If you are in the market for a new Bluetooth headset or even a wireless sound system for your TV, you need to understand at least the basics of Bluetooth audio codecs. This helpful bit of knowledge can help you make a purchase decision more tailored toward your specific needs, which will also give you the most satisfaction.
Qualcomm’s aptX was developed back in the 80s. Since then, it has evolved into a few versions, such as aptX HD, that offer stable, low latency, CD-like audio quality. LDAC is the brainchild of Sony and can provide higher bitrates than aptX HD but uses adaptive transfer rates to maintain a connection.
It would be easy to conclude that because LDAC has the highest potential bitrate, it has to be the better codec between the two. But unfortunately, it isn’t quite that simple. Fortunately, I can help you navigate a lot of the jargon and hopefully steer you on the right course.
Audio Codecs Explained
Before continuing, let’s briefly deal with the term “audio codec,” which you have likely heard in a conversation with your audiophile friend.
The term “codec” is a mashup of the words “encode” and “decode.” So, for example, when we are recording analog instruments in a studio, we encode the sound waves into digital code, which is then decoded again by your speakers or headphones back into analog sound waves that you can hear.
Think of digital audio as a photographer taking rapid-fire snapshots, only these snapshots are of sound, and we call them ‘samples’. The more snapshots you take, the more you capture the essence of the sound. Standard CD-quality audio, for instance, takes 44,100 snapshots every second, also known as a sampling rate of 44.1 kHz. If you slow down this rate, you might miss some of the sound’s finer nuances.
Now, each snapshot is not just a flat image; it captures a range of detail. This is where ‘bit depth’ comes in, defining the amount of information each sample contains. You might have heard of 16-bit or 24-bit audio. The higher the bit depth, the more dynamic range it can capture, meaning it can represent a wider range between the softest and loudest parts of the sound.
Once we’ve got our detailed snapshots, it’s time to pack them into a selected format, like an MP3. This process involves encoding the sampled audio data into binary bits. And here’s where ‘bitrate’ steps in, signifying the number of these bits processed each second in the audio file. It’s calculated by multiplying the sampling rate by the bit depth, and if applicable, the number of channels (for stereo or multi-channel audio).
For instance, CDs, with their bitrate of 1,411 kbps (44,100 samples/second * 16 bits/sample * 2 channels), technically offer superior audio quality. They’re like high-definition photographs.
On the flip side, MP3 files can have bitrates up to 320 kbps. They’re a compressed format, meaning they smartly reduce the file size by using an algorithm based on human hearing patterns. This algorithm selectively discards parts of the audio that are less noticeable, effectively shrinking the ‘bitrate’ and the file size. Despite the significant difference in bitrate and file size, the perceived audio quality difference between a high bitrate MP3 and a CD is often negligible to most listeners. It’s like having a smaller, yet still clear, photograph.
Bluetooth Audio Codecs Explained
Bluetooth audio codecs are specific codecs that transfer audio files over a Bluetooth signal. Like any signal, such as WiFi or radio, Bluetooth can handle only so much traffic. Think of Bluetooth like a highway, which can only handle so many trucks carrying data.
Codecs are the methods or blueprints for how data is disassembled, packed onto the trucks, and reassembled when they arrive at the end of the road. Different codecs allow for different sample rates, bit rates, and bit depths, affecting your sound quality.
LDAC Has The Highest Bitrate (Maybe)
Between LDAC and aptX, LDAC potentially has the highest sample rate and bit rate. As we briefly mentioned earlier, there are a few different versions of aptX, one of which is aptX HD, which offers high-definition sound at a bitrate of 566 kbps. Well above the maximum bitrate of MP3s, they are high enough for most HD users.
But not quite as high as LDAC, which uses very complex coding to hit bitrates of up to 990 kbps and sample rates of 96 kHz. This makes LDAC the obvious choice for high-end sound equipment users who listen to high-fidelity audio. But there is a slight catch.
Unlike aptX HD, LDAC uses adaptive bitrates, meaning that it will automatically switch between 990 kbps, 660 kbps, and 330 kbps, depending on the quality of the Bluetooth signal it’s using.
So, while LDAC running at full steam offers the best audio quality, its jumping between various bitrates isn’t a great listening experience.
However, this doesn’t have to be a complete deal breaker. Suppose your wireless speaker setup is stationary, or you sit still and enjoy music on your headset. In that case, there shouldn’t be crazy amounts of interference.
aptX Is The Most Stable With The Lowest Latency
While aptX can’t quite compete with the top-end 990 kbps of LDAC, the ace up its sleeve is that it is much better at maintaining a stable connection. Like LDAC, aptX does have a version that auto-selects bitrates, known as aptX Adaptive. Still, even this adaptive version is less likely to jump between bitrates.
This means that you’ll get a more consistent listening experience if you move around and through places of interference.
Moreover, aptX has a lower latency than LDAC. Latency refers to the delay in the signal being transmitted and received. Imagine a delay of a few split seconds between when a character in a movie speaks and when you hear it in your headset. Few things on earth are quite so irritating.
In fact, aptX has a separate codec dedicated entirely to delivering as low latency as possible, called aptX LL. This codec could be ideal for competitive gaming, where you can’t afford a delay, giving your opponent the upper hand to sneak up on you.
LDAC Isn’t As Widely Available
A final important consideration is that LDAC isn’t as widely adopted by manufacturers and is still primarily found in Sony devices. This isn’t quite as bad as you may think because all Bluetooth devices will fall back to a codec known as low complexity subband coding, or “SBC.”
SBC is like the common tongue of Bluetooth codecs, so where two devices have different codecs, they will revert to SBC as a third, common codec.
But SBC doesn’t deliver nearly as high quality as most other codecs, so you won’t get the full LDAC experience if you aren’t using compatible hardware.
On the other hand, aptX has been around much longer, so it is more widely used on many devices.
Conclusion
Both aptX and LDAC are excellent Bluetooth codecs with slightly different focuses. LDAC uses a variable bitrate that can hit 990 kbps if the Bluetooth signal is clear and strong. This makes LDAC great for movies and high-fidelity music. aptX focuses more on having a stable connection and low latency, making it a good option for general listening while moving around and gaming.
