Bluetooth audio codecs explained: what’s the best codec for audio among AAC, aptX, LDAC, and more | 91mobiles.com
In this article, we take a look at the technology behind the wireless audio
The removal of headphone jacks from smartphones, for better or worse, has resulted in consumers shifting to wireless audio gear. While this shift to wireless audio was happening there was an intense debate among audio enthusiasts on which is better: wireless audio or wired audio? The argument is that wired audio is somehow better because wires are efficient at transferring data and audio. And wired audio was working just fine and didn’t need to be replaced – until most manufacturers started removing the beloved headphone jack from smartphones.
Bluetooth technology, meanwhile, was also suffering from bandwidth and latency issues but all that changed with newer Bluetooth releases such as Bluetooth 5.0 and above, which brought huge improvements in bandwidth, latency, and coverage.
In addition, Bluetooth audio codecs such as AAC, Qualcomm’s aptX (and the related codecs), Sony’s LDAC, and more also played a big part in bringing wireless audio on par with wired audio. While diehard fans of wired audio may disagree with the quality offered by wireless audio accessories, most can agree that the audio quality now offered by the latest generation earbuds and headphones is more than sufficient for the general audience. But what’s behind these audio codec technologies, how do they work, and what are the things you should keep in mind before purchasing your next pair of earbuds? These are some of the questions that we will discuss in this article.
What’s a Bluetooth audio codec?
Before we talk about codecs in general, we need to talk about audio compression. There is a lossy compression- and lossless compression technique in audio. Lossy compression is a technique used to reduce the overall file size by removing the audio frequencies most people cannot hear using complex algorithms. Lossless compression, as the name suggests, retains all the nuances of the originally recorded music. In simple terms, the original audio file is untouched to the most extent in a lossless audio file.
Much like the usual audio codecs such as MP3, AAC, Ogg, and more; Bluetooth audio codecs are used for transferring high bandwidth audio files at reduced bit rates while minimally losing audio quality as much as possible. Modern Bluetooth audio compression technologies such as aptX use advanced algorithms, to make music sound much better at reduced bit rates. As explained above, this is achieved by cutting down audio frequencies humans cannot hear using psychoacoustic models. This data removal results in much smaller audio files, making them easier to transfer over low-bandwidth wireless technologies such as Bluetooth.
Each audio codec does this compression differently, that’s why one may have much better audio quality than the other — as is the case with the SBC (Subband Codec), the mandatory audio codec on all Bluetooth A2DP (Advanced Audio Distribution Profile) enabled devices and a fallback codec in most earbuds and headphones. Though at the surface level, SBC may seem like a low-quality audio codec, it is capable of offering CD-quality audio. But most of the time, it suffers from bad implementation (more on this below).
List of Bluetooth audio codecs: Bitrate, Bit depth, and sampling rate
Bluetooth audio codecs
Bitrate
Bit depth
Sampling rate
SBC
Up to 328kbps
16-bit
Up to
48kHz
AAC
Up to 320kbps
24-bit
Up to
44.1kHz
aptX
Up to 352kbps
16-bit
48kHz
aptX Adaptive
279kbps to 420kbps
––aptX HD
576kbps
24-bit
48kHz
aptX Low Latency–
16-bit
–LDAC
Up to 990kbps
24-bit
Up to 96kHz
LHDC
Up to 900kbps
24-bit
Up to 96kHz
LC3 (Bluetooth LE audio)
345kbps
32-bit
Up to 48kHz
Bluetooth audio codecs
SBC
-
Bitrate: 328kbps
- Bit depth:
16-bit
- Sampling rate: Up to
48kHz
SBC is the standard audio codec for all Bluetooth-enabled devices using Advanced Audio Distribution Profile (A2DP) and is a fallback codec in most earbuds and headphones where higher quality codecs are installed. In fact, the SBC codec is mandatory to get Bluetooth certification on all headphones and earphones. That’s why you’ll find it alongside any other supported Bluetooth audio codecs on the headphones — offering universal compatibility with all connected devices. SBC is found on most budget audio devices. The standard SBC codec offers up to 48kHz audio sampling rates in a 16-bit depth resolution. It offers bitrates up to 320kbps. Most of the time, the codec suffers from insufficient audio quality and higher latency. That’s why most premium headphones geared towards audiophiles include other premium codecs such as aptX-HD.
SBC may seem like a low-quality audio codec on the surface, however, as demonstrated by the Lineage OS project, SBC can sound just as better as higher-quality audio codecs such as the aptX HD, if implemented using SBC Dual Channel mode. Indicating audio quality-related issues are an implementation issue rather than the codec itself. Though, the SBC’s successor LC3 (Bluetooth LE Audio), aims to solve all issues of SBC and bring it on par with the other premium audio codecs (more on this below).
