The iTweakiOS team (www.itweakios.com) has released a hacked version of IOS for T-Mobile USA Apple iPhones, adding HD voice support for the iPhone 4 and 4S. It will be interesting to see if the hack propagates around the world.
As previously noted by HD Voice News, the Apple iPhone 4 and 4S are both clearly capable of supporting HD voice from a hardware standpoint. Apple chose to limit use of the AMR-WB codec to the iPhone 5, most likely because it wanted people to upgrade sooner. The company has been particularly
T-Mobile rolled out support for HD voice and the AMR-WB codec in the late fall of 2012 and officially announced it at CES 2013 in January. The carrier has a policy of allowing any unlocked GSM device to connect to its network, including “jailbroken” Apple phones.