Viber vs Mumble

Viber has native apps for both Windows and Mac that allow you to send and receive messages from your desktop. You can also use the desktop to make and receive calls. Synchronizes between all devices you are using Viber on. Allows transferring calls between devices.

Viber has really well implemented voice tech. It has comparable quality to Skype and you can even tranfer calls from your phone to your desktop seamlessly.

Viber uses data connection and the app is free.

The interface is simple, functional and intuitive.

Viber is tied to your phone number so it can quickly see who else in your contacts list is using the application.

Viber includes Android Wear support on Android 4.3 or higher and Viber 5.3 or higher.

Viber's protocol uses the same concepts of the "double ratchet" protocol used in Open Whisper Systems Signal application.

It's possible to be a fly on the wall on other group or one-to-one chats that have been opened up to the public. These public chats are often promotional chats with celebrities.

Can call friends using voice or video options.

This has an advantage in that if you text someone who uses Viber it will be free, if not it will just revert to SMS. This means you can replace your standard messaging app with Viber as well.

Starting with Viber 6.0 the encryption keys are stored only on the clients themselves, not even Viber itself has access to them.

One of the best things about Viber is how it handles setup and sending messages. Viber uses your existing number as your ID, so you don't need to create a separate Viber account.

Viber allows creating groups of up to 200 people on the Android version of Viber. It also has a cool "smart notifications" feature to prevent being overwhelmed with notifications if a lot of people are active in a chat group.

Viber has made a documentation available, explaining in great details their encryption system and giving good insight on how it works.

Mumble is available as a free download and source code is available on GitHub.

The server software Murmur is licensed under a free and open-source BSD-style license.

Available on Windows, Linux, OS X, Android and iOS which allows for the user to choose what operating system works for them and still be able to use Mumble.

Since version 1.2.4, Mumble uses an audio codec named Opus that's specifically developed to provide low-latency voice communication over Internet. This means that there is no delay time, while audio still comes out clear.

Dedicated servers and low overhead allows Mumble to have the least delay between users speaking and others hearing their speech, which can be very important for fast paced games.

A push-to-talk key allows you to only transmit audio when you want it. Others won't hear you chewing or your mom entering the room unless you want to.

Mumble is completely free, even hosting your own server.

Mumble uses certificates for user identification. A certificate can be generated by the user himself or issued by a third-party organization with organization certificates having 2 classes. A self-generated certificate is not tied to anything, a Class 1 certificate is tied to an e-mail address and a Class 2 certificate requires proof of identity. Depending on the server a different level of certification might be required.

Mumble server side is easy to setup and works smooth even on Raspberry Pi, which is pretty short on resources.

An in-game overlay can be enabled to show users in the channel or users talking. Overlay can be disabled completely or on a per-game basis by going to Settings->Overlay. This allows for users to see their chat but not obstruct the game they are playing.

By default, only users in the same channel can hear each other. Channels can be nested to better organize yourself according to what you want to be talking about.

This encryption is mandatory and cannot be disabled. The so-called control channel, which transports your chat messages and other non-time critical information, is encrypted with TLS using 256 bit AES-SHA. The voice channel carrying speech and positional audio is encrypted with OCB-AES 128 bit.

Mumble includes great automatic volume adjustment functionality that can be used to prevent big volume changes while still allowing good communication.

Mumble supports positional audio for over 50 games, including versions of Call of Duty, Battlefield and Counter-Strike. This allows you to hear the audio from the direction of the player speaking, making gameplay more immersive and giving competitive players an edge. You can find a full list of supported games here.

Version 1.3 introduced skins, allowing you to customize your UI, either on your own (tutorial here) or by using one of the skins found here.