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aptX Voice: what it means for Bluetooth call quality

Qualcomm's aptX Voice codec supports end-to-end super wideband voice calls over Bluetooth.

Published onNovember 20, 2019

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One notable improvement made to today’s 4G networks is support for high-quality voice calls. New muffled 8kHz narrowband technologies (like AMR) from the 2G and 3G days have made way for 16kHz wideband (AMR-WB) and even 32kHz super-wideband codecs like EVS. EVS is a core technology of VoLTE, which now is supported by most carriers, enabling VoWiFi as well.

In a nutshell, higher quality call codecs not only improve the sound of the human voice, but also let us perceive more details about the environment on the other end of the phone. Super-wideband calls sound the most realistic. Unfortunately, Bluetooth headsets don’t always play nicely with these improved carrier capabilities. This leads to inferior sounding calls from your wireless headphones compared to your phone’s speaker.

How Enhanced HD Voice makes your calls crisp and clear

Enter Qualcomm’s aptX Voice, designed to tackle the calling side of the Bluetooth audio problem. aptX Voice promises improved super-wideband call quality (32kHz), as well as low latency, and robustness against signal drops.

aptX Voice is an optional subset of Qualcomm’s aptX Adaptive codec. As such, devices on both ends must support Adaptive and Voice for this enhanced calling functionality to work, but you can have aptX Adaptive without Voice. After all, many music products have nothing to do with voice calls. We’ll have to see how products handle passing this compatibility information on to consumers without causing too much confusion.

The problem: Getting the best out of Bluetooth calls

EVS ultra wideband voice frequencies

4G carriers with EVS offer excellent call quality from your smartphone. However, the technology is too memory heavy to run directly over a Bluetooth connection. A data saving conversion is required to sending voice data to and from your headphones back and handset through the rather tight Bluetooth pipe.

There are a few further complications to this problem. First, memory and power constraints in the headset mean that you need a codec that’s lightweight. Second, latency must be very low because we’re dealing with real-time voice calls. This rules out the use of frequency-domain conversion codecs like AAC, which offer great compression but take a while to crunch the numbers.

Default Bluetooth codecs are the weak link in the super-wideband voice chain.

Out of the box, Bluetooth devices support either basic SBC/CVSD encoding capped at an 8kHz sample rate or mSBC with a 16kHz sample rate. SBC/CVSB effectively limits the quality of calls to narrowband, even if you’re on a VoLTE network. mSBC sounds much better, but it doesn’t fully leverage super-wideband voice capabilities. You won’t always know if a headset supports mSBC, although it is now the preferred default standard.

aptX Voice supports the full super-wideband sample rate of 32kHz. This means you’ll get the full benefits of super-wideband voice quality over a Bluetooth connection. According to Qualcomm, aptX Voice earns a Perceptual Evaluation of Audio Quality (PEAQ) score of 4.7 out of 5. That’s ahead of mSBC (4.31) and a smidgen ahead of even EVS (4.69).

Also read: The ultimate guide to Bluetooth headphones: AAC only acceptable on Apple phones

Ultimately the leap between wideband and super-wideband isn’t as significant as the jump from narrowband. However, there’s still a perceivable improvement in quality that Bluetooth consumers will appreciate.

What else is new and when can I get it?

ultra wideband voice end to end aptX Voice

aptX Voice is part of the second revision of Qualcomm’s aptX Adaptive codec. This update will also bring support for hi-res music playback over Bluetooth. aptX Adaptive r2 supports 24-bit 96kHz audio files by extending the codec’s bit-rate above 600kbps. Currently, aptX Adaptive caps out at 420kbps for 16-bit 48kHz quality. This is undoubtedly a welcome addition for the audiophile community, although there will probably be a little wait for headphones sporting the updated technology.

Qualcomm’s latest aptX improvements require new hardware. Currently, Qualcomm’s Fast Connect 6800 chip supports aptX Voice, along with Bluetooth 5.1 and Wi-Fi 6. On the integrated mobile side, the Qualcomm Snapdragon 865 announcement is right around the corner, which could well bring these capabilities to 2020’s flagship smartphones.

Keep an eye out for smartphones, headphones, and other products supporting aptX Voice next year. We’ll also likely hear much more about Qualcomm’s plans for audio and voice at this year’s Snapdragon Tech Summit. Which runs from December 3 to December 5.