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What is Voice SDK

What is Voice SDK

In terms of voice SDK, the word voice refers to real-time voice communication. Typically, real-time voice allows users to do one-on-one voice calls like what they do on phone calls. SDK refers to a Software Development Kit, a collection of software modules bundled together, and exposes interfaces as APIs to allow developers to integrate and call for specific functions.

Voice SDK refers to software modules allowing developers to integrate and build real-time voice call features into their apps or platforms. Much great voice call SDK vendors is on the market for your choice, including ZEGOCLOUD and Twilio Voice SDK.

Usually, voice SDK, also called voice call SDK, is a whole system that can be divided into the back end and front end. The rear end refers to the cluster of servers, including signaling and media servers. The servers are deployed on the cloud, and developers don’t have to care about where they are. The front end refers to the software package the developer can install on a terminal device as libraries and use by calling the voice APIs.

Why Shall We Use Voice Call SDK

The simple answer to this question is that the time and money you will invest will outweigh the budget for using voice call SDK.

Real-time voice technology is about algorithms, math, acoustic science, and engineering, which is problematic. There is a high entry barrier to developing something like voice call SDK. If you take WebRTC as a reference, you will understand that your development team will encounter some challenging things, including QoS of voice data transmission and voice data preprocessing ( preprocessing cancellation, acoustic noise suppression, and automatic gain control). You will have to set up a minimal 4-member team (1 engineer for acoustic algorithms, 1 engineer for Qos, 1 for the iOS platform, and the other for the Android platform) to develop the technology. Delivering the first viable version will take your team at least 6 months.

Simply put, the time and money required for in-house development are incredibly high. The real-time voice SDK these vendors offer have encapsulated the whole technology into their cloud-based system and exposed a few simple voice APIs for your development team to integrate and call. You don’t have to worry about investment in development and maintenance. You will incorporate the voice call SDK in a few hours and then try your app to verify your business idea.

What Are The Common Use Cases of Voice SDK

There are various use cases of voice call SDK. The most common ones include social, gaming, and education scenarios.piscine et toboggan gonflable

Social Scenarios

This category is comprehensive; it refers to internet-based online entertainment and social networking scenarios. One example of this kind would be online stranger social networking. Social platforms set up voice chat rooms of various schemes, and users join rooms according to their interests. Users will get started with a group voice chat. They will be guided to play games or sing karaoke. When they chat via real-time voice, background music is playing to nurture a friendly atmosphere. Some online voice-based games, such as Werewolf Killer, can be built with real-time voice, and users can chat via real-time voice to carry out the werewolf game.

Gaming Scenarios

Music is the common language of all humankind, and games are the standard language for netizens. There is a need for socializing and collaboration. For example, gamers want to share their thoughts, feelings, and know-how about games on forums, they want casual chat during games like poker games or mahjong, and they need team collaboration to win a game battle. Real-time voice has been a must-have for games. Gaming platforms can integrate voice SDK into their game app to bring a better user experience to users.

In addition, there is common practice in the gaming industry, i.e., gaming platforms build social channels for gamers to share their thoughts and experiences through comments or even voice chat rooms. They launch events for games to attend online through live streaming shows or group chat rooms, which build stronger stickiness and attractiveness for the game platforms.

Education Scenarios

Online education can never be ignored. With the persistence of the global pandemic, cities and towns are locked down, and students are forced to study online through video conferences or live streaming. However, in online classes, the value of video is arguably diminishing. Students receive information from teachers mainly through voice and visual materials like PowerPoint slides and whiteboard writing. They don’t have to look at the teachers’ faces to study. Therefore, teachers and students occasionally turn off cameras in some classes to avoid video buffering.

Some innovations have been happening in some online educational apps with no video. With the aids of screen sharing, document sharing, and whiteboard, teachers use real-time voice to interact with students. These online educational apps integrated voice call SDK offered by RTC vendors like ZEGOCLOUD and delivered online courses effectively.

What Are The Typical Features of Voice Call SDK

One-on-one, Multiple, or Live Streaming Shows

Real-time voice SDK allows users to conduct one-on-one voice calls, many-to-many group voice chats, or live voice-streaming shows. The most fundamental but essential feature of a voice call SDK is to allow users to make real-time voice communication with the best voice quality. The quality of real-time voice can be determined by a few metrics, such as bandwidth and sampling rate.

High-Fidelity Voice Quality

ZEGOCLOUD’s voice call SDK supports full-band voice ranging from 8kHz to 48kHz. The bandwidth of voice stream ranges from tens of kbps to more than 100 kbps. The voice quality can replicate the quality in offline situations. We use intelligent algorithms to support the human voice and music sound, including different voice codecs and coding tactics. This way, the voice call SDK can switch intelligently between music and a human voice scenario.

Acoustic Voice Pre-processing

SPreprocessingg issues, such as noise and echo, are inevitable in practice. Noise refers to environmental noise that degrades voice quality. Echo refers to the situation where the far end’s voice is picked up and transmitted back to the far end, and the distant end user is disturbed by the lagging and repetitive voice. There are some acoustic processing that is carried out before coding, and we call them pre-processing, preprocessing ANS(Acoustic Noise Suppression), AEC( Acoustic Echo Cancellation), and AGC ( Acoustic Gain Control). They are must-have features for a voice call SDK.