AAC
-
Bitrate: 320kbps
- Bit depth:
24-bit
- Sampling rate: Up to
44.1kHz
Advanced Audio Coding or AAC is the next popular audio codec used on headphones and is found on all Apple devices including the Apple Airpods. It is also the file format used to store local music on several devices including Apple devices. It offers a maximum bitrate of 320kbps and a higher bit depth of up to 24-bit resolution. The AAC codec offers better audio quality than the standard SBC codec, especially on Apple devices, even though it offers lower bitrates and sampling rates than SBC because of the efficient implementation and processing on Apple devices. Though, the quality seems to drop on most Android devices as observed by the SoundGuys. Another thing to note here is that when the files are encoded using the AAC format they don’t need to be compressed again. For instance, if you have a locally stored AAC audio file, it’ll be sent to the headphones as it is, no extra processing is needed on the smartphone or PC. This makes AAC files sound much better since no additional compression is taking place. All the music storage and music streaming on Apple devices either happen in AAC or the SBC codec. This may be the reason why AAC codec performs so well on Apple devices.
aptX
- aptX:
352kbps, 16-bit, 48kHz
- aptX Adaptive:
279kbps to 420kbps
- aptX HD:
576kbps, 24-bit, 48kHz
aptX is actually an umbrella term for a series of codecs for Bluetooth audio that Qualcomm has designed for a range of audio devices. Qualcomm offers aptX in several flavors — aptX, aptX HD, aptX Adaptive, and aptX Low Latency. Each comes with its pros and cons. For instance, the standard flavor of the aptX codec lets manufacturers offer up to 352kbps bit rate and 16-bit bit depth with up to 48kHz sampling rate.
The aptX Adaptive on the other hand strives to offer the best audio quality as well as minimal latency whenever possible. This ensures no lip-syncing issues in movies and the overall gaming experience will be better thanks to the on-the-fly adaptive bitrates. aptX Adaptive can change bit rates between 279kbps to 420kbps and offers latencies as low as 80ms. The codec is backward compatible with aptX and aptX HD.
A better alternative for hardcore music fans, aka the audiophiles, will be aptX HD, which is designed to offer a high-quality premium (CD-like) audio experience at all costs. The aptX HD codec allows audio to be sampled at 48kHz with bitrates as high as 576kbps with 24-bit bit depth.
aptX Low Latency was designed to offer a low latency experience at all costs, something which is critical to gaming. It’s a specialised Bluetooth codec that offers an impressive 40ms low latency with consistent 16-bit audio streaming quality. This sample-based audio codec is what competitive multiplayer gamers need.
LDAC
-
Bitrate: Up to 990kbps
- Bit depth:
24-bit
- Sampling rate: Up to
96kHz
Another codec that promises to provide CD-like audio quality is Sony’s LDAC. The codec is so premium in providing the highest wireless audio that it has received a ‘Hi-Res Audio Wireless‘ Hi-Res certification at 990kbps audio quality. However, the codec offers a variety of presets to meet most users’ needs while in different network conditions. This is to say, the codecs auto automatically changes depending on the Bluetooth connection quality between 330kbps, 660kbps, and 990kbps. To make sure you’re getting the highest audio possible audio quality from LDAC, you need to select the ‘Best effort’ mode from settings. Android allows you to select this mode quite easily from the developer settings (more in the FAQ section). LDAC source code was added to the AOSP (Android Open Source Project) in recent years allowing manufacturers to easily enable the codec on most devices. LDAC has a maximum sampling rate of 96kHz and up to 24-bit bit depth.
LHDC
-
Bitrate: 900kbps
- Bit depth:
24-bit
- Sampling rate: Up to
96kHz
LHDC (Low Latency High-Definition Audio Codec) is another Hi-Res certified Bluetooth audio codec and is developed by Savitech. The LHDC provides high-quality audio streaming with adaptive bitrate with adaptive low latency with up to 96kHz sampling rate with up to 24-bit/900kbps quality. LHDC competes with other high-resolution codecs such as aptX HD/Adaptive, LDAC, and others. More and more manufacturers have started including LHDC codec in their smartphones and audio accessories in recent times. The Huawei Mate 10 was the first smartphone to include this codec with recent examples being the Find X2 and Find X2 Pro phones, OnePlus Nord 2/2T, OnePlus 9 Pro/9, and more, as well as TWS earbuds such as Oppo Enco X/X2 and OnePlus Buds Pro, and more.
