[3.8.1] Transport Control - VST 3 Developer Portal

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[3.8.1] Transport Control

On this page:

Introduction
Example

Related pages:

Example plug-in: Transport Control

Introduction

This interface Vst:: ITransportControl allows a plug-in to request transport-related actions from the host.

[host imp]
[extends Vst:: IComponentHandler]
[released: 3.8.1]
[optional]

Typical use cases include:

Jumping (locating) to a position
Starting or stopping playback or recording
Adjusting loop/cycle regions
Enabling or disabling cycle playback

All calls must be made from the UI thread. Hosts may accept or deny requests depending on their internal policies or the current editing mode (e.g., offline rendering, write-protected state, etc.).

Enumerator	Description
Locate	Locate transport to a new position. Requires a valid `TransportPosition`.
PlaybackStart	Start playback at the current position.
PlaybackStop	Stop playback and keep the current position.
LocateAndPlaybackStart	Locate to the specified position and start playback (position required).
PlaybackStopAndLocate	Stop playback and locate to the specified position (position required).
RecordOnPlaybackStart	Start recording and playback at the current position.
LocateAndRecordOnPlaybackStart	Locate to the specified position and start recording and playback (position required).
RecordOff	Stop recording and continue playback.
RecordOffPlaybackStop	Stop recording and playback and keep the current position.
RecordOffPlaybackStopAndLocate	Stop recording and playback, then locate to the specified position (position required).
SetCycleStart	Sets the first sample included in the cycle region (position required).
SetCycleEnd	Sets the sample position immediately after the end of the cycle region (exclusive end position, position required). The cycle length in samples is `end - start`. For example, `SetCycleStart(100)` and `SetCycleEnd(200)` define a cycle of 100 samples. Sample positions included in the cycle are `{100 ... 199}`, while sample position `200` is outside the cycle.
CycleOn	Enable looping/cycle mode.
CycleOff	Disable looping/cycle mode.

Example

In mycontroller.cpp

bool mycontroller::startPlayback ()
{
    // the hostContext was given in the function ComponentBase::initialize (FUnknown* context)
    if (!hostContext)
        return false;

    Vst::ITransportControl* transportControl = nullptr;
    hostContext->queryInterface (Vst::ITransportControl::iid, (void**)&transportControl);

	if (transportControl && transportControl->isActionSupported (Vst::ITransportControl::PlaybackStart) == kResultTrue)
	{
        transportControl->requestAction (Vst::ITransportControl::PlaybackStart);
        return true;
    }
    return false;
}