What Are the Advanced Features of Voice SDK

On top of basic voice features, many more advanced features allow developers to improve user experience and system efficiency. We will use ZEGOCLOUD’s voice SDK as an example to demonstrate the advanced features of voice call SDK.

1. In-ear Monitor

It won’t seem strange to you if you are a musician or a singer. In some complicated sound fields, such as musical concerts, mega-meeting halls, or noisy sites, speakers can not even hear their own voices clearly since it is too loud, or they will hear their voice from speakers just too late, and they won’t adjust their voice to correct mistakes dynamically. In-ear monitors are head-phone-like devices allowing you to listen to your voice clearly and timely. ZEGOCLOUD’s voice calls SDK support in-ear monitor, allowing you to hear your agent fully, clearly, and timely.

2. Stereo Sound Effect

In our “real world,” we hear sound with two ears. Sound from a single source arrives in our ears with minor different angles and distances, which lets us sense the position and angle of the sound source. We call this a stereo sound effect. In the “real world,” two lines of sound waves arrive in our ears from a single sound. However, in the “cyber world,” a smartphone can only sample and pick sound signals with one single sound channel, which produces no spatial sound effect. ZEGOCLOUD voice calls SDK can create dual sound channels based on one single sound channel and replicate the stereo sound effect. It allows users to sense the position and angle of the sound source preciously. In this way, it produces the stereo sound effect.

3. Voice Changing

In social networking or other relevant scenarios, there is a need to hide the speaking users’ identities or create more fun. ZEGOCLOUD Voice SDK allows developers to change users’ voices from a girl to a man, from a young person to an old person, etc. ZEGOCLOUD’s algorithm changes voice tone and pitch to realize voice-changing effects. It is a popular feature in social scenarios.

4. Reverberation Effect

You may have got the experience of hearing sound reverberation in a big concert or in a vast church hall. The echo created the feeling of open space and being with a big crowd together. The reverberation effect is created by a sound or signal is reflected, causing numerous reflections to build up and then decay as the sound is absorbed by the surfaces of the hall. ZEGOCLOUD’s voice call SDK similarly created a reverberation effect. We make many duplicates of a sound signal, change their wave phases, and combine the signal waves to generate a sound wave. The final sound wave will present a reverberation effect.

How to Choose The Right Voice Call SDK

Usually, the typical way to choose the correct voice SDK will involve evaluation in four aspects:

1. Comprehensiveness of Features

You need to review the documentation of voice call SDK, the include/import files of voice call SDK itself, and see if it contains all the essential features you want and the extendable features you might need for future business innovations. One feasible way to do it is to run and test a vendor’s demo of voice call SDK and get a feeling of its features. Typically, a demo app only demonstrates the key attributes. You have to dive into the include/import files to see the complete list of features.

2. Performance Quality

The most important metrics to evaluate performance quality include latency, smoothness, echo cancellation, noise suppression, and high concurrency. One quick way to understand and test these metrics is to run the corresponding demon app. However, you cannot test high concurrency with a single demo. You won’t get fully convinced even if you have integrated the voice SDK and tested it in production unless you have a massive volume of daily active users for testing. One feasible way in this regard is to check its successful customer cases. We will cover it in the next paragraph.

3. Successful Customer Cases

It is paramount to check successful customer cases. It can help you to avoid being a white trial rat. A successful customer case of a big brand demonstrates two things. First, the voice call SDK has passed the complex evaluation process of the big platform’s competitive technical team. You can be a free rider on the evaluation result. Second, if the big platform’s user volume is big enough, then the platform’s voice chat performance will be evidence of exemplary support of high concurrency. To be sure about these, you have to consult insiders about these successful customer cases.

4. Friendly Integration

To make integration quick and easy, you have to evaluate three factors, i.e., simplicity of APIs, comprehensiveness of documentation, and richness of demonstration APPs. You will have to dive into the include/import files of the voice SDK and see if it is easy to integrate. In addition, you can check if the voice SDK vendor provides low code or no code editions of the voice call SDK. It lets you finish the integration by making configurations on a visual panel and writing a few lines of necessary code. Recently ZEGOCLOUD has launched a low code edition of its voice call SDK, which is called UIKit. ZEGOCLOUD UIKit allows you to integrate faster and easier and provides UI components like blocks to let you integrate easily, like building LEGO.

5. Technical Support Service

This is always a hidden but essential factor. Using voice SDK is technical work and requires a large amount of support service. ZEGOCLOUD has built a professional technical support team and empowered the technical team with software developers who developed the voice call SDK themselves. ZEGOCLOUD aims to enhance the technical support team’s service abilities and let the software developers eat their dog food.

Of course, you need to consider the pricing factor. In this article, we will focus on technical aspects.


Voice SDK has become a common way for companies to acquire real-time voice communication ability for their APPs or platforms. It can save you from a large amount of investment and risk and let you focus on your core business. With the development of technology and the market, voice calls SDK vendors, like ZEGOCLOUD, have launched their UIKits edition of voice call SDK to help developers integrate easier and faster. Voice SDK has become a fundamental building block of APPs like utility services for your home.

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