（四）qt中使用ffmpeg播放视频，可暂停恢复

一、在qt中添加ffmpeg库及头文件

INCLUDEPATH += /usr/local/ffmpeg/include
LIBS += -L/usr/local/lib -lavutil -lavcodec -lavformat -lswscale

二、详细代码

FFempegVideoDecode 视频解码类（放入线程中）

ffmpegvideodecode.h

#ifndef FFMPEGVIDEODECODE_H
#define FFMPEGVIDEODECODE_H
#include 
#include 
#include 
#include 
struct AVCodec;
struct AVCodecContext;
struct AVFrame;
struct AVFormatContext;
struct SwsContext;
struct AVPacket;
class FFmpegVideoDecode : public QObject
{
    Q_OBJECT
public:
    explicit FFmpegVideoDecode(QObject *parent = nullptr);
    ~FFmpegVideoDecode();
    bool initFFmpeg(QString fileName);
    void clear();
private:
    void inputError(int ret, QString funName);
signals:
    void sigToStart();
    void sigToUpdateImage(const QImage &image);
public slots:
    void onStartPlay(QString name);
    void onStopPlay();
    void onFinish();
    void onUpdateRead();
private:
    AVFormatContext* pFormatCtx = nullptr;
    AVCodecContext* pCodecCtx = nullptr;
    AVFrame* pAvFrame = nullptr;
    AVFrame* pFrameRGB32 = nullptr;
    AVPacket* packet = nullptr;
    uint8_t *out_buffer = nullptr;
    SwsContext *img_convert_ctx = nullptr;
    int videoIndex;
    bool is_stop = false;
    bool is_finish = true;
};
#endif // FFMPEGVIDEODECODE_H

ffmpegvideodecode.cpp

#include "ffmpegvideodecode.h"
extern "C"
{
#include "libavutil/avutil.h"
#include "libavcodec/avcodec.h"
#include "libavformat/avformat.h"
#include "libswscale/swscale.h"
#include "libavutil/imgutils.h"
}
#include 
#include 
#include 
/**
 * @brief      非阻塞延时
 * @param msec 延时毫秒
 */
void  sleepMsec(int msec)
{
    if(msec duration / (AV_TIME_BASE / 1000); // 计算视频总时长（毫秒）
    qDebug() nb_streams; ++i)
    {
        if (pFormatCtx->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
            videoIndex = i;
            break;
        }
    }
    */
    if (videoIndex streams[videoIndex]->codecpar;
    /*
     * avcodec_find_decoder 通过解码器ID获取视频解码器（新版本返回值必须使用const）
    */
    const AVCodec* _pCodec = avcodec_find_decoder(parmeter->codec_id);
    if (_pCodec == NULL)
    {
        inputError(AVERROR_DECODER_NOT_FOUND,"avcodec_find_decoder");
        clear();
        return false;
    }
    /*
     * avcodec_alloc_context3 用于分配一个编解码器上下文（AVCodecContext）结构体
     * AVCodecContext结构的主要作用是设置编码过程的参数
    */
    pCodecCtx = avcodec_alloc_context3(_pCodec);//初始化一个编解码上下文
    /*
     * avcodec_parameters_to_context 该函数用于将流里面的参数，也就是AVStream里面的参数直接复制到AVCodecContext的上下文当中
    */
    ret = avcodec_parameters_to_context(pCodecCtx, parmeter);
    if (ret 对分配内存瓜分
    */
    int size = av_image_get_buffer_size(AV_PIX_FMT_RGB32, pCodecCtx->width, pCodecCtx->height,4);
    out_buffer = (uint8_t *)av_malloc(size);
    ret = av_image_fill_arrays(pFrameRGB32->data,pFrameRGB32->linesize, out_buffer, AV_PIX_FMT_RGB32, pCodecCtx->width, pCodecCtx->height,1);
    if (ret width * pCodecCtx->height);//分配packet的有效载荷并初始化其字段
    //qDebug() width, pCodecCtx->height, QImage::Format_RGB32);
                Q_EMIT sigToUpdateImage(image);
                //sleepMsec->非阻塞(点击播放可直接重头播放) QThread::msleep(40)->阻塞
                //方法1：由于子线程阻塞式延时读取视频帧，无法修改视频的暂停状态，可通过修改connect的连接方式在主线程中修改暂停状态
                QThread::msleep(40);
                //方法2：将子线程阻塞式延时修改未非阻塞式，可直接修改视频的暂停状态
//                sleepMsec(40);
            }
            /*
             * av_packet_free和av_packet_unref都是FFmpeg库中的函数，用于释放AVPacket结构体中的资源。
             * av_packet_free函数会释放AVPacket结构体中的所有资源，包括存储数据的缓冲区等。
             * av_packet_unref函数只会释放AVPacket结构体中的部分资源，例如释放存储数据的缓冲区等，但不会释放AVPacket结构体本身。
            */
            av_packet_unref(packet);
        }
        else
        {
            qDebug()moveToThread(thread_decode);
    connect(thread_decode,&QThread::finished,ffmpeg_decode,&FFmpegVideoDecode::deleteLater);
    connect(thread_decode,&QThread::finished,thread_decode,&QThread::deleteLater);
    connect(ffmpeg_decode,&FFmpegVideoDecode::sigToUpdateImage,this,&VideoPlayer::onUpdateImage);
    connect(this,&VideoPlayer::sigToStart,ffmpeg_decode,&FFmpegVideoDecode::onStartPlay);
    connect(this,&VideoPlayer::sigToFinish,ffmpeg_decode,&FFmpegVideoDecode::onFinish,Qt::DirectConnection);
    //方法1：由于子线程阻塞式延时读取视频帧，无法修改视频的暂停状态，可通过修改connect的连接方式在主线程中修改暂停状态
    connect(this,&VideoPlayer::sigToStop,ffmpeg_decode,&FFmpegVideoDecode::onStopPlay,Qt::DirectConnection);
    //方法2：将子线程阻塞式延时修改未非阻塞式，可直接修改视频的暂停状态
//    connect(this,&VideoPlayer::sigToStop,ffmpeg_decode,&FFmpegVideoDecode::onStopPlay);
    thread_decode->start();
}
VideoPlayer::~VideoPlayer()
{
    delete ui;
    Q_EMIT sigToFinish();
    thread_decode->quit();
    thread_decode->wait();
}
void VideoPlayer::onUpdateImage(const QImage &image)
{
    m_mutex.lock();
    pixmap_video = QPixmap::fromImage(image);
    m_mutex.unlock();
    update();
}
void VideoPlayer::paintEvent(QPaintEvent *event)
{
    if(!pixmap_video.isNull())
    {
        QPainter painter(this);
        m_mutex.lock();
        QPixmap pixmap = pixmap_video.scaled(this->size(), Qt::KeepAspectRatio);
        m_mutex.unlock();
        int x = (this->width() - pixmap.width()) / 2;
        int y = (this->height() - pixmap.height()) / 2;
        painter.drawPixmap(x, y, pixmap);
    }
    QWidget::paintEvent(event);
}

