# System.unloadplugin(uint handle) not working **URL:** \ **Category:** FMOD Engine\ **Created:** [March 21, 2020, 12:24am UTC](https://qa.fmod.com/t/system-unloadplugin-uint-handle-not-working/15565 "2020-03-21T00:24:57Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![spootymilk](https://avatars.discourse-cdn.com/v4/letter/s/9fc348/32.png) [@spootymilk](https://qa.fmod.com/u/spootymilk)\ **Post date:** [March 21, 2020, 12:24am UTC](https://qa.fmod.com/t/system-unloadplugin-uint-handle-not-working/15565/1 "2020-03-21T00:24:57Z")
Hi, I’m creating a dsp using the system.loadplugin() (it is a .dll VST2 plugin) I call after that createDSPPlugin(). Everything is working as expected. When i call the system.unloadPlugin() it seems it does not unload it. I mean FMOD returns FMOD.RESULTS.OK but i can still access the handle with an external tool that communicates with the VST. Is this a bug ? Is there any other options to destroy a plugin handle ? ---
**Author:** ![spootymilk](https://avatars.discourse-cdn.com/v4/letter/s/9fc348/32.png) [@spootymilk](https://qa.fmod.com/u/spootymilk)\ **Post date:** [March 27, 2020, 11:35am UTC](https://qa.fmod.com/t/system-unloadplugin-uint-handle-not-working/15565/2 "2020-03-27T11:35:19Z")
I need help ! It make crash the Unity Editor and my software because i need to destroy an recreate my FMOD system and reload the vst plugin. By doing that it spaw one instance of the vst each time i destroy and recreate the FMOD system ! I need to destroy the FMOD system because I need to go from RAW mode to automatic mode to be able to use 3d sounds positionning… ---
**Author:** ![cameron-fmod](https://yyz2.discourse-cdn.com/flex036/user_avatar/qa.fmod.com/cameron-fmod/32/261_2.png) [@cameron-fmod](https://qa.fmod.com/u/cameron-fmod)\ **Post date:** [March 31, 2020, 4:29am UTC](https://qa.fmod.com/t/system-unloadplugin-uint-handle-not-working/15565/3 "2020-03-31T04:29:59Z")
What version of FMOD are you using? If you try to access the handle, through FMOD, after it has been unload you should get `FMOD_ERR_PLUGIN_MISSING`. ---
**Author:** ![spootymilk](https://avatars.discourse-cdn.com/v4/letter/s/9fc348/32.png) [@spootymilk](https://qa.fmod.com/u/spootymilk)\ **Post date:** [March 31, 2020, 10:31am UTC](https://qa.fmod.com/t/system-unloadplugin-uint-handle-not-working/15565/4 "2020-03-31T10:31:26Z")
Hi Cameron ! I’m using FMOD Studio 2.00.04 when i destroy the System here is the code i execute before : ``` if (0 != Handle) { FMOD.RESULT result; do { CoreSystem.update(); result = CoreSystem.unloadPlugin(Handle); } while (result == FMOD.RESULT.ERR_DSP_INUSE); } else Debug.LogWarning("No handle so no need to clean it !"); FMOD.RESULT test = CoreSystem.createDSPByPlugin(Handle, out FMOD.DSP dsp); Debug.LogError(test); ``` The last Debug.LogError says exactly what you expectec : `FMOD_ERR_PLUGIN_MISSING` . ---
**Author:** ![cameron-fmod](https://yyz2.discourse-cdn.com/flex036/user_avatar/qa.fmod.com/cameron-fmod/32/261_2.png) [@cameron-fmod](https://qa.fmod.com/u/cameron-fmod)\ **Post date:** [April 2, 2020, 2:38am UTC](https://qa.fmod.com/t/system-unloadplugin-uint-handle-not-working/15565/5 "2020-04-02T02:38:10Z")
That is expected. What is the issue? ---
