# AVAudioEngineManualRenderingBlock The type that represents a block that renders the engine when operating in manual rendering mode. ``` typealias AVAudioEngineManualRenderingBlock = (AVAudioFrameCount, UnsafeMutablePointer, UnsafeMutablePointer?) -> AVAudioEngineManualRenderingStatus ``` ## Parameters `numberOfFrames` The number of PCM sample frames to render. `outBuffer` The PCM buffer the engine must render the audio for. `outError` On exit, if an error occurs during rendering, a description of the error. ## Return Value One of the status codes from [`AVAudioEngineManualRenderingStatus`](/documentation/AVFAudio/AVAudioEngineManualRenderingStatus). Irrespective of the returned status code, on exit, the output buffer’s [`frameLength`](/documentation/AVFAudio/AVAudioPCMBuffer/frameLength) indicates the number of PCM samples the engine renders. ## Discussion --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)