---
title: unitRenderAction_OutputIsSilence
framework: audiotoolbox
role: symbol
role_heading: Type Property
path: audiotoolbox/audiounitrenderactionflags/unitrenderaction_outputissilence
---

# unitRenderAction_OutputIsSilence

This flag can be set in a render input callback (or in the audio unit’s render operation itself) and is used to indicate that the render buffer contains only silence. It can then be used by the caller as a hint to whether the buffer needs to be processed or not.

## Declaration

```swift
static var unitRenderAction_OutputIsSilence: AudioUnitRenderActionFlags { get }
```

## See Also

### Constants

- [unitRenderAction_PreRender](audiotoolbox/audiounitrenderactionflags/unitrenderaction_prerender.md)
- [unitRenderAction_PostRender](audiotoolbox/audiounitrenderactionflags/unitrenderaction_postrender.md)
- [offlineUnitRenderAction_Preflight](audiotoolbox/audiounitrenderactionflags/offlineunitrenderaction_preflight.md)
- [offlineUnitRenderAction_Render](audiotoolbox/audiounitrenderactionflags/offlineunitrenderaction_render.md)
- [offlineUnitRenderAction_Complete](audiotoolbox/audiounitrenderactionflags/offlineunitrenderaction_complete.md)
- [unitRenderAction_PostRenderError](audiotoolbox/audiounitrenderactionflags/unitrenderaction_postrendererror.md)
- [unitRenderAction_DoNotCheckRenderArgs](audiotoolbox/audiounitrenderactionflags/unitrenderaction_donotcheckrenderargs.md)