Understanding Bluetooth codecs (2024)

Thanks to the frustrating demise of the cellphone headphone jack, Bluetooth’s presence is more ubiquitous than ever. Now, you don’t have to be an audio geek for Bluetooth codecs to be of importance: as well as audio quality variations, different codecs introduce different latencies, have varying degrees of energy efficiency, and different levels of stability. These might be important considerations, depending on your use case. If you’re going wireless, it’s worth knowing what you’re getting yourself into. In order to bring you up to speed in a matter of minutes, we’ve put together this guide for understanding Bluetooth codecs.

Editor’s note: this article was updated on August 22, 2023, to update formatting, information, and links.

What you should know about audio and compression

What are Bluetooth codecs?

A codec determines how Bluetooth transmits from the source device to your headphones. It encodes and decodes digital audio data into a specific format. In an ideal world, a high-fidelity signal would be possible at the minimum specified bit rate, resultingin the least amount of space and bandwidth required for storage and transmission. Lower bitrates actually mean better compression but often mean worse sound quality, a high bitrate usually means better sound quality and worse compression. So how do codecs navigate this compromise?

Low-complexity sub-band codec (SBC)

SBC divides the signal into multiple frequency bands and encodes each one independently. Think of SBC as the lowest common denominator among Bluetooth codecs. It’s not the best. It is, however, mandatory among allA2DP-enabled devices, making it virtually universal. Manageable transfer rates (192-320kbps) are delivered at the expense of significant data loss.

Qualcomm aptX, aptX LL, aptX HD, and aptX Adaptive

Qualcomm’s proprietary codecs, aptX, aptX LL,and aptX HD receive frequent recommendations here at SoundGuys, not to mention aptX Adaptive. Though only aptX LL supports a latency of fewer than 40 milliseconds. What’s more, Android’s wireless efficiency is inconsistent depending on what source device is used.

Bluetooth's Achilles' Heel is its limited bandwidth. High transfer rates may overload available bandwidth, causing a stutter—or complete crash—of the service.

Why choose aptX over SBC? aptX’s greater transfer rates are able to preserve more data than SBC, allowing for better overall sound quality. The simpler aptX codec supports 48kHz/16-bit LPCM audio data (352kbps), while aptX HD supports 48kHz/24-bit LPCM audio data (576kbps). Though both are lossy formats, they’re leagues ahead of SBC. Plus, they support a fine enough bit rate to keep everything running smoothly and sounding decent enough.

Advanced audio coding (AAC)

AAC is the audio standard for lossy digital audio compression. It also happens to be the license-free standard for YouTube, and for Apple devices. By using a psychoacoustic model to compress the audio being sent to your headphones, AAC is one of the more popular methods to get reasonably good audio quality over a heavily compressed stream.

If you have an Android phone, you’re at the mercy of your phone’s power handling to get the most out of this codec, and our testing has shown that Android devices don’t always handle it effectively. However, it should be pointed out that this data was collected several years ago, and better chipsets and phones have come out in the interim. Additionally, the worst offenders in our tests have since bowed out of the space.

iPhone users will certainly benefit from its higher-resolution playback though. It has a transfer rate cap of 250kbps, creating a file similar to that of a standard-quality MP3.

Like aptX, AAC is a much more complex codec than SBC. As such, it offers much better audio quality than SBC, even though it offers lower bitrates and sampling rates. AAC’s efficient implementation on Apple devices specifically makes it a no-brainer if you are embedded in the Apple ecosystem. If you use other platforms like Android, however, you might not be getting the most out of AAC and aptX might be the better overall choice for you.

Sony LDAC

Like Qualcomm, Sony has its own Bluetooth codec, LDAC. Its variable bit rate is the defining feature. In theory, it should consistently transfer up to 3x the data compared to SBC. But both aptX and SBC outperform LDAC when it streams at 330kbps, which is the default chosen by many phones. In order to change this, you have to enter developer settings and enable a setting called “Best effort.” That said, various smartphones vary in the degree to which they can maximize this LDAC’s potential. You may be better off with AAC or aptX for sound quality if your device is not properly optimized for LDAC.

LDAC was initially limited to Sony products but has been part of the Android Open Source Project (AOSP) since Android 8.0 “Oreo.”

HWA Alliance’s LHDC and LLAC codecs

LHDC stands for low-latency and high-definition audio codec and was developed by the Hi-Res Wireless Audio (HWA) Union and Savitech. This codec allows for three times the data transmission afforded by SBC and supports a maximum bitrate of 900kbps with a max sample rate of 96kHz. The Huawei Mate 10 was the first smartphone to support LHDC. It’s supported by Android 10 and up, and is part of the AOSP.

LHDC can be a suitable alternative to high-definition audio codecs like LDAC and aptX HD/Adaptive depending on your use case. It is, however, optimized for only a narrow set of hardware, such as the Huawei Mate 10 and the OnePlus Nord 2/2T, though more and more manufacturers have started to include support for LHDC in their smartphones and audio accessories.

The low-latency audio codec (LLAC/LHDC LL) is an alternative to LHDC and boasts low-latency features that are ideal for gamers. End-to-end latency is as low as 30ms, and it supports bitrates of 400/600kbps with a max sample rate of 48kHz up to 24bits. The Huawei P30 was the first smartphone to support LLAC.

LC3 supports sample rates of up to 48kHz and up to 345kbps bit rate, a considerable improvement over SBC that puts it in the same league as aptX and AAC.

LE Audio benefits the hearing impaired by expanding the functionality of Bluetooth hearing aids due to multi-stream support. Multi-stream audio allows multiple audio streams to be transmitted between a smartphone and earbuds simultaneously. In practice, this means your hearing aids can stream audio while also keeping you aware of your surroundings.

Similarly, it can transmit different streams to a pair of true wireless earphones simultaneously: rather than a single 160kbps stream, it may send two streams of 80kbps each. If you and your friend are at a bar watching a game, one of you can tune into the home team’s announcer with the left earbud while the other can opt for information about the visitors via the right bud.

Samsung Scalable Codec

The Samsung Scalable Codec was announced with the Samsung Galaxy Buds which was developed with AKG. It prioritizes stability by making constant adjustments to streaming rates, so listeners are less likely to experience connection stutters and drops. It’s similar to how LC3 audio is said to manage packet loss, both result in less audio chopping by actively accommodating bitrate to signal strength.

The Samsung Scalable Codec is capable of supporting a wide range of bitrates, from 88kpbs to 512kpbs. Depending on the strength of your Bluetooth connection, the codec will adjust your streaming rate within this spectrum to ensure optimal quality and stability. It is, however, limited to Samsung devices, specifically the Galaxy Buds, and is thus of little use to those outside the Samsung ecosystem.

We’ve barely scratched the surface here. In fact, we’re just beginning to look upon the surface. If you want to learn more, head over to our all-encompassing Bluetooth codec guide.

Frequently Asked Questions

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