G.711: 300 Hz to 3.4 kHz
G.722: 200 Hz to 7 kHz
The wider frequency response of G.722 and the proprietary "Wideband" codec have more than double the width of G.711. As a result, fidelity is much better, and music even sounds good. It doesn't meet the audiophile's strict standards for a home theatre, but from a phone handset or headset, the difference is striking. Keep in mind that a wideband headset or handset is required to realize the audio performance benefits of G.722. As an added benefit, G.722 consumes the same amount of bandwidth (64 kb/s) as G.711.
Not all devices and features support G.722. As such, be careful where G.722 is enabled within your enterprise. For example, problems with call park and ad hoc conferences arise when G.722 is enabled. When you use the enterprise parameter with features such as ad hoc conferencing and call park, change the setting to "Disabled" and update the device pools for the phones.
Enabling G.722 Across the Cluster
By default, the cluster is enabled to advertise G.722 as an available codec if both phones support the codec.
Codec negotiation involves two steps. First, the phone must advertise the supported codec(s) to Cisco Unified Communications Manager (not all phones support the same set of codecs). Second, when Cisco Unified Communications Manager gets the list of supported codecs from all phones that are involved in the call attempt, it chooses a commonly supported codec based on various factors, including the region pair setting.
The following phones support G.722 as either SCCP or SIP devices:
- Cisco Unified IP Phone 7971G-GE
- Cisco Unified IP Phone 7970G
- Cisco Unified IP Phone 7961G-GE
- Cisco Unified IP Phone 7961G
- Cisco Unified IP Phone 7941G-GE
- Cisco Unified IP Phone 7941G
The default for the Advertise G.722 Codec enterprise parameter enables G.722 on all phones in the cluster. The default value of the phone configuration Advertise G.722 Codec Product-Specific parameter uses the value that the enterprise parameter setting specifies.
If the Advertise G.722 Codec enterprise parameter is set to Enabled, the administrator can override this by using the G.722 Codec Enabled service parameter. This service parameter determines whether Cisco Unified Communications Manager supports G.722 negotiation for none, some, or all devices. Valid values specify "Enabled for All Devices" (support G.722 for all devices), "Enabled for All Devices Except Recording-Enabled Devices" (support G.722 for all devices except those that have call recording enabled), or "Disabled" (do not support G.722 codec).
More detail found here.