There is another variant of this codec called LHDC LL, which is geared toward gamers who need low-latency audio feedback. Both LHDC and LHDC LL Bluetooth codecs are a part of the AOSP since Android 10.
LC3
-
Bitrate: 345kbps
- Bit depth:
32-bit
- Sampling rate: Up to
48kHz
LC3 or Low Complexity Communications Codec was developed by Bluetooth SIG as a much-improved sequel to the SBC codec. It aims to improve upon most cons of its predecessor, promising much improved audio quality and lower latencies along with several other improvements such as lower power consumption and more. It supports sample rates of up to 48kHz and up to 32-bit bit depth, and up to 345kbps bit rate. LC3 was recently finalized and should hit a broad range of audio devices in the upcoming months and years to come.
Things to consider while buying Bluetooth earbuds or headphones
Earbuds and device compatibility
Both devices need to support the said Bluetooth codec to take advantage of the higher audio quality and lower latencies. For instance, if your smartphone supports aptX audio codec then the TWS earbuds or headphones you’re purchasing must also support the same codec. Otherwise, both the smartphone and the earbuds will fall back to the default SBC codec.
Latency
Latency is another factor you need to consider to avoid lip synchronization issues in videos. Moreover, if you’re a gamer, the requirement of lower latencies becomes even more critical in the competitive gaming environment. Headphone manufacturers usually state the latency numbers on the product spec sheet.
Wireless range
Finally, keep in mind the wireless range of the headphones, so you can move to the adjacent room, for instance, without having to take the smartphone with you. Most wireless headphones have up to a 10-meter range before their connection quality significantly drops.
FAQ
How to check the supported Bluetooth codec on your smartphone?
On Android devices, this can be done easily by going to developer options. Usually, you have to enable the Developer option by going to System settings > About device > Version and tapping several times on the Build number until you see the ‘You’re now a developer’ message. This will enable the Developer options. Now, go to System settings > Developer options, and in the Networking section tap on the Bluetooth audio codec option to display the supported Bluetooth codec by your device.
You can also view the codec information by going to Bluetooth > Paired devices (while connected) > tap on the ‘i‘ or ‘>‘ button. The following screen shows the Bluetooth codec currently in use by the connected audio device.
Which is better AAC or aptX?
As discussed above, the AAC codec seems to perform much better on Apple hardware while Android devices offer better compatibility with the aptX codecs. So, if you’re already in the Apple ecosystem, getting the Apple Airpods seems like a better option for now.
Does latency depend on the Bluetooth codec used?
Yes, as seen with the aptX adaptive, LDAC LL, and other audio codecs, the latency offered by the earbuds depends on the codec used.
Why does Bluetooth need real-time codecs?
Real-time Bluetooth codecs are needed to avoid lip-syncing issues in movies and audio lag in games. If you’re a professional gamer, you may need to consider specialized low-latency codecs such as aptX LL or LDAC LL to avoid any significant audio lag issues. Otherwise, most Bluetooth audio codecs including the standard aptX, LDAC, and others provide acceptable latencies for most users to avoid audio synchronization issues while watching movies or YouTube, for instance.
Do MediaTek devices support aptX and other Qualcomm Bluetooth audio codecs?
Recent Android devices from OnePlus (OnePlus 10 Pro), Realme (realme 10 Pro+ 5G), and others powered by Mediatek chipsets indicate support for the aptX codec, implying Qualcomm is licensing the codec to these manufacturers. However, there is no information as to whether Qualcomm officially licenses the aptX codec technology to other chip makers.
Is it possible to add support for a particular Bluetooth audio codec to your device?
No, you cannot add support for a particular codec on your smartphone by yourself. Most Bluetooth audio codecs on the market are licensed to manufacturers so they can officially support it on their devices. If your smartphone lacks a particular codec, contact the manufacturer to see if they are planning to support that specific codec in the future.
While some have succeeded in adding support for various Bluetooth codecs using unofficial methods, we don’t recommend them.
Verdict
Audiophiles may prefer audio codecs such as aptX HD, LDAC, and LHDC while gamers may prefer specialized low-latency codecs such as aptX LL and LHDC LL. Most Apple device users may want to stick with the AAC codec as it seems to perform better there. And as discussed above, we don’t recommend SBC codec due to quality/implementation issues on most devices. As usual, there is no one-size-fits-all in the Bluetooth audio codec space. One needs to evaluate the needs, and based on the performance of the codec, you may choose the one that fits your needs.
