SC4 Background Audio Fix  1.0.0

SimCity 4 Background Audio Fix
SC4 Background Audio Fix is a small DLL mod for SimCity 4 Deluxe that allows the game’s music and sound effects to keep playing while the game is not focused, such as when Alt-Tabbing to another window.

WHAT IT DOES:

1. Allows SC4 audio/music to continue while tabbed out
2. Works without modifying SimCity 4.exe
3. Does not replace game audio files
4. Can be removed by deleting the DLL

HOW IT WORKS:
The fix is a 32-bit DirectSound proxy. It loads the real Windows DirectSound library, forwards the normal API calls, and applies three compatibility changes for SimCity 4:

1. Secondary sound buffers are allowed to continue playing globally.
2. Exclusive DirectSound requests are reduced to priority-level access.
3. Focus-loss messages that cause SC4 to pause its own audio stream are hidden from the game. Focus-gain messages are delivered normally when you return.
 

MANUAL INSTALLATION:

1. Close SimCity 4.
2a. If on Steam, right-click SimCity 4 Deluxe and select Manage → Browse local files
2b. If on GOG, right-click SimCity 4 Deluxe and select Manage Installation → Show folder
3. Open the Apps folder.
4. Place dsound.dll and sc4-background-audio.ini beside SimCity 4.exe.
5. Launch the game normally through Steam.

!! IMPORTANT INSTALLATION NOTE !!

This is a DirectSound proxy, not a standard SC4 plugin DLL. Do not place it in SimCity 4 Plugins folder.

Never replace, rename, or remove the Windows system copy of dsound.dll. Only use the local copy placed beside SimCity 4.exe.

MANUAL UNINSTALL/REMOVAL:
Remove the following files from the 'Apps' folder containing SimCity 4.exe:
- dsound.dll
- sc4-background-audio.ini
- sc4-background-audio.log, if diagnostic logging was enabled in sc4-background-audio.ini

Removing the local files completely restores the game's original behavior.

CONFIGURATION:
The settings are stored in sc4-background-audio.ini:
- GlobalFocus=1
Allows secondary DirectSound buffers to continue while SC4 is unfocused.

- DowngradeExclusive=1
Prevents SC4 from taking exclusive ownership of DirectSound.

- HideFocusLoss=1
Prevents SC4's task-switch handler from pausing its audio stream.

- Logging=0
Diagnostic logging is disabled by default. Change this to Logging=1 when troubleshooting. The resulting sc4-background-audio.log file is written beside the DLL and grows while the game remains open.

COMPATIBILITY AND LIMITATIONS:
- Windows only. The DLL is 32-bit because SimCity 4 is a 32-bit game.
- The fix cannot coexist with another wrapper named dsound.dll in the same directory.
- Hiding focus loss may allow the simulation to continue while SC4 is in the background. Pause the game before switching applications when necessary.
- Steam and GOG releases have been tested. Any other Windows releases remain unverified.

TROUBLESHOOTING:
If the fix has no effect:

1. Confirm that dsound.dll is directly beside SimCity 4.exe in the Apps folder, rather than in Plugins or the main installation folder.
2. Confirm that the file is still named dsound.dll.
3. Check for another DirectSound wrapper or compatibility tool using the same filename.
4. Set Logging=1 in sc4-background-audio.ini, restart SC4, reproduce the problem, and inspect sc4-background-audio.log.

If SC4 stops launching after installation, remove the local dsound.dll and INI file to restore the original configuration.