aptX Adaptive takes Bluetooth audio up another level

A more in-depth article originally appeared on our sister site, SoundGuys.com

At IFA in Berlin, Qualcomm unveiled its latest Bluetooth audio codec for smartphones and headphones: aptX Adaptive. This isn't the 24-bit/96kHz codec from Qualcomm that some have been clamoring for, but don't be disheartened. aptX Adaptive sets out to solve a number of the biggest issues in the Bluetooth audio space and could be the codec we've been waiting for if it works as well as promised.

Headphone jacks are quickly disappearing from many smartphones, so handsets and headphones are in need of a codec that works well not just for high-quality music, but increasingly for voice calls, video, and gaming too. aptX Adaptive steps in to support all of these use cases, along with ensuring a consistent connection even in crowded radio environments.

What's new with aptX Adaptive

As the name suggests, aptX Adaptive is an adjustable codec. Rather than being set at a locked bitrate like aptX Classic, Low Latency, and aptX HD, the new version of the codec dynamically scales the bitrate to adjust its quality. The codec also incorporates aptX Low Latency technology by enabling it to work with a shared, rather than dedicated, wireless antenna. As a result, this standard is being phased out in the future. aptX Adaptive remains backward compatible with Classic and HD.

The codec supports audio file playback with 16 and 24 bit-depths at 44.1 and 48kHz sample rates. Algorithm latency is also down to less than 2ms at 48kHz, with a system round trip falling somewhere between 50 and 80ms depending on the implementation. This isn't quite as fast as Low Latency's sub 40ms speed but should be virtually imperceivable. Other codecs can reach over 200ms latency, and even the old aptX clocked in at around 150ms.

aptX Adaptive caters for aptX HD music quality and low latency gaming

aptX Adaptive's bitrate scales between 279kbps and 420kbps for CD and Hi-Res quality music. You'll notice that these bitrates are lower than the 352kbps and 576kbps of aptX Classic and HD respectively. Qualcomm states that the new codec is much more efficient than the previous version, producing the same sound quality with an even smaller amount of data. This dynamic scaling is very different from codecs like LDAC, which jumps between just a few preset quality levels, and should see smaller losses in quality when adjusting the transmission bit rate.

Why use a variable bitrate?

There are several reasons why you might want a variable bitrate codec. The first is the power trade-offs versus quality. There's no point encoding, transmitting, and decoding high-resolution audio if you are only streaming music from a so-so quality source, such as any number of music streaming services. This just wastes power and precious playback hours.

Scaling back bitrate avoids signal dropout in busy radio frequency environments such as near WiFi hubs.

Secondly, the high bandwidth and transmission speeds required for high bitrate codecs are more susceptible to errors and packet drops from radio interference and blockage. There's a good chance that you've heard your Bluetooth headphones drop out randomly. Qualcomm's adaptive codec monitors the quality of the connection and surrounding radio environment using your smartphone and adjusts its bitrate to ensure a consistent playback experience.

aptX Adaptive is the right call

Although another codec might sound like the last thing the Bluetooth headphone ecosystem needs right now, Qualcomm has clearly put a lot of thought and technology into Adaptive. Although the usual crowds might still be hankering for higher data throughput, Qualcomm has avoided the tunnel vision of projects like LDAC and has rightly focused on the bigger picture and the need for lower latency.

aptX Adaptive is designed as a one size fits all solution that not only caters to high-quality music over Bluetooth but also to the growing demand for watching videos and playing games while wearing wireless headphones. No other Bluetooth codec currently boasts this range of versatility. However, we are losing the appeal of consistent quality from previous generation aptX codecs.

The smartphone aptX Adaptive encoder is scheduled to appear on the first Android P devices sometime in December 2018. On the headphone side, products built on the Qualcomm CSRA68100 and QCC5100 chipsets will gain aptX Adaptive support from September 2018.

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