Common VoIP Codecs

Popular codecs used in VoIP applications and devices

When making voice calls over the Internet using Voice over IP (VoIP) or other digital networks, the voice must be encoded into digital data and vice versa. In the same process, the data is compressed for faster transmission and improved call quality. This encoding is achieved using codecs (which is short for encoder-decoder).

There are many codecs for audio, video, fax and text. Below is a list of the most common codecs for VoIP. As a user, you may think you have nothing to do with what these are, but it is always good to know the bare minimum as you may one day have to make a decision about VoIP related codecs in your company; or at least one day can understand some of the words in the Greek VoIP people.

One specific scenario where you may be asked to understand codecs is when you need to review a piece of software or hardware before purchasing it. For example, you can decide whether to install it as the calling application or as an application based on the codecs they provide for your calls, depending on your needs. Some phones also have built-in codecs that you may want to consider before investing.

Common VoIP Codecs

codec td> Bandwidth/kbps td> Comments td>
TR>
G.711TD> 64TD> Provides accurate voice transmission. Very low CPU requirements. Requires a minimum of 128 kbps for two-way communication. It’s one of the oldest codecs (1972) and works best with high bandwidth, making it a little dated for the Internet, but still good for LANs. This gives a MOS of 4.2, which is quite high, but optimal conditions must be met. Td>
TR>
G.722TD> 48/56/64TD> Adapts to different compressions and conserves bandwidth due to network congestion. It captures frequency ranges up to twice that of G.711, resulting in better quality and clarity close to or even better than PSTN. Td>
TR>
G.723.1TD> 5.3/6.3TD> High compression with high sound quality. Can be used with dial-up and low-bandwidth environments as it operates at very low data rates. However, this requires more processing power. Td>
TR>
G.726TD> 16/24/32/40TD> Improved version of G.721 and G.723 (other than G.723.1) td>
TR>
G.729TD> 8TD> Excellent bandwidth usage. fault tolerant. It’s an improvement over other similar names, but it’s licensed, which means it’s not free. End users pay for this license indirectly when purchasing the hardware (phones or gateways) that implement this license. Td>
TR>
GSM TD> 13TD> High compression ratio. Free and available on many hardware and software platforms. The same encryption is used in GSM mobile phones (improved versions are often used today). It offers MOS 3.7, which is not bad. Td>
TR>
Ilbc TD> 15TD> indicates a low speed internet codec. it has now been acquired by Google and is free. It resists packet loss and is used by many VoIP applications, especially open source applications. Td>
TR>
Speex TD> 2.15/44td> Minimizes bandwidth usage by using a variable bit rate. It is one of the most preferred codecs used in many VoIP applications. Td>
TR>
SILKTD> from 6 to 40 td> SILK was developed by Skype and is now licensed as it is available as free and open source software, which allows it to be used by many other applications and services. This is the basis for the latest codec called Opus. WhatsApp is an example of an application that uses the Opus codec for voice calls. Td>
TR>
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