264Stream(j, cvMatVec[j]))
            {
                LOG(ERROR) << "Encode cv::Mat failed";  
            }
        }
        openCVH264Encoder.Flush();

        auto encode_end = std::chrono::system_clock::now();

        LOG(INFO) << "编码耗时 = " << std::chrono::duration_cast<std::chrono::milliseconds>(encode_end - encode_start).count() << "ms";

        // 解码h264
        OpenCVH264Decoder openCVH264Decoder;
        openCVH264Decoder.Init(width, height);

        std::vector<unsigned char> h264Stream = openCVH264Encoder.GetEncodeH264Stream();
        openCVH264Decoder.DecodeH264StreamToCvMat(h264Stream.data(), h264Stream.size());
        openCVH264Decoder.Flush();

        std::vector<cv::Mat> cvMatDecodeVec = openCVH264Decoder.GetDecodeOpencvMat();

        std::cout << "cvMatVec.size = " << cvMatDecodeVec.size() << std::endl;
        for (int m = 0; m < cvMatDecodeVec.size(); ++m)
        {
            cv::imshow("result", cvMatDecodeVec[m]);
            cv::waitKey(40);
        }

    }

    cv::destroyAllWindows();

    return 0;
}

1.2 OpenCVH264Encoder编码类