**Author:** ![spootymilk](https://avatars.discourse-cdn.com/v4/letter/s/9fc348/32.png) [@spootymilk](https://qa.fmod.com/u/spootymilk)\ **Post date:** [April 6, 2020, 11:09am UTC](https://qa.fmod.com/t/system-unloadplugin-uint-handle-not-working/15565/6 "2020-04-06T11:09:33Z")
Hi Cameron, The issue is that the instance of the VST seams to continue to be active some how. Any way i try to find a workaround. Now i need to destroy it because i need to reset FMOD (destroy and create system again) to detect output changes. I’m trying to avoid to reset FMOD completly. This is the only part where i’ve not found a solution. i’ve implemented the callbacks for that. It return all the time a FMOD.SYSTEM\_CALLBACK\_TYPE.RECORDLISTCHANGED but not very often the FMOD.SYSTEM\_CALLBACK\_TYPE.DEVICELISTCHANGED… it seams that the recordlistchanged trigger because of the loopback of the outputs… and i need to detect both changes. Is there a way to make FMOD detect DeviceListChanged and the Driver order to reset (to use with System.SetDriver()) ? ``` [AOT.MonoPInvokeCallback(typeof(FMOD.SYSTEM_CALLBACK))] static FMOD.RESULT DevicesChangedCallback(IntPtr system, FMOD.SYSTEM_CALLBACK_TYPE type, IntPtr commanddata1, IntPtr commanddata2, IntPtr userdata) { lock (callback_lock) { if (userdata != IntPtr.Zero) { Debug.Log($"FMOD Devices has Changed {type}"); GCHandle objecthandle = GCHandle.FromIntPtr(userdata); var manager = (objecthandle.Target as FMODCallBacksParameters); switch (type) { case FMOD.SYSTEM_CALLBACK_TYPE.DEVICELISTCHANGED: manager.HS_OutputDevicesChanged = true; break; case FMOD.SYSTEM_CALLBACK_TYPE.RECORDLISTCHANGED: manager.HS_InputDevicesChanged = true; break; } } } return FMOD.RESULT.OK; } ``` FInally, i’ve found a workaround. The callbacks seams not working properly. Here is my solution to run in the FixedUpdate() in Unity : ``` public static bool CheckOutputListChange() { result = FMODLowLevelSystems[ECanal.Canal1].getNumDrivers(out int NumDrivers); ERRCHECK(result, instance.name); if (instance.DevicesName.Count == NumDrivers || !isFMODInit) return false; else return true; } public static bool CheckInputListChange() { result = FMODLowLevelSystems[ECanal.Canal1].getRecordNumDrivers(out _, out int NumConnected); ERRCHECK(result, instance.name); if (instance.RecordDevicesName.Count == NumConnected || !isFMODInit) return false; else return true; } ``` ---
**Author:** ![cameron-fmod](https://yyz2.discourse-cdn.com/flex036/user_avatar/qa.fmod.com/cameron-fmod/32/261_2.png) [@cameron-fmod](https://qa.fmod.com/u/cameron-fmod)\ **Post date:** [April 8, 2020, 6:04am UTC](https://qa.fmod.com/t/system-unloadplugin-uint-handle-not-working/15565/7 "2020-04-08T06:04:15Z")
> [@spootymilk](#): > > The issue is that the instance of the VST seams to continue to be active some how. If you were to try to release a plugin while it is in use you will get an error (`FMOD_ERR_DSP_INUSE`), and if you try to use a plugin after it has been released you will get (`FMOD_ERR_PLUGIN_MISSING`). I’m not sure how it is still active. Are you able to send us a project that reproduces this? > [@spootymilk](#): > > Is there a way to make FMOD detect DeviceListChanged and the Driver order to reset (to use with System.SetDriver()) ? `FMOD.SYSTEM_CALLBACK_TYPE.DEVICELISTCHANGED` should be doing this, otherwise that could be a bug. > Using [`FMOD_SYSTEM_CALLBACK_DEVICELISTCHANGED`](https://fmod.com/resources/documentation-api?version=2.0&page=core-api-system.html#fmod_system_callback_devicelistchanged) (Windows only) will disable any automated device ejection/insertion handling. Use this callback to control the behavior yourself.