aptX Lossless: what it is, and why it requires a dragon

aptX Lossless is two things really: it is the first and only Bluetooth codec capable of losslessly (that’s important) streaming CD-quality audio, and it is part of a package of Qualcomm audio technologies called Snapdragon Sound that will feature in a number of next year’s Android phones and wireless earbuds and speakers.

aptX Lossless was announced in September 2021 and is just starting to appear in the first trickle of devices, with more expected in 2023.

While Qualcomm’s aptX Bluetooth codecs (aptX, aptX HD and aptX Adaptive, to list them in chronological and capability order) are among the better-sounding methods in which we listen to music over Bluetooth, alongside the likes of Sony’s LDAC and Apple’s ALAC, the latest aptX Lossless is the first codec that is claimed to transmit CD quality music losslessly, without using a compression method that degrades sound quality. Other Bluetooth codecs ‘support’ CD-quality and even high-res audio, but they compress it lossily during transmission in a way that could detrimentally affect sound quality.

The compression inherent in transmitting audio over Bluetooth has become more efficient over the years, and aptX Lossless is, on paper, a culmination of Qualcomm’s progress in this arena so far. Qualcomm told us that CD-quality (16-bit/44.1kHz) audio transmission with aptX Lossless is achieved between 1.1Mbps and 1.2Mbps (1100 and 1200kbps). As a rough reference, aptX Adaptive’s maximum bit-rate is 420kbps, while the older and less efficient aptX HD can stream at 576kbps, and LDAC uses up to 990kbps. A CD audio file is 1411kbps, higher still, but lossless methods can achieve some data compression without data loss, and the claimed aptX Lossless figures fall within that limit. Qualcomm says that ‘no data is lost when audio is encoded and decoded with aptX Lossless’.

As with Sony’s LDAC, whether you get the full flow of quality can depend on your environment. The codecs need to dynamically scale the bit-rate to adapt to and accommodate busier radio environments without cutting out, and the maximum bit-rates may typically be rarely met. Qualcomm says it has built a bigger radio data pipe in order to sustain the required higher bit-rate, although in “challenging” situations it will “back off smoothly”. But James Chapman, Qualcomm’s VP and GM for Voice, Music and Wearables told us that: “It works. We’ve done it in our office in China — a regular Chinese office where there’s lots of Wi-Fi. We stood 10 metres away from the phone and it was holding it up.”

Snapdragon exclusive

aptX Lossless is part of Qualcomm’s Snapdragon Sound platform, which is available on phones, headphones and speakers that use the company’s Snapdragon 8 Gen 1 phone chip and S3 and S5 audio chips. So it will become available on devices in 2023 and beyond boasting the justannounced Gen 2 versions of those chips.

Examples of gen-1 devices on the market now are the ASUS Zenfone 9 phone and Nura NuraTrue Pro wireless earbuds (pictured), with which we experienced aptX Lossless recently, finding audible differences with the new codec discernible, though by no means night and day.

There aren’t many aptX Lossless-supporting devices out right now; these evolutions often take two to three years to become meaningfully prevalent on the consumer-facing hardware side.

It will also be limited by Qualcomm’s confirmation that it does not plan to license out aptX Lossless separately to Snapdragon Sound, indicating that something about the package enables optimisations that allow the codec to work optimally. So it will only be available to those using the full package of Snapdragon Sound audio technologies. These also include dynamic spatial audio, and the LE Audio Bluetooth standard, and so also Auracast, where owners of compatible headphones can zone into a choice of channels broadcast by, say, multiple screens of content in a bar or airport.

Qualcomm has also reduced Bluetooth latency by roughly 50% to 48 milliseconds, so that the time between seeing the gaming action on your (compatible) phone and hearing it through your (compatible) earbuds should be reduced. Active noise cancellation is also getting a facelift to enhance wind noise suppression and achieve a more natural ANC effect. Becky Roberts