Real-time preview of effects

Peter 03Jan15: I added an H2 section for text-based RTP controls and made some changes to the existing page.

ToDo-2 Please review.

Some types of effects in Audacity support real-time preview. These types are: LADSPA, VST, and Audio Unit effects.

Effects that support real-time preview are different from regular effects in the following ways:

• They can be opened when audio is playing or paused
• They can be opened even when no audio is selected
• The effect settings can be changed while audio is playing
• You can start and stop audio playback, change the selection, and solo or mute tracks while the effect dialog is open
• You will hear the effected track in the context of the mix

Real-Time preview with graphical icon-based controls

• Bill 04Jan2015: ToDo-1 We need a new image of the "control panel" of a VST effect in graphical mode. We may also want an example of a LADSPA effect in text mode.

When you open an effect that supports real-time preview with graphical buttons it will have these icons at the bottom of the effect dialog.

•   Manage Effect menu:
  • User presets: If any user presets exist for this effect this menu will list them. Select one of the user presets to load it into the effect.
  • Factory presets: If any factory presets exist for this effect this menu will list them. Select one of the factory presets to load it into the effect.
  • Delete preset: Select this option to delete the currently-loaded user preset.
  • Save as... Select this option to save the current settings as a user preset.
  • Export... Select this option to export one or more presets (for sharing with other users or to move to another computer running the same effect).
  • Import... Select this option to import a presets file.
  • Options... Displays the options dialog for this type of effect. See the sections for each type of effect for a description of the options available.
    • LADSPA Options
    • VST Options
    • Audio Unit Options
  • About: Displays the effect type, effect name, version, vendor, and description.
•   On/Off button: When this button is lit up (blue) the effect is on, otherwise the effect is off (inactive or bypassed). This is a convenient way to do a quick A/B comparison of how your project sounds with and without the effect.
•   Play/Stop button: Click this button to begin playback. It changes to the Stop button  . Click it again to stop playback.
•   Skip Back button: When playback is stopped, clicking this button will move the playback cursor to the beginning of the track. During playback, each click of this button will perform a short seek back.
•   Skip Forward button: When playback is stopped, clicking this button will move the playback cursor to the end of the track. During playback, each click of this button will perform a short seek forward.
• Close button: Click this button to close the effect dialog.
• Apply button: Click this button to apply the effect to the selected audio. The effect dialog will remain open after the effect is applied.

The Import and Export options behave differently for the different classes of effect that support them. See the appropriate sections below in the descriptions of each effect class. LADSPA effects do not support Import and Export.

Real-Time preview with text-based controls

Some effects use a text-based real-time preview control panel:

The checkbox  Enable is equivalent to the On/Off button in the graphical button mode.