linux下使用QT调用FFMPEG读取摄像头一帧数据显示到标签控件上

 下面代码调用FFMPEG库，读取摄像头的一帧数据，转换为RGB888，加载到QImage，再显示到标签控件上。

开发环境:

操作系统： ubuntu18.04 64位

QT版本： QT5.12

代码包已经上传到CSDN，需要的可以去下载。

https://download.csdn.net/download/xiaolong1126626497/12233526

mainwindow.cpp文件代码:

#include "mainwindow.h"
#include "ui_mainwindow.h"

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    FFMPEG_Init_Config();
}


MainWindow::~MainWindow()
{
    delete ui;
}

int MainWindow::FFMPEG_Init_Config()
{
    AVInputFormat   *ifmt;
    AVFormatContext *pFormatCtx;
    AVCodecContext  *pCodecCtx;
    AVCodec         *pCodec;
    AVDictionary    *options=nullptr;
    AVPacket        *packet;
    AVFrame         *pFrame,*pFrameYUV;

    int videoindex;
    int i,ret,got_picture;
    /*1. FFMPEG初始化*/
    av_register_all();
    avcodec_register_all();
    avdevice_register_all(); //注册多媒体设备交互的类库
    /*2. 查找用于输入的设备*/
    ifmt=av_find_input_format("video4linux2");
    pFormatCtx=avformat_alloc_context();
    av_dict_set(&options,"video_size","640x480",0); //设置摄像头输出的分辨率
    //av_dict_set(&options,"framerate","30",0);     //设置摄像头帧率. 每秒为单位,这里设置每秒30帧.
    //一般帧率不用设置，默认为最高，帧率和输出的图像尺寸有关系
    if(avformat_open_input(&pFormatCtx,"/dev/video0",ifmt,&options)!=0)
    {
        qDebug("输入设备打开失败: /dev/video0\n");
        return -1;
    }
    if(avformat_find_stream_info(pFormatCtx,nullptr)<0)
    {
        qDebug("查找输入流失败.\n");
        return -2;
    }
    videoindex=-1;
    for(i=0;i<pFormatCtx->nb_streams;i++)
    {
        if(pFormatCtx->streams[i]->codec->codec_type==AVMEDIA_TYPE_VIDEO)
        {
            videoindex=i;
            break;
        }
    }

    if(videoindex==-1)
    {
        qDebug("视频流查找失败.\n");
        return -3;
    }
    pCodecCtx=pFormatCtx->streams[videoindex]->codec;
    qDebug("摄像头尺寸(WxH): %d x %d \n",pCodecCtx->width, pCodecCtx->height);
    pCodec=avcodec_find_decoder(pCodecCtx->codec_id);
    if(pCodec==nullptr)
    {
        qDebug("找不到编解码器。\n");
        return -4;
    }
    if(avcodec_open2(pCodecCtx, pCodec,nullptr)<0)
    {
        qDebug("无法打开编解码器。\n");
        return -5;
    }

    packet=(AVPacket *)av_malloc(sizeof(AVPacket));
    pFrame=av_frame_alloc();
    pFrameYUV=av_frame_alloc();
    unsigned char *out_buffer=(unsigned char *)av_malloc(av_image_get_buffer_size(AV_PIX_FMT_YUV420P, pCodecCtx->width, pCodecCtx->height,16));   // avpicture_get_size

    av_image_fill_arrays(pFrameYUV->data,pFrameYUV->linesize,out_buffer, AV_PIX_FMT_YUV420P, pCodecCtx->width, pCodecCtx->height,16);

    struct SwsContext *img_convert_ctx;
    img_convert_ctx=sws_getContext(pCodecCtx->width, pCodecCtx->height, pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height, AV_PIX_FMT_YUV420P, SWS_BICUBIC, NULL, NULL, NULL);

    //读取一帧数据
    if(av_read_frame(pFormatCtx, packet)>=0)
    {
        //输出图像的大小
        qDebug("数据大小=%d\n",packet->size);
        //判断是否是视频流
        if(packet->stream_index==videoindex)
        {
            //解码从摄像头获取的数据，pframe结构
            ret=avcodec_decode_video2(pCodecCtx, pFrame,&got_picture,packet);
            if(ret<0)
            {
                qDebug("解码Error.\n");
                return -6;
            }
            if(got_picture)
            {
                 size_t y_size=pCodecCtx->width*pCodecCtx->height;
                 sws_scale(img_convert_ctx,(const unsigned char* const*)pFrame->data, pFrame->linesize, 0, pCodecCtx->height, pFrameYUV->data, pFrameYUV->linesize);  //根据前面配置的缩放参数，进行图像格式转换以及缩放等操作

                 unsigned char *p=new unsigned char[y_size]; //申请空间
                 unsigned char *rgb24_p=new unsigned char[pCodecCtx->width*pCodecCtx->height*3];

