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Is Qualcomm’s New ‘aptX Lossless’ Technology The Holy Grail of Bluetooth?

by February 10, 2022
Qualcomm aptX Lossless

Qualcomm aptX Lossless

The first truly lossless Bluetooth codec will soon be a reality, according to the wireless telecommunications company Qualcomm Technologies. To understand the significance of this development, we must first understand the current state of Bluetooth. Bluetooth audio has certainly come a long way since the first hands-free mobile headset was introduced in 1999. For convenience, it’s hard to argue with a system that’s so ubiquitous. And for non-audiophiles, like my girlfriend Hannah, the sound quality of current Bluetooth devices is more than adequate. At home, Hannah uses an iFi Zen Blue Bluetooth DAC connected to an old pair of powered speakers from Audioengine. She isn’t downloading 24/192 high-res files or streaming them on Qobuz; she listens to Spotify and watches music videos on YouTube, like most normal people. With that content, I’ve never had any reason to think that the iFi Zen Blue’s use of Bluetooth technology was the limiting factor of the system’s overall sound-quality. It’s not just listenable — it’s enjoyable! When Hannah’s on the go, she uses a pair of Sony WH-1000XM4 wireless noise-cancelling headphones. In a loud environment, the Sony’s impressive noise-cancelling more than makes up for any fidelity lost by its use of a Bluetooth connection instead of a cable. Hannah also has a nice pair of wired Sennheiser headphones. With a good DAC/amp, they can sound excellent in a quiet room, but on a plane or a bus, I’d take the XM4s any day. Hannah hasn’t touched the Sennheisers since I gave her the Sonys for her birthday last July.

So, if Bluetooth audio is so popular with the millions of regular folks who use it happily every day, why are there so many audiophiles who wouldn’t touch it with a 10-foot wireless pole? One explanation is that audiophiles have more resolving playback equipment. A compressed audio stream that sounds perfectly fine on a consumer-grade Bluetooth speaker might sound noticeably lacking on better gear. That’s probably part of the issue. But for audio purists, I think the aversion to Bluetooth is — at least partially — a matter of principle. Bluetooth uses lossy compression, meaning that some of the music is lost in order to shrink the files into a more manageable size. For many audiophiles, that makes Bluetooth a nonstarter. In many ways, Bluetooth is like the dreaded mp3, which was also born out of the need to shrink audio files so that they could be downloaded or streamed more easily. These sonic compromises made sense when storage and bandwidth were more limited — the important thing was being able to fit as many songs as possible on an iPod, or deliver an uninterrupted stream via a slow internet service. Similarly, Bluetooth has always used lossy compression simply because the connection has lacked sufficient bandwidth to transmit full-fat audio. Like USB, Bluetooth wasn’t originally designed for audio; it was designed for transmitting data, and was actually conceived as a wireless alternative to RS-232 data cables. Lossy compression made it work for audio, and the rest is history. But Bluetooth doesn’t have to stay lossy forever. Consider the fate of the mp3. Nowadays, there’s really no reason for it to exist. A typical broadband or cellular connection is now more than fast enough to stream (or download) lossless audio without even trying. And in a world dominated by streaming, file storage isn’t an issue for most people. These improvements to our internet infrastructure have allowed audiophile streaming services, such as Tidal and Qobuz, to ditch lossy compression for good. Now, even mass-market streaming services, like Apple Music and Amazon Music Unlimited, serve up their entire catalogs (~75 million tracks) in lossless formats that are equivalent to, or better than, a CD. (Spotify has announced a similar upgrade to its service, but hasn’t yet delivered.) Even if audiophiles are the only ones really reveling in this new age of lossless music streaming, interest in high-quality audio experiences has been growing across a variety of services, from streaming video, to gaming, to video conferencing, to virtual and augmented reality.

