How to use ZEGOCLOUD SDK to implement Voice change/Reverb/Virtual stereo in iOS
Tags: ios, swift, tutorial, zegoclou
Published: 2022-05-27 06:50:14

![cover](https://resource.zegocloud.com/content_resource/2022/05/27/pexelsandreapiacquadio3761509.jpg)

## Introduction

In the live broadcast, chat room, and karaoke room scenes, in order to increase the fun and interactivity, players can change the voice to make things funny, reverberate the atmosphere, and use stereo to make the sound more three-dimensional. ZegoExpress SDK provides a variety of preset voice change, reverberation, reverberation echo, and stereo effects. Developers can flexibly set the sound they want. If you need to listen to it, you can enable ear return for testing.

* Voice change: By changing the user's pitch, the output sound is sensory different from the original sound, and various effects such as changing male voice to female voice are realized.
* Reverberation: Through special processing of the sound, the reverberation effect of different environments is created, making the sound appear as if it is in a concert hall, a cathedral, etc.
* Reverberation echo: Through special processing of the sound, it can be matched with voice change and reverberation to achieve a variety of custom sound effects, such as ethereal and robot sounds.
* Virtual stereo: Through the deep use of dual-channel technology, each position and angle of the sound source is virtualized to achieve stereo sound, 3D surround sound, and sound discrimination.

<div class="mk-hint">

The function is only effective for the sound collected by the SDK. The developer can dynamically adjust the voice change, reverberation, reverberation echo, and virtual stereo during a call or live broadcast.  
</div>


## Prerequisites

Before proceeding with voice change/reverb/stereo, please make sure:

- Create a project in [ZEGOCLOUD Admin Console](https://console.zegocloud.com?_source=dev&article=9), and get the AppID of your project.
- The ZEGO Express SDK has been integrated into the project. For details, see [Integration](https://docs.zegocloud.com/article/195?_source=dev&article=9) and [Implementation](https://docs.zegocloud.com/article/10836?_source=dev&article=9).


## Voice Change

### Set Preset Voice Changer

Call `setVoiceChangerPreset` method to use SDK preset voice changer effect.

`ZegoVoiceChangerPreset` preset voice changing effects are as follows, developers can choose according to their needs:

![ZegoVoiceChangerPreset](https://resource.zegocloud.com/content_resource/2022/05/27/16536324495070.jpg)


The following sample code takes a male voice to a child voice as an example:

```objc
[[ZegoExpressEngine sharedEngine] setVoiceChangerPreset:ZegoVoiceChangerPresetMenToChild];
```

### Set Custom Voice Changer

If the sound changing effect preset by the SDK cannot meet the demand, the developer can call the `ZegoVoiceChangerParam` method to pass the pitch parameter "pitch" sets custom voice change, the value range of this parameter is [-8.0, 8.0], the larger the value, the sharper the sound, the default value is "0.0" (that is, no voice change).

```objc
ZegoVoiceChangerParam *param = [[ZegoVoiceChangerParam alloc] init];
param.pitch = 2.0;
[[ZegoExpressEngine sharedEngine] setVoiceChangerParam:param];
```

## Reverberation

### Set Preset Reverb

Call `setReverbPreset` to set reverberation through preset enumeration.

`ZegoReverbPreset` preset reverb effects are as follows, developers can choose according to their needs:

![ZegoReverbPreset](https://resource.zegocloud.com/content_resource/2022/05/27/16536324903541.jpg)


The following sample code takes the large room mode as an example:

```objc
[[ZegoExpressEngine sharedEngine] setReverbPreset:ZegoReverbPresetLargeRoom];
```

### Set Custom Reverb

If the SDK preset reverb type cannot meet the requirements, the developer can call the `ZegoReverbAdvancedParam` method, and match the relevant parameters Settings to achieve the reverberation effect required by the developer (for detailed parameter descriptions, please refer to the API documentation).

```objc
ZegoReverbAdvancedParam *reverbParam = [[ZegoReverbAdvancedParam alloc] init];
reverbParam.damping = 50.0; // Reverberation damping
reverbParam.reverberance = 50.0; // Reverberation
reverbParam.roomSize = 50.0; // room size
reverbParam.wetOnly = false;
reverbParam.wetGain = 5.0;
reverbParam.dryGain = 5.0;
reverbParam.toneLow = 80.0;
reverbParam.toneHigh = 80.0;
reverbParam.preDelay = 20.0;
reverbParam.stereoWidth = 0.0;

[[ZegoExpressEngine sharedEngine] setReverbAdvancedParam:reverbParam];
```

<div class="mk-warning">

After setting the custom reverb parameters, the preset reverb effect set when reverb is enabled will be invalid. If you want to use the SDK preset parameters again, you can use `setReverbPreset` method to set.
</div>

## Reverberation Echo

Call the `setReverbEchoParam` method to achieve the reverberation required by the developer through the configuration of related parameters Echo effect (please refer to API documentation for detailed parameter description).

The following sample code takes the ethereal effect as an example:

```objc
ZegoReverbEchoParam *echoParamEthereal = [[ZegoReverbEchoParam alloc] init];
echoParamEthereal.inGain = 0.8;
echoParamEthereal.outGain = 1.0;
echoParamEthereal.numDelays = 7;
echoParamEthereal.delay = @[@230, @460, @690, @920, @1150, @1380, @1610];
echoParamEthereal.decay = @[@0.41f, @0.18f, @0.08f, @0.03f, @0.009f, @0.003f, @0.001f];
[[ZegoExpressEngine sharedEngine] setReverbEchoParam:echoParamEthereal];
```

## Virtual Stereo

### Set the Number of Streaming Audio Channels

If you need to turn on the virtual stereo function, you must first call the `setAudioConfig` method to set before pushing the stream The audio encoding channel is Stereo dual channel (default is Mono).

The example here uses the preset enumeration structure `ZegoAudioConfig` to be set to dual-channel.

```objc
ZegoAudioConfig *config = [ZegoAudioConfig configWithPreset:ZegoAudioConfigPresetStandardQualityStereo];

[[ZegoExpressEngine sharedEngine] setAudioConfig:config];
```

### Set Virtual Stereo Parameters

After setting the audio encoding channel to dual channel, call the `enableVirtualStereo` method, turn on the virtual stereo through the enable parameter, and set the sound source angle of the virtual stereo through the angle parameter to have the stereo effect. The angle range is 0 to 360, and generally can be set to 90 degrees (that is, straight ahead).

<div class="mk-hint">

Starting from the **2.15.0** version, the SDK supports the all-around virtual stereo. To enable it, set the `angle` parameter to `-1`.
</div>

The following shows how to turn on the virtual stereo and set the angle to 90 degrees:

```objc
[[ZegoExpressEngine sharedEngine] enableVirtualStereo:YES angle:90];
```
The following shows how to enable the all-around virtual stereo:

```objc
[[ZegoExpressEngine sharedEngine] enableVirtualStereo:YES angle:-1];
```