AT&T already announced plans to turn on HD Voice, aka, wideband audio support, later this year through a carrier update for iPhone users in the US. Today, iTweakiOS announced an update for one of its hacked carrier profiles that it claims will allow AT&T users to access HD Voice, as well as the recently announced CMAS government and Amber alert update, ahead of a full roll out of the feature later this year.
This hack fixes the reported issue of unstable HSPA+ speeds/signal and iPad users having trouble updating and losing all signal. This hack enables, along with the previous enabled features, HD Voice for all iPhone models running on AT&T so users can now use the UMTS/HSPA/HSPA+ network for HD qaulity calling on their 4S and 5. This hack also enables Release 7 HSDPA speeds for the iPhone 4S, giving it a new maximum theoretical downlink of 21Mbps, which AT&T does indeed support. Signal improvements from the previous release have not changed and are still present in this release along with unthrottled LTE and HSPA+.
Apple has actually supported the feature since the iPhone 5 launched last fall, but only around 20 international carriers currently support the feature. Unfortunately, the HD Voice feature, even with the hack, won’t yet work for all users, as AT&T is still currently in the process of rolling out support:
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AT&T is also currently in the process of enabling AMR-WB (AMR 13) which is the codec that enables HD Voice so you may not recieve HD Voice in every area but is set for public release sometime this year. If you are in an area that does not support HD Voice (AMR-WB) then your iPhone will auto default back to the standard CS AMR 5 codec which is voice over 2G.
Sprint and Verizon haven’t announced plans to roll out support for wideband audio, but earlier this year T-Mobile became the first to officially support the feature with its launch of the iPhone 5. Check out our hands on of the feature from T-Mobile’s event back in March.