如何修改Elgato Game Capture HD的.dll实现录制前存删提示功能？

Hey there! Let's break down how you can tackle this problem since you already have C++ skills—great start! Here's a step-by-step guide to get you going:

1. First, map out the software's core workflow #

You need to identify which DLL in Elgato Game Capture HD handles video file writing to the disk. Start with these steps:

• Use tools like Dependency Walker or x64dbg to scan the software's DLL dependencies. Look for modules related to file I/O or recording logic (likely named something like GameCaptureHD.dll or similar).
• Track the software's behavior with Process Monitor: Watch for calls to Win32 APIs like CreateFile or WriteFile when a recording starts. This will tell you exactly when the software begins writing a new video file—your trigger point for the prompt.

2. Use API Hooking to insert your logic #

The most reliable way to inject your prompt before the software writes a video is API hooking—intercepting the software's calls to key system functions and inserting your code. Here's what you need to know:

• Pick a mature hooking library to avoid reinventing the wheel: MinHook (lightweight, open-source) or Microsoft's Detours (well-documented for Windows) are both great choices.
• Target the right API: Focus on CreateFileW (since most modern software uses wide-character paths) — this is the function the software will call to create a new video file.

3. Write your hook logic (C++ framework) #

Here's a simplified outline of what your code would look like:

// Include necessary headers (MinHook/Detours, Windows.h)
#include <Windows.h>
#include "MinHook.h"

// Define the original function pointer
typedef HANDLE(WINAPI* pCreateFileW)(LPCWSTR, DWORD, DWORD, LPSECURITY_ATTRIBUTES, DWORD, DWORD, HANDLE);
pCreateFileW OriginalCreateFileW = nullptr;

// Your hooked function
HANDLE WINAPI HookedCreateFileW(LPCWSTR lpFileName, DWORD dwDesiredAccess, DWORD dwShareMode, LPSECURITY_ATTRIBUTES lpSecurityAttributes, DWORD dwCreationDisposition, DWORD dwFlagsAndAttributes, HANDLE hTemplateFile)
{
    // Check if this is a new recording file (match file extension like .mp4/.mov, or path to Elgato's recording folder)
    if (wcsstr(lpFileName, L".mp4") != nullptr && wcsstr(lpFileName, L"Elgato") != nullptr)
    {
        // Show prompt to user
        int result = MessageBoxW(nullptr, L"Delete previous recording?", L"Elgato Recording Prompt", MB_YESNOCANCEL | MB_ICONQUESTION);
        
        if (result == IDYES)
        {
            // Delete the old recording (you'll need to hardcode or fetch the path to previous files)
            DeleteFileW(L"C:\\Users\\YourUser\\Documents\\Elgato\\OldRecording.mp4");
        }
        else if (result == IDCANCEL)
        {
            // Cancel the recording by returning an invalid handle
            return INVALID_HANDLE_VALUE;
        }
        // If IDNO, just proceed to create the new file
    }

    // Call the original function
    return OriginalCreateFileW(lpFileName, dwDesiredAccess, dwShareMode, lpSecurityAttributes, dwCreationDisposition, dwFlagsAndAttributes, hTemplateFile);
}

// Initialize the hook when your DLL is loaded
BOOL APIENTRY DllMain(HMODULE hModule, DWORD ul_reason_for_call, LPVOID lpReserved)
{
    switch (ul_reason_for_call)
    {
        case DLL_PROCESS_ATTACH:
            // Initialize MinHook and hook CreateFileW
            MH_Initialize();
            MH_CreateHook(&CreateFileW, &HookedCreateFileW, reinterpret_cast<LPVOID*>(&OriginalCreateFileW));
            MH_EnableHook(&CreateFileW);
            break;
        case DLL_PROCESS_DETACH:
            // Clean up the hook
            MH_DisableHook(&CreateFileW);
            MH_Uninitialize();
            break;
    }
    return TRUE;
}

• Key notes: You'll need to adjust the file path checks to match Elgato's default recording directory, and handle edge cases like multiple old files.

4. Inject your DLL into Elgato's process #

To make your code run alongside the Elgato software, you need to inject your compiled DLL into its process:

• Manual injection: Use tools like Process Hacker, or write a simple injector using CreateRemoteThread and LoadLibraryW to load your DLL into the Elgato process.
• Automatic injection: For convenience, you can modify the Elgato main executable's import table to load your DLL on startup, or use the AppInit_DLLs registry key (note: modern Windows versions have restrictions on this method).

5. Critical things to keep in mind #

• EULA compliance: Modifying commercial software's DLLs may violate Elgato's End User License Agreement. Be sure to review it first to avoid legal issues.
• Software updates: If Elgato pushes an update, their DLL structure or API calls might change—you may need to rework your hook logic to match.
• Debugging: Use x64dbg or Visual Studio to attach to the Elgato process and debug your DLL. This will help you fix issues like incorrect path detection or hook failures.

内容的提问来源于stack exchange，提问作者Chase Burleson