HD VoIP and HD Voice Codecs

Have you ever been on a business call that had crystal clear sound? Or maybe you've overheard a call on your coworker's speakerphone and you could've sworn that the person who your coworker was speaking with was actually in the room!

These types of calls are high-definition calls, but you might know them as wideband audio or "HD Voice," just to name a few synonyms. In this blog, we'll present some introductory information on what HD calls are and how they work.

Quick Intro to HD Voice Codecs and Wideband Technology

Audio Codec

A codec is a program or algorithm that is used to convert audio (voice sounds) into a compressed, digitally-encoded form, and then back into uncompressed audio at the other end. The word "codec" is actually short for "coder-decoder," and there are quite a few different codecs, each of which may have different bandwidth and computational requirements. Many codecs are formalized by the International Telecommunications Union (ITU) into standards for use across different countries and devices.

The traditional telephone network is limited to the G.711 codec due to the technology and user devices that it relies on. While the standard for landline phone calls, this "narrowband" codec typically results in grainy or static-y sounding calls (no doubt you've experienced many of these types of calls yourself!).

Wideband audio codecs expand the sound frequencies that narrowband codecs transmit, enabling HD VoIP calls.
Audio spectrum— displaying narrowband and wideband frequencies. (Source)

Wideband Audio

Wideband audio technology uses a "wideband" codec that makes use of a greater frequency range of the audio spectrum when compared to narrowband codecs. Wideband technology transmits audio beyond the narrowband limit of 3.4 kHz, all the way up to 7 kHz. This expanded range results in excellent sound and speech quality: clearer phone calls and sharper, crisper voices.

The first standardized wideband codec, G.722, was developed in the late 1980s. It is now freely available as its patent has expired. Another HD voice codec, G.722.2, offers high-definition voice quality over smaller bandwidth transfer rates. However, the current 'gold standard' of the wideband audio codecs is called Opus, and it's the default codec that's used by all WebRTC technology and apps currently available.

There are actually many different names used when referring to wideband audio technology. It is most commonly referred to as "HD Voice," a term trademarked and popularized by well-known communications and collaboration technology provider, Polycom. Other players in the industry may have other branded names— for example, Aastra calls their HD audio "Hi-Q." Typically, these names refer to a combination of the manufacturer's hardware/software design with wideband audio codecs.

How Do VoIP Phones Work out Which Codec to Use?

End user devices, such as IP phones and softphones, typically support several different audio codecs. When two of these devices begin to talk with each other, they will negotiate which codec to use by looking at which ones they have in common. You can think of codecs as the different types of audio files on your computer. Just as a .wav player would not be able to play an .mp4, an IP phone would not be able to successfully communicate with another end user device if they did not share at least one codec.

2 VoIP phones will negotiate which HD voice codec to use when transmitting a VoIP call.

OnSIP HD VoIP and High-Definition Calls

OnSIP was built from the ground up using open source projects such as OpenSIPS, FreeSwitch, and Asterisk. Our service is also device-agnostic (as long as the device follows the SIP-RFC standards). Customers can bring their preferred IP phones and devices that support HD audio and they'll be compatible with OnSIP's HD VoIP and cloud phone system.

We're also huge supporters of WebRTC and have built a few features and apps that use this innovative technology. One such WebRTC application is the OnSIP app, our business softphone available in-the-browser or via a desktop application. Free for all OnSIP users, the OnSIP app also supports wideband audio codecs. Equip your staff members with this customizable app and they'll be able to make high-definition calls right from their computers or laptops.

Topics: About VoIP, Business Technology, IP phone