在windows cpp 动态库读取test.mp4视频流到Windows窗口的离屏表面，在Qt调用该动态库。完整源码

以下是一个简单的示例代码，演示如何使用Windows动态库来读取视频流并在Qt中显示：

Windows动态库代码（video_player.cpp）：

#include <windows.h>
#include <d3d9.h>
#include <d3dx9.h>
#include "video_player.h"

#pragma comment(lib, "d3d9.lib")
#pragma comment(lib, "d3dx9.lib")

// 定义窗口宽高
#define WINDOW_WIDTH 640
#define WINDOW_HEIGHT 480

// 定义视频帧缓冲区大小
#define FRAME_SIZE (WINDOW_WIDTH * WINDOW_HEIGHT * 4)

// 全局变量
LPDIRECT3D9 g_pD3D;
LPDIRECT3DDEVICE9 g_pDevice;
LPDIRECT3DSURFACE9 g_pSurface;
BYTE* g_pFrameBuffer = NULL;

// 初始化Direct3D
bool InitD3D(HWND hWnd)
{
    g_pD3D = Direct3DCreate9(D3D_SDK_VERSION);
    if (!g_pD3D)
        return false;

    D3DPRESENT_PARAMETERS d3dpp;
    ZeroMemory(&d3dpp, sizeof(d3dpp));
    d3dpp.Windowed = TRUE;
    d3dpp.SwapEffect = D3DSWAPEFFECT_DISCARD;
    d3dpp.BackBufferFormat = D3DFMT_UNKNOWN;

    if (FAILED(g_pD3D->CreateDevice(D3DADAPTER_DEFAULT, D3DDEVTYPE_HAL, hWnd,
        D3DCREATE_SOFTWARE_VERTEXPROCESSING, &d3dpp, &g_pDevice)))
        return false;

    return true;
}

// 释放Direct3D资源
void ReleaseD3D()
{
    if (g_pSurface)
    {
        g_pSurface->Release();
        g_pSurface = NULL;
    }

    if (g_pDevice)
    {
        g_pDevice->Release();
        g_pDevice = NULL;
    }

    if (g_pD3D)
    {
        g_pD3D->Release();
        g_pD3D = NULL;
    }
}

// 创建离屏表面
bool CreateOffscreenSurface()
{
    HRESULT hr = g_pDevice->CreateOffscreenPlainSurface(WINDOW_WIDTH, WINDOW_HEIGHT, D3DFMT_X8R8G8B8,
        D3DPOOL_SYSTEMMEM, &g_pSurface, NULL);

    return SUCCEEDED(hr);
}

// 读取视频帧到离屏表面
bool LoadFrameToSurface(BYTE* pBuffer)
{
    D3DLOCKED_RECT LockedRect;
    HRESULT hr = g_pSurface->LockRect(&LockedRect, NULL, D3DLOCK_DISCARD);

    if (FAILED(hr))
        return false;

    BYTE* pDest = (BYTE*)LockedRect.pBits;
    int nDestPitch = LockedRect.Pitch;

    for (int y = 0; y < WINDOW_HEIGHT; ++y)
    {
        memcpy(pDest, pBuffer, WINDOW_WIDTH * 4);
        pBuffer += WINDOW_WIDTH * 4;
        pDest += nDestPitch;
    }

    hr = g_pSurface->UnlockRect();
    return SUCCEEDED(hr);
}

// 在窗口中显示离屏表面
void PresentOffscreenSurface(HWND hWnd)
{
    RECT rect;
    GetClientRect(hWnd, &rect);

    D3DXMATRIX matProj;
    D3DXMatrixOrthoOffCenterLH(&matProj, 0, (FLOAT)WINDOW_WIDTH, (FLOAT)WINDOW_HEIGHT, 0, 0, 1);
    g_pDevice->SetTransform(D3DTS_PROJECTION, &matProj);

    g_pDevice->StretchRect(g_pSurface, NULL, g_pDevice->GetBackBuffer(0, 0, D3DBACKBUFFER_TYPE_MONO), &rect, D3DTEXF_NONE);
}

// 打开视频文件，读取视频流并显示
bool PlayVideo(HWND hWnd, const char* szFileName)
{
    // 打开视频文件
    FILE* file = fopen(szFileName, "rb");
    if (!file)
        return false;

    fseek(file, 0, SEEK_END);
    int nFileSize = ftell(file);
    fseek(file, 0, SEEK_SET);

    // 初始化视频帧缓冲区
    g_pFrameBuffer = new BYTE[FRAME_SIZE];

    // 初始化Direct3D
    if (!InitD3D(hWnd))
        return false;

    // 创建离屏表面
    if (!CreateOffscreenSurface())
        return false;

    // 读取视频流
    while (true)
    {
        int nFrameSize;
        if (fread(&nFrameSize, sizeof(nFrameSize), 1, file) != 1)
            break;

        if (fread(g_pFrameBuffer, nFrameSize, 1, file) != 1)
            break;

        // 将视频帧加载到离屏表面
        if (!LoadFrameToSurface(g_pFrameBuffer))
            break;

        // 在窗口中显示离屏表面
        PresentOffscreenSurface(hWnd);

        // 等待一段时间，以便视频流显示更流畅
        Sleep(33);
    }

    // 释放资源
    delete[] g_pFrameBuffer;
    ReleaseD3D();
    fclose(file);

    return true;
}

Windows动态库头文件（video_player.h）：

#ifndef VIDEO_PLAYER_H
#define VIDEO_PLAYER_H

#include <windows.h>

// 播放视频
bool PlayVideo(HWND hWnd, const char* szFileName);

#endif // VIDEO_PLAYER_H

Qt代码（mainwindow.cpp）：

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

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

    // 创建按钮
    QPushButton* btnPlay = new QPushButton("Play", this);
    btnPlay->setGeometry(10, 10, 80, 30);
    connect(btnPlay, SIGNAL(clicked()), this, SLOT(OnBtnPlayClicked()));
}

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

// 点击播放按钮
void MainWindow::OnBtnPlayClicked()
{
    PlayVideo((HWND)winId(), "test.mp4");
}

请注意，此示例代码仅演示了如何在Windows和Qt中使用动态库读取视频流并在窗口中显示。实际应用中，您需要根据您的需求进行修改和调整。