Tips and Training >> Definitions >> G.722
What is G.722?
The G.722 ITU Standard is a wideband audio codec that operates at a data sampling rate of 16kbps (which is double that of a traditional Pulse Code Modulated telephone). The higher sampling rate allows the G.722 codec to provide higher clarity of audio signals than G.711. The G.722 codec can provide 7 kHz wideband speech at transmission rates of 48Kbps, 56Kbps and 64Kbps.
A key reason the G.722 codec is used by broadcasters to transmit speech via telephone lines [ISDN 64Kbps B Channels can carry G.722] is the greater level of audio clarity it provides. In practice, this codec generally negotiates at 64Kbps even though it can operate at lower bandwidth rates.
Are G.722.1 and G.722.2 just better versions of G.722?
No. They are different codecs altogether, each with their own benefit and capability. G.722.1 was developed by Polycom as their Siren codec. G.722.1 provides 7 kHz wideband encoding and operates at transmission rates of 24Kbps and 32Kbps, which are both, lower than the G.722 standard. Polycom notes that it has an extension that operates as low as 16Kbps. This codec, when negotiated properly between devices is capable of producing excellent audio clarity and tone.
G.722.2 is a wideband codec that offers the ability to adaptively change compression rates in response to changes in available bandwidth. Changing in bandwidth availability can sometimes be initiated at a user's request, for example in a video conference when a user causes some bandwidth to be used for a presentation. In this case, if the video systems have successfully negotiated G.722.2 audio, the audio bandwidth can be reduced and thereby additional bandwidth can be used for the video content.
G.722.1 and G.722.2 are not just variants of G.722, they have their own benefits and applications.
What do I need to know about G.722?
G.722 audio codecs must be negotiated between endpoints or devices. If this negotiation or "capabilities exchange" fails, then G.722, G.722.1 or G.722.2 will not function. Generally, if this "caps exchange" as it is often called fails, a lower efficiency codec is invoked and negotiates between the pieces of equipment that are communicating. For example, if a G.722 codec fails to negotiate, then a G.711 codec may negotiate instead.
When setting up and installing a video conferencing system, selecting all the available codecs for use may seem like a good idea, however, negotiations between video systems can be complex, even within a single manufacturer's product line. We recommend selecting only reliable, high quality codecs in a setup configuration, if possible, and minimizing the use of every available codec. Where possible, we recommend selecting the following codecs for regular video conferencing meeting rooms: G.711, G.722, G.722.1, G.722.2 and G.728. If you experience problems with audio negotiation, rather than adding codecs to this list of system capabilities, we recommend removing one at a time until you attain acceptable audio.
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