利用qt基于ffmpeg写出一个视频播放界面，包括所有需要的文件

实现视频播放界面需要用到Qt和FFmpeg库。下面是一个简单的Qt视频播放器的示例代码，包括所有需要的文件。

首先，创建一个Qt项目，然后将以下文件添加到项目中：

1. main.cpp

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

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

2. mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QTimer>
#include "videoplayer.h"

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();

private slots:
    void on_actionOpen_triggered();
    void updatePlayer();

private:
    Ui::MainWindow *ui;
    VideoPlayer *player;
    QTimer *timer;
};

#endif // MAINWINDOW_H

3. mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QFileDialog>

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    player = new VideoPlayer(this);
    ui->centralWidget->layout()->addWidget(player);
    timer = new QTimer(this);
    connect(timer, SIGNAL(timeout()), this, SLOT(updatePlayer()));
    timer->start(40);
}

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

void MainWindow::on_actionOpen_triggered()
{
    QString fileName = QFileDialog::getOpenFileName(this, tr("Open Video"), "/", tr("Video Files (*.avi *.mp4 *.flv)"));
    if (!fileName.isEmpty())
        player->openFile(fileName);
}

void MainWindow::updatePlayer()
{
    player->update();
}

4. videoplayer.h

#ifndef VIDEOPLAYER_H
#define VIDEOPLAYER_H

#include <QWidget>
#include "libavcodec/avcodec.h"
#include "libavformat/avformat.h"
#include "libswscale/swscale.h"

class VideoPlayer : public QWidget
{
    Q_OBJECT
public:
    explicit VideoPlayer(QWidget *parent = 0);
    ~VideoPlayer();

    bool openFile(QString fileName);
    void update();

private:
    AVFormatContext *formatCtx;
    AVCodecContext *codecCtx;
    AVCodec *codec;
    AVFrame *frame;
    AVPicture picture;
    int videoStream;
    struct SwsContext *swsCtx;
    QTimer *timer;
    QImage image;

    void free();
};

#endif // VIDEOPLAYER_H

5. videoplayer.cpp

#include "videoplayer.h"
#include <QTimer>
#include <QDebug>

VideoPlayer::VideoPlayer(QWidget *parent) :
    QWidget(parent),
    formatCtx(NULL),
    codecCtx(NULL),
    codec(NULL),
    frame(NULL),
    swsCtx(NULL),
    timer(NULL)
{
}

VideoPlayer::~VideoPlayer()
{
    free();
}

bool VideoPlayer::openFile(QString fileName)
{
    free();

    formatCtx = avformat_alloc_context();
    if (avformat_open_input(&formatCtx, fileName.toUtf8().data(), NULL, NULL) != 0)
        return false;
    if (avformat_find_stream_info(formatCtx, NULL) < 0)
        return false;

    videoStream = -1;
    for (unsigned int i = 0; i < formatCtx->nb_streams; ++i)
    {
        if (formatCtx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO)
        {
            videoStream = i;
            break;
        }
    }
    if (videoStream == -1)
        return false;

    codecCtx = formatCtx->streams[videoStream]->codec;
    codec = avcodec_find_decoder(codecCtx->codec_id);
    if (codec == NULL)
        return false;
    if (avcodec_open2(codecCtx, codec, NULL) < 0)
        return false;

    frame = avcodec_alloc_frame();
    avpicture_alloc(&picture, PIX_FMT_RGB24, codecCtx->width, codecCtx->height);

    swsCtx = sws_getContext(codecCtx->width, codecCtx->height, codecCtx->pix_fmt,
                            codecCtx->width, codecCtx->height, PIX_FMT_RGB24,
                            SWS_BILINEAR, NULL, NULL, NULL);

    image = QImage(codecCtx->width, codecCtx->height, QImage::Format_RGB888);

    return true;
}

void VideoPlayer::update()
{
    if (formatCtx == NULL || codecCtx == NULL || frame == NULL || swsCtx == NULL)
        return;

    AVPacket packet;
    while (av_read_frame(formatCtx, &packet) >= 0)
    {
        if (packet.stream_index == videoStream)
        {
            int frameFinished;
            avcodec_decode_video2(codecCtx, frame, &frameFinished, &packet);
            if (frameFinished)
            {
                sws_scale(swsCtx, frame->data, frame->linesize, 0, codecCtx->height, picture.data, picture.linesize);
                image = QImage(picture.data[0], codecCtx->width, codecCtx->height, QImage::Format_RGB888);
            }
        }
        av_free_packet(&packet);
    }

    if (!image.isNull())
        this->update();
}

void VideoPlayer::free()
{
    if (formatCtx)
    {
        avformat_close_input(&formatCtx);
        formatCtx = NULL;
    }

    if (codecCtx)
    {
        avcodec_close(codecCtx);
        codecCtx = NULL;
    }

    if (frame)
    {
        av_free(frame);
        frame = NULL;
    }

    avpicture_free(&picture);

    if (swsCtx)
    {
        sws_freeContext(swsCtx);
        swsCtx = NULL;
    }
}

这个简单的示例代码可以让你通过QT界面显示视频文件。请注意，这个示例代码没有处理音频，只能显示视频内容。如果你想要增加音频，你需要添加更多的代码。