                 //将YUV数据拷贝到缓冲区
                 memcpy(p,pFrameYUV->data[0],y_size);
                 memcpy(p+y_size,pFrameYUV->data[1],y_size/4);
                 memcpy(p+y_size+y_size/4,pFrameYUV->data[2],y_size/4);
                 //将YUV数据转为RGB格式
                 YUV420P_to_RGB24(p,rgb24_p,pCodecCtx->width,pCodecCtx->height);
                 //加载到QIMAGE显示到QT控件
                 QImage image(rgb24_p,pCodecCtx->width,pCodecCtx->height,QImage::Format_RGB888);
                 QPixmap my_pixmap;
                 my_pixmap.convertFromImage(image);
                 ui->label_DisplayImage->setPixmap(my_pixmap);

                 delete[] p; //释放空间
                 delete[] rgb24_p; //释放空间
            }
        }
    }
    sws_freeContext(img_convert_ctx);
    av_free(out_buffer);
    av_free(pFrameYUV);
    avcodec_close(pCodecCtx); //关闭编码器
    avformat_close_input(&pFormatCtx); //关闭输入设备
}

/**
 * YUV420P转RGB24
 * @param data
 * @param rgb
 * @param width
 * @param height
 */
void MainWindow::YUV420P_to_RGB24(unsigned char *data, unsigned char *rgb, int width, int height)
{
    int index = 0;
    unsigned char *ybase = data;
    unsigned char *ubase = &data[width * height];
    unsigned char *vbase = &data[width * height * 5 / 4];
    for (int y = 0; y < height; y++) {
        for (int x = 0; x < width; x++) {
            //YYYYYYYYUUVV
            u_char Y = ybase[x + y * width];
            u_char U = ubase[y / 2 * width / 2 + (x / 2)];
            u_char V = vbase[y / 2 * width / 2 + (x / 2)];
            rgb[index++] = Y + 1.402 * (V - 128); //R
            rgb[index++] = Y - 0.34413 * (U - 128) - 0.71414 * (V - 128); //G
            rgb[index++] = Y + 1.772 * (U - 128); //B
        }
    }
}


//FFMPEG推流线程执行起始点
void Thread_ffmpgVideo::run()
{
    int ret,got_picture;
    while(1)
    {
        sleep(1);

    }
}

mainwindos.h代码：

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QImage>
#include <QThread>

extern "C"{
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <math.h>

#include <libavutil/avassert.h>
#include <libavutil/channel_layout.h>
#include <libavutil/opt.h>
#include <libavutil/mathematics.h>
#include <libavutil/timestamp.h>
#include <libavformat/avformat.h>
#include <libswscale/swscale.h>
#include <libswresample/swresample.h>
#include "libavdevice/avdevice.h"
#include "libavutil/imgutils.h"
#include "libavutil/intreadwrite.h"
#include "libavutil/opt.h"
#include "libavutil/pixdesc.h"
#include "libavutil/imgutils.h"
/*
FFmpeg多媒体设备交互的类库：Libavdevice。
使用这个库可以读取电脑（或者其他设备上）的多媒体设备的数据或者输出数据到指定的多媒体设备上。
*/
}

class MainWindow;
//线程类的子类化
class Thread_ffmpgVideo : public QThread
{
public:
    MainWindow *mianwindow;  //指向widget的指针
protected:
    void run();  //线程执行的函数
};

QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = nullptr);
    ~MainWindow();
    int FFMPEG_Init_Config();
    void YUV420P_to_RGB24(unsigned char *data, unsigned char *rgb, int width, int height);
private:
    Ui::MainWindow *ui;
};
#endif // MAINWINDOW_H

main.cpp:

#include "mainwindow.h"
#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();
    return a.exec();
}

.pro 工程文件

QT       += core gui

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

CONFIG += c++11

# The following define makes your compiler emit warnings if you use
# any Qt feature that has been marked deprecated (the exact warnings
# depend on your compiler). Please consult the documentation of the
# deprecated API in order to know how to port your code away from it.
DEFINES += QT_DEPRECATED_WARNINGS

# You can also make your code fail to compile if it uses deprecated APIs.
# In order to do so, uncomment the following line.
# You can also select to disable deprecated APIs only up to a certain version of Qt.
#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0

SOURCES += \
    main.cpp \
    mainwindow.cpp

HEADERS += \
    mainwindow.h

FORMS += \
    mainwindow.ui

# Default rules for deployment.
qnx: target.path = /tmp/$${TARGET}/bin
else: unix:!android: target.path = /opt/$${TARGET}/bin
!isEmpty(target.path): INSTALLS += target

#指定库的路径
unix:LIBS += -L$$PWD/ffmpeg_x264_lib/lib -lavcodec
unix:LIBS += -L$$PWD/ffmpeg_x264_lib/lib -lavfilter
unix:LIBS += -L$$PWD/ffmpeg_x264_lib/lib -lavutil
unix:LIBS += -L$$PWD/ffmpeg_x264_lib/lib -lavdevice
unix:LIBS += -L$$PWD/ffmpeg_x264_lib/lib -lavformat
unix:LIBS += -L$$PWD/ffmpeg_x264_lib/lib -lpostproc
unix:LIBS += -L$$PWD/ffmpeg_x264_lib/lib -lswscale
unix:LIBS += -L$$PWD/ffmpeg_x264_lib/lib -lswresample
unix:LIBS += -L$$PWD/ffmpeg_x264_lib/lib -lx264

#制定头文件的路径
INCLUDEPATH+=$$PWD/ffmpeg_x264_lib/include

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