How to install MetaAudio on Half-Life (25th Anniversary update) - Restore EAX/A3D Audio

How to install MetaAudio on Half-Life (post-25th anniversary update)

The content on this Pastebin may be changed in future, the W.I.P version of the plugins now works with 25th anniversary. See the GitHub issues here: https://github.com/LAGonauta/MetaAudio/issues/57

WARNING: You cannot play any servers with VAC Enabled if you launch the game with MetaHook/MetaHookSv.

Step 1. Download MetaHookSv (latest version): https://github.com/hzqst/MetaHookSv/releases

Step 2. Download the work-in-progress version at https://github.com/LAGonauta/MetaAudio/actions (Actions tab)
Select the most recent one on Actions tab > Under Artifacts > Click on MetaAudio, and it will be downloaded automatically.

Step 3. Extract everything on MetaHookSv to a folder, go to "MetaHookSv-windows-x86\Build\valve" folder,
DELETE the "resource" folder, this will avoid breaking the Video Options, hiding the new "Enable texture filtering".
then run "install-to-HalfLife.bat"
Wait and then, close the Notepad window that opens up the plugins.lst file (used to add dll plugins). There should be a shortcut to launch MetaHook ("MetaHook for HalfLife") near the extracted folder.

If you forgot to remove that folder, don't worry, you can just verify the game files.

Step 4. Open MetaAudio.zip, then go to "Release" folder > drop MetaAudio.dll to "...\Steam\steamapps\common\Half-Life\valve\metahook\plugins" folder (if its doesnt exist, create one)

Step 5. Go to "...\common\Half-Life\valve\metahook\configs" and open plugins.lst, replace everything or keep everything, and type metaaudio.dll (or copy paste) on the top, save.

Step 6. Edit the shortcut ("MetaHook for HalfLife") by right click > Properties > Put +al_doppler 0.3 after the end of the Target. It should look like this: "...\Steam\steamapps\common\Half-Life\metahook.exe -insecure -game valve +al_doppler 0.3"

Launch the game on the "MetaHook for HalfLife" shortcut and it should work.

This will also fix the low quality audio on the restored Valve intro.

### KNOWN ISSUES
- This may not work on Goldberg Emu, only legit copy of the game (including free to keep during Nov 17 to Nov 20). Launch the executable on the shortcut instead.
- Valve may update the game at any time, which could break MetaHookSv. Wait for them to be updated and download the latest version and install it again.
A small detail this guide misses is that the current versions (as of October 2024) of Meta Audio don't include the sndlib.dll file that is necessary for it to work and it needs to de downloaded separately from another github: https://github.com/libsndfile/libsndfile
This guide doesnt work for me. When trying to open MetaHook for HalfLife file it throws a error message MH_LoadEngine: Failed to locate Videomode_Searchbase.
I think the error message was due to running Half Life in software mode. Switched it to Opengl and now the error message doesnt show up but ultimately nothing happens when executing MetaHook for HalfLife file.
Ok I managed to make it work (this will be my last post, I promise!). It's very important that you use the SND file that can be found on the latest uplodaded version of Metaaudio by Lagonauta (dated 19/12/2023). Using the SND file mentioned by user MRPIRATEFOX in the first post just did not work for me. It needs to be placed on the Half Life folder (where the .exe is located).