If you’re serious about music you’re probably well aware that wireless headphones aren’t always as impressive as when you hear the same recording on a pair of wired headphones. That’s because when you’re streaming over Bluetooth, you’re limited by how much audio data can be streamed to your ears. aptX and its even better versions, aptX HD, aptX Adaptive and aptX Lossless, are designed to change that and deliver amazing audio from any device – especially if it’s Android. But what is aptX?
What does aptX stand for?
aptX stands for Audio Processing Technology X. The HD in aptX HD stands for High Definition.
Where did aptX come from?
aptX has been around for decades: Steven Spielberg used it to record audio for Jurassic Park all the way back in 1993, and it has been a favourite technology of radio and film studios for since its introduction.
aptX was based on an algorithm developed at Queen’s University Belfast in the 1980s, and found a market inside devices that automated music playback in radio studios. After many years of different companies buying and selling one another, aptX was acquired by chip-making giant Qualcomm in 2015.
The fact that Qualcomm’s pushing aptX is important, because its Snapdragon processors power pretty much every well-known Android device. That means aptX already has a huge and growing user base, even if not all its users even know it’s there. The only really big phone firm that isn’t supporting aptX is, you’ve guessed it, Apple. Apple prefers to do things its own way, and for the foreseeable future that means sticking with its preferred AAC technology instead.
aptX was introduced to Android smartphones as a better alternative to SBC, which is the standard Bluetooth audio codec. Codec is short for “encoder/decoder” or “compressor/decompressor” and it’s a method for reducing the size of files to make them easier to transmit. Most audio codecs, SBC included, are “lossy”: that is, when you make files smaller you have to remove quite a lot of the original audio data. aptX is lossy too, but it is slightly less lossy than SBC. It can reduce file sizes by about three-quarters without seriously degrading the sound.
What are aptX HD and aptX Adaptive?
aptX HD and aptX Adaptive are versions of aptX that deliver much better sound quality. Like aptX they can squeeze music down to roughly 1/4 of its original size, but they deliver higher quality because they have higher bitrates. Bitrates are literally how many bits of data are sampled or transmitted in a single second; where normal aptX streams at up to 352 kilobits per second, aptX HD streams at 577kbps.
aptX Adaptive is likely to replace aptX HD eventually, because it’s even better. It delivers the same sound quality as aptX HD, but it also does so with very low latency. Latency is the gap between data being transmitted and it being received, and if you need low latency audio – because you’re playing a fast-paced video game, or because you’re recording yourself playing an instrument – you’ll know that many Bluetooth headphones just aren’t fast enough. aptX adaptive changes that, and massively reduces the risk of drop-outs and signal loss too. In the right hands it’s capable of streaming 96KHz hi-res audio files.
Qualcomm has also announced an even newer aptX: aptX Lossless. That’s even higher quality, but it’s still a newish standard so manufacturer take-up isn’t huge just yet. If you’re buying headphones or other Bluetooth audio kit we’d recommend bearing it in mind from a future-proofing perspective.
What do I need for aptX HD and aptX Adaptive?
In order to stream with aptX HD or aptX Adaptive, you need two things: an audio source that has the appropriate Qualcomm Bluetooth audio chips, such as a fairly recent Android smartphone; and headphones that also support the appropriate aptX flavour. aptX support is built into the chips inside the device, so it’s not something you can add to a phone that wasn’t made with one of those chips inside it.
You can add aptX HD or aptX adaptive to your existing home entertainment system, however. A high-resolution Bluetooth DAC such as iFi’s award-winning Zen Blue enables you to stream to pretty much any analogue or digital audio kit from your computer, smartphone or tablet. It supports multiple codecs including both aptX HD and aptX Adaptive.
If your sound source supports aptX HD but your headphones only have aptX, you can still stream to them – but you’ll be streaming in aptX, not the higher quality aptX HD.
What is aptX Lossless?
Announced in 2021, this latest codec brings full CD-quality audio to Bluetooth headphones with aptX Lossless. It is starting to arrive in headphones on the shelf, albeit rather slowly. It’s supported only if you use them with Qualcomm’s Snapdragon 8 Gen 1 and Gen 2 chipsets. The combo is part of what Qualcomm calls Snapdragon Sound, though this is more of a marketing term than anything truly meaningful.