That all sounds promising, but the reality is that Bluetooth audio has not kept up with the recent improvements in quality that we’ve seen in streamable source content. You might be able to stream lossless tunes via Apple Music to your iPhone or laptop, but if you’re listening via AirPods (or any other Bluetooth headphones, speaker, or audio device), the benefits of that lossless stream are not making it into your ears. Bluetooth still throws away musical information in order to compress file size. It’s not as bad as it used to be — the inherent bandwidth limitations that most of us associate with bluetooth are really tied to the codec used, and as time has marched on, newer and better codecs have breathed new life into Bluetooth audio. An audio codec is a computer program implementing an algorithm that compresses and decompresses digital audio data. The codec determines how bluetooth transmits audio from a source device, such as a phone, to a receiving device, such as wireless headphones. But although today’s codecs are better than those from years past, no Bluetooth codec currently in use in a consumer product has achieved the holy grail of true, lossless audio. About 5 years ago, when Apple was preparing to introduce the first-gen AirPods, there was some speculation that the new earbuds would set themselves apart from the competition by using a new, lossless wireless audio standard. The same rumors surrounded the release of Apple’s current flagship headphone, the $550 AirPods Max, which were released a year ago. But both use an existing Bluetooth codec called AAC, which has a maximum transfer rate of just 264 Kbps. To put that into perspective, a lossy stream from Spotify is delivered at a rate of 320 Kbps, and a lossless CD-quality stream would require more than 3 times that bandwidth. Apple’s Bluetooth devices may be good at preventing audio drop-outs and glitches from interrupting your content, but they aren’t capable of delivering the lossless audio quality that Apple Music began dishing out in June of 2021.

Achieving true hi-res audio requires more than simply finding a service that offers lossless streaming. Rather, you need to assure your audio is part of a full end-to-end solution, and for those interested in a wireless solution, not all Bluetooth solutions are created equal.

— Qualcomm

Generally speaking, things have been a little rosier for Android users. In 2009, Sennheiser became the first headphone maker to use Qualcomm’s aptX codec, which uses higher transfer rates (352 Kbps) and better compression methods to improve audio quality. While iPhone users were left out in the cold, makers of Android phones began adopting aptX as a go-to solution for Bluetooth audio. According to Qualcomm, aptX is based on ADPCM (Advanced Pulse Code Modulation) techniques and is a “non-destructive” codec, meaning that the post-processed audio is very similar to the original uncompressed file. (Launched in 2015, Sony’s LDAC codec had similar goals of improving audio quality). In 2016, Qualcomm introduced aptX HD, with a higher bit-rate of 576 Kbps. And in 2017, with the release of Android Oreo, aptX (along with LDAC) became part of the Android Open Source Project, meaning that every Android phone maker could integrate aptX into their own Android devices freely. (For all of the codecs discussed here, both the transmitting device and receiving device must incorporate the appropriate technology in order to deliver the sonic benefits.) These codecs represent significant improvements to Bluetooth audio performance, but they still can’t manage to deliver lossless, CD-quality wireless audio. For those of us following along at home, it could get confusing at times. Both LDAC and aptX HD boast the ability to transmit 24-bit hi-res audio, and technically, they can. That is to say, you can send a high-res file over Bluetooth using these codecs, and sound will come out of the receiving device. As a result, some Bluetooth devices that use these codecs (such as Hannah’s iFi Zen Blue DAC) are advertised as “Hi-Res Audio” devices. But the fact remains that musical information is still being discarded along the Bluetooth path. Whether the original audio file is a master-quality download, a 24-bit high-res stream from a streaming service, or a plain old 16-bit, 44.1kHz CD, Bluetooth audio uses lossy compression, and because of this, many audiophiles will stay away.

Qualcomm aptX Lossless 2 

Lossless Bluetooth a Reality?

