Bluetooth has been a game-changer for personal audio, and ever-evolving Bluetooth standards have made wireless headphones and earbuds more popular than ever. Not only that, wireless personal audio devices are so affordable these days, that they’re often preferred over wired earbuds and headphones. Wired headphones are still the preferred choice for audiophiles due to their superior sound quality, but if you’re looking for new headphones or earbuds right now, you’re probably shopping for something wireless to use with your smartphone, tablet, or laptop.
You’ve likely heard the term “Bluetooth Codec,” and it’s one of the key specifications to watch when buying wireless headphones and headphones. Supporting the correct Bluetooth codec can make a big difference to audio quality. But what exactly is a Bluetooth codec, and why is it important? Read on to find out.
What is a Bluetooth codec?
Without going into the details of audio formats or how streaming services work, we’ll first try to explain what a Bluetooth codec is and how different Bluetooth codecs work. To understand this, it is important to first know how Bluetooth itself works.
Bluetooth is a set of wireless standards that ensure that a digital signal from the source device can be interpreted by the receiver. In the case of audio, a source such as a smartphone converts the audio data into radio waves. A receiver, such as an amplifier or a pair of headphones, uses a digital-to-analog converter (DAC) to convert this signal into audio that the listener can hear.
This whole process is usually done quickly and consistently, to ensure that the listening experience is not hampered in any way. The higher the sound quality you want, the more data will need to be transferred. To achieve this, the digital audio signal is compressed so that more data can be transmitted wirelessly at the same time. This needs to be decompressed on the receiving end. A Bluetooth codec (which is short for “coder/decoder”), is basically a set of parameters and instructions for how this compression and decompression should occur. Both devices need to support the same codec in order to use it, and their maximum bandwidth is an indication of their capabilities.
Bluetooth codecs work differently, and some basic software such as the sub-band codec or SBC tend to discard a lot of signal data during the compression phase. This greatly reduces the quality of the digital audio signal and the later analogue audio you hear. Advanced Bluetooth codecs such as aptX and LDAC are able to carry more data wirelessly and can achieve higher stable bit rates, ensuring better quality signal is received on the audio output device.
Compatibility with Bluetooth codec required at both ends; Essentially, the receiver should be able to understand the “language” of the source device, so to speak. Thus, the Bluetooth codec can only be used if both the source and the receiver support it. If there is a mismatch, the link will fall back to whatever standard is common to the two devices. This makes it important to match codec support on your wireless headphones, earbuds, or speaker to your smartphone, tablet, or laptop.
Popular bluetooth codec explained
SBC (Subdomain Encoding)
The simplest Bluetooth encoding is SBC, which is supported almost universally because it is part of the underlying Bluetooth protocol. Practically every device capable of sending or receiving Bluetooth audio supports this codec, and this ensures that any Bluetooth headset can be interoperable with any Bluetooth enabled phone. If no other codecs are present, the devices will default to SBC.
As mentioned earlier, SBC is very basic when it comes to data transfer and bit rates. Connection stability and power efficiency are preferred over sound quality. SBC supports a data transfer rate of about 345 kilobits per second, or kilobits per second, but typically operates at lower bit rates to improve stability and reduce lag.
Many entry-level Bluetooth headphones and earbuds only support the SBC Bluetooth codec. This naturally means that the received audio signal is highly compressed, and the audio quality is usually limited.
AAC (Advanced Audio Coding)
Not to be confused with the audio file format of the same name, the AAC Bluetooth codec is a step above SBC in terms of being able to transmit audio data stably over Bluetooth. It supports a maximum data transfer rate of 320 kbps, and is usually able to maintain a high bit rate without the need for frequent tuning for stability. Notably, this is the default Bluetooth codec on Apple devices such as iPhones and iPads as well as Apple’s range of AirPods for Bluetooth headphones.
AAC is also widely supported on Android devices and many wireless headphones and earbuds, across its price range. Although AAC offers better sound quality than SBC, it still puts a lot of pressure on the audio signal compared to more advanced Bluetooth codecs.
However, it is a popular and practical codec, and you should look for it if you intend to use your wireless headphone with Apple devices.
Qualcomm aptX, aptX LL, aptX HD, aptX Adaptive
The Qualcomm aptX codec family has been around for years, and since the original version was introduced, there have also been new and improved iterations such as aptX HD and aptX Adaptive. With bitrates up to 576 kbps, and the aptX Adaptive codec even implements variable bit rates for flexibility and better connection stability, aptX offers a significant improvement over both SBC and AAC.
Support for aptX codecs is common on Android devices, and is also available on some Apple Macs, but not on iOS devices yet. Although aptX has an impact on energy efficiency and battery life, it offers a significant improvement in audio quality over SBC and AAC, particularly the newer aptX HD and aptX Adaptive implementations.
Many headphones and earbuds across price ranges support the aptX codec, usually by using a compatible Qualcomm Bluetooth solution as part of a hardware setup. It is worth looking for support for this codec if you have a compatible source device, which can be almost any Android smartphone.
Scalable from Samsung
Samsung introduced its scalable Bluetooth codec recently. It has a variable transfer rate, constantly tuned up to 512kbps, and is said to enable high-quality data transfer even in environments with a lot of wireless interference. It is widely considered to be on par with aptX HD and aptX Adaptive in terms of transmission quality.
However, Samsung has kept this technology as proprietary, and the Scalable codec is only supported on Samsung devices at this time. This includes many of the company’s true wireless earbuds and headphones across the Samsung and AKG product ranges, as well as most Samsung smartphones and tablets running Android 7 and above.
A headset that supports Scalable encoding makes sense if you have a compatible Samsung smartphone or tablet to use it with. Most recent Samsung audio products, including the Galaxy Buds series, support the Scalable codec.
LHDC (Low Latency High Definition Codec)
On paper, LHDC is among the best Bluetooth codecs out there with support for a flexible bit rate of up to 900 kbps. However, the biggest drawback of this codec is hardware compatibility. It does not support a lot of wireless headphones and LHDC source devices, and so far only a few brands like Xiaomi, Oppo, and Huawei have launched products that support it.
Matching these wireless headphones or earbuds to an LHDC-compliant source device is particularly challenging at the moment, and this has led to their waning popularity. The more widespread compatibility and adoption of the other codecs on this list, especially aptX and LDAC, gives them an advantage over LHDC.
Among the top popular Bluetooth codecs, Sony LDAC has variable bit rates that range across three settings – 330 kbps for stable connection, 990 kbps for focusing on audio quality, and 660 kbps, striking a balance between the two. Although LDAC was originally limited to Sony products, it is now supported on a wide range of devices including headphones of various brands, and many compatible Android smartphones and tablets.
LDAC is among the best Bluetooth codecs at the moment, allowing more details and insights into the transmitted audio than other codecs. It is commonly seen in high-end wireless audio products, although there are some more affordable products that support it. Many mid- and high-end Sony headphones and earphones support LDAC, and it’s a good idea to look for this codec if you’re using an Android phone.