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Q: How is a normalized value converted to a discrete integer value in VST 3?

A detailed description of parameter handling is provided here: Parameters.

Q: What is the return value tresult?

Almost all VST 3 interfaces return a tresult value. This integer value allows to return to the caller more differentiated error/success information than just a boolean value with its true and false.

The various possible values are defined in funknown.h. They are the same values as used in COM. Be careful when checking a tresult return value, because on success kResultOk is returned which has the integer value 0:

// this is WRONG!!!!!
if (component->setActive (true))
// this is CORRECT!!!!!
if (component->setActive (true) == kResultOK)
// or
// this is CORRECT too!!!!!
if (component->setActive (true) != kResultOK)
    // error message....

Q: Which version of Steinberg Sequencers support VST 3?

In order to load VST 3 plug-ins you need at least:

  • For VST 3.0.0 Cubase/Nuendo 4.1.2 is needed.
  • For VST 3.0.1 features Cubase 4.2 is needed.
  • For VST 3.5.0 features Cubase 6.0 is needed.
  • see other VST 3 Hosts

Q: Why do plug-ins need subcategories?

When you export your plug-in in the factory instance (check againentry.cpp: DEF_CLASS2), you have to define a subcategory string (can be a combination of more than one string: like "Fx|Dynamics|EQ" for example).

Currently the subcategory string is used by Cubase/Nuendo to organize the plug-ins menu in the following way:

// Computation of Folder Name (SubCategories => folder in menu)
"Fx"                        => "Other"
"Fx|Delay"                  => "Delay"
"Fx|Mastering|Delay"        => "Mastering"
"Spatial|Fx"                => "Spatial"
"Fx|Spatial"                => "Spatial"
"Instrument|Fx"             => if used as VSTi "" else if used as Insert "Other"
"Instrument|Sampler"        => "Sampler"
"Fx|Mastering|Surround"     => "Mastering\Surround"
"Fx|Mastering|Delay|Stereo" => "Mastering\Stereo"
"Fx|Mastering|Mono"         => "Mastering\Mono"

This string should only be a hint what type of plug-in it is. It's not possible to define all types. If you have wishes for new categories, please discuss them in the VST Developer Forum (https://sdk.steinberg.net) and we can add them to future versions of the SDK.

Q: Is it possible to define a plug-in as Fx and Instrument?

Yes it is possible, you can use the CString kFxInstrument ("Fx|Instrument") as subcategories (check DEF_CLASS2). In this case Steinberg Sequencers will allow the user to load it as an effect and as an instrument. The plug-in as instrument (in case of current Steinberg Sequencers <= 5.5) will not enable the Audio Input busses.

Q: Is it possible to ask a plug-in about which speaker arrangements are supported?

No, not before the plug-in is instantiated, there is no way to ask the factory about which arrangements are supported for a given plug-in. The host can instantiate the plug-in and before start processing then set some different speaker Arrangements and check if the plug-in supports them.

Q: Which version of Steinberg Sequencers support VST 3 Note Expression?

In order to use Note Expression with VST 3 plug-ins you need at least Cubase/Nuendo 6.0.

Q: When compiling for Mac AudioUnit, I have a compiler error in AUCarbonViewBase.cpp. What can I do?

Due to an issue in the Mac CoreAudio SDK, not yet fixed by Apple, you have to apply a small patch to the file AUCarbonViewBase.cpp (located in CoreAudio/AudioUnits/AUPublic/AUCarbonViewBase):
=> Change:

HISize originalSize = { mBottomRight.h, mBottomRight.v };
// to
HISize originalSize = { static_cast<CGFloat>(mBottomRight.h),
                        static_cast<CGFloat>(mBottomRight.v) };

Q: How can I develop a SurroundPanner plug-in which is integrated in Nuendo as Panner?

In order to make a surroundPanner plug-in selectable as panner (Post-fader) in Nuendo, this plug-in should have as subCategories: kSpatial or kSpatialFx (in order to use it as insert too). For example:

DEF_CLASS2 (INLINE_UID_FROM_FUID(Steinberg::Vst::SPannerProcessor::cid),
            Vst::PlugType::kSpatial ,
            FULL_VERSION_STR, // plug-in version (to be changed)

Be sure that you overwrite the function "tresult PLUGIN_API setBusArrangements ..." which allows you to get the current bus arrangements.

Q: How can I validate my plug-in?

You have the Validator command line which can be automatically called after you compile your plug-in (when you use the cmake defined by the SDK). This will apply some standard validations. The 2cd validation tool is the VST 3 plug-in Test Host: check its menu entry: View => Open plug-in Unit Tests Window

You have to adapt your Windows right access to allow creation of symbolic links for VST 3 plug-ins: Check HERE!

Q: My generated VST 3 plug-in is not visible in my preferred host?

If your plug-in is visible in the VST 3 plug-in Test Host but not in your DAW, this is maybe due to the fact:

  • this host could not resolve symbolic link! You could try to copy your plug-in directly in the main VST3 folder (C:\Program Files\Common Files\VST3)

Q: What is a GUID and how can I create it?

GUID is a 32 hexadecimal digits. VST 3 uses GUID (aka UUID) to identify a plug-in (one for the processor and one for the controller). These Globally Unique IDentifiers have to be generated when you create new plug-in and they should be unique. Here an example of GUID: (0x84E8DE5F, 0x92554F53, 0x96FAE413, 0x3C935A18)

This has to be used in the declaration of your processor part like here in the AGain example (againentry.cpp):

static const FUID AGainProcessorUID (0x84E8DE5F, 0x92554F53, 0x96FAE413, 0x3C935A18);

BEGIN_FACTORY_DEF (stringCompanyName, stringCompanyWeb, stringCompanyEmail)
	//---First plug-in included in this factory-------
	// its kVstAudioEffectClass component
                PClassInfo::kManyInstances,	// cardinality
				kVstAudioEffectClass,	// the component category
				stringPluginName,		// here the plug-in name
				AGainVST3Category,		// Subcategory
				FULL_VERSION_STR,		// Plug-in version
				kVstVersionString,		// the VST 3 SDK version

If you use the VST 3 Project Generator, new GUIDs will be generated automatically for you. You could use your IDE (like Visual Studio) to create GUID or use some online generators (for example: https://guidgenerator.com/).

GUIDs are also used as interface identifier in VST 3 (check in the VST SDK source code where the macro DECLARE_CLASS_IID is used).