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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 Software Development Kit, which literally is a collection of software modules bundled together, and exposes interfaces as APIs to allow developers to integrate and call for certain functions.

Voice SDK refers to a collection of software modules that allow developers to integrate and build real-time voice call features into their own apps or platforms. There are many great voice call SDK vendors on the market for your choice, including ZEGOCLOUD voice SDK and Twilio voice SDK.

Normally, voice SDK, also called voice call SDK, is a whole system that can be divided into the back end and front end. The back end refers to the cluster of servers, including signaling servers 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 that 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 a hard thing. 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 a number of challenging things including QoS of voice data transmission and voice data preprocessing ( acoustic echo 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. It will take your team at least 6 months to deliver the first viable version.

Simply put, the time and money required for in-house development are incredibly high. Most companies will opt for voice call SDK from top vendors like ZEGOCLOUD or Twilio. The real-time voice SDK that 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, what you will do is integrate the voice call SDK in a few hours, and then trial 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 scenarios, gaming scenarios, and education scenarios.

  1. Social Scenarios

This category is very broad, 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 own interests. Users will get started with a group voice chat. They will be guided to play games or sing karaoke. When they are chatting via real-time voice, there is background music playing to nurture a nice atmosphere. Some online voice-based games such as Werewolf Killer can be built with real-time voice, users can chat via real-time voice to carry out the werewolf game.

  1. Gaming Scenarios

Music is the common language of all humankind, games are the common language for netizens. There are needs 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 in the form of live streaming shows, or group chat rooms, which build stronger stickiness and attractiveness for the game platforms.

  1. 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. I mean, 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, in some classes, teachers, and students choose to turn off cameras to avoid video buffering from time to time.

There have been some innovations happening in some online educational apps where there is 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

  1. One-on-one, Multiple, or Live Streaming Show

Real-time voice SDK allows your users to conduct one-on-one voice calls or many-to-many group voice chats, or even live voice streaming shows. The most fundamental but important 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.

  1. High Fidelity Voice Quality

ZEGOCLOUD’s voice 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, including different voice codecs and coding tactics, to support the human voice and music sound. In this way, the voice call SDK can switch intelligently between a music scenario and a human voice scenario.

  1. Acoustic Voice Pre-processing

In practice, some challenging issues, such as noise and echo, are inevitable. 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 far end user is disturbed by the lagging and repetitive voice. There are some acoustic processing that are carried out before coding, and we call them pre-processing, which includes 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, there are many more advanced features that 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 noisy, 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 that allow you to hear your own voice clearly and timely. ZEGOCLOUD’s voice call SDK support in-ear monitor, and it allows you to hear your own voice with full fidelity, clearly, and timely.

  1. 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”, there are two lines of sound waves arriving 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 call 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.

  1. 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. Basically, ZEGOCLOUD‘s algorithm changes voice tone and pitch to realize voice-changing effects. It is a popular feature in social scenarios.

  1. Reverberation Effect

You may have got the experience of hearing sound reverberation in a big concert or in a huge church hall. The reverberation effect created the feeling of open space and being with a big crowd together. The reverberation effect is created by a sound or signal being 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 created a reverberation effect in a similar way. We make many duplicates of a sound signal, change their wave phases, and then compose the signal waves together to generate a sound wave. The final sound wave will present a reverberation effect.

How to Choose The Right Voice Call SDK

Normally, the typical way to choose the right voice SDK will involve evaluation in four aspects:

  1. Comprehensiveness of Features

You need to go through the documentation of voice call SDK, the include/import files of voice call SDK itself, and see if it contains all the important features that you want, and also the extendable features that you might need in 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 what features it possesses. Normally, a demo app only demonstrates the key features, you have to dive into the include/import files to see the full list of features.

  1. Performance Quality

The most important metrics to evaluate performance quality include latency, smoothness, echo cancellation, noise suppression, and high concurrency. One quick way to get a sense of and test these metrics is to run the corresponding demon app. However, you cannot test high concurrency with a single demo, and you won’t get fully convinced in this regard 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.

  1. Successful Customer Cases

It is paramount to check successful customer cases. It can help you to avoid being a trial white rat. A successful customer case of a big brand demonstrates two things. First, the voice call SDK has passed the hard 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 good support of high concurrency. To be sure about these, you have to consult insiders about these successful customer cases.

  1. 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 allows you to finish the integration by making configurations on a visual panel and write 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 also provides UI components like blocks to let you integrate easily like building LEGO.

  1. Technical Support Service

This is always a hidden but important 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 service abilities of the technical support team, and also 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 factors.


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 call SDK vendors, like ZEGOCLOUD, have launched their UIkit 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.

ZEGOCLOUD With our fully customizable and easy-to-integrate Live SDK, you can quickly build reliable, scalable, and interactive live streaming into your mobile, web, and desktop apps.

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