Originally Posted by
acejavelin Understanding how cellular and VoIP networks function, I find it interesting that Movistar is getting HD voice over 3G without special device support... what codec does it use, how is it implemented, and how do you know you were getting HD voice on these devices in a 3G environment? (I googled, didn't really find a technical answer)
Not only Movistar but also Vodafone in Spain long support HD calls over 3G network. Let's see, human voice frequency ranges from 80 - 14.000 Hz, but most 3G networks only operate in 300 - 3400 Hz range. Movistar and Vodafone upgraded their 3G networks to operate in the range of 50 - 7000 Hz, achieving a much better, cristal clear, accurate voice quality. Apart from upgrading the network the compression codecs were also upgraded to a tweaked AMR-WB codec and, on top of that, the number of samples processed before the sound is transmitted has been multiplied. You only need a device with 3G support (duh...) and capable to properly "render" sounds in the 50-7000 Hz range.
Here you have an example of a voice call using normal 3G then 3G HD, "listen" for yourself (HD voice over 3G is 1:23 onwards)