# Audio extension (/en/realtime-media/marketplace/build/build-your-own-extension/audio-filter/ios)

> For AI agents: see the complete documentation index at [llms.txt](/llms.txt).

The audio filters you create are easily integrated into apps to supply voice effects and noise cancellation.

      
  
      
## Understand the tech

An audio filter accesses voice data when it is captured from the user's local device, modifies it, then plays the updated data to local and remote video channels.

![Audio extension pipeline](https://assets-docs.agora.io/images/video-sdk/extension-audio-filter.png)

A typical transmission pipeline consists of a chain of procedures, including capture, pre-processing, encoding, transmitting, decoding, post-processing, and playback. To modify the voice or video data in the transmission pipeline, audio extensions are inserted into either the pre-processing or post-processing stage.

## Prerequisites

* Xcode 12.0 or higher.
* A device running iOS 9.0 or higher.
* A project to develop in.

## Project setup

In order to integrate an extension into your project:

* Follow the iOS SDK setup flow in [Quickstart - integrate an extension](../../quickstart-integrate.mdx).
* Prepare the project structure, frameworks, and signing settings needed for your extension package.

You are now ready to develop your extension.

## Create an audio extension

Package the extension as an iOS framework or xcframework, register it with the SDK, and provide the metadata Agora needs for Marketplace integration.

## Test your implementation

* Run functional and performance tests.
* Validate the extension listing in Agora's test environment.
* Prepare the public integration document and update it after end-to-end verification.

You are then ready to [Publish your extension](../publish-extension.md).

## Reference

* [RTC iOS API reference](../../../../api-reference/rtc/ios.md)
* [RTC iOS API reference](../../../../api-reference/rtc/ios.md)