Widget类（主界面）

widget.h

#include "videoplayer.h"
#include "ui_videoplayer.h"
#include 
VideoPlayer::VideoPlayer(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::VideoPlayer)
{
    ui->setupUi(this);
    ffmpeg_decode = new FFmpegVideoDecode;
    thread_decode = new QThread;
    ffmpeg_decode->moveToThread(thread_decode);
    connect(thread_decode,&QThread::finished,ffmpeg_decode,&FFmpegVideoDecode::deleteLater);
    connect(thread_decode,&QThread::finished,thread_decode,&QThread::deleteLater);
    connect(ffmpeg_decode,&FFmpegVideoDecode::sigToUpdateImage,this,&VideoPlayer::onUpdateImage);
    connect(this,&VideoPlayer::sigToStart,ffmpeg_decode,&FFmpegVideoDecode::onStartPlay);
    connect(this,&VideoPlayer::sigToFinish,ffmpeg_decode,&FFmpegVideoDecode::onFinish,Qt::DirectConnection);
    //方法1：由于子线程阻塞式延时读取视频帧，无法修改视频的暂停状态，可通过修改connect的连接方式在主线程中修改暂停状态
    connect(this,&VideoPlayer::sigToStop,ffmpeg_decode,&FFmpegVideoDecode::onStopPlay,Qt::DirectConnection);
    //方法2：将子线程阻塞式延时修改未非阻塞式，可直接修改视频的暂停状态
//    connect(this,&VideoPlayer::sigToStop,ffmpeg_decode,&FFmpegVideoDecode::onStopPlay);
    thread_decode->start();
}
VideoPlayer::~VideoPlayer()
{
    delete ui;
    Q_EMIT sigToFinish();
    thread_decode->quit();
    thread_decode->wait();
}
void VideoPlayer::onUpdateImage(const QImage &image)
{
    m_mutex.lock();
    pixmap_video = QPixmap::fromImage(image);
    m_mutex.unlock();
    update();
}
void VideoPlayer::paintEvent(QPaintEvent *event)
{
    if(!pixmap_video.isNull())
    {
        QPainter painter(this);
        m_mutex.lock();
        QPixmap pixmap = pixmap_video.scaled(this->size(), Qt::KeepAspectRatio);
        m_mutex.unlock();
        int x = (this->width() - pixmap.width()) / 2;
        int y = (this->height() - pixmap.height()) / 2;
        painter.drawPixmap(x, y, pixmap);
    }
    QWidget::paintEvent(event);
}

widget.cpp

#include "widget.h"
#include "ui_widget.h"
#include 
Widget::Widget(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::Widget)
{
    ui->setupUi(this);
    player = new VideoPlayer(ui->widget_play);
    ui->horizontalLayout->addWidget(player);
}
Widget::~Widget()
{
    delete ui;
}
void Widget::on_pushButton_start_clicked()
{
    Q_EMIT player->sigToFinish();
    Q_EMIT player->sigToStart(ui->lineEdit_path->text());
    ui->pushButton_stop->setText("暂停");
}
void Widget::on_pushButton_stop_clicked()
{
    Q_EMIT player->sigToStop();
    if(ui->pushButton_stop->text() == "暂停")
        ui->pushButton_stop->setText("恢复");
    else if(ui->pushButton_stop->text() == "恢复")
        ui->pushButton_stop->setText("暂停");
}
void Widget::on_pushButton_select_clicked()
{
    QString fileName = QFileDialog::getOpenFileName(this, tr("Open File"),
      "/home",
      tr("Video (*.mp4 *.flv)"));
    if(fileName.isEmpty()) return;
    ui->lineEdit_path->setText(fileName);
    qDebug()