What’s The Difference Between Bluetooth A2DP And aptX?


Bluetooth headphones are all the rage now, after spending the better part of a decade as a niche restricted to tech enthusiasts. Now you can find an incredible variety of Bluetooth headphones on electronic store shelves, and even more online. But as with almost all product categories, not every set of wireless headphones is created equal.

We’re going to talk about three Bluetooth technologies that relate to exactly how good your Bluetooth headset sounds, and what you’re looking for in a new pair. A2DP is the basic Bluetooth stereo streaming protocol, aptX is an advanced codec specifically designed for Bluetooth, and Apple’s W1 chip system is proprietary and only works with Apple hardware.

A2DP: The Default

A2DP stands for Advanced Audio Distribution Profile, which means—well it doesn’t mean a whole lot in the context of something that’s already streaming audio. But as one of the oldest parts of the combined Bluetooth specification, A2DP is more or less the default for streaming audio over Bluetooth. Any Bluetooth audio product you purchase—headphones, speakers, mobile phones, laptops—will support A2DP at the very least, whether or not it can also work with aptX.

My trusty, rusty Motorola s305 Bluetooth headphones from 2009 only support A2DP.

The A2DP standard operates in stereo and supports most of the standard audio compression codecs. The recommended sub-band coding (SBC) codec supports up to 345 kilobits per second at 48 kilohertz. That’s approximately one third the quality of standard CD audio—roughly the equivalent of a high-quality MP3 recording. Due to high “lossy” compression in the SBC codec, the reality of the audio quality is considerably lower, somewhere in the range of 256kbit/s.

The system also supports other popular methods of encoding and compressing audio, like MP3 itself. If the audio source is already compressed in a format like MP3, AAC, or ATRAC, then it doesn’t need to be re-encoded in SBC in order to be broadcast from the source device. With A2DP’s maximum audio bandwidth of 728kbit/s, it’s at least possible to start approaching what we’d call “high-quality audio” with the basic standard alone. (CD quality audio, uncompressed, is approximately 1400kbit/s.)

Unfortunately, very few hardware makers seem to be actually using this capability, and most A2DP-only devices are re-encoding audio to SBC and de-encoding on the receiver end. This makes the whole process more complicated, resulting in poorer audio quality.

aptX: The Upgrade

Mobile chip maker Qualcomm bought CSR and its aptX tech in 2015. It licenses the codec to a variety of phone and audio companies.

AptX is also a compression standard, like SBC or MP3. But it’s an altogether better one, and one that’s designed to work within the limited bandwidth and low power…

Sasha Harriet

Sasha Harriet

As content editor, I get to do what I love everyday. Tweet, share and promote the best content our tools find on a daily basis.

I have a crazy passion for #music, #celebrity #news & #fashion! I'm always out and about on Twitter.
Sasha Harriet

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