But now, finally, that appears to be changing. Since 2018, Qualcomm has offered a codec called aptX Adaptive, which is an adjustable codec with a variable bitrate. The bitrate can scale between the quality of aptX Classic and aptX HD, depending on the quality of the connection and the amount of radio frequency (RF) inference in the surrounding environment. The codec also incorporates Qualcomm’s latest Low Latency technology. Now, Qualcomm has announced a new capability of the aptX Adaptive codec called aptX Lossless audio technology. Qualcomm says that aptX Lossless is designed to deliver CD quality (16-bit, 44.1kHz) lossless audio over Bluetooth, with no caveats or provisos. In order to achieve this, Qualcomm says it was necessary to take a “systems level approach,” optimizing a number of core wireless connectivity and audio technologies so that they work together to “auto detect and scale-up.” Simply put, the technology can detect when the user is listening to a lossless music file, and then it checks to see if RF conditions are suitable for delivering lossless audio. The bitrate then scales up to approximately 1Mbps in order to deliver the lossless transfer. The company is adding aptX Lossless to its suite of audio technologies collectively called Snapdragon Sound Technology. Qualcomm says that “Snapdragon Sound with aptX Lossless technology retains all of the original content, bit for bit, resulting in music identical to the original recording. It’s designed to scale up to deliver 16-bit 44.1kHz lossless CD-quality when users are listening to lossless streaming source content, like Amazon HD.” According to Qualcomm, the aptX Adaptive codec works seamlessly with another bit of proprietary tech called Qualcomm Bluetooth High Speed Link technology to deliver the required sustainable data throughput at 1Mbps and beyond. In busy RF environments, the bit-rate will automatically scale back (all the way down to 140Kbps in extreme cases) to ensure that there are no drop-outs or audio glitches.

At Qualcomm Technologies we’re excited about the future of sound, and we’re continually looking for ways to help our customers deliver new and exciting listening experiences. Lossless audio means mathematically bit-for-bit exact, with no loss of the audio file and up to now the necessary bit rate to deliver this over Bluetooth has not been available. With many leading music streaming services now offering extensive lossless music libraries, and consumer demand for lossless audio growing, we’re pleased to announce this new support for CD lossless audio streaming for Bluetooth earbuds and headsets which we plan to make available to customers later this year. Sound quality is the most critical purchase driver across all audio devices according to our 2021 State of Sound survey, which also shows increasing demand for higher quality streaming audio. Over half of respondents are seeking either lossless or high-resolution audio quality, and a massive 64% saying that lossless audio quality is likely to influence their decision to purchase wireless earbuds. Currently lossless audio is only supported on client devices such as phones, PCs, and tablets. By supporting lossless audio on next-gen earbuds and headphones, we’re providing our customers another way to deliver sound the way the artist intended, as well as a significant opportunity to differentiate and be among the first to develop products with this feature.

— James Chapman, vice president and general manager, Qualcomm Technologies International, Ltd.

Perhaps the most interesting piece of this puzzle is that Qualcomm has taken such an integrated approach in order to achieve lossless Bluetooth audio transmission. The company must control the source and receiving devices, the codec itself, and optimized software from end-to-end in order to deliver the needed data throughput. This level of integration is something we might expect to see from Apple, with its tight grip over every aspect of the hardware/software ecosystem. And yet it appears that the first devices to cross this finish line will be an Android phone, with its open-source operating system, and a third-party headphone from one of Qualcomm’s many partners. That list currently includes Audio Technica, Bang and Olufsen, Beyerdynamic, Bose, Bowers and Wilkins, Sennheiser, Shure, and many others. Will Apple deliver its own lossless Bluetooth codec in order to fulfill the promise of lossless Apple Music? Or will Tim Cook and company finally cave, and start supporting Qualcomm’s aptX tech in iPhones and AirPods? Will the advent of lossless Bluetooth allow audiophiles to embrace the technology once and for all? Share your thoughts in the related forum thread below. 

 

About the author:
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Jacob is a music-lover and audiophile who enjoys convincing his friends to buy audio gear that they can't afford. He's also a freelance writer and editor based in Los